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normdowling
2007-Oct-08, 01:03 PM
"Since Time and space seem to have began with the big bang, we simply dont have any way of understanding anything outside of it . the best we can do is say that it appears the universe is infinite in size and is expanding and accelerating. It looks like there is no end point of the universe.Its hard to accept . But it would be equally hard to accept if there was an end point. "



WHAT DOES THAT MEAN??????

:)

Sp1ke
2007-Oct-08, 01:31 PM
Which bits are you asking about, Norm? There are several statements here, such as:

1) Time and space seem to have began with the big bang
2) It appears the universe is infinite
3) [The universe] is expanding and accelerating
4) It looks like there is no end point of the universe
5) It would be equally hard to accept if there was an end point

Which do you understand or agree with?
I'd say that:
1) is probably true.
Not sure about 2).
3) appears to be correct from reported observations of the recession of distant galaxies.
For 4), there doesn't have to be an end point of the universe if it encompasses all of time and space
So 5) is reasonable - if there was an end point then you could stand there and ask what's just beyond the end point.

Neverfly
2007-Oct-08, 01:44 PM
Also, what or who are you quoting from?

antoniseb
2007-Oct-08, 01:47 PM
I moved this thread to Q&A from Astronomy.

You seem to have quoted something, but not indicated where the quote came from. I agree with Sp1ke that point two (infinite universe) has room for doubt, and is not currently the mainstream thinking.

I'm assuming that you are questioning the final clause about acceptability of an end point. Do you have a reason that you think it would be not equally hard to accept?

normdowling
2007-Oct-08, 01:55 PM
this is my own quote.,

antoniseb
2007-Oct-08, 02:16 PM
this is my own quote.,

Are you asking us what your own quote means? I'm not sure I follow what you are really asking then.

Kaptain K
2007-Oct-08, 02:16 PM
Then, there is the question in the thread title:

" big bang into what???"

For which the answer is that there doesn't have to be anything for the universe to expand into.

jlhredshift
2007-Oct-08, 02:29 PM
Then, there is the question in the thread title:

" big bang into what???"

For which the answer is that there doesn't have to be anything for the universe to expand into.

This is the hard part when trying to explain the beginning of the universe, for the first time, to a student. In your minds eye, i.e. your imagination, you could think of being situated so as to witness from a distance the expanding shell of energy and gas that would become our universe, but, you see, you would have to be in the shell for the energy to reach your detectors, your eyes, mind, machines, etc. For us to detect we have to be within the expansion. As to "what is outside" is left to theory; multiverse, Linde, Smolin, etc., and metaphysics.

Kaptain K
2007-Oct-08, 02:47 PM
I understand what you mean. While I can talk about it and understand some of the math involved, I really can't visualize expansion without "something" to expand into.

EvilEye
2007-Oct-08, 03:00 PM
The problem is that you are thinking of the universe as an object. But the big bang starting point is everywhere. 14 billion lightyears away, and right next to your nose. It is all the same place, just moving away from itself at lightspeed. It isn't expanding into anything. It already is everything.

jlhredshift
2007-Oct-08, 03:04 PM
The problem is that you are thinking of the universe as an object. But the big bang starting point is everywhere. 14 billion lightyears away, and right next to your nose. It is all the same place, just moving away from itself at lightspeed. It isn't expanding into anything. It already is everything.

Absolutely correct, and the hardest point to communicate to the uninitiated.

Tim Thompson
2007-Oct-08, 03:21 PM
"Since Time and space seem to have began with the big bang, we simply don't have any way of understanding anything outside of it. The best we can do is say that it appears the universe is infinite in size and is expanding and accelerating. It looks like there is no end point of the universe. It's hard to accept. But it would be equally hard to accept if there was an end point."
Time & space seem to have begun in the big bang, but only in a classically limited sense. Reality is more complicated than that. It is not altogether clear that time and space even exist as fundamentals of the universe, as opposed to being simply constructs that we invented in order to explain the universe to ourselves (see, for instance, Edward Witten's essay Refelctions on the Fate of Spacetime in the April 1996 issue of Physics Today (PDF here (http://www.sns.ias.edu/~witten/papers/Reflections.pdf))). But even setting aside that uncertainty, once a quantized theory of general relativity becomes available, it can in principle eliminate the singularity of the bang in classical physics and open the door to all manner of pre big bang cosmologies (i.e., Bojowald, 2007 (http://adsabs.harvard.edu/abs/2007PhRvD..75l3512B); Steinhardt & Turok, 2005 (http://adsabs.harvard.edu/abs/2005NewAR..49...43S); Gasperini & Veneziano, 2003 (http://adsabs.harvard.edu/abs/2003PhR...373....1G)).

There are plenty of ways to "understand" anything outside the observable universe. However, the level of "understanding" is obviously limited, since we eventually require all of our theories & hypotheses to be consistent with observation. Clearly, the latter constraint applies only to the observable universe. So we infer the properties of the unobservable universe from observations of the observable universe, and the assumption that we are seeing the effect of the former on the latter. Needless to say, I hope, one should not overestimate the depth of "understanding" that comes from this approach.

The universe does not appear to be infinite in size. It appears to be finite in size, if only because we can see almost all the way back to the beginning, a finite number of years ago (roughly 13.7 billion years if you are a fan of WMAP press releases). The observable universe is definitely finite. The unobservable universe beyond could be infinite, but how could we say "for sure" if we can't see it? A finite unobservable universe would impose repeated circular patterns on the cosmic microwave background, according to standard theory, which astronomers have looked for but don't see. That tells us that the sum of the observable & unobservable universe is not likely smaller than roughly 78,000,000,000 light years across (i.e., Key, et al., Physical Review D 75(8): 084034, April 2007 (http://adsabs.harvard.edu/abs/2006astro.ph..4616S)).

The expansion of the visible universe certainly does appear to be accelerating, but it is only a snap shot of the current state of the universe. Since the cause of this behavior is completely unknown, its future behavoir is equally unknown. In the absence of a functional (mathematical) description of the cause of the acceleration, one can easily imagine a cosmological scalar field that simply reverses itself, as would any periodic function, and recollapse. So the future fate of the universe remains unknown.

And whether or not any of this is hard for you to accept is your own affair.

jlhredshift
2007-Oct-08, 04:08 PM
Thanks Tim. One of the reasons that I am on this board is because of the relevant papers that occur as links. However, these are going to take a while. First, I need to make a fresh pot of coffee and find my bottle of asprin.

normdowling
2007-Oct-09, 12:00 AM
Which bits are you asking about, Norm? There are several statements here, such as:

1) Time and space seem to have began with the big bang
2) It appears the universe is infinite
3) [The universe] is expanding and accelerating
4) It looks like there is no end point of the universe
5) It would be equally hard to accept if there was an end point

Which do you understand or agree with?
I'd say that:
1) is probably true.
Not sure about 2).
3) appears to be correct from reported observations of the recession of distant galaxies.
For 4), there doesn't have to be an end point of the universe if it encompasses all of time and space
So 5) is reasonable - if there was an end point then you could stand there and ask what's just beyond the end point.

any and all of them

normdowling
2007-Oct-09, 12:04 AM
Are you asking us what your own quote means? I'm not sure I follow what you are really asking then.

the words i wrote are just memorised, my understanding is still no better off.

normdowling
2007-Oct-09, 12:10 AM
The problem is that you are thinking of the universe as an object. But the big bang starting point is everywhere. 14 billion lightyears away, and right next to your nose. It is all the same place, just moving away from itself at lightspeed. It isn't expanding into anything. It already is everything.

i agree , but the finite or infinite idea then springs to mind,. It seems that 14 billion years old suggests a finite universe, .

And : expanding at faster than the speed of light, or einsteins constant, suggests an infinite universe.

In the end , arn`t we stuck with " We dont know????????"

normdowling
2007-Oct-09, 12:17 AM
Time & space seem to have begun in the big bang, but only in a classically limited sense. Reality is more complicated than that. It is not altogether clear that time and space even exist as fundamentals of the universe, as opposed to being simply constructs that we invented in order to explain the universe to ourselves (see, for instance, Edward Witten's essay Refelctions on the Fate of Spacetime in the April 1996 issue of Physics Today (PDF here (http://www.sns.ias.edu/~witten/papers/Reflections.pdf))). But even setting aside that uncertainty, once a quantized theory of general relativity becomes available, it can in principle eliminate the singularity of the bang in classical physics and open the door to all manner of pre big bang cosmologies (i.e., Bojowald, 2007 (http://adsabs.harvard.edu/abs/2007PhRvD..75l3512B); Steinhardt & Turok, 2005 (http://adsabs.harvard.edu/abs/2005NewAR..49...43S); Gasperini & Veneziano, 2003 (http://adsabs.harvard.edu/abs/2003PhR...373....1G)).

