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hawipapa
2013-Oct-22, 01:45 AM
a couple of questions:
1. if i accept that this universe began with a bang at a point, and that all the known galaxies, nebulae(?), etc. are receding from each other, then isn't it likely that at that initial point, everything has departed and what remains is rather empty? perhaps seeming like a hole in space? and if there is no existing empty spot, perhaps new matter is arriving (converting from dark matter/energy or something else we haven't yet detected). or has it been known and i'm the one in the dark? I've never heard of the empty spot where it all began...?

then 2. if the galaxies are known to all be receding from us, with the ones twice as far away receding at twice the rate of the nearer ones, and the ones three times as far away receding at three times the rate, and all the rates are accelerating, would you suppose that something larger is exerting a pull? the first bang wouldn't be causing the accelerations. is that larger item what has been given the name of dark matter/energy? or is there something in the center, repelling everything?

NEOWatcher
2013-Oct-22, 12:07 PM
a couple of questions:
1. if i accept that this universe began with a bang at a point, and that all the known galaxies, nebulae(?), etc. are receding from each other, then isn't it likely that at that initial point, everything has departed and what remains is rather empty? perhaps seeming like a hole in space? and if there is no existing empty spot, perhaps new matter is arriving (converting from dark matter/energy or something else we haven't yet detected). or has it been known and i'm the one in the dark? I've never heard of the empty spot where it all began...?
No bang. No explosion. Big bang was just something coined by Fred Hoyle to sarcastically refer to George Lemaitre's theory.

The proper term is expansion. Just like a rising loaf of raisin bread.



then 2. if the galaxies are known to all be receding from us, with the ones twice as far away receding at twice the rate of the nearer ones, and the ones three times as far away receding at three times the rate, and all the rates are accelerating, would you suppose that something larger is exerting a pull? the first bang wouldn't be causing the accelerations. is that larger item what has been given the name of dark matter/energy? or is there something in the center, repelling everything?
If there was something at the center repelling everything, then the stuff closer in would be experiencing a stronger effect than the stuff farther away. So; the increase in velocity would not be the same with different distances.

Swift
2013-Oct-22, 01:32 PM
Hi hawipapa, welcome to CQ.

Another analogy that people use is to think of the universe is as the SURFACE of a balloon, with the stars and galaxies on the surface. The balloon started very tiny and has been expanding, which means the galaxies slowly move away from each other. But if you only think of the surface, there is no center to the surface of the balloon. If you were an ant crawling around on that surface, you would never find a center.

Hornblower
2013-Oct-22, 01:43 PM
a couple of questions:
1. if i accept that this universe began with a bang at a point, and that all the known galaxies, nebulae(?), etc. are receding from each other, then isn't it likely that at that initial point, everything has departed and what remains is rather empty? perhaps seeming like a hole in space? and if there is no existing empty spot, perhaps new matter is arriving (converting from dark matter/energy or something else we haven't yet detected). or has it been known and i'm the one in the dark? I've never heard of the empty spot where it all began...?

then 2. if the galaxies are known to all be receding from us, with the ones twice as far away receding at twice the rate of the nearer ones, and the ones three times as far away receding at three times the rate, and all the rates are accelerating, would you suppose that something larger is exerting a pull? the first bang wouldn't be causing the accelerations. is that larger item what has been given the name of dark matter/energy? or is there something in the center, repelling everything?

First, it is commendable that you started with "if." Your idea resembles Lemaitre's hypothesis of the 1920s which is easy to visualize. It has been superseded by models which I cannot visualize, but it is fine for an entry level thought exercise.

You appear to be envisioning a primordial body surrounded by empty space into which it explodes. Whether or not a void remains at the center may depend on the characteristics of the blast. If the impetus was the explosion of something at the center of an otherwise inert mass of stuff, then I would expect a void surrounded by flying ejecta that forms an expanding shell. If instead the whole body behaved like a ball of TNT that "cooked off" in a fire and rapidly expanded uniformly, then I would expect something more like what Hubble was observing at the time, with no void. To be in good agreement with what Hubble could see back then, we only need to have the ejecta dispersed over a radius much larger than his observable radius, with our viewpoint not too close to the edge.

For the current acceleration I would go with a pervasive repulsive tendency that becomes stronger with increasing separation, and does not require any particular center. It may be counterintuitive but it cannot be ruled out from first principles.

Noclevername
2013-Oct-22, 01:47 PM
The center is EVERYWHERE, man!

...No, I mean that literally. The entire universe-- all of space, time, and existence-- was and is the expansion zone. There is, as far as we know, no space or time outside the Universe so we are not expanding "into" anything. The points we use for spatial reference are all internal to the Universe.

Hornblower
2013-Oct-22, 02:00 PM
The center is EVERYWHERE, man!

...No, I mean that literally. The entire universe-- all of space, time, and existence-- was and is the expansion zone. There is, as far as we know, no space or time outside the Universe so we are not expanding "into" anything. The points we use for spatial reference are all internal to the Universe.

That is an example of what I cannot visualize, but nevertheless is in better agreement with up-to-date observations than is something like Lemaitre's model. I must simply put my limitations aside and trust the work of our astrophysicists and cosmologists. The universe is what it is and does what it does, and it does not care one iota about my inability to visualize it.

Jeff Root
2013-Oct-22, 02:44 PM
I like to use the balloon analogy, but what Swift just said may
be very misleading because he didn't explain how the analogy
works. You may misunderstand what he meant by the Universe
being the SURFACE of a balloon.

First, the balloon we are talking about is a rubber one, which
expands as it is blown up and contracts as it is deflated. That
is useful for an analogy because the Universe is expanding, too,
and the geometry of the expansion is quite similar. There are
different geometries possible, different ways that things could
expand, and the expansion of rubber balloon material is a good
analogy to the observed expansion of the Universe.

Probably the easist way to understand why it is the surface of
the balloon -- the material -- that represents the Universe, rather
than the volume of the balloon, is to think of how photographs
and maps work. Photographs and maps are flat, two-dimensional
representaions of three-dimensional objects. Everything in a
photograph is in the same plane, on computer screen or a sheet
of paper or maybe even a thin sheet of rubber. A tall building
is usually represented on a map only by the two dimensions of
its horizontal extent. The vertical dimension is usually ignored.
If you place dots on a thin sheet of rubber, like the surface of
a balloon, to represent galaxies or clusters of galaxies, you are
ignoring the third dimension. You are showing what you would
see on a map or in a photograph of the Universe. Everything is
compressed to two dimensions for one reason: So that it can be
put on the surface of the balloon, and expansion demonstrated
by blowing up the balloon.

It might be a better analogy to use the volume of the balloon
instead, and show expansion in three dimensions, but there is
no easy way to do that. It can't be done with a rubber balloon,
just as there is no easy way to make and display a photograph
with three dimensions. There are ways to make photographs
look as if they were three-dimensional, using stereo pairs,
holograms, or virtual computer environments where the point
of view or the scene can be moved around interactively (the
latter two of which substitutes time for the third dimension),
but none of these are actually three-dimensional images.

The balloon analogy is like ordinary photos and maps in that
it is simple and easy to do, and is missing a dimension.

A flat sheet of rubber would work fine for one of the main
points of the analogy, except that it is far more difficult to
stretch a flat sheet of rubber than to blow up a balloon.
Also, a balloon has an advantage over a flat sheet in that
it can demonstrate how the expansion does not necessarily
have a center.

The expansion of the Universe is believed to have no center.
The Universe itself is believed to have no center.

This is the point Swift was making, and is why the balloon
analogy is so useful. But you need to see that it is only the
balloon's surface, not its volume, that you need to watch, or
you will likely misunderstand the point being demonstrated.

Let's cover our rubber balloon with a thin layer of slightly
sticky grease. Then sprinkle some metal sequins all over it.
The sequins stick to the grease. As we blow the balloon up,
the sequins get farther and farther apart from one another.
An ant living on this balloon universe would find no place
on the balloon that was the center of the expansion. All the
sequins would be moving away from their neighbors, and
more distant sequins would be moving away faster than
closer sequins.

The cosmic expansion is like that. The geometry is similar.
More distant clusters of galaxies are moving apart from one
another faster than closer ones. There is no place that is
seen as being different. There does not appear to be any
center of the Universe.

-- Jeff, in Minneapolis

.

Jeff Root
2013-Oct-22, 03:15 PM
I have no problem with the term "Big Bang". I think it
accurately characterizes how the Universe is believed to
have got started. Extremely dense, extremely energetic,
extremely hot, and expanding extremely rapidly. That
is an explosion.

However, the expansion has a certain geometry which
evolves over time, and that geometry cannot be described
in terms of matter in ordinary Euclidean space operating
according to Newtonian mechanics, but instead requires
matter-energy in Reimannian space operating according
to Einsteinian general relativity. So it's a bit complicated.

-- Jeff, in Minneapolis

Strange
2013-Oct-22, 04:05 PM
then 2. if the galaxies are known to all be receding from us, with the ones twice as far away receding at twice the rate of the nearer ones, and the ones three times as far away receding at three times the rate, and all the rates are accelerating, would you suppose that something larger is exerting a pull?

That is just a simple consequence of the fact that distances are scaling by the same amount.

Consider some equally spaced galaxies:
A.B.C.D.E
Over time, they move apart:
A..B..C..D..E
A...B...C...D...E

The distance between A and C is increasing faster than the distance between A and B. The distance between A and E is increasing even faster. This is true for any pair of points you choose. In other words, the speed at which they are separating is proportional to how far apart they are (even though they are all separating at the same rate).

WayneFrancis
2013-Oct-23, 12:00 AM
a couple of questions:
1. if i accept that this universe began with a bang at a point, and that all the known galaxies, nebulae(?), etc. are receding from each other, then isn't it likely that at that initial point, everything has departed and what remains is rather empty? perhaps seeming like a hole in space? and if there is no existing empty spot, perhaps new matter is arriving (converting from dark matter/energy or something else we haven't yet detected). or has it been known and i'm the one in the dark? I've never heard of the empty spot where it all began...?

then 2. if the galaxies are known to all be receding from us, with the ones twice as far away receding at twice the rate of the nearer ones, and the ones three times as far away receding at three times the rate, and all the rates are accelerating, would you suppose that something larger is exerting a pull? the first bang wouldn't be causing the accelerations. is that larger item what has been given the name of dark matter/energy? or is there something in the center, repelling everything?

I'm sure others have explained this already but I'll read their posts after I put my 2 cents in.
The Answer : No!
The Explanation : Your understanding of the scientific explanation is faulty. Like some creationist claiming "Evolution is just a 'theory'!" but either not knowing the difference in definitions of a "Scientific theory" and a common definition of a "theory" or in some cases knowing but preaching to those that don't in hopes they'll agree without questioning the logic.

The big bang wasn't an explosion "in" space. The big bang was an explosion of space. The "centre" isn't a point in our 3 spatial dimensions but a point in our 4th dimension of time. The features of the 2 are different and it is these differences that have been observed leading us to the the current model. It can be a lot to get your head around and my suggestion is read, listen, watchand, like you are doing now, question. Read as much as you want from reputable sources. Wikipedia Big Bang article (http://en.wikipedia.org/wiki/Big_Bang) is a good start. Subscribe to astronomy/cosmology podcasts like Star Talk Radio (http://www.startalkradio.net/). Watch astronomy/cosmology lectures given by professors like Alex Filippenko on YouTube (http://www.youtube.com/watch?v=VM8CfRtXWTM). As you do come back here with questions for more in depth answers.

WayneFrancis
2013-Oct-23, 02:00 AM
I'll also mention not to take any one of the analogies to literally because they are just that, analogies. Thus they have their limits and break down at different points. Like the great balloon analogy. As Jeff points out you have to think of it as a projection of 3d space on to a 2D surface or even just a 2D slice of a 3D universe. Just don't think of the 3D balloon as 3D. You have to treat the surface for what it is ... a 2D object even though we perceive it in 3 dimensions. That is where that analogy breaks downs when people go "what about the inside of the balloon?". The loaf of raisin bread is another good analogy except the raise bread has a outer boundary and even if the universe is finite in size it is thought to be unbounded, which means it loops back on itself, so there is no "edge".

Just food for thought as you look at different models to help you understand what is being explained.

Jeff Root
2013-Oct-23, 04:34 AM
I prefer to think of the balloon as representing a slice, and
started my post intending to get to that after describing it
in terms of a photo or map (it is why I mentioned the tall
building -- any floor of which can be represented by a floor
plan), but my post was long enough as it was. It is pretty
difficult to visualize the changes in the balloon required to
match different plane slices through the Universe.

-- Jeff, in Minneapolis

wd40
2013-Oct-24, 09:39 AM
Have there been any cosmological discoveries since George Elllis said in 1981 that "I can construct for you a spherically symmetrical universe with Earth at its center, and you cannot disprove it based on observations. You can only exclude it on philosophical grounds. In my view there is absolutely nothing wrong in that. What I want to bring into the open is the fact that we are using philosophical criteria in choosing our models. A lot of cosmology tries to hide that" to change his view that a universe with a center is possible?

Noclevername
2013-Oct-24, 09:49 AM
Have there been any cosmological discoveries since George Elllis said in 1981 that "I can construct for you a spherically symmetrical universe with Earth at its center, and you cannot disprove it based on observations. You can only exclude it on philosophical grounds. In my view there is absolutely nothing wrong in that. What I want to bring into the open is the fact that we are using philosophical criteria in choosing our models. A lot of cosmology tries to hide that" to change his view that a universe with a center is possible?

His description seems to confuse "center" with "reference frame".

Jeff Root
2013-Oct-24, 12:58 PM
I don't really know, but it looks to me like he used "center"
correctly. What we observe makes it appear that we happen
to be right at or very close to the center of the Universe.
To most people who think about it, that seems a wildly
unlikely explanation for the observations. Although it is
certainly possible that we happen to be close to the center,
it seems a much more reasonable explanation that every
observer sees pretty much the same as we see.

I want to point out that the two are not necessarily
mutually exclusive. The Universe might have no center,
but it is also possible that it does have a center, and we
might be very close to that center, yet the fundamental
explanation for why the Universe looks pretty much the
same in every direction could still be that it looks that
way for everybody, not just those near the center.

-- Jeff, in Minneapolis

dgavin
2013-Oct-24, 01:46 PM
Actually the center of the universe could be defined from the point of view of any observer, as being where the observer is, as any observation the observer makes will be cut off at by distance where space expansion is accelerating from them faster then light. This does mean that any observer by the act of observation, defines their own center of the universe, At least in a visual distance limited sense.

Of course this does mean your visually defined center of the universe moves with you, indicating that indeed, there is no real center of the universe. Just sight limited ones.

wd40
2013-Oct-26, 04:30 PM
“There must be no favoured location in the universe, no center, no boundary; all must see the universe alike. And, in order to ensure this situation, the cosmologist postulates spatial isotropy and spatial homogeneity, which is his way of stating that the universe must be pretty much alike everywhere and in all directions” (Edwin Hubble)

publiusr
2013-Oct-26, 08:42 PM
That is true. If you wanted an arbitrary center for navigation, the big Cold Spot might be a good "central point"

hawipapa
2013-Oct-27, 12:52 AM
Well, I'll try to digest these answers, thanks to all. I'm still puzzled over the idea that the galaxies are accelerating. F=MA makes me wonder about the force, be it repulsive or attractive. Is this why Dark Matter/Energy ideas have been developed? Especially thanks for the mention of the programs on the Universe, etc. on TV. I do watch those, all of them I find. Therefore I'm here. And I will be reading the many ideas presented, thanks.

Thanatos
2013-Oct-27, 01:22 AM
The consensus among modern cosmologists is the big bang occurred everywhere in the universe, not at some arbitrary point in some preexisting space. There is also nothing to suggest the big bang was not infinite in extent.

Jeff Root
2013-Oct-27, 02:16 AM
If the Big Bang occurred everywhere in an infinite universe,
what co-ordinated it so that it occurred everywhere at once?

For that matter, if the Big Bang occurred everywhere in a
large but finite universe, what co-ordinated it so that it
occurred everywhere at once?

-- Jeff, in Minneapolis

Thanatos
2013-Oct-27, 02:49 AM
That question only applies if you assume the big bang occurred in some preexisting space.

Noclevername
2013-Oct-27, 02:57 AM
If the Big Bang occurred everywhere in an infinite universe,
what co-ordinated it so that it occurred everywhere at once?

For that matter, if the Big Bang occurred everywhere in a
large but finite universe, what co-ordinated it so that it
occurred everywhere at once?

-- Jeff, in Minneapolis

If the universe was infinitely dense at time zero, the "everywhere" would consist of a single point, or more accurately, of all points overlapping.

korjik
2013-Oct-27, 05:15 AM
If the Big Bang occurred everywhere in an infinite universe,
what co-ordinated it so that it occurred everywhere at once?

For that matter, if the Big Bang occurred everywhere in a
large but finite universe, what co-ordinated it so that it
occurred everywhere at once?

-- Jeff, in Minneapolis

The big bang did not occur in the universe, it was, and is, the universe. All points in this universe started inside the big bang, there was no outside to expand into.

Shaula
2013-Oct-27, 06:05 AM
Well, I'll try to digest these answers, thanks to all. I'm still puzzled over the idea that the galaxies are accelerating. F=MA makes me wonder about the force, be it repulsive or attractive. Is this why Dark Matter/Energy ideas have been developed?
Modern models don't represent expansion as a force, it is modelled as a expansion of the underlying metric. Galaxies are not being accelerated by some force acting on them, they are being affected by an underlying expansion of the metric we use to describe spacetime. This is why you end up with causal horizons beyond which stuff is moving at greater than c relative to us. You cannot do that with simple acceleration in GR, however an expansion of the underlying metric can produce the illusion of superluminal velocities.

Shaula
2013-Oct-27, 06:06 AM
If the Big Bang occurred everywhere in an infinite universe, what co-ordinated it so that it occurred everywhere at once?

For that matter, if the Big Bang occurred everywhere in a large but finite universe, what co-ordinated it so that it occurred everywhere at once?

-- Jeff, in Minneapolis
Please refer to any one of the dozen other threads you have derailed with this question and the ensuing circular discussions.

Jeff Root
2013-Oct-27, 02:42 PM
The consensus among modern cosmologists is the big bang
occurred everywhere in the universe, not at some arbitrary
point in some preexisting space. There is also nothing to
suggest the big bang was not infinite in extent.


If the Big Bang occurred everywhere in an infinite universe,
what co-ordinated it so that it occurred everywhere at once?

For that matter, if the Big Bang occurred everywhere in a
large but finite universe, what co-ordinated it so that it
occurred everywhere at once?


That question only applies if you assume the big bang
occurred in some preexisting space.
No, the fact that the Big Bang did not occur in some
preexisting space does not prevent you from answering
the question. You claimed that "There is also nothing
to suggest the big bang was not infinite in extent."
If that is true, then what co-ordinated it so that it
occurred everywhere at once?

-- Jeff, in Minneapolis

.

Jeff Root
2013-Oct-27, 02:55 PM
If the universe was infinitely dense at time zero, the
"everywhere" would consist of a single point, or more
accurately, of all points overlapping.
Thanatos claimed that there is nothing to suggest
that the Big Bang was not infinite in extent. If it
was infinite in extent, then it was not pointlike.

If the density of the Universe was infinite, it would
have been infinite throughout the infinite extent.

-- Jeff, in Minneapolis

.

korjik
2013-Oct-27, 04:50 PM
Thanatos claimed that there is nothing to suggest
that the Big Bang was not infinite in extent. If it
was infinite in extent, then it was not pointlike.

If the density of the Universe was infinite, it would
have been infinite throughout the infinite extent.

-- Jeff, in Minneapolis

.

And?

That point expanded into a not point, making an infinite density not infinite.

Jeff Root
2013-Oct-27, 05:38 PM
Thanatos claimed that there is nothing to suggest
that the Big Bang was not infinite in extent. If it
was infinite in extent, then it was not pointlike.

If the density of the Universe was infinite, it would
have been infinite throughout the infinite extent.
And?

That point expanded into a not point, making an infinite
density not infinite.
What point?

Jeff, in Minneapolis

Noclevername
2013-Oct-27, 09:11 PM
If it
was infinite in extent, then it was not pointlike.
.

I did not say infinite in extent, I said if it was infinite in mass.