There are plenty of ways to "understand" anything outside the observable universe. However, the level of "understanding" is obviously limited, since we eventually require all of our theories & hypotheses to be consistent with observation. Clearly, the latter constraint applies only to the observable universe. So we infer the properties of the unobservable universe from observations of the observable universe, and the assumption that we are seeing the effect of the former on the latter. Needless to say, I hope, one should not overestimate the depth of "understanding" that comes from this approach.

The universe does not appear to be infinite in size. It appears to be finite in size, if only because we can see almost all the way back to the beginning, a finite number of years ago (roughly 13.7 billion years if you are a fan of WMAP press releases). The observable universe is definitely finite. The unobservable universe beyond could be infinite, but how could we say "for sure" if we can't see it? A finite unobservable universe would impose repeated circular patterns on the cosmic microwave background, according to standard theory, which astronomers have looked for but don't see. That tells us that the sum of the observable & unobservable universe is not likely smaller than roughly 78,000,000,000 light years across (i.e., Key, et al., Physical Review D 75(8): 084034, April 2007 (http://adsabs.harvard.edu/abs/2006astro.ph..4616S)).

The expansion of the visible universe certainly does appear to be accelerating, but it is only a snap shot of the current state of the universe. Since the cause of this behavior is completely unknown, its future behavoir is equally unknown. In the absence of a functional (mathematical) description of the cause of the acceleration, one can easily imagine a cosmological scalar field that simply reverses itself, as would any periodic function, and recollapse. So the future fate of the universe remains unknown.

And whether or not any of this is hard for you to accept is your own affair.

interesting description, but not much help," One can not easily imagine"

do u understand that im not a physics professor .

normdowling
2007-Oct-09, 12:20 AM
so far my original quote still stands.

if im asked what is the universe expanding into.

Neverfly
2007-Oct-09, 01:03 AM
so far my original quote still stands.

if im asked what is the universe expanding into.

So, is this an actual question?
Or an ATM theory that the Universe is infinite presented in Q&A?

normdowling
2007-Oct-09, 01:52 AM
So, is this an actual question?
Or an ATM theory that the Universe is infinite presented in Q&A?

If i need money ill go to an ATM ( Automatic Teller Machine)

I suppose Im looking for a better conceptual understanding .

But when people ask what the universe is expanding into, It seems the answer is ; No one really knows .

normdowling
2007-Oct-09, 01:58 AM
Infinite or finite? No-one knows

Surely , what is outside our universe could be derived by study of the way our universe acts??????????????

If u dont understand the question, sorry but i dont understand it either.

Neverfly
2007-Oct-09, 02:14 AM
Infinite or finite? No-one knows

Surely , what is outside our universe could be derived by study of the way our universe acts??????????????

If u dont understand the question, sorry but i dont understand it either.

Exactly. And that is the trouble.

Observing the universe can tell us quite a lot.
We can't just stroll on out to the edge- to take a look and really know for certain...

But the universe isn't necessarily expanding INTO anything. It is what is expanding.
Living in our 3 dimensional world, we only understand concepts like that around us.

Try explaining the Solar system to a Gibbon. He will ask what trees the planets are swinging from.
You will try to explain gravity but he won't get it. If these planets are swinging around, there must be trees to swing from.

This is an analogy- I am not calling you an ape;)

normdowling
2007-Oct-09, 02:26 AM
Exactly. And that is the trouble.

Observing the universe can tell us quite a lot.
We can't just stroll on out to the edge- to take a look and really know for certain...

But the universe isn't necessarily expanding INTO anything. It is what is expanding.
Living in our 3 dimensional world, we only understand concepts like that around us.

Try explaining the Solar system to a Gibbon. He will ask what trees the planets are swinging from.
You will try to explain gravity but he won't get it. If these planets are swinging around, there must be trees to swing from.

This is an analogy- I am not calling you an ape;)


I feel like an ape , maybe the planets are trees? that would be much easier.

Im a carpenter, so ape isnt a bad description in regard to my knowledge in physics and astronomy.

Neverfly
2007-Oct-09, 02:28 AM
I feel like an ape , maybe the planets are trees? that would be much easier.

Im a carpenter, so ape isnt a bad description in regard to my knowledge in physics and astronomy.

Frame Form and Finish? I am too, but these days the money is in plumbing so
I'm a plumber;)

normdowling
2007-Oct-09, 02:59 AM
Frame Form and Finish? I am too, but these days the money is in plumbing so
I'm a plumber;)

maybe u r telling fibs

Neverfly
2007-Oct-09, 03:05 AM
maybe u r telling fibs

Um. No.
What would be the point of that? :doh:

Sp1ke
2007-Oct-09, 01:48 PM
Norm,
There have been some carefully thought out replies to your question but you don't sound satisfied. At the risk of repeating my first post, let's go back to your original quotation.

You start with:

1) Time and space seem to have began with the big bang

Do you disagree with this? Do you think time and space can exist outside our universe?

jlhredshift
2007-Oct-09, 01:51 PM
Infinite or finite? No-one knows

Surely , what is outside our universe could be derived by study of the way our universe acts??????????????

If u dont understand the question, sorry but i dont understand it either.

I understand your frustration.

No, we really do not know for certain, we only know what we can experience, and that is this universe.

From Wiki (http://en.wikipedia.org/wiki/Turtles_all_the_way_down)


The most widely known version today appears in Stephen Hawking's 1988 book A Brief History of Time, which begins with an anecdote about an encounter between a scientist and an old lady:

A well-known scientist (some say it was the philosopher Bertrand Russell) once gave a public lecture on astronomy. He described how the Earth orbits around the sun and how the sun, in turn, orbits around the centre of a vast collection of stars called our galaxy.
At the end of the lecture, a little old lady at the back of the room got up and said: "What you have told us is rubbish. The world is really a flat plate supported on the back of a giant tortoise."
The scientist gave a superior smile before replying, "What is the tortoise standing on?"
"You're very clever, young man, very clever," said the old lady. "But it's turtles all the way down!"

So, as a metaphor, the Universe sits on the back of a turtle, and it is turtles all the way down.:)

normdowling
2007-Oct-09, 02:12 PM
Norm,
There have been some carefully thought out replies to your question but you don't sound satisfied. At the risk of repeating my first post, let's go back to your original quotation.

You start with:

1) Time and space seem to have began with the big bang

Do you disagree with this? Do you think time and space can exist outside our universe?

i dont know.

it might exist outside the universe but in a different form???

I dont dissagree with the big bang or any other mainstream theory.

but, just being able to repeat the words, isnt enough for me.

normdowling
2007-Oct-09, 02:20 PM
With regard to the universe being finite or infinite.

Both seem to me to be right.

Finite = 14 billion yrs old

infinite = expanding faster than the speed of light


they both feel correct to me ?????


Im sure this is boring everyone.

Neverfly
2007-Oct-09, 02:39 PM
It's never boring:D
However, on what basis do you say it is expanding faster than the speed of light?

normdowling
2007-Oct-09, 02:46 PM
the space between is expanding faster the light .

Based on Alex Filapenko saying so and others

Neverfly
2007-Oct-09, 02:58 PM
the space between is expanding faster the light .

Based on Alex Filapenko saying so and others

Someone else is going to have to feild this one, as my ignorance factors just skyrocketed...

I'm aware (now) of "Apparent faster than light"... But not true faster than light expansion.

Cougar
2007-Oct-09, 02:59 PM
The universe is expanding into itself. There is no other place for it to expand into.

EvilEye
2007-Oct-09, 03:39 PM
I think the idea has finally come around.

When we try to look back toward the big bang with telescopes, we aren't looking for a place. We are looking for a TIME. The farther you look into space, the earlier period you can see. And then we use that information to guage what may happen in the future.

Neverfly
2007-Oct-09, 03:44 PM
The universe is expanding into itself. There is no other place for it to expand into.

I did that a few nights ago.
Ate too much...

It was worth it though, I tell you what...

speedfreek
2007-Oct-09, 08:18 PM
Normdowling, this needs a lot of consideration! I will present to you some possibilities but will try to keep my post as simple as possible.

If we consider that the universe is comprised of at least 3 dimensions - dimensions which contain all the matter and all the space, then we might consider that when the universe didn't exist, nor did any dimensions or any space exist.

So if we want to think about concepts like "what is the universe expanding into?" we have to consider that whatever it might be expanding into is whatever was there before the universe existed. But considering something like "before" the universe, would have us assuming that time existed before the universe! If we consider that time and space and the dimensions did not exist until the universe existed, then we might come to the conclusion that there was nothing before the universe.