EDIT: And I was mistaken in saying so, I should have said infinite in density, not mass. :doh:

Jeff Root
2013-Oct-27, 10:30 PM
If it was infinite in extent, then it was not pointlike.
I did not say infinite in extent, I said if it was infinite
in mass.
Thanatos said it. I said so in the sentence immediately
preceeding the sentence you quoted. If you had quoted
both sentences instead of just the second, it would have
been completely obvious that we were talking about an
infinite extent:


Thanatos claimed that there is nothing to suggest
that the Big Bang was not infinite in extent. If it
was infinite in extent, then it was not pointlike.
I understood what you said and showed a problem with it.
Namely, your assertion that "everywhere" would consist of
a single point conflicts with Thanatos' assertion that the
Big Bang may have been infinite in extent.

-- Jeff, in Minneapolis

Noclevername
2013-Oct-27, 10:34 PM
Thanatos said it. I said so in the sentence immediately
preceeding the sentence you quoted. If you had quoted
both sentences instead of just the second, it would have
been completely obvious that we were talking about an
infinite extent:

I understood what you said and showed a problem with it.
Namely, your assertion that "everywhere" would consist of
a single point conflicts with Thanatos' assertion that the
Big Bang may have been infinite in extent.

-- Jeff, in Minneapolis

No, it could have been a point containing infinite overlapping points. IE, infinite density.

Jeff Root
2013-Oct-27, 10:47 PM
Thanatos said "infinite extent", and that is what I was
asking about. A point is not an extent, nomatter what
the density might be there. In particular, it is not an
infinite extent.

-- Jeff, in Minneapolis

Noclevername
2013-Oct-27, 11:09 PM
Thanatos said "infinite extent", and that is what I was
asking about. A point is not an extent, nomatter what
the density might be there. In particular, it is not an
infinite extent.

-- Jeff, in Minneapolis

Ah, I understand the confusion now.

tusenfem
2013-Oct-28, 05:56 AM
Moved to Astronomy, this is way beyond Q&A.

korjik
2013-Oct-28, 09:39 AM
Thanatos said "infinite extent", and that is what I was
asking about. A point is not an extent, nomatter what
the density might be there. In particular, it is not an
infinite extent.

-- Jeff, in Minneapolis

I see now too. Add 'other than a mechanism to coordinate the whole thing at once' to the end of his statement. If I remember right, inflation will flatten out almost anything. It is one of the problems of current theory for when time goes back to zero.

On the other hand, it is 4:30 am here and I am rather ill and hopped up on cold meds, so I could be completely wrong :)

Noclevername
2013-Oct-28, 12:20 PM
If you try to picture expansion as having to "coordinate" across space like a propagated signal, it doesn't work for several reasons. Signals can't cross space at infinite speed. If you picture expansion signals having a finite speed, then you have an expanding area of low pressure pushing out against an unexpanded space of high pressure. If the outward pressure was simply the hot dense space of the early universe pushing mass apart to release thermal pressure, the expansion would have slowed, while by all current observations it's accelerating.

The more likely scenario is that expansion is an innate property of space.

Jeff Root
2013-Oct-28, 02:46 PM
I think what I'm trying to get at with the question I asked
Thanatos...



If the Big Bang occurred everywhere in an infinite universe,
what co-ordinated it so that it occurred everywhere at once?

For that matter, if the Big Bang occurred everywhere in a
large but finite universe, what co-ordinated it so that it
occurred everywhere at once?
... is that (1) the Big Bang is an expansion (what we see
now is both coasting after an initial expansion and new,
currently continuing expansion (acceleration), as opposed
to an instantaneous magical jump from nothing to infinite
extent), and (2) there was no magical co-ordination of the
expansion throughout a volume. Instead, the Big Bang must
be finite in extent, and although the Universe it created is
now mind-bogglingly huge, it must have begun as pointlike,
and expanded over time to its current extent. So the bottom
line, if one is needed, is that we can rule out the possibility
that the Big Bang involved or resulted in an infinite universe.

That is not to say the Universe cannot be infinite -- only that
the Big Bang was finite, and what resulted from it is finite.
If the Universe is infinite, then the Big Bang must have
involved only a finite portion of it.

-- Jeff, in Minneapolis

wd40
2013-Oct-28, 05:50 PM
If the universe is isotropic but inhomogeneous, it allows for a center, since only from an isotropic
center can the universe appear the same in all directions, but appear different when not observed from the center.

Grey
2013-Oct-28, 06:25 PM
That is not to say the Universe cannot be infinite -- only that
the Big Bang was finite, and what resulted from it is finite.
If the Universe is infinite, then the Big Bang must have
involved only a finite portion of it.I'm with Shaula: you've brought this up multiple times now in previous threads. In those threads, several people have brought up issues with your conclusion, and in each case, rather than addressing those issues, you've just stopped responding, only to bring it up again in some other thread. In this case, it really seems like the mostly likely outcome is that you end up further confusing hawipapa, a new member of the board who is already struggling to understand a complicated subject. I'd suggest that you start a separate thread if you really want to discuss this yet again.


I'm still puzzled over the idea that the galaxies are accelerating. F=MA makes me wonder about the force, be it repulsive or attractive. Is this why Dark Matter/Energy ideas have been developed?As Shaula points out, it's not quite as simple as F = ma, but your general point here is pretty close. The fact that we observer the expansion of the universe to be accelerating* (which was a surprising result) is why the term "dark energy" was introduced. At this point, "dark energy" is really just a placeholder term for "whatever is causing the expansion of the universe to accelerate". There are a few possible models, but we really don't have enough information to know for sure what's going on.

For the record, dark matter is something different. Given the rotation speeds of stars in galaxies, there must be significantly more matter there than what we can see, distributed somewhat differently than the luminous matter (hence why we call it "dark"). We've got a better handle on dark matter than we do on dark energy (and there's a large amount of corroborating evidence that it's there from a number of different types of observations), but we still don't know exactly what it is. Dark energy was given its name by analogy to dark matter, but they don't really have much to do with each other directly. So it was probably a poor choice of name, but now we're stuck with it. ;)

* Important note: The observation that the expansion is accelerating is not just that more distant objects are receding faster. For that, it's not that the galaxies speed up as they get farther away. The stretching rubber sheet or Strange's little diagram is a good way to see how recession speed is proportional to distance. The fact the expansion as a whole is accelerating is something a little more subtle, and was first noticed about 15 years ago.

Noclevername
2013-Oct-28, 07:17 PM
I think what I'm trying to get at with the question I asked
Thanatos...


... is that (1) the Big Bang is an expansion (what we see
now is both coasting after an initial expansion and new,
currently continuing expansion (acceleration), as opposed
to an instantaneous magical jump from nothing to infinite
extent), and (2) there was no magical co-ordination of the
expansion throughout a volume. Instead, the Big Bang must
be finite in extent, and although the Universe it created is
now mind-bogglingly huge, it must have begun as pointlike,
and expanded over time to its current extent. So the bottom
line, if one is needed, is that we can rule out the possibility
that the Big Bang involved or resulted in an infinite universe.

That is not to say the Universe cannot be infinite -- only that
the Big Bang was finite, and what resulted from it is finite.
If the Universe is infinite, then the Big Bang must have
involved only a finite portion of it.

-- Jeff, in Minneapolis

You are still describing the BB as if it were an expansion of energy/mass into a space, rather than an expansion of space that happens to drag mass along with it. BB was the beginning of all space and time. If a finite space can come from wherever it came from, so can an infinite space. We don't know where or how "nothing" became something (if it indeed was nothing), because our observations are all from inside of spacetime.

korjik
2013-Oct-28, 09:32 PM
I think what I'm trying to get at with the question I asked
Thanatos...


... is that (1) the Big Bang is an expansion (what we see
now is both coasting after an initial expansion and new,
currently continuing expansion (acceleration), as opposed
to an instantaneous magical jump from nothing to infinite
extent), and (2) there was no magical co-ordination of the
expansion throughout a volume. Instead, the Big Bang must
be finite in extent, and although the Universe it created is
now mind-bogglingly huge, it must have begun as pointlike,
and expanded over time to its current extent. So the bottom
line, if one is needed, is that we can rule out the possibility
that the Big Bang involved or resulted in an infinite universe.

That is not to say the Universe cannot be infinite -- only that
the Big Bang was finite, and what resulted from it is finite.
If the Universe is infinite, then the Big Bang must have
involved only a finite portion of it.

-- Jeff, in Minneapolis

You have two errors in your conclusions. We cannot prove a negative, so your conclusion that the universe must be finite is in error. We dont know a mechanism either way, so the conclusion cannot be drawn with certainty. The second error is the seperation of universe and Big Bang. The big bang is the universe and the universe is the big bang. You cannot seperate them.

Jeff Root
2013-Oct-29, 04:47 AM
I think what I'm trying to get at with the question I asked
Thanatos...

... is that (1) the Big Bang is an expansion (what we see
now is both coasting after an initial expansion and new,
currently continuing expansion (acceleration), as opposed
to an instantaneous magical jump from nothing to infinite
extent), and (2) there was no magical co-ordination of the
expansion throughout a volume. Instead, the Big Bang must
be finite in extent, and although the Universe it created is
now mind-bogglingly huge, it must have begun as pointlike,
and expanded over time to its current extent. So the bottom
line, if one is needed, is that we can rule out the possibility
that the Big Bang involved or resulted in an infinite universe.

That is not to say the Universe cannot be infinite -- only that
the Big Bang was finite, and what resulted from it is finite.
If the Universe is infinite, then the Big Bang must have
involved only a finite portion of it.
You are still describing the BB as if it were an expansion
of energy/mass into a space, rather than an expansion
of space that happens to drag mass along with it.
I don't see that I'm doing that. I think I'm describing it
in a way that is compatible with both views. Nothing
about my description requires the Big Bang to occur in
an existing space or to expand into an existing space.

What it *does* require is for the Universe to expand,
rather than to instantaneously become infinite in extent,
since expansion is what we actually observe it doing.



BB was the beginning of all space and time.
I'm not disagreeing with that as a likely description of
the actual Universe. For the purpose of this thread, I
would consider it to be a given if you didn't keep telling
me that what I'm saying conflicts with it. But as long
as you bring it up, there is no way you can possibly
know whether or not what you said is true. You cannot
know whether the Big Bang was the beginning of all
space and time. At the most, you can be pretty sure
that it was the beginning of the space and time that
we inhabit. Our Universe. There is no reason to think
that our Universe is the only universe, or that the Big
Bang which marked the beginning of this Universe was
the first such event, or the last.



If a finite space can come from wherever it came from,
so can an infinite space.
How do you know that?

A small or infinitesimal thing can expand to become
large, given time. A small or infinitesimal thing cannot
expand to become infinite in extent. A thing which is
infinite in extent cannot simultaneously begin expanding
everywhere without supernatural control.

If the Universe began small, the observed expansion
would adequately explain its current enormous size.
But expansion could not explain the Universe becoming
infinite in extent. For the Universe to result from the Big
Bang and quickly or instantly be infinite in extent would
require some new mechanism completely different from
expansion and completely unlike anything ever observed.

-- Jeff, in Minneapolis

Jeff Root
2013-Oct-29, 04:51 AM
I think what I'm trying to get at with the question I asked
Thanatos...

... is that (1) the Big Bang is an expansion (what we see
now is both coasting after an initial expansion and new,
currently continuing expansion (acceleration), as opposed
to an instantaneous magical jump from nothing to infinite
extent), and (2) there was no magical co-ordination of the
expansion throughout a volume. Instead, the Big Bang must
be finite in extent, and although the Universe it created is
now mind-bogglingly huge, it must have begun as pointlike,
and expanded over time to its current extent. So the bottom
line, if one is needed, is that we can rule out the possibility
that the Big Bang involved or resulted in an infinite universe.

That is not to say the Universe cannot be infinite -- only that
the Big Bang was finite, and what resulted from it is finite.
If the Universe is infinite, then the Big Bang must have
involved only a finite portion of it.
You have two errors in your conclusions. We cannot prove a
negative, so your conclusion that the universe must be finite
is in error.
It is my assertion against your assertion. My assertion has
the advantage that it accords with known physical laws.



We dont know a mechanism either way, so the conclusion
cannot be drawn with certainty.
Nothing is completely certain, but this is about as certain
as anything can be. The Big Bang could not result in an
infinite universe in a finite time. (It couldn't result in an
infinite universe in an infinite time, either, but that would
be more difficult to show, and doesn't matter anyway since
we all agree that the Big Bang occurred a finite time ago.)



The second error is the seperation of universe and Big Bang.
The big bang is the universe and the universe is the big bang.
You cannot seperate them.
Yes, I can.

We have no way of knowing whether the Big Bang was a
unique event. There may be many universes which resulted
from different "bangs". More generally, we have no way of
knowing whether anything exists apart from the Universe
created in the Big Bang.

In the quote above, when I asserted that "If the Universe is
infinite, then the Big Bang must have involved only a finite
portion of it," I used the term "Universe" to refer everything,
whether it was involved in the Big Bang which created our
own Universe or not. Some people use the term "multiverse"
to refer to that overarching Universe, but I'm not sufficiently
familiar with the term to be happy using it.

In any case, *our* Universe clearly came from the one Big
Bang we are aware of, and everything we are aware of is part
of that Universe.

Is that okay with you?

-- Jeff, in Minneapolis

korjik
2013-Oct-29, 06:09 AM
It is my assertion against your assertion. My assertion has
the advantage that it accords with known physical laws.

Incorrect. I am not asserting, I am telling you what the current theory holds.



Nothing is completely certain, but this is about as certain
as anything can be. The Big Bang could not result in an
infinite universe in a finite time. (It couldn't result in an
infinite universe in an infinite time, either, but that would
be more difficult to show, and doesn't matter anyway since
we all agree that the Big Bang occurred a finite time ago.)

Again, an infinite universe is not forbidden, if a mechanism is found that can give the correct values. Yes, it has to start infinite if it is infinite, and that isnt likely, but it isnt forbidden. There is a difference.



Yes, I can.

We have no way of knowing whether the Big Bang was a
unique event. There may be many universes which resulted
from different "bangs". More generally, we have no way of
knowing whether anything exists apart from the Universe
created in the Big Bang.

In the quote above, when I asserted that "If the Universe is
infinite, then the Big Bang must have involved only a finite
portion of it," I used the term "Universe" to refer everything,
whether it was involved in the Big Bang which created our
own Universe or not. Some people use the term "multiverse"
to refer to that overarching Universe, but I'm not sufficiently
familiar with the term to be happy using it.

In any case, *our* Universe clearly came from the one Big
Bang we are aware of, and everything we are aware of is part
of that Universe.

Is that okay with you?

-- Jeff, in Minneapolis

Wether it is Ok with me is irrelevant. You useage of 'universe' is not the mainstream. All evidence is that this universe is closed. Say whatever you want about what is outside, but that is not mainstream. The mainstream view is that there is no space outside the universe. The universe does not expand into an empty external space, it just gets bigger.

Jeff Root
2013-Oct-29, 08:51 AM
It is my assertion against your assertion. My assertion has
the advantage that it accords with known physical laws.
Incorrect. I am not asserting, I am telling you what the
current theory holds.
That's an assertion.

So the "current theory" is unphysical. I have something
more up-to-date than the "current theory", then.



Again, an infinite universe is not forbidden, if a mechanism
is found that can give the correct values. Yes, it has to start
infinite if it is infinite, and that isnt likely, but it isnt forbidden.
There is a difference.
Okay, so you are positing an infinite universe which is always
infinite, not one which becomes infinite due to expansion.
You agree with me that a finite or infinitesimal universe
cannot become infinite by expanding.

But you say it isn't forbidden that the universe started
infinite. The problem with that is you also said that "The
big bang is the universe and the universe is the big bang."
I take that to mean everything in the Universe came from
and began with the Big Bang. It is a problem because the
Big Bang was an event. It happened at a particular time.
So if the Big Bang involved the entire Universe and the
Universe was infinite in extent when it occurred, it had to
be co-ordinated to occur everywhere simultaneously by
some kind of supernatural force. So what you should have
said is that it isn't possible that the Universe started
infinite. If it did start infinite, it didn't start with a Big
Bang. It couldn't. If it did start with a Big Bang, it didn't
start infinite. It couldn't. Since we have quite a lot of
evidence pointing to the Universe starting with a Big Bang,
and no evidence suggesting that it is infinite, my choice
is to go with the Big Bang.




We have no way of knowing whether the Big Bang was a
unique event. There may be many universes which resulted
from different "bangs". More generally, we have no way of
knowing whether anything exists apart from the Universe
created in the Big Bang.

In the quote above, when I asserted that "If the Universe is
infinite, then the Big Bang must have involved only a finite
portion of it," I used the term "Universe" to refer everything,
whether it was involved in the Big Bang which created our
own Universe or not. Some people use the term "multiverse"
to refer to that overarching Universe, but I'm not sufficiently
familiar with the term to be happy using it.

In any case, *our* Universe clearly came from the one Big
Bang we are aware of, and everything we are aware of is part
of that Universe.

Is that okay with you?
Wether it is Ok with me is irrelevant.
Clearly it *is* relevant to you. You replied exactly because
it is relevant to you.



Your useage of 'universe' is not the mainstream. All evidence
is that this universe is closed. Say whatever you want about
what is outside, but that is not mainstream. The mainstream
view is that there is no space outside the universe.
So you are asserting that the mainstream view is that the
hypotheses by Linde and others of chaotic inflation, eternal
inflation, branes, and multiverse in general are all wrong.
No chance any of them are right. There can be only one Big
Bang and one Universe, according to the mainstream view.



The universe does not expand into an empty external space,
I didn't claim it does.



... it just gets bigger.
Which would be a particularly strange thing for an infinite
universe to do.

-- Jeff, in Minneapolis

Noclevername
2013-Oct-29, 02:25 PM
Which would be a particularly strange thing for an infinite
universe to do.

-- Jeff, in Minneapolis

Not really:


http://en.wikipedia.org/wiki/Hilbert%27s_paradox_of_the_Grand_Hotel

Noclevername
2013-Oct-29, 02:47 PM
A small or infinitesimal thing can expand to become
large, given time. A small or infinitesimal thing cannot
expand to become infinite in extent. A thing which is
infinite in extent cannot simultaneously begin expanding
everywhere without supernatural control.

If the Universe began small, the observed expansion
would adequately explain its current enormous size.
But expansion could not explain the Universe becoming
infinite in extent. For the Universe to result from the Big
Bang and quickly or instantly be infinite in extent would
require some new mechanism completely different from
expansion and completely unlike anything ever observed.

-- Jeff, in Minneapolis

But we have no evidence that it began small. We know that all of it was hot and dense, and beyond that we have no other information. If it began infinite, the observations would be just the same.

Jeff Root
2013-Oct-29, 05:23 PM
The Hilbert Hotel is not physical. It is mathematical.
There is no reason to think this particular math applies
to the physical Universe.

The Hilbert Hotel, being infinite, doesn't get bigger when
rooms are added to it.

-- Jeff, in Minneapolis

Jeff Root
2013-Oct-29, 05:23 PM
A small or infinitesimal thing can expand to become
large, given time. A small or infinitesimal thing cannot
expand to become infinite in extent. A thing which is
infinite in extent cannot simultaneously begin expanding
everywhere without supernatural control.

If the Universe began small, the observed expansion
would adequately explain its current enormous size.
But expansion could not explain the Universe becoming
infinite in extent. For the Universe to result from the Big
Bang and quickly or instantly be infinite in extent would
require some new mechanism completely different from
expansion and completely unlike anything ever observed.
But we have no evidence that it began small. We know
that all of it was hot and dense, and beyond that we
have no other information. If it began infinite, the
observations would be just the same.
If it began infinite, we have to assume an unphysical
supernatural explanation for how it all simultaneously
existed with nearly identical properties throughout an
infinite volume despite no part of it ever having any
contact or ancestral linkage with any other part.

In post #23, you said:



If the universe was infinitely dense at time zero, the
"everywhere" would consist of a single point, or more
accurately, of all points overlapping.
I prefer that idea to the idea of a supernatural force
affecting an infinite volume simultaneously.

-- Jeff, in Minneapolis

Noclevername
2013-Oct-29, 05:33 PM
If it began infinite, we have to assume an unphysical
supernatural explanation for how it all simultaneously
existed with nearly identical properties throughout an
infinite volume despite no part of it ever having any
contact or ancestral linkage with any other part.


Why unphysical/supernatural? How is an infinite universe beginning any more unexplainable than a finite universe beginning? Both are "something from nothing".

Noclevername
2013-Oct-29, 06:04 PM
If it began infinite, we have to assume an unphysical
supernatural explanation for how it all simultaneously
existed with nearly identical properties throughout an
infinite volume despite no part of it ever having any
contact or ancestral linkage with any other part.