By nothing, I mean no dimensions, no space, no time, no up or down, no in or out, not even any blackness! Nothing! Now that is a difficult concept to comprehend, but comprehend it we must, if we are to continue down this road. Lets call this nothingness a "void". This void has no dimensions, no space, no time - nothing. Don't confuse this "void" with the void you know as space. This "void" is no space!

So when we introduce the dimensions and space of our universe into this "void", there is only the universe! The only dimensions are inside our universe - there is no outside (or "outside" is the void - no dimensions, no space and no time)! We cannot consider the "outside" to be something, if it is literally nothing, so we cannot consider that our universe would expand into that nothing.

But perhaps there was a dimension before our universe existed! A dimension that our universe might reside within, but isn't one of the dimensions within our universe. An extra dimension perhaps...

Before I go further, let's try considering that the universe is not infinite. A better description is that the universe might be "finite but unbounded".

So what does "unbounded" mean, in this context? Does it simply mean that the universe has no edge? If that is the case, then how can it be finite? How can something be finite, but unbounded?

Well, a simple example is the surface of a sphere. That surface is finite but unbounded. It has a finite area, but no edge or end. You can circumnavigate the sphere and end up where you started, so it has a finite size, but that surface has no edge or end.

But that surface is only 2 dimensional. Lets imagine that the inhabitants of that surface live in a 2 dimensional universe, with no knowledge of the 3rd dimension that would allow them to understand the actual shape of their universe. They might work out that their universe is wrapped around another unseen dimension when they circumnavigate it, but they cannot see that other dimension.

This is an example of something called a manifold. A manifold is an abstract mathematical space. In a manifold, wherever you are, the space around you looks a certain way, but in fact there is another hidden dimension that you cannot see for yourself. Let me explain further.

In a one-dimensional manifold (a 1-manifold), every point has a neighbourhood that looks like a segment of a line. So if you were an entity that lived in that manifold, you would only be able to see in one dimension, and you would see a line. Now, an example of a one-dimensional manifold is a circle, a 2-dimensional object. If you live on the line that defines that circle, all you see is a line in front of you and line behind you and you would only realise it was a circle once you travelled far enough along the line to get back to where you started (you cannot tell the line is curved as you can only see in 1 dimension).

My surface of a sphere example earlier was an example of a 2-dimensional manifold. You can only see 2 dimensions, so all you see is a flat disk around you. Again, you might only work out that you live on the surface of a 3 dimensional object by circumnavigating it, as you cannot perceive that 3rd dimension.

Now we come to a 3-manifold, which is getting closer to possibly describing the universe (but we aren't there yet!). In a 3-manifold, you see in 3 dimensions, and your neighbourhood looks like a sphere. If you were able to travel far enough in one direction, you might come back to where you started, but, and here's the kicker - the shape has one more dimension than you can perceive. A 3-dimensional manifold is a 4-dimensional shape!

These are examples of static spaces that have a finite size but have no edge and they reside in a higher unseen dimension. If we introduce time into the picture, we might add yet another dimension to the model we are examining and end up with a 4-manifold.

So perhaps, our universe is an expanding 4-manifold that resides within nothing and expands within itself.

Ahh, that expands within itself thing... well, consider that we observe distant galaxies that recede from us at speeds faster than light. We don't think anything can actually travel faster than light, so we explain those distant galaxies apparent speeds with the expansion of space. Those galaxies aren't actually moving away from us faster than light, but the space in between us and them is growing. If those distant galaxies aren't actually moving faster than light, but the space in between us has expanded faster than light, then from a certain viewpoint space has expanded within itself!

Put that into the context of a finite but unbounded 4-manifold (with more than 4 dimensions!) and we have a finite universe that expands within itself and has no edge!

I know none of this is observable or provable, but we are just considering possibilities here and these concepts might be considered to be consistent (or at least, not in conflict!) with the current best model in cosmology, the Lambda-CDM concordance model (but I apologize to the regulars here for my ham-fisted metaphysical explanations and simplistic butchery of physical cosmology!)

But as you said earlier, the bottom line is "we don't know".

EvilEye
2007-Oct-09, 09:10 PM
The answer above is the best I have ever read. Makes perfect mental sense, and is concise.

THANK YOU.

I have printed it and the next time my 13 year old son brings this subject up (for the 33rd time) I will show it to him.

speedfreek
2007-Oct-10, 12:10 AM
I am glad to be able to help in my small way. :)

I feel I should add just a little substance to my previous post and the concepts it is based on.

In general relativity, space-time is treated as a four dimensional pseudo-Riemannian manifold (http://en.wikipedia.org/wiki/Pseudo-Riemannian_manifold).

The lower bound of 78 billion light years (24 gigaparsecs) placed on the size of the whole universe (not the observable universe) comes from a paper by Neil Cornish and his group - Extending the WMAP Bound on the Size of the Universe (http://www.citebase.org/abstract?id=oai:arXiv.org:astro-ph/0604616).

From that paper:
"While it is certainly possible that the Universe extends infinitely in each spatial direction, many physicists and philosophers are uncomfortable with the notion of a universe that is infinite in extent. It is possible instead that our three dimensional Universe has a finite volume without having an edge, just as the two dimensional surface of the Earth is finite but has no edge. In such a universe, it is possible that a straight path in one direction could eventually lead back to where it started. For a short enough closed path, we expect to be able to detect an observational signature revealing the specific topology of our Universe."

This is the matching circle analysis mentioned earlier in this thread. They found no matching circles in their search, up to a distance of 24 gigaparsecs. This is claimed to mean that the whole universe is larger than our observable universe! There was a possibility the whole universe might have been smaller than our observable universe, and if that were the case then light might have had time to circumnavigate our universe and we might be seeing the same region of space when looking in different directions - the problem being that we would be seeing the same region of space but the light would be from different epochs and so we might not recognise it for what it is!

They establish that space is within 2% of being flat, and state that "This means that even if space in not quite flat, the radius of curvature of the Universe is at least of order the size of the observable Universe, and space can be considered to be nearly flat."

So all we think we know so far is that space is nearly flat, and so a straight line might only be nearly straight and could be part of a loop with a radius larger than our observable universe! ;)

EvilEye
2007-Oct-10, 01:50 AM
I am glad to be able to help in my small way. :)

I feel I should add just a little substance to my previous post and the concepts it is based on.

In general relativity, space-time is treated as a four dimensional pseudo-Riemannian manifold (http://en.wikipedia.org/wiki/Pseudo-Riemannian_manifold).

The lower bound of 78 billion light years (24 gigaparsecs) placed on the size of the whole universe (not the observable universe) comes from a paper by Neil Cornish and his group - Extending the WMAP Bound on the Size of the Universe (http://www.citebase.org/abstract?id=oai:arXiv.org:astro-ph/0604616).

From that paper:
"While it is certainly possible that the Universe extends infinitely in each spatial direction, many physicists and philosophers are uncomfortable with the notion of a universe that is infinite in extent. It is possible instead that our three dimensional Universe has a finite volume without having an edge, just as the two dimensional surface of the Earth is finite but has no edge. In such a universe, it is possible that a straight path in one direction could eventually lead back to where it started. For a short enough closed path, we expect to be able to detect an observational signature revealing the specific topology of our Universe."

This is the matching circle analysis mentioned earlier in this thread. They found no matching circles in their search, up to a distance of 24 gigaparsecs. This is claimed to mean that the whole universe is larger than our observable universe! There was a possibility the whole universe might have been smaller than our observable universe, and if that were the case then light might have had time to circumnavigate our universe and we might be seeing the same region of space when looking in different directions - the problem being that we would be seeing the same region of space but the light would be from different epochs and so we might not recognise it for what it is!

They establish that space is within 2% of being flat, and state that "This means that even if space in not quite flat, the radius of curvature of the Universe is at least of order the size of the observable Universe, and space can be considered to be nearly flat."

So all we think we know so far is that space is nearly flat, and so a straight line might only be nearly straight and could be part of a loop with a radius larger than our observable universe! ;)

I've always actually believed that, but could neve express it that way.

I look at Orion and think..."Where is it right NOW?" or even if it is still around.

All of the things we see with our telescopes could have been right there, in front of us, but because we didn't look until now, we see them as very far away.

normdowling
2007-Oct-10, 07:28 AM
I've always actually believed that, but could neve express it that way.

I look at Orion and think..."Where is it right NOW?" or even if it is still around.

All of the things we see with our telescopes could have been right there, in front of us, but because we didn't look until now, we see them as very far away.