There is no "ancestral" linkage because there was no time before that. Existence wasn't, then it was. It may simply be that that's how spacetime is when it first starts-- full of mass/energy. In which case it could not be anything but universally consistent. No magical "coordination" is required.

wd40
2013-Oct-29, 06:17 PM
In the cosmology proposed by George Ellis in the 70s he believes in a spherical dipole universe in which the Earth is the south pole position anticenter, while the point at which the Big Bang exploded is the north pole or “center.” The diameter between the center and anticenter is the longest distance in the universe.

Van Rijn
2013-Oct-29, 07:10 PM
That's an assertion.

So the "current theory" is unphysical. I have something
more up-to-date than the "current theory", then.


If you have something more up to date, why don't you get it published in a peer-reviewed journal? But, I agree with others on this thread: This appears to be the same argument from incredulity you've posted again and again.

Jeff Root
2013-Oct-29, 11:25 PM
Why unphysical/supernatural? How is an infinite universe
beginning any more unexplainable than a finite universe
beginning? Both are "something from nothing".
"Something from nothing" is not a big problem for me.
It has nothing to do with what I'm objecting to. Whether
the Universe came from something or from nothing is not
a question that I'm examining here.

It is unphysical in that it is a behavior completely at
odds with all observed behavior of physical things.

Every event that has ever been observed requires time
to occur. One way to describe why that is so is to say
that information has to be transferred. You are asking
people to accept that information would be transferred
to every part of an infinite extent instantaneously. No
observed physical process acts like that. There is no
reason to think any physical process could act like that.

The hypothesised Inflation does not behave like that.
Inflation is a very rapid expansion. It does not involve
anything happening at a distance or anything happening
instantaneously. It only involves a region which has
an ancestral causal connection.

A Big Bang which instantaneously affects an infinite
extent of space breaks the rest of physics. Nothing
else works if such an event is assumed.

-- Jeff, in Minneapolis

Jeff Root
2013-Oct-29, 11:28 PM
If it began infinite, we have to assume an unphysical
supernatural explanation for how it all simultaneously
existed with nearly identical properties throughout an
infinite volume despite no part of it ever having any
contact or ancestral linkage with any other part.
There is no "ancestral" linkage because there was no
time before that.
That's correct.



Existence wasn't, then it was.
That's one way of describing what may be the most
popular view currently of the Beginning. I pretty much
ascribe to that view myself, and I'm assuming it in
this thread whenever I don't explicitly say otherwise.



It may simply be that that's how spacetime is when it
first starts-- full of mass/energy.
Sure, but in that case you still need to explain how it
starts everywhere simultaneously throughout an infinite
volume.



In which case it could not be anything but universally
consistent. No magical "coordination" is required.
Why did spacetime come into existence here at the same
instant it came into existence there, and there, and there,
and there and there and there? Something would have to
co-ordinate it. Something would have to make spacetime
exist in an infinity of completely separate and independent
locations simultaneously. It could not expand to infinite
extent from a finite or pointlike origin, because that would
take infinite time, nomatter how rapid the expansion.

-- Jeff, in Minneapolis

Jeff Root
2013-Oct-29, 11:41 PM
So the "current theory" is unphysical. I have something
more up-to-date than the "current theory", then.
If you have something more up to date, why don't you
get it published in a peer-reviewed journal?
What I've argued here is terribly obvious. It isn't
anything new or surprising. It is only more up-to-date
than the BAUT version of "current theory".



But, I agree with others on this thread: This appears
to be the same argument from incredulity you've
posted again and again.
It is. Hopefully, explained a little better.

-- Jeff, in Minneapolis

Noclevername
2013-Oct-30, 12:03 AM
Sure, but in that case you still need to explain how it
starts everywhere simultaneously throughout an infinite
volume.
That's no more or less difficult than explaining how you think it came into being in one place.


Why did spacetime come into existence here at the same
instant it came into existence there, and there, and there,
and there and there and there? Something would have to
co-ordinate it. Something would have to make spacetime
exist in an infinity of completely separate and independent
locations simultaneously.


No. If that's the way space comes into existence, then that's the way it would have to be, everywhere; the only way it could be. Why do you keep insisting that some outside or previous "coordination" is needed?



It could not expand to infinite
extent from a finite or pointlike origin, because that would
take infinite time, nomatter how rapid the expansion.


Correct, it could not. It could be one or the other, finite or infinite. Point, or hotel. If it expanded from a point, it would show in our observations. It does not.

Shaula
2013-Oct-30, 05:56 AM
What I've argued here is terribly obvious. It isn't anything new or surprising. It is only more up-to-date than the BAUT version of "current theory".
It is obvious only if you make a series of assumptions about the underlying causal and spacetime structures of the early universe based on current structures. There is no reason to do this as has been pointed out to you ad nauseum.


It is. Hopefully, explained a little better.
Nope, same old same old. You just keep saying "It is obvious though" without questioning your underlying assumptions and ignoring the fact that the models you are using to make your claims are not tested that far back. Although your claims to be ahead of researchers into stuff like LQG and CDT are new.

korjik
2013-Oct-30, 10:00 AM
That's an assertion.

So the "current theory" is unphysical. I have something
more up-to-date than the "current theory", then.

Even more incorrect. You have an outmoded understanding.



Okay, so you are positing an infinite universe which is always
infinite, not one which becomes infinite due to expansion.
You agree with me that a finite or infinitesimal universe
cannot become infinite by expanding.

No I dont. It isnt relevant to the situation at hand


But you say it isn't forbidden that the universe started
infinite. The problem with that is you also said that "The
big bang is the universe and the universe is the big bang."
I take that to mean everything in the Universe came from
and began with the Big Bang.

This is the basis of your misunderstanding. It isnt everything in the universe came from the big bang, but that the universe itself came from the big bang.


It is a problem because the Big Bang was an event. It happened at a particular time.
So if the Big Bang involved the entire Universe and the
Universe was infinite in extent when it occurred, it had to
be co-ordinated to occur everywhere simultaneously by
some kind of supernatural force.

not supernatural, just unknown


So what you should have
said is that it isn't possible that the Universe started
infinite.

Only if I want to make the same mistake you do


If it did start infinite, it didn't start with a Big
Bang. It couldn't. If it did start with a Big Bang, it didn't
start infinite. It couldn't. Since we have quite a lot of
evidence pointing to the Universe starting with a Big Bang,
and no evidence suggesting that it is infinite, my choice
is to go with the Big Bang.

Choice is irrelevant, and again, this is the mistake you keep making. You are assuming that the universe works the way you want it to, so after that you only accept information that corresponds to that view.



Clearly it *is* relevant to you. You replied exactly because
it is relevant to you.


So you are asserting that the mainstream view is that the
hypotheses by Linde and others of chaotic inflation, eternal
inflation, branes, and multiverse in general are all wrong.
No chance any of them are right. There can be only one Big
Bang and one Universe, according to the mainstream view.

No I am not. Like every string theory, once they have some proof, they will have some relevance. That is called science


I didn't claim it does.


Then why does everyone say you do?


Which would be a particularly strange thing for an infinite
universe to do.

-- Jeff, in Minneapolis

That you find it strange dosent mean it dosent happen

mkline55
2013-Oct-30, 01:21 PM
You are assuming that the universe works the way you want it to, so after that you only accept information that corresponds to that view.


I actually had to double check to see which of you said that. In my humble opinion it's applicable for both sides of this argument. Reading this thread is like reading a philosophical debate. I read one post and say to myself that 's a good point. I read the response and say, well that's a good point, too. Back and forth it goes.

Backing away, I see one side of the argument is logic-based, while the other appears more faith based. Of course, if you simply have faith in logic, it's hard to tell the difference. So, anyone care to weigh in on which arguments are logical in origin and which are just faith?

Shaula
2013-Oct-30, 02:46 PM
Backing away, I see one side of the argument is logic-based, while the other appears more faith based. Of course, if you simply have faith in logic, it's hard to tell the difference. So, anyone care to weigh in on which arguments are logical in origin and which are just faith?
Easy, for both sides the answer is "My arguments are logical, his are faith based"

The trouble is the underlying assumption made by both sides are not testable. Jeff assumes that the causal and geometric structure of space time go all the way back and bases his deductions on this untested (and increasingly unlikely if you give any credence at all to modern speculative theories such as LQG, CDT and even some SSM ones) assumption. Korjik is assuming that the point where spacetime can be said to have 'appeared' is correlated to the appearance of matter and energy. The simple problem is that we have no models that currently do a good enough job prior to the initial conditions of the BBT to test or even weigh the likelihood of different ideas.

This is why this debate is so pointless. If anyone actually had any valid way to extend our knowledge beyond the initial conditions then they should be publishing it. Instead people bang on about what is 'logical' or 'makes sense' and generally get nowhere. The evolution of the universe prior to the initial conditions of the BBT is a hugely complex topic given our incomplete knowledge of physical theory, the incompatibility of GR and the SM being a frequently used and pertinent example. Honestly, I don't think anyone on this board (obviously including myself in that) has anything like the background to be making such definitive statements as people are here.

Grey
2013-Oct-30, 05:50 PM
It's important to remember that logic isn't so much about the specific statements being made, it's about the process of going from one statement to another. Given some things that you already "know" are true, logic tells you how you can make other statements that you know must also be true. The tricky part is that you always have to start with some statements that you assume to be true (we call them axioms) without being able to prove them logically from other statements, because otherwise you have nowhere to start. Obviously, choosing your axioms carefully is very important.

One of the classic examples is that of Euclid, who came up with some very good axioms for geometry, that all seemed reasonable to assume at the outset, and that stood for thousands of years. And yet, eventually we realized that it was possible to change at least one of his axioms, and we came up with new realms of geometry where space itself can be curved. And far from being just a curiosity for abstract mathematicians to ponder, it looks like understanding gravity in our universe actually requires the use of such a curved metric.

Jeff has taken as one of his axioms that there can be no correlations between events in the universe that are spacelike separated. That is, if two events are not close enough together in space and time for a light signal to get from one to the other, then there can't be correlations between them. This is called locality, the assumption that events can only be correlated with each other if there can be a causal link between them. If you accept this axiom (and perhaps a few others; whenever you make a set of axioms, you're almost always assuming a few additional things that haven't been explicitly stated, maybe even without realizing it), then it does seem to follow that the Big Bang could not have been infinite in extent, since there would be no way to coordinate an infinite Big Bang to all happen at the same moment.

As I pointed out here (http://cosmoquest.org/forum/showthread.php?108282-Size-of-the-Big-Bang-singularity&p=1801168#post1801168), though, it's probably not a good idea to draw conclusions about what the universe must be like based on philosophical assumptions. The track record for that is not very good. There are a number of ways out of the conundrum that Jeff seems to present here.

For example, we've already run into the problem that opposite sides of the sky seem to be correlated better than they should be given their separation. This is a pretty similar issue to Jeff's, actually. We came up with inflation as a way to solve that issue and still preserve causality. The current models of inflation assume a finite but large expansion, but that doesn't mean that such a correlation couldn't also be explained by some new mechanism that allows correlation between separated events. My point here is that, when faced with an observed correlation that seemed better than it should be, we did not respond by insisting that the correlation couldn't really be there, but by coming up with a mechanism that might explain such an unexpected correlation.

We know that our descriptions of the laws of physics break down at a certain energy density. So assuming that some of those laws (such as the light speed limit for communication) still hold would seem to be a mistake. Very explicitly, we do not know what rules govern the universe under those circumstances. Causal effects might not be limited to the speed of light, and indeed might have no speed limit at all. I'm certainly not saying that this must be true; I'm only pointing out that it's probably not wise to assume that it cannot be true.

Indeed, we already have an example of events that appear to be correlated better than they should be if locality holds: quantum entanglement. Here we see precisely what locality forbids, which is correlations between arbitrarily distant events. So Jeff is implicitly assuming that causal influences can only travel at some finite velocity; you can have an infinite universe where everything participated in an event at the same moment if you relax that requirement. And it's not a particularly great loss, since John Bell long since demonstrated that no purely local theory can properly describe the quantum facts. We know that it's possible for arbitrarily distant events to be correlated, even though it seems like that doesn't make sense.

So, that's just one possible objection to Jeff's idea. As I noted, there are almost always more additional unstated assumptions for any philosophical position. Even if you want to keep a local description for some reason (and I'm not sure why you'd insist on it, since we know it can't work for quantum mechanics), you might still be able to keep an infinite universe all involved in a single big bang by discarding one of those other unstated assumptions instead.

My personal preference is to think of the universe as finite but unbounded. But I acknowledge that as a philosophical preference (I have a hard time envisioning an infinite universe), which is consistent with the currently available evidence, but not necessarily guaranteed by it. We may never be able to conclusively say whether the universe is finite or infinite, and I don't think it's a good plan to make conclusions about it based on preconceived notions.

Jeff Root
2013-Oct-30, 11:24 PM
This and the following replies were written before I saw
Grey's excellent post immediately above.




Sure, but in that case you still need to explain how it
starts everywhere simultaneously throughout an infinite
volume.
That's no more or less difficult than explaining how you
think it came into being in one place.
It is infinitely more difficult.

If the Big Bang began as "pointlike" -- involving only a
small or infinitesimal volume of space, in which everything
is causally-connected because it is all at one place, then
it consists of just a single event, and without any particular
constraints on that event.

In contrast, if the Big Bang occurred everywhere throughout
an infinite extent, then not only are there an infinite number
of independent creation events, but they are all coordinated
such that they occur simultaneously.

They must be independent because they cannot be causally-
connected by any physical means. But they obviously are
not independent because the simultaneous occurrance could
not be by random chance. So the coordination would have
to be supernatural, not due to anything in nature or physics.




It could not expand to infinite extent from a finite or pointlike
origin, because that would take infinite time, nomatter how
rapid the expansion.
Correct, it could not. It could be one or the other, finite or
infinite. Point, or hotel. If it expanded from a point, it would
show in our observations. It does not.
This is surprising. Are you saying that observations would
show if the the Universe expanded from a point, and they do
not show that, so the Universe did not expand from a point?

A few hours earlier, in post #49, you said the observations
would be the same whether it began small or infinite:


But we have no evidence that it began small. We know
that all of it was hot and dense, and beyond that we have
no other information. If it began infinite, the observations
would be just the same.
Are you now contradicting what you said then?

-- Jeff, in Minneapolis

Jeff Root
2013-Oct-30, 11:25 PM
It is obvious only if you make a series of assumptions
about the underlying causal and spacetime structures
of the early universe based on current structures.
Correct. I'm assuming that causality applies, I'm
assuming what causality actually *is*, and I'm
assuming that the known laws of physics apply.

There is also unknown physics, but the actions of
unknown physics should not make known physics stop
working.



There is no reason to do this as has been pointed out
to you ad nauseum.
I think there is sufficient reason to believe that causality
and known physics apply to the early universe to assume
that they do. The main reason being that we won't ever
know anything about the early Universe if we don't
assume they apply.

I think Stephen Hawking has a very spotty record for
ideas, but he has a lot of very good stuff in with the
garbage. That's why he's famous. In particular, one
paragraph from his book 'The Universe in a Nutshell':



We are used to the idea that events are caused by
earlier events, which in turn are caused by still earlier
events. There is a chain of causality stretching back
into the past. But suppose this chain has a beginning.
Suppose there was a first event. What caused it? This
was not a question that many scientists wanted to
address. They tried to avoid it, either by claiming, like
the Russians, that the universe didn't have a beginning
or by maintaining that the origin of the universe did
not lie within the realm of science but belonged to
metaphysics or religion. In my opinion, this is not a
position any true scientist should take. If the laws of
science are suspended at the beginning of the universe,
might not they fail at other times also? A law is not
a law if it only holds sometimes. We must try to
understand the beginning of the universe on the basis
of science. It may be a task beyond our powers, but
we should at least make the attempt.

-- Jeff, in Minneapolis

Jeff Root
2013-Oct-30, 11:27 PM
So the "current theory" is unphysical. I have something
more up-to-date than the "current theory", then.
Even more incorrect. You have an outmoded understanding.
The problem isn't that my understanding is outmoded or
incorrect, but that it is different from your understanding.

As I said, it is my assertion versus yours. Your assertion
contradicts known physics while mine does not.

That's why I keep posting on the subject. When I see
a credible poster here claim something which violates
known physics, I'm going to complain. I expect that
you're doing the same when you reply to me.




Okay, so you are positing an infinite universe which is always
infinite, not one which becomes infinite due to expansion.
You agree with me that a finite or infinitesimal universe
cannot become infinite by expanding.
No I dont. It isnt relevant to the situation at hand
It must be relevant to the situation at hand because
it is the question we have been discussing.

You did agree with me in post #46 when you said:


Again, an infinite universe is not forbidden, if a mechanism
is found that can give the correct values. Yes, it has to
start infinite if it is infinite, and that isnt likely, but it
isnt forbidden. There is a difference.
You said that if the Big Bang results in an infinite universe,
it has to start out infinite. In other words, the universe
cannot become infinite by expanding. But now you don't
agree with me or with what you said yesterday. And no
explanation except that you think it isn't relevant.




But you say it isn't forbidden that the universe started
infinite. The problem with that is you also said that "The
big bang is the universe and the universe is the big bang."
I take that to mean everything in the Universe came from
and began with the Big Bang.
This is the basis of your misunderstanding. It isnt
everything in the universe came from the big bang,
but that the universe itself came from the big bang.
I may print that out and frame it.




It is a problem because the Big Bang was an event.
It happened at a particular time. So if the Big Bang
involved the entire Universe and the Universe was infinite
in extent when it occurred, it had to be co-ordinated to
occur everywhere simultaneously by some kind of
supernatural force.
not supernatural, just unknown
It had to be supernatural because it violates known
physical law (AKA "nature"), which does not permit
coordinated events in places that are not causally
connected. What you claim goes far beyond that by
having infinitely many such coordinated events.




If it did start infinite, it didn't start with a Big Bang.
It couldn't.n If it did start with a Big Bang, it didn't
start infinite. It couldn't. Since we have quite a lot of
evidence pointing to the Universe starting with a Big
Bang, and no evidence suggesting that it is infinite,
my choicen is to go with the Big Bang.
Choice is irrelevant, and again, this is the mistake you
keep making. You are assuming that the universe works
the way you want it to, so after that you only accept
information that corresponds to that view.
Correct.

I am assuming that the Universe works according to the
laws of physics. When you claim that it does not, but fail
to acknowledge that that is what you are claiming, I argue
in favor of it working according to the laws of physics.

Of course there are unknown laws of physics, and certainly
unknown physics is required to explain the early Universe,
and of course the physical laws we have are always subject
to revision, but I'm not going to throw out known physics
and replace it with nothing just so that we can retain the
possibility that an infinite universe could have come from
the Big Bang.




So you are asserting that the mainstream view is that the
hypotheses by Linde and others of chaotic inflation, eternal
inflation, branes, and multiverse in general are all wrong.
No chance any of them are right. There can be only one Big
Bang and one Universe, according to the mainstream view.
No I am not.
You did assert it in post #46:


The mainstream view is that there is no space outside the
universe.
You say it, and the next day deny you are saying it.



Like every string theory, once they have some proof, they
will have some relevance. That is called science
Some of those cosmologies come from string theory, most
do not. Whether they come from string theory or not, they
are all about the possibility of other universes which contain
space, like the universe we are in. You said the mainstream
view is that there is no space outside the universe. So you
asserted that those theories are rejected by the mainstream,
whether you intended to or not.





The universe does not expand into an empty external space,
I didn't claim it does.
Then why does everyone say you do?
Everyone does not say I do. Not even everyone posting
in this thread says it. Not even everyone who disagrees
with me in this thread says it. You say it, Noclevername
said it. Two people. Yourself and one other.

Curious definition of "everyone".

-- Jeff, in Minneapolis

Jeff Root
2013-Oct-30, 11:31 PM
Of course, if you simply have faith in logic, it's hard to
tell the difference.
Nailed me. But I also have faith in science, so when my
logic is faulty, I expect it to be caught.

-- Jeff, in Minneapolis

Jeff Root
2013-Oct-30, 11:32 PM
The trouble is the underlying assumption made by both
sides are not testable.
I agree with that.



Jeff assumes that the causal and geometric structure of
space time go all the way back ...
Yes!



... and bases his deductions on this untested (and
increasingly unlikely if you give any credence at all to
modern speculative theories such as LQG, CDT and even
some SSM ones) assumption. Korjik is assuming that the
point where spacetime can be said to have 'appeared' is
correlated to the appearance of matter and energy.
I do that, too. In this thread, always. Outside the
thread, almost always. It is implicit (if not explicit)
in general relativity. So when he and Noclevername
say I'm considering the Big Bang as if it occurred in
some existing space, it is frustrating.