Ive never understood What is meant by flat universe.

is there a different more conceptual way of explaining it.

normdowling
2007-Oct-10, 07:31 AM
sorry , that was directed at speed freaks post

normdowling
2007-Oct-10, 07:36 AM
Ive just read speedfreeks post again , and im starting to get a feel for flat universe. Maybe u dont learn this stuff. u just get a feel for it ???

Neverfly
2007-Oct-10, 08:16 AM
I think "unlearning" might apply.

We need to suspend our common notions of what we "see" in the space around ourselves.
Walls. Cabinets. There's always SOMETHING outside or on the other side.
Unlearning this habit can help to clarify a situation where there is not something "outside" because there is not an outside to be in the outside.

3dknight
2007-Oct-10, 09:00 AM
I was doing a report on the big bang theory and it has nothing to do with how the univers got started. Even that it is called the big bang theory it has nothing to do with a bang that started the universe. It is a theory on how the universe expands... I will say again it is not a theory on the origin of the universe.

Neverfly
2007-Oct-10, 09:21 AM
I was doing a report on the big bang theory and it has nothing to do with how the univers got started. Even that it is called the big bang theory it has nothing to do with a bang that started the universe. It is a theory on how the universe expands... I will say again it is not a theory on the origin of the universe.

It isn't?:neutral:

normdowling
2007-Oct-10, 09:46 AM
I was doing a report on the big bang theory and it has nothing to do with how the univers got started. Even that it is called the big bang theory it has nothing to do with a bang that started the universe. It is a theory on how the universe expands... I will say again it is not a theory on the origin of the universe.

that seems to be a play on words,

the very very very early universe may be some weird quatum fluctuation rising from nothing at all. But surely , the Big Bang , to a first approximation, covers origins in some way ???????

Doesnt it ???:hand::hand:

astromark
2007-Oct-10, 09:46 AM
You are almost there... All you have said is reasonable enough, just one step more. If it had a beginning then it can not be infinite. It is expanding ever more rapidly. So the word unbound is introduced. Finite but unbound.

No, this is not boring. This is why we come here. To help people gain a understanding of astronomy.


I digress... I visit a zoo regularly as my daughter works there. Recently while waiting for her I asked the gorilla what he thought about it so far... He looked at me and then looked at the moon. Grunted and swung away.... I may never know what he was thinking. Or if he was thinking. It just looked that way.

I can not help you answer this question of yours completely. I can only provide the most widely excepted understanding at this point in time.
Never stop asking.

'Oops! just noted the page 2...sorry'

Neverfly
2007-Oct-10, 09:50 AM
I digress... I visit a zoo regularly as my daughter works there. Recently while waiting for her I asked the gorilla what he thought about it so far... He looked at me and then looked at the moon. Grunted and swung away.... I may never know what he was thinking. Or if he was thinking. It just looked that way.


He said: "The aliens from the hidden moon base on the outside of the moon promised to come get me out of here."

astromark
2007-Oct-10, 10:05 AM
Neverfly; take your medication... :) (thinks gorilla's talk.)Lol

Neverfly
2007-Oct-10, 10:26 AM
That's nothing. Orangutans like to discuss philosophy.

And TRY to get a chimpanzee to shut up! It's next to impossible:rolleyes:

Tim Thompson
2007-Oct-10, 03:34 PM
I was doing a report on the big bang theory and it has nothing to do with how the univers got started. Even that it is called the big bang theory it has nothing to do with a bang that started the universe. It is a theory on how the universe expands... I will say again it is not a theory on the origin of the universe.

It isn't?

But surely, the Big Bang, to a first approximation, covers origins in some way ???????
The confusion here comes the fact that science is a moving target. Science changes as scientists learn more about it. 3dknight is correct in that big bang cosmology has classically been a study of the evolution of the universe, without regard to its origin. Stephen Hawking's PhD thesis proved that, in general relativity, the initial condition of the universe cannot be defined. In the language of mathematics, the initial state of the universe is singular (http://en.wikipedia.org/wiki/Mathematical_singularity). That makes it impossible to know anything about the origin of the universe in classical physics. So, naturally, classical big bang cosmologists don't bother with it at all, and concentrate on understanding the evolution of the universe, post creation.

However, it has long been understood by scientists that classical general relativity (http://en.wikipedia.org/wiki/General_relativity) must be replaced (or modified) by an equivalent quantum mechanical theory. Such a theory should eliminate the singularity that makes the initial state of the universe undefined in classical general relativity, which in turn makes the origin of the universe accessible to science. Both loop quantum gravity (http://en.wikipedia.org/wiki/Loop_quantum_gravity) & string theory (http://en.wikipedia.org/wiki/String_theory) are examples of quantun theories of general relativity; they are the leading candidates, but there are others. Both allow for the bang to become a transition from one state to another, a "bounce" in loop quantum gravity (i.e., Bojowald, 2007a (http://adsabs.harvard.edu/abs/2007PhRvD..75h1301B); Bojowald, 2007b (http://adsabs.harvard.edu/abs/2007PhRvD..75l3512B)), or perhaps colliding "branes" in string theory (i.e., Steinhardt & Turok, 2005 (http://adsabs.harvard.edu/abs/2005NewAR..49...43S)), or maybe some more exotic solution that has not yet been suggested. All of this has sparked a cottage industry in pre big bang cosmology (http://www.ba.infn.it/~gasperin/).

Hence, in the last decade or so, cosmology has changed radically. The origin of the universe, which was not previously included in big bang cosmology, is now included. But since there is no complete quantum theory of general relativity, nobody is quite sure how to explain or include the origin in cosmological models. So it's a wide open field at the moment.

Neverfly
2007-Oct-10, 03:45 PM
The Marble and the Wood.

My Big Bang education may be outdated...:p I need to study up on some refreshers.

astromark
2007-Oct-10, 06:41 PM
Facts have been presented to support this beginning of all at a moment 0. We have given it the name 'The big bang' because it would have been. Some 14 or so billion years later we have not modified this name. Its time we did.
I like the term. 'In the beginning' I just think it says it better.:)...

speedfreek
2007-Oct-10, 06:55 PM
Yes, Fred Hoyle has a lot to answer for! His use of the term "big-bang" was intended to be derogatory as he was opposed to the theory. It is a great pity that the term has stuck around for so long, and has been responsible for so many misconceptions.

EvilEye
2007-Oct-10, 07:54 PM
Another way of looking at the "beginning" of the Universe, is how useless the question of what was before it is.

Ask yourself "where were my memories before I had them?"

They simply just began to accumulate from nothing.

normdowling
2007-Oct-11, 09:25 AM
isnt all the history of the universe its origins?????

when we say, origin of the universe.., do we only mean before the expansion??????????

normdowling
2007-Oct-11, 11:47 AM
Someone else is going to have to feild this one, as my ignorance factors just skyrocketed...

I'm aware (now) of "Apparent faster than light"... But not true faster than light expansion.

Neverfly, I cant believe u have never heard of this faster than light idea.

r u saying that it isnt true, or just that u hadnt heard of it???????

is it true???????????

Neverfly
2007-Oct-11, 02:35 PM
Neverfly, I cant believe u have never heard of this faster than light idea.

r u saying that it isnt true, or just that u hadnt heard of it???????

is it true???????????

Yes, You are right. I was wrong.

It can expand faster than the speed of light. But points in spacetime cannot communicate with eachother faster than the speed of light.

It's relative. Because spacetime itself is expanding, the laws don't forbid it.

3dknight
2007-Oct-12, 03:42 AM
we keep on saying Blah blah blah is faster than the speed of light. If we know it goes faster than the speed if light suddent we know something that actually goes faster than the speed of light? then we may get somewhere. Another thing I am reading angels and demons by Dan Brown he too has a confused idea of what the big bang stands for but thats not the point. They say that this character recreated the big bang or what people think is the big bang? it say he "accelerated two ultrathinparticle bems in opposite directions around the accelerated tube. The two beams collided head on at enormous speeds,driving into one another and compressing all thier energy into a single pinpoint. He acheived extreme energy densities. Without warning, inside the accelerator tube, at this point of highly focused energy, particles of matter began appearing out of nowhere." Is this possible or our they just trying to make the story more interesting?

Tim Thompson
2007-Oct-12, 05:45 AM
It say he "accelerated two ultrathinparticle bems in opposite directions around the accelerated tube. The two beams collided head on at enormous speeds,driving into one another and compressing all thier energy into a single pinpoint. He acheived extreme energy densities. Without warning, inside the accelerator tube, at this point of highly focused energy, particles of matter began appearing out of nowhere." Is this possible or our they just trying to make the story more interesting?
That description looks impossible to me, as you cannot get more energy out of the collisions than you put in. But it may be possible, at least in theory, to create a microscopic black hole in a high energy beam collider. But it is doubtful that such a thing can happen in practice.