-- Jeff, in Minneapolis

Noclevername
2013-Oct-31, 12:08 AM
So when he and Noclevername
say I'm considering the Big Bang as if it occurred in
some existing space, it is frustrating.


It is equally frustrating that you don't see that you are still treating the BB as if it were an explosion in space. And blowing off all those who try to explain what you're doing wrong.

Shaula
2013-Oct-31, 12:13 AM
Correct. I'm assuming that causality applies, I'm assuming what causality actually *is*, and I'm assuming that the known laws of physics apply.
So you'd assume that classical laws apply to quantum objects? See the issue? Causality is a consequence of the causal structure of the manifolds or underlying structures of current theories. Just like in the case of comparing classical and quantum theories there is no reason to assume that they are preserved in areas outside current physics. And as I have said, looking at LQG, CDT and other theories there is a strong hint that they may not be. As for "I'm assuming that the known laws of physics apply" - we know they don't. GR and QM break down. So your assumption breaks down well outside the area you are applying it to. Your idea is unsupportable and your assertions that it is obvious and clearly right are simply unjustified statements of belief which you insist on promoting to the detriment of threads like this. We have yet another multi-page epic where you refuse to accept that your ideas are not the only possibility.

And:

There is also unknown physics, but the actions of unknown physics should not make known physics stop working.
Provably false. QM replaced Classical descriptions of the atom. Known physics was shown to stop working at small scales. GR replaced Newton. Newtonian physics was shown to stop working under some conditions. So there is simply no justification for asserting that known physics must still apply outside its domain of applicability.


I think there is sufficient reason to believe that causality and known physics apply to the early universe to assume that they do
You think wrong. LQG, CDT and so on use the formation of the causal structure of physics as part of their domain. So there is just as much reason to assume that these concepts are simply not applicable.


The main reason being that we won't ever know anything about the early Universe if we don't assume they apply.
Provably false. LQG and other theories show that we can know things about the early universe in the absence of the current causal structure.

I do wish you would stop baldly asserting stuff like this. I wish more you would stop ignoring the responses you get to this and bringing it up over and over again. The universe doesn't care how hard to believe you find it.

Strange
2013-Oct-31, 12:41 AM
...

Times like this we need a "Like" button. :)

Jeff Root
2013-Oct-31, 06:56 PM
So you'd assume that classical laws apply to
quantum objects?
Yes. Although quantum effects become more and more
significant when looking at smaller and smaller objects,
making classical laws less and less useful for describing
their behavior, classical laws still apply to electrons as
much as they do to elephants. Quantum effects mask
the classical effects at small scales much like the light
of the daytime sky masks the visibility of faint stars,
but in the case of quantum effects, there is no way to
get around them as there is with daylight.



See the issue? Causality is a consequence of the causal
structure of the manifolds or underlying structures of current
theories. Just like in the case of comparing classical and
quantum theories there is no reason to assume that they
are preserved in areas outside current physics.
There is no reason to assume that they aren't preserved
in the early universe, as classical effects are preserved
on quantum scales. Electrons have electric charge and
mass just as macroscopic objects do. Those properties
don't go away just because quantum effects dominate.
If causality is not preserved, nothing is. You might as
well assert that the rules of arithmetic don't apply.



And as I have said, looking at LQG, CDT and other theories
there is a strong hint that they may not be.
Change that to "weak" and I'll agree.

The chance that any of those theories will be found
to work is very low. I'm not going to be convinced by
examples of theories which probably don't work.



As for "I'm assuming that the known laws of physics apply" -
we know they don't. GR and QM break down.
They do not break down. They lose their ability to make
predictions under certain conditions. Neither theory is
necessarily incorrect -- it is only necessary that at least
one of them is incomplete, because in extreme conditions
their predictions conflict. That is what we know. Both
GR and QM apply in all situations, but which tells us more
varies with the conditions, and unknown physics may tell
us more than either GR or QM under some conditions.

General relativity can be applied to the early universe all
the way back to a singularity. Close to that point, quantum
mechanics no longer gives useful predictions. That doesn't
mean QM breaks down or doesn't apply in those conditions.
It might be that some new effect becomes dominant close
to the singularity, masking the QM effects or preventing the
approach to singularity.

I have no reason to think that GR and QM do not apply to
all situations.



So your assumption breaks down well outside the area
you are applying it to.
Leave the word "So" off the beginning of that sentence.
You can assert that my assumption breaks down, but you
haven't shown it. All you have shown is that known laws
of physics do not describe everything. You have not shown
that known laws of physics do not apply in all situations,
and you have not shown that causality doesn't apply in all
situations.



Your idea is unsupportable
No more so than yours.



... and your assertions that it is obvious and clearly right
are simply unjustified statements of belief ...
I only believe these things because they are clear to me.
If they were not clear to me, I wouldn't believe them.
My beliefs are dependent on what I observe, not the other
way around.



... which you insist on promoting to the detriment of
threads like this. We have yet another multi-page epic
where you refuse to accept that your ideas are not the
only possibility.
I am assuming and asserting that laws of physics apply
everywhere, and that causality applies everywhere, and
asserting one logical consequence of those assumptions
when someone contradicts that logical consequence
without saying or acknowledging that he is assuming
that the known laws of physics and / or causality are
violated.

This discussion has now lead to what is likely a solution
to your Jeff problem. In the future I can just point out
that the idea of an infinite universe springing from the
Big Bang assumes that either known laws of physics do
not apply, or causality does not apply, or both, and that
can be the end of it if I get no argument.




There is also unknown physics, but the actions of
unknown physics should not make known physics
stop working.
Provably false. QM replaced Classical descriptions of
the atom. Known physics was shown to stop working
at small scales.
Wrong. Known physics became inadequate to describe
what is happening at small scales. That doesn't mean
the physical properties and processes described by
classical physical laws don't exist at those scales.



GR replaced Newton. Newtonian physics was shown
to stop working under some conditions.
Wrong. Newtonian laws become inadequate to
describe what is happening under some conditions.
That doesn't mean the physical properties and
processes described by Newtonian laws go away
under those conditions.



So there is simply no justification for asserting
that known physics must still apply outside its
domain of applicability.
There is no justification for asserting that it doesn't.




I think there is sufficient reason to believe that causality
and known physics apply to the early universe to assume
that they do
You think wrong. LQG, CDT and so on use the formation
of the causal structure of physics as part of their domain.
So there is just as much reason to assume that these
concepts are simply not applicable.
If LQG and CDT don't work, it doesn't matter what they
use for what.

My take on it is that these theories give some promising
results as long as you ignore known laws of physics or
drop requirements for causality. Not very impressive.




The main reason being that we won't ever know anything
about the early Universe if we don't assume they apply.
Provably false.
Let's see you prove it.



LQG and other theories show that we can know things
about the early universe in the absence of the current
causal structure.
If a theory has to assume that causality is absent in
order to give useful predictions, then the predictions
are worthless.

What has any such theory ever predicted that has then
been shown to actually be so? I think your problem will
come in proving that these theories actually throw out
causality and / or other laws of physics.



I do wish you would stop baldly asserting stuff like this.
I wish more you would stop ignoring the responses you
get to this and bringing it up over and over again. The
universe doesn't care how hard to believe you find it.
So far it is just my assertions against yours. Neither
of us has presented any supporting evidence that known
physics and causality do or do not apply to the early
universe.

-- Jeff, in Minneapolis

Jeff Root
2013-Oct-31, 07:02 PM
It is equally frustrating that you don't see that
you are still treating the BB as if it were an
explosion in space. And blowing off all those who
try to explain what you're doing wrong.
So pick out an instance where you think I treated
the Big Bang as if it were an explosion in space,
rather than an explosion of space, and explain to
me exactly why what I said there treats the Big
Bang as if it were an explosion in space.

That is certainly on topic for the original question
of this thread.

-- Jeff, in Minneapolis

Selfsim
2013-Oct-31, 08:28 PM
You have not shown that known laws of physics do not apply in all situations … Laws are often described in a mathematical statement of how two or more quantities relate to each other. So to think that mathematics, which articulates some physical Law, describes the real universe, is a known failure in conceptual understanding. If the universe does not follow the mathematical description pertaining to a known Law, no explanation is called for. We know what Physics and Math are. We don't know what reality is. We need no explanations for when reality departs from the math, because that's exactly what we should always expect .. ie: the default mode of science. Reality has never followed a mathematical formula precisely.

Physics has always been an approximation that will always be discovered to be wrong. Math is pure tautology, which by definition, will not be wrong.

Noclevername
2013-Oct-31, 08:30 PM
So pick out an instance where you think I treated
the Big Bang as if it were an explosion in space,
rather than an explosion of space, and explain to
me exactly why what I said there treats the Big
Bang as if it were an explosion in space.

That is certainly on topic for the original question
of this thread.

-- Jeff, in Minneapolis


I have no problem with the term "Big Bang". I think it
accurately characterizes how the Universe is believed to
have got started. Extremely dense, extremely energetic,
extremely hot, and expanding extremely rapidly. That
is an explosion.

No. An explosion is a physical expansion of matter that sends out a shockwave of force through space from thermal increase. It cannot produce FTL expansion of space, as the BB observably did.



However, the expansion has a certain geometry which
evolves over time, and that geometry cannot be described
in terms of matter in ordinary Euclidean space operating
according to Newtonian mechanics, but instead requires
matter-energy in Reimannian space operating according
to Einsteinian general relativity. So it's a bit complicated.

-- Jeff, in Minneapolis

Correct. Contrast with your first paragraph. An explosion is, by definition, energy acting on matter in Euclidean space.

Shaula
2013-Oct-31, 08:32 PM
Quantum effects mask the classical effects at small scales much like the light of the daytime sky masks the visibility of faint stars,
This is totally backwards. Classical laws are approximations to quantum laws that hold for larger scales.


Electrons have electric charge and mass just as macroscopic objects do. Those properties don't go away just because quantum effects dominate.
Who said they did? Mass and charge are not intrinsically classical concepts.


If causality is not preserved, nothing is. You might as well assert that the rules of arithmetic don't apply.
Nope. As CDT and LQG show, as I have told you over and over again. They represent a class of theories that show potential.