3dknight
2007-Oct-12, 02:00 PM
ooooooook I see now in this book he puts a lot of theories in his book to make it interesting.

Neverfly
2007-Oct-12, 02:00 PM
ooooooook I see now in this book he puts a lot of theories in his book to make it interesting.

<chuckle> Datburned scientist salesman!;)

John Mendenhall
2007-Oct-12, 03:07 PM
The universe does not appear to be infinite in size. It appears to be finite in size, if only because we can see almost all the way back to the beginning, a finite number of years ago (roughly 13.7 billion years if you are a fan of WMAP press releases). The observable universe is definitely finite. The unobservable universe beyond could be infinite, but how could we say "for sure" if we can't see it? A finite unobservable universe would impose repeated circular patterns on the cosmic microwave background, according to standard theory, which astronomers have looked for but don't see. That tells us that the sum of the observable & unobservable universe is not likely smaller than roughly 78,000,000,000 light years across (i.e., Key, et al., Physical Review D 75(8): 084034, April 2007 (http://adsabs.harvard.edu/abs/2006astro.ph..4616S)).



Is finite but unbounded acceptable?

Tim, you might post the entire paragraph above to the 'size of the universe' thread in Q&A. Your summation is very concise, and that 78 billion figure makes sense. Thank you.

speedfreek
2007-Oct-12, 07:12 PM
we keep on saying Blah blah blah is faster than the speed of light. If we know it goes faster than the speed if light suddenly we know something that actually goes faster than the speed of light? then we may get somewhere.

The metric expansion of space is theorised to cause objects to become more distant from us. These objects didn't move further away due to their own velocities, but the space in between them and us has grown due to the metric expansion of space.

The metric expansion is theorised to occur only in the space between clusters of galaxies that are not bound gravitationally. Where galaxies cluster together due to gravity, no expansion seems to occur.

So it seems that any gravitational attraction between objects will prevent the metric expansion of space. This allows galaxies to cluster together, swirling around each other and into each other due to gravity. If there is any galaxy that is attracted gravitationally towards that cluster, it is considered to be gravitationally bound to that cluster. But another, more distant cluster that is not gravitationally attracted to the first cluster will be receding from that first cluster due to the metric expansion.

In essence, we can consider all those separate gravitationally bound clusters of galaxies (including our own cluster) to be at rest. The only movement that occurs is within each separate cluster, where gravity causes that movement. But outside of all those clusters, space is expanding, causing them to be more distant from each other. We can think of it as if the space in between those clusters growing, or that more space is being introduced!

But what is metric expansion? It is defined as a process where the metric that defines distance changes, over time. How can this cause objects to recede at speeds faster than light? I will provide a quick and simple example.

Imagine for example that outside of gravity-bound clusters, the rate of expansion was such that it took 10 billion years for 1 meter double in size and become what 2 metres was to begin with. Coordinates that were originally at 1m, 2m, 3m, and 4m have, over 10 billion years become 2m, 4m, 6m and 8m. So, if it took 10 billion years for 1 meter to double in size, then in that same time all distances will double in size! Why? Because all metres double in size!

What this means is that in this example, over 10 billion years, 1 metre became 2 metres, 1 light year became 2 light years and so on... so 10 billion light years became 20 billion light years and the universe doubled in size!

Now the expansion of 1 metre to become 2 metres in 10 billion years is incredibly slow indeed - it is almost unnoticeable. But the expansion of 10 billion light years to become 20 billion light years over 10 billion years is expansion at the speed of light! Anything more distant than 10 billion light years will have expanded away faster than light.

(These numbers are arbitrary, just used to make the example simple!)

The above is an example of expansion at a constant rate. Even with a constant rate of expansion, the further away an object is the faster it will seem to be receding from us.

Unfortunately for us, it seems the rate of expansion has not been constant, but was incredibly fast early on, slowing down towards the present day (and we have made recent observations that lead us to believe that the rate of expansion might have started to speed up again). This means the relationship between distance and apparent speed of recession is not linear.

For the record, the distance where galaxies seem to be receding from us at the speed of light is the distance where the light from those galaxies is something between 9 and 10 billion years old. Anything more distant is thus receding faster than light. But remember, all these separate gravity-bound clusters can be considered to be at rest themselves and it is purely the metric expansion of space that increases their distance from us.

3dknight
2007-Oct-13, 01:39 AM
So your saying the metric expansion of space is faster than light? I wish we could use that as fuel.

speedfreek
2007-Oct-13, 02:35 AM
In a way it could almost be considered as the opposite of fuel. What I mean is if you somehow found yourself outside of any gravity-bound system, in the large space between our local cluster of galaxies and the other clusters (you would be something over 1 billion light years away from here!) and you let the metric expansion do its work, over a long period of time, you would find that everything was further away from you than before! Nothing would have moved towards you. The closest cluster would have only receded a little whereas the most distant clusters would seem to have receded from you at superluminal speeds. If you wanted to exploit the expansion, all you could achieve is to put yourself further away from everything else (or put everything else further away from you).

3dknight
2007-Oct-13, 08:46 AM
what is this expansion. What I mean is what makes it go faster than the speed off light. Something must be making the universe expand. All I heard so far is that it expands faster than the speed of light. Why?

Kaptain K
2007-Oct-13, 05:42 PM
what is this expansion. What I mean is what makes it go faster than the speed off light. Something must be making the universe expand. All I heard so far is that it expands faster than the speed of light. Why?
It appears that you are misreading and over-interpreting the responses you are getting.

Yes, the universe is expanding. It has been since the big bang.

<simplification>

The expansion is proportional to distance. This relationship is known as the Hubble constant (72kms/mega parsec). At a great enough distance, an object will (following the expansion of space) be moving away from us at more than the speed of light.

Neverfly
2007-Oct-13, 10:43 PM
I said it aside, but I'd like to also say it publically.

3dknight asks intelligent questions and seems to show a sincere desire to really learn about these topics rather than speculate wildly.

A lot of the adults here could learn a thing or two from this one.;)

normdowling
2007-Oct-13, 11:32 PM
what is this expansion. What I mean is what makes it go faster than the speed off light. Something must be making the universe expand. All I heard so far is that it expands faster than the speed of light. Why?

we dont know why its expanding. maybe it was very hot and dense like a bomb like a Big Bang. we dont know why it is accelerating in its expansion either, but its been given a name:Dark Energy

Cougar
2007-Oct-14, 12:03 AM
All I heard so far is that it expands faster than the speed of light.
Well, you heard wrong. Or you're interpreting what you heard incorrectly. Is there space between you and your computer screen? Yes! That's space. There are gases in that space, but it's still space. Is your screen traveling away from you at the speed of light? No! Not even at a rate of 1 inch per year. Not at all! If there is any expansion of space there, it is completely undetectable. Therefore, "space" is not expanding faster than 'c'. At least, not this chunk of space. So what "space" are you talking about?

Oh, you mean the space in the entire universe? The space between here and some galaxy 5 billion lightyears away? From all indications, that space is expanding. When you look at any local chunk of it, the expansion is so small that it's undetectable. But when you consider a whole lot of space, or observe objects billions of lightyears away, the effect becomes increasingly enormous. And it piles up. It's cumulative. The problem is, I suppose, we have no conception of how far away a billion lightyears is. That's A LOT of space.


...what makes it go faster than the speed off light.
For each megaparsec distance of space, add something like 70 km/sec as a measure of the 'expansion effect' across that distance. If you add up enough 70s, you eventually get to 300,000 km/sec, or the speed of light. And you can keep adding - no rules broken there. The object we're tracking at that distance doesn't really have any appreciable intrinsic motion itself, but it "looks like" it is receding faster than light because of the HUGE amount of expanding space between here and there.


Something must be making the universe expand.
I believe the rate of outward expansion was for some time thought to be a result of the "big bang." This may still be a general view -- I don't know -- but it has gotten a lot more complicated, especially since the expansion appears to be accelerating at this point in the universe's history. It is certainly unknown what could cause the acceleration to occur - it was only noticed about a decade ago - but that doesn't mean there aren't any good ideas about it. I suppose the prevailing hypothesis is vacuum energy. A chunk of 'empty' space is not empty. It contains a tiny amount of energy, which is apparently somehow related to all the quantum mechanical vacuum fluctuations that are occuring in any region of space at any time.... But it is unknown how such quantum activity can 'grow' space.....

Neverfly
2007-Oct-14, 12:23 AM
This is an excellent answer.
Similar to if you line up people side by side over a distance of 300,000 kilometers, then have them all turn and point in one direction at the same time, it will appear as if the 'line' made by their pointing covered the 300,000 km faster than light.

3dknight
2007-Oct-14, 12:52 AM
Ok so the anwer to my question "Something must be making the universe expand" Is we don't know yet all we have are some good ideas on why it's happening or theories right?


I said it aside, but I'd like to also say it publically.

3dknight asks intelligent questions and seems to show a sincere desire to really learn about these topics rather than speculate wildly.

A lot of the adults here could learn a thing or two from this one.

Thank you for the compliment neverfly some people thought all I do is speculate because of all the threads I made in the "Life In Space" section but I like to know the facts too.

Neverfly
2007-Oct-14, 01:11 AM
Ok so the anwer to my question "Something must be making the universe expand" Is we don't know yet all we have are some good ideas on why it's happening or theories right?



Thank you for the compliment neverfly some people thought all I do is speculate because of all the threads I made in the "Life In Space" section but I like to know the facts too.

Some people?:whistle:

speedfreek
2007-Oct-14, 02:00 AM
Ok so the anwer to my question "Something must be making the universe expand" Is we don't know yet all we have are some good ideas on why it's happening or theories right?

Yes, that is correct. :)

We think space expands where there are no gravity bound systems, but we only have theories as to why this might be the case.

normdowling
2007-Oct-14, 03:25 AM
what is this expansion. What I mean is what makes it go faster than the speed off light. Something must be making the universe expand. All I heard so far is that it expands faster than the speed of light. Why?

3d knight. here is great explanation on the expansion of the universe. and all other astronomy stuff.

http://webcast.berkeley.edu/course_details.php?seriesid=1906978334

scroll down to the one you want,. Actually this is Alex philapenko s astronomy lectures , they r simply the best ... u might need to get the right software to watch the lectures but it is definately worth it.

here is the software.http://www.realplayer.com/realplayer.html?pageid=404Page&pageregion=main&src=404__404_index.html&pcode=rn&opage=404__404_index.html

frankuitaalst
2007-Oct-14, 11:46 AM
Maybe something very stupid ...
The universe is expanding , so far ok , but i have difficulty with the fact that the rate of expansion is growing . Its hard to explain or even to "get the picture " . Seems as if some attractors must be somewhere ...or there must be "repellers" at the inside .
How about the idea of "negative mass" ? . Antimatter is proven to exist as being normal matter with the opposite charge , but what about really negative matter , matter with a negative matter ?
Negative matter should be able to attract negative matter as normal matter does , but would repell normal matter .
Due to this repelling force the negative matter cannot come close to regular matter , so its hard to detect .
But negative matter could exist on "islands" far from ordinary matter , could build up gallaxies even , repelling galaxies made from ordinary matter .
Visible or not visible ?
Someone has some links to this ?

speedfreek
2007-Oct-14, 02:33 PM
You seem to be describing Dark Energy (http://en.wikipedia.org/wiki/Dark_energy)

"In physical cosmology, dark energy is a hypothetical form of energy that permeates all of space and tends to increase the rate of expansion of the universe. Assuming the existence of dark energy is the most popular way to explain recent observations that the universe appears to be expanding at an accelerating rate. In the standard model of cosmology, dark energy currently accounts for almost three-quarters of the total mass-energy of the universe."

frankuitaalst
2007-Oct-14, 03:11 PM
Maybe one could call it dark energy , but a didn't read in the link something as negative mass , although the effect might be the same .
If negative mass should exist it could also have negative energy ....
reducing the singularity at the big bang on energy level tot E=0=mc+ -mc, providing the universe was in total at energylevel zero , resulting in the separation of this energy in two kind of masses.
???

normdowling
2007-Oct-14, 11:43 PM
Maybe one could call it dark energy , but a didn't read in the link something as negative mass , although the effect might be the same .
If negative mass should exist it could also have negative energy ....
reducing the singularity at the big bang on energy level tot E=0=mc+ -mc, providing the universe was in total at energylevel zero , resulting in the separation of this energy in two kind of masses.
???

sorry frankuitaalst, i have no idea what u r getting at . please define negative mass??? is there any evidence for negative mass?????

normdowling
2007-Oct-14, 11:45 PM
ive heard the idea that the total energy of the universe could be zero, but never heard of the "negative mass"???????????????????????

3dknight
2007-Oct-15, 03:32 AM
Mass is a body of coherent matter, usually of indefinite shape and often of considerable size: a mass of dough. I wanna reapeat that it is a body of coherent matter which means if you have negative mass (seems like antimass) you would have to have negative matter (seems like antimatter). So are you trying to say antimass and not negative mass?

Another thing I was wondering, how can there be to matter and antimatter? For matter and antimatter to exist they must not touch or they will cancel each other out. Since everything we know is made up of matter how would they not touch. Is there a force field between them or is there another kind of matter separating the two? maybe dark energy separates them. Wait I forgot about dark matter thats 3 types of matter.

Tim Thompson
2007-Oct-15, 03:44 AM
Another thing I was wondering, how can there be to matter and antimatter? For matter and antimatter to exist they must not touch or they will cancel each other out. Since everything we know is made up of matter how would they not touch. Is there a force field between them or is there another kind of matter separating the two?
Everything we can see is matter. Antimatter exists only in extremely small amounts, and it does annihilate with matter whenever they come in contact. That annihilation reaction creates a very specific and easy to identify high energy radiation, usually in the form of X-rays. The reason for the universe being very dominated by matter, rather than hosting equal amounts of both, remains unknown. But theory favors a breaking of natural symmetries during the infancy of the universe. But that's the best answer we can give for now.

As you have already realized, the universe cannot be made of equal amounts of matter and antimatter, or there would be another "big bang" of sorts, follwed by no matter at all.


Wait I forgot about dark matter that's 3 types of matter.
Probably not. It is a good bet that dark matter is just another example of the "matter" as opposed to "antimatter" type of matter. Of course, we don't know that, but it is the easy guess, so we assume that is the case in the absence of evidence to the contrary.

3dknight
2007-Oct-15, 04:17 AM
In theory can we make antimatter? I know it wouldn't last long but can it be done? I wonder how fast antimatter can go I mean light is matter right? Maybe antimatter may have some thing even faster that it makes up.

Tim Thompson
2007-Oct-15, 04:40 AM
In theory can we make antimatter? I know it wouldn't last long but can it be done?
Easy. I have made antimatter myself in the particle accelerator in the physics department (http://www.calstatela.edu/dept/physics/) at Cal State LA. It is easy in principle to make antimatter, but it takes a lot of energy to do it, and you can make only microscopic amounts of it.


I wonder how fast antimatter can go I mean light is matter right? Maybe antimatter may have some thing even faster that it makes up.
Light is not matter, it is an electromagnetic wave, or an electromagnetic "particle", a photon, depending on how you look for it. Antimatter moves like matter, and is required to obey the same laws of physics as regular matter, so it cannot go faster then light (in a vacuum).

Kaptain K
2007-Oct-15, 04:54 AM
In theory can we make antimatter? I know it wouldn't last long but can it be done?
Yes! Not only in theory, but in practice. Usually in the form of positrons (anti-electrons). If you have ever had a PET scan, you might want to know the PET stands for Positron Emmision Tomography.

I wonder how fast antimatter can go I mean light is matter right?
No! Light is energy.

Maybe antimatter may have some thing even faster that it makes up.
No! Matter and antimatter are identical as far as mass goes.

frankuitaalst
2007-Oct-15, 05:50 AM
Negative mass :
We know positive charges and negative ones . We know North poles and South Poles . Similar charges repell as opposite charges attract .
We know that matter attracts .
But by analogy : can some matter exist which repells normal matter just by beeing "negative matter " .
Remember : F= m1*m2/r . Inverse the sign of m1 and you get a repelling force . Inverse but signs and you get an attracting force . Thats what I mean with negative matter .
It is clear that "negative matter" shouldn't exist on earth as it is repelled , into space .
But if it exists it might be possible that the negative matter even may build galaxies , away from normal matter .
This is just a thought.
I was just curious if some people here were familiar with this idea.

3dknight
2007-Oct-15, 07:29 AM
negative matter = antimatter

thats what I'm understanding.

3dknight
2007-Oct-15, 07:32 AM
energy is not matter. I've learned something new today. I think I found a way to store antimatter contain it in light! or did you already think of that?

astromark
2007-Oct-15, 07:54 AM
How do you contain light? If it is not tearing about at C it simply does not exist. Oh ya, a trick with mirrors:) Light is photons not matter. more closely akin to electrons than matter. You can not have a light battery... or can you?