The chance that any of those theories will be found to work is very low. I'm not going to be convinced by examples of theories which probably don't work.
And what do you base that on? From what I have seen so far you don't even understand these theories well enough to discuss them! They represent classes of theories which show that your assertions about what 'must' be true are simply not required to be true.

... and I give up. I was going to write a long and detailed reply but it is pointless. You don't understand what you are dismissing, use your own idiosyncratic definitions of classical and quantum to try to score points and basically are repeating your behaviour from a number of other threads.

Suffice to say there are two positions to take here:
1) Jeff is right. His own gut feelings about theories, assertions about what 'has' to be true and mighty, mighty logic are better than all the maths, theoretical frameworks and deep study that professional physicists spend decades working on, developing and trying to test.
2) Jeff has his own beliefs and is taking yet another opportunity to foist them on other people in the guise of science.

Selfsim
2013-Oct-31, 08:55 PM
Suffice to say there are two positions to take here:
1) Jeff is right. His own gut feelings about theories, assertions about what 'has' to be true and mighty, mighty logic are better than all the maths, theoretical frameworks and deep study that professional physicists spend decades working on, developing and trying to test.
2) Jeff has his own beliefs and is taking yet another opportunity to foist them on other people in the guise of science.Unfortunately, Jeff is not alone in either of these positions ...

speach
2013-Oct-31, 10:44 PM
Well we are the centre, and if were somewhere else that would be the centre. Look at it this way at the big bang, witch wasn't a BANG like a stick of explosive going off, everything started to move away from each other. There were localized condensation which formed the galaxies, stars within them and all the other "things". But overall it (the universe) kept expanding. To say the universe is like a balloon is incorrect that would leave a vacuum in the centre, and it can't be because we are there. It has to be as so as everything is moving away from us. Except our local group of galaxies which is one entity. QED I think! I hope. Well it makes sense to me.

Jeff Root
2013-Nov-01, 03:43 AM
Noclevername,

Two questions:

1) What is "thermal increase" ?

2) What is "Euclidean space" ?

I don't need detailed explanations, I just need to
know what you are referring to, to avoid ambiguity.

-- Jeff, in Minneapolis

Jeff Root
2013-Nov-01, 05:02 AM
Quantum effects mask the classical effects at small scales
much like the light of the daytime sky masks the visibility
of faint stars,
This is totally backwards. Classical laws are approximations
to quantum laws that hold for larger scales.
I disagree that classical laws are approximations to
quantum laws. Classical laws give accurate results at
larger scales. Attempting to scale quantum laws up to
those scales usually gives inaccurate results. It would
be more accurate -- certainly more accurate with regard
to the historical development of the laws -- to say that
quantum laws are approximations to classical laws.




Electrons have electric charge and mass just as
macroscopic objects do. Those properties don't go
away just because quantum effects dominate.
Who said they did?
Nobody. That's the point.



Mass and charge are not intrinsically classical concepts.
They are classical concepts, and they apply at the
quantum level as well as the classical level.




If causality is not preserved, nothing is. You might as
well assert that the rules of arithmetic don't apply.
Nope. As CDT and LQG show, as I have told you over
and over again. They represent a class of theories
that show potential.
Theories that work only if laws of physics which
describe everything ever observed are set aside.




The chance that any of those theories will be found to
work is very low. I'm not going to be convinced by
examples of theories which probably don't work.
And what do you base that on?
The general direction of "progress" in those theories
in the decades since they began, the nature of the
"successes", which don't look much like sucesses to
me, and the methods they use to construct them,
which have only extremely tenuous connections with
observations.



From what I have seen so far you don't even
understand these theories well enough to discuss
them!
I can discuss some aspects of them, not others.



They represent classes of theories which show that
your assertions about what 'must' be true are simply
not required to be true.
They would, if they worked.



... and I give up. I was going to write a long and
detailed reply but it is pointless.
It should not be surprising that it takes a very large
effort to convince me that the foundations of physics
can be set aside. The fact that you present no actual
evidence, but refer to a couple of extremely speculative
theories to support your assertion, doesn't help.

I haven't presented any evidence, either, but I really
don't have much need to because causality and the
known laws of physics are so familiar.



You don't understand what you are dismissing, use
your own idiosyncratic definitions of classical and
quantum to try to score points and basically are
repeating your behaviour from a number of other
threads.
I'm doing the best I can with what I've got. When I
make a mistake, and I see that it is a mistake, I will
admit it. But what I see here is somebody claiming
that an infinite universe could result from the Big
Bang, and I know that isn't right. I see now that
instead of saying it isn't right, I should just say that
it requires setting aside causality and / or known
laws of physics.

-- Jeff, in Minneapolis

.

Noclevername
2013-Nov-01, 05:25 AM
Noclevername,

Two questions:

1) What is "thermal increase" ?

2) What is "Euclidean space" ?

I don't need detailed explanations, I just need to
know what you are referring to, to avoid ambiguity.

-- Jeff, in Minneapolis

Thermal increase is a localized increase in heat relative to the immediate environment. In the case of an explosion is an increase rapid enough to release supersonic gasses.

Example: 500 pounds of dynamite on the Earth's surface, if ignited by a proper detonator, would produce an explosion. Putting 500 pounds of dynamite in the core of the Sun would not produce an explosion, as the matter there is already hotter and more energetic than the dynamite itself. The dynamite and detonator would be vaporized and crushed at the same time, to conform to its hot, dense environment.

http://en.wikipedia.org/wiki/Euclidean_space


In mathematics, particularly in geometry, the concept of a Euclidean space encompasses Euclidean plane and the three-dimensional space of Euclidean geometry as spaces of dimensions 2 and 3 respectively. It is named after the Ancient Greek mathematician Euclid of Alexandria. The term “Euclidean” distinguishes these spaces from other types of spaces considered in modern geometry. Euclidean spaces also generalizes these ideas to higher dimensions.

Selfsim
2013-Nov-01, 06:07 AM
I disagree that classical laws are approximations to quantum laws. Classical laws give accurate results at larger scales. Attempting to scale quantum laws up to those scales usually gives inaccurate results. It would be more accurate -- certainly more accurate with regard to the historical development of the laws -- to say that quantum laws are approximations to classical laws.Well then how do you account for the UV Catastrophe, (http://en.wikipedia.org/wiki/Uv_catastrophe) (of about 113 years ago), whereupon quantum mechanics became established as the preferred explanation over a hugely inaccurate macro-scale prediction made by classical?

Jeff Root
2013-Nov-01, 06:16 AM
Noclevername,

Thanks.

Two more questions I should have thought of:

3) Is my use of the term "explosion" to refer to the Big Bang
the main indicator that I'm treating it as if it were an explosion
in space rather than an explosion of space? Are there any other
indicators of comparable significance?

4) Your definition of "explosion" is quite detailed. Can you say
when and where you got it?

-- Jeff, in Minneapolis

tusenfem
2013-Nov-01, 07:25 AM
I am going to allow only a little leeway here, either Jeff Root is going to learn from what the mainstream posters are teaching, or this will be dumped in ATM.

Shaula
2013-Nov-01, 07:42 AM
So, Jeff the argument goes like this.

J - I assume causality is a core part of any and all physical theories
S - Here are examples of theories which are based in physics but show that causality evolved from something else
J - I don't like those theories. They seem unphysical. Because they throw out causality and causality has to be part of any physics model
.... This is why I hate seeing this argument develop. It is pointless. You believe you are right and will make any ridiculous claim or justification to support it. Among those are "Quantum physics is an approximation to classical physics" "Charge is a classical concept" and so on.

As for the rest of it... I am not arguing that you are wrong. I am arguing that your assertion and assumptions are not as obviously true as you keep saying. I am arguing that we don't know enough about physics at the era you are talking about to make such strong claims as you do.

Anyway that really is it from me. We are not having a debate about science, we are having a debate about faith.

Noclevername
2013-Nov-01, 08:14 AM
Noclevername,

Thanks.

Two more questions I should have thought of:

3) Is my use of the term "explosion" to refer to the Big Bang
the main indicator that I'm treating it as if it were an explosion
in space rather than an explosion of space? Are there any other
indicators of comparable significance?

Everything about the way you describe it.


4) Your definition of "explosion" is quite detailed. Can you say
when and where you got it?


For as long as I've been able to read, I've read dictionaries and encyclopedias. Every description of "explosion" says basically the same thing. I learned even more about explosions from watching military documentaries and, of course, Mythbusters.

The dynamite-in-the-Sun example I thought of myself, if it's wrong in some way would someone with a physics background please provide correction.

mkline55
2013-Nov-01, 01:40 PM
if the galaxies are known to all be receding from us, with the ones twice as far away receding at twice the rate of the nearer ones, and the ones three times as far away receding at three times the rate, and all the rates are accelerating, would you suppose that something larger is exerting a pull? the first bang wouldn't be causing the accelerations. is that larger item what has been given the name of dark matter/energy? or is there something in the center, repelling everything?
Returning to one of the original questions, NEOWatcher gave a good initial response. In addition, at some large scale, some force may be dominating over gravity to push distant galaxies apart or to increase the space between them.

Grey
2013-Nov-01, 02:37 PM
I disagree that classical laws are approximations to
quantum laws. Classical laws give accurate results at
larger scales. Attempting to scale quantum laws up to
those scales usually gives inaccurate results. It would
be more accurate -- certainly more accurate with regard
to the historical development of the laws -- to say that
quantum laws are approximations to classical laws.This is simply wrong. A quantum description of a system is always accurate*, even at classical scales. Indeed, an important test of any new quantum theory is just that: that in the limit as you move to large quantum numbers, it should match what we see at macroscopic levels as well. It is well established that classical physics is just an approximation to quantum mechanics. We still use classical physics because there are many cases where it's a sufficiently good approximation that it still works, and it's usually much easier to work through the math.

Jeff, I'd still be interested in your response to the issue of quantum entanglement. Here we have demonstrated a case where there are correlations between arbitrarily distant events, which cannot be explained by any purely local model. (But also, I really think you should create a separate thread to discuss this, rather than continuing to insist on hijacking every thread where someone asks a question about the Big Bang to bring this up).

*Well, okay, unless it's a situation that also requires the use of general relativity, and then we can't actually make a quantum description of the system. We still don't have a theory that merges both general relativity and quantum mechanics, so we can't really say what happens in those situations. Fortunately, cases where both are required are quite rare, although it's notable that one of those circumstances is precisely the first instant of the Big Bang, where Jeff is claiming with certainty that he knows what was going on.