3dknight
2007-Oct-15, 08:06 AM
You could do what they did in Angels and Demons make an air tight canister the bottom and top are magnets and suspend the antimatter in the middle. The magnets keep it balanced and since the canisters are air tight no air meaning no matter touching anti matter.

Antimatter can survive in energy it could be many palces in the universe according to that.

astromark
2007-Oct-15, 09:11 AM
A... What?

No. This looks just a whole lot like science fiction....
I like the other kind.

normdowling
2007-Oct-15, 10:06 AM
You seem to be describing Dark Energy (http://en.wikipedia.org/wiki/Dark_energy)

"In physical cosmology, dark energy is a hypothetical form of energy that permeates all of space and tends to increase the rate of expansion of the universe. Assuming the existence of dark energy is the most popular way to explain recent observations that the universe appears to be expanding at an accelerating rate. In the standard model of cosmology, dark energy currently accounts for almost three-quarters of the total mass-energy of the universe."

I thought dark energy was jus t a name given to what ever the cause of acceleration is.??????????????????????

or is that what u just said???????????????

frankuitaalst
2007-Oct-15, 01:44 PM
negative matter = antimatter
thats what I'm understanding.

It may be confusing . I'll try to explain :

Antimatter is in fact normal matter with this difference that protons in this case are NEGAtively charged and electrons are POSItively charged .
Antimatter exists , or may be created in small quantities . One of the correspondents here has made antimatter . Antimatter seems to behave as normal matter , in this way that it obeys the laws of gravity .

Matter with NEGATIVE mass however is something totally different . As far as I know no one has seen this or has detected it . So it's theoretical or hypothetical . In the meantime I found some links about it . Heres one : http://www.daviddarling.info/encyclopedia/N/negative_mass.html
One of the properties of matter with negative mass could be that a particle with negative mass is repelled by normal matter instead of being attracted .
Two particles with negative mass however can attract each other .

3dknight
2007-Oct-15, 02:35 PM
Two particles with negative mass however can attract each other .
Don't opposites attract?

frankuitaalst
2007-Oct-15, 02:59 PM
Don't opposites attract?
:lol:
in real life persons get attracted by the opposite sex in general , so do charges . Matter however attracts matter .

speedfreek
2007-Oct-15, 09:40 PM
I thought dark energy was jus t a name given to what ever the cause of acceleration is.??????????????????????

or is that what u just said???????????????

Yup, that's what I just said. :shifty:

3dknight
2007-Oct-15, 10:34 PM
in real life persons get attracted by the opposite sex in general , so do charges . Matter however attracts matter .

I'm matter I don't attract any other matter that I know of except the opposite sex like you already mensioned but thats a mental attraction mostly.

Neverfly
2007-Oct-16, 05:42 AM
By the way, one thing the "Backlit eagle nebula" thread reminded me of...

One idea of how we know the Universe isn't infinite is because if it was, we would see stars in every single direction.

3dknight
2007-Oct-16, 05:53 AM
One idea of how we know the Universe isn't infinite is because if it was, we would see stars in every single direction.

You make a good point even the planets in our solar system orbit the sun in about the same plain or level.

astromark
2007-Oct-16, 05:58 AM
By the way, one thing the "Backlit eagle nebula" thread reminded me of...

One idea of how we know the Universe isn't infinite is because if it was, we would see stars in every single direction.

But... We do.
and there are........
In what direction are there no stars.?

Neverfly
2007-Oct-16, 06:04 AM
But... We do.
and there are........
In what direction are there no stars.?

Uhhh... The dark directions:neutral:

astromark
2007-Oct-16, 09:12 AM
Up the exposure time and magnifie... we are surrounded. there are no empty places. There is no dark. Only light and, enlightenment. sorry, I could not resist.:)

Svemir
2007-Oct-16, 10:00 AM
Frankuitaalst probably thinks of "negative" gravity as a main property of antimass (atractive force between masses, atractive force between "antimasses" and repulsive force between mass and "antimass")
But, those terms are still Newtonian, if we move to Einstein things get more clearer.
The gravity is not property of the mass but of the space (or space/time).
It's regarded not as a force but as a curvature of space/time manifold
(Yes, manifold, we learned what it is :-))
In that view, negative gravity is just negative curvature
(some think Dark Energy might be just that).
Another view is that gravity is a pressure while negative gravity is negative pressure
(some think Dark Energy might be just that).
Any carrier (if any) of such negative pressure/curvature could be regarded as "antimass".

Kaptain K
2007-Oct-16, 01:05 PM
astromark,
Neverfly was referring to Euler's paradox. If the universe were truly infinite, then no matter how finely you divided the sky, everywhere you looked, you would be looking at the surface of a star! The whole sky would be as bright as the Sun!!

3dknight
2007-Oct-16, 11:56 PM
If the universe were truly infinite, then no matter how finely you divided the sky, everywhere you looked, you would be looking at the surface of a star! The whole sky would be as bright as the Sun!!

Why would this be so?

Neverfly
2007-Oct-16, 11:58 PM
Why would this be so?

Because in an infinite universe, the odds are that no matter what direction you look in, a star must be there at some distance.

3dknight
2007-Oct-17, 12:59 AM
Umm you just repeated what Kaptain K said this doesn't help me understand this any better.

Neverfly
2007-Oct-17, 01:23 AM
Ok let me try again...

In an finite universe- there is a limit. At some point if you go far enough- there will be nothing past that point. Literally nothing. no stars. No molecules- Utter VOID.

In an infinite universe- there is no end... so there will be stars. Keep going forever and there will still be stars.

Since, in an infinite universe there is no boundry at which the possibility of stars existing in that space exists, then there must be stars forever as far as the eye can see.

Apply this to looking in any direction and somewhere- in that direction, there must be stars because there is an infinite distance to work the odds with that stars will be present.

3dknight
2007-Oct-17, 03:08 AM
there must be stars because there is an infinite distance to work the odds with that stars will be present.

So just because there is infinite space means stars will have to take up the whole space?

I'm not understanding this paradox easily.

Kaptain K
2007-Oct-17, 04:04 AM
Not the whole space, the whole area of the sky. There are 4pi steradians of area (~41252.96 square degrees) on the surface of a sphere. This number is constant. It is an inherent property of a sphere. As the radius of the sphere of the universe increases, the number of stars increases by the cube of the radius. Eventually (given an infinite universe), you will reach a point where every single square micro-arc-second of the sphere will contain stars.

3dknight
2007-Oct-17, 04:15 AM
Eventually (given an infinite universe), you will reach a point where every single square micro-arc-second of the sphere will contain stars.

Maybe our universe is infinite and the universe is to young for this to happen yet.

normdowling
2007-Oct-17, 05:44 AM
may be if it was infinite, it would take an infinite amount of time for this to happen???????????/

normdowling
2007-Oct-17, 05:47 AM
i think the universe is infinite . At least in any practical sense. the rest is for the future?????????????????????

astromark
2007-Oct-17, 06:05 AM
There are two possibilities here....
The first suggests that I am the only person I have yet met that actually understands this....
The second suggests I am wrong....
I now must share with you all what my thoughts on this are. Remembering that to be wrong is not a crime and shows that I have thought about this a little to much maybe.
No. the sky would not be white with the light of billions of stars. The immense distances we are dealing with brings in what I call the inverse law. Each and every star emits its energies 360deg. At the distances we speak of here insufficient light reaches us to be seen. Obviously the greater the distance the less visible any image can be.
You are all well educated people and I fear I have oversimplified what is not. Does any of this find favor with you?

Tim Thompson
2007-Oct-17, 06:09 AM
So just because there is infinite space means stars will have to take up the whole space?
No. But it does mean that every one of the infinite number of lines of sight must eventually intercept the surface of a star.

The key concept you are missing is the idea of surface brightness, or brightness per unit area on the sky. When you look at a star, you see all of its light at once. The brightness you see (the apparent brightness) depends on the inverse square of the distance between you and the source. So, move the source 3 times farther away, and it looks 1/32 = 1/9 times as bright, and so on. However, the area of the solid angle (http://en.wikipedia.org/wiki/Solid_angle) of the source on the sky also decreases by the same amount. So if you take the ratio of the brightness (which decreases as the inverse square of the distance) over the solid angle (which also decreases as the inverse square of the distance), the ratio must be constant. That ratio is the surface brightness of the object, and you see that it is independent of the distance between you and the source.

So, the sun for instance, will look dimmer as it is moved away from you. But its surface brightness remains the same. Now, fill a solid angle that is the same size as the apparent size of the sun with points, all of which have the same surface brightness as the sun. That solid angle will have the same apparent brightness as the sun.

And so it is that for an infinite universe, every line of sight must eventually intercept the surface of a star. On average, all stars will have approximately the same surface brightness as the sun. So every point on the sky will have the same surface brightess as does the sun. So the whole sky will have the same apparent brightness as the sun has, which is obviously not the case. This famous problem in astronomy is known as Olber's paradox (http://en.wikipedia.org/wiki/Olbers'_paradox). See the animation of Olber's paradox in action on the linked webpage.

astromark
2007-Oct-17, 07:57 AM
No... You just don't get it do you. Olber's paradox does not work. Its based on nonsence. Go out at night, look up. I rest my case.

Neverfly
2007-Oct-17, 08:27 AM
No... You just don't get it do you. Olber's paradox does not work. Its based on nonsence. Go out at night, look up. I rest my case.

Saying it is nonsense only seeks to justify the infinite universe model.

Almost 14 billion years is long enough I think to light up the night sky fairly well:p
Tim_Thompson, thank you for comming to the rescue:D

astromark
2007-Oct-17, 09:36 AM
Seeing a black sky does not make the universe any less infinite than before. Or any more infinite than it is now. It is not. You are not understanding me. I do not support the infinite universe model. I support the ' Finite while unbound' I do not see the contradiction you do. I only see a misunderstanding of what is visible. As for Tim striding in to your rescue. No, I agree with him. Every line of sight might intersect a star., but we will never see their light. The space between us has expanded and, continues to do so. But do not miss my point. The universe is not infinite. If it had a beginning it can not be. We seem to agree that it did. So it is.
Saying it is nonsense does not mean I support the wrong conclusion. The logic of this argument of Alber's is flawed.

Neverfly
2007-Oct-17, 09:42 AM
Seeing a black sky does not make the universe any less infinite than before. Or any more infinite than it is now. It is not. You are not understanding me. I do not support the infinite universe model. I support the ' Finite while unbound' I do not see the contradiction you do. I only see a misunderstanding of what is visible. As for Tim striding in to your rescue. No, I agree with him. Every line of sight might intersect a star., but we will never see their light. The space between us has expanded and, continues to do so. But do not miss my point. The universe is not infinite. If it had a beginning it can not be. We seem to agree that it did. So it is.
Saying it is nonsense does not mean I support the wrong conclusion. The logic of this argument of Alber's is flawed.

The 'rescue' I refer to is that I seem to not be very good at expressing something and making sense at the same time.
I try... But in the end there are a great many people here that are just plain better at it:p

As to the rest of your statement, these are ideas.
I do not personally have any reason to believe that Olbers paradox is flawed, even considering expansion and the speed limit on light.

Although we may say that the night sky won't look like one big star... It still would be considerably much more dense than it is now.

astromark
2007-Oct-17, 10:19 AM
But I can sagest that as the expansion continues the density decreases and the image as a whole gets dimmer. The same amount of material just spread thinner. Eventually ( back to this thread ) this universe is going to get darker as stars use up the material available to them. Star forming regions will decrease and darkness will engulf all. Do not expect this to happen quickly. Its taken 14 odd billion years to reach this point. I do not imagine this dimming of the universe to be detectable for hundreds of billions of years yet.

Neverfly
2007-Oct-17, 10:25 AM
But I can sagest that as the expansion continues the density decreases and the image as a whole gets dimmer. The same amount of material just spread thinner. (snip).

Like Capt. Picards head?

Look out rogaine! I found the cure...
Shrunken heads.

astromark
2007-Oct-17, 10:38 AM
John Luke would not be pleased... while I fell of my chair laughing.:)

Svemir
2007-Oct-17, 11:35 AM
There is a reason why Olber's paradox is just vaguely mentioned in some papers against Infinite Universe.
Olber's paradox solved (http://home.wanadoo.nl/ronald.koster/olber.pdf)
is just one paper about the issue.
Another thing; if you argue for an Infinite Universe (in time and space) you should be prepared (and dismiss them, accordingly) for assumptions that the other side will try to put in your mouth and they are:
Assumption from Bing Bang Cosmology that the Universe is isotropic and homogenous at the largest scales (which absolutely doesn't have to be true, especially homogenity)
Asumption that the Universe should be static (e.g. stars in our visible Universe, have to have counterparts on the other side, at the same stage)
Assumption that the Universe is not expanding (it may well be Infinite end expanding)
etc.

Neverfly
2007-Oct-17, 11:58 AM
There is a reason why Olber's paradox is just vaguely mentioned in some papers against Infinite Universe.
Olber's paradox solved (http://home.wanadoo.nl/ronald.koster/olber.pdf)
is just one paper about the issue.
Another thing; if you argue for an Infinite Universe (in time and space) you should be prepared (and dismiss them, accordingly) for assumptions that the other side will try to put in your mouth and they are:
Assumption from Bing Bang Cosmology that the Universe is isotropic and homogenous at the largest scales (which absolutely doesn't have to be true, especially homogenity)
Asumption that the Universe should be static (e.g. stars in our visible Universe, have to have counterparts on the other side, at the same stage)
Assumption that the Universe is not expanding (it may well be Infinite end expanding)
etc.

All irrelevent to that fact that the infinite universe model has very little basis of evidence much less realistic conclusions.

Finite universe model has a lot of evidence through both measurement and observation.

Kaptain K
2007-Oct-17, 12:08 PM
astromark,
You are missing the point! Tim Thompson explained it very well. I suggest you read it again.
Look at it this way. The full Moon is not as bright as a desert at noon, right? Well, news flash. The exposure time for a photo of the Moon is exactly the same as for a photo of the desert. Why? Because the light per unit area is the same!
Olber's paradox says that the universe is not infinite because the sky is dark, not as bright as the Sun. You say that Olber's paradox is wrong because the universe is not infinite. Do you see the disconnect here???

Tim Thompson
2007-Oct-17, 03:11 PM
Seeing a black sky does not make the universe any less infinite than before. ... Every line of sight might intersect a star, but we will never see their light.
Well, I disagree. Seeing a black sky does make the universe non-infinite, which is the whole point of the "paradox". It is not a matter of "might; if the universe is spatially infinite and static, then every line of sight must intersect a star. Therefore the entire sky must have the same surface brightness as a star. Olber's paradox proves that the universe cannot be both infinite and static.

At least in principle, you could get around the paradox by invoking an infinite universe that is expanding. The expansion can then be invoked to redshift the starlight to infinite wavelength and zero energy. I have seen people try to do that, but they wind up with the same problems that caused them to seek an alternative to big bang cosmology; i.e., they fail to conserve energy in an even more spectacular manner then does big bang cosmology, and the universe must eventually expand with infinite velocity in order to force an infinite redshift. It hardly seems a superior solution to standard cosmology.

Tim Thompson
2007-Oct-17, 03:22 PM
There is a reason why Olber's paradox is just vaguely mentioned in some papers against Infinite Universe.
Olber's paradox solved (http://home.wanadoo.nl/ronald.koster/olber.pdf) is just one paper about the issue.
Koster's "solution" is based on the obviously false assumption that the radiation energy density in the universe must look like the average mass density. That might work in a universe with a finite age, but Koster postulates a universe with an infinite age. In that case, while the average mass density is "local", meaning that it is affected only by local physics, the radiation density is not. If the universe has an infinite age, as he postulates, then there has been time for any point in the universe to come into radiative contact with all other points. And therefore Older's paradox will be in effect; in his model universe, every line of sight must intersect a stellar surface, and he avoids this by simply postulating the impossible.

Svemir
2007-Oct-18, 07:23 PM
All irrelevent to that fact that the infinite universe model has very little basis of evidence much less realistic conclusions.

Finite universe model has a lot of evidence through both measurement and observation.
And this is irrelevent for Olber's paradox discussion.
Do I smell a logical fallacy here?

Neverfly
2007-Oct-18, 10:10 PM
And this is irrelevent for Olber's paradox discussion.
Do I smell a logical fallacy here?

No. Because I am talking about the evidence.

You were talking about tips to avoid "falling into a (supposed) trap" laid by finite universe supporters. Your tips are based on assumptions on both sides. So their relevency is lost.

astromark
2007-Oct-19, 06:08 AM
No. Because I am talking about the evidence.

You were talking about tips to avoid "falling into a (supposed) trap" laid by finite universe supporters. Your tips are based on assumptions on both sides. So their relevency is lost.

RELEVANCY.

I may be wrong about this as being wrong seems to be the other thing I am really good at. The universe is finite. Is there any argument with that?

The sky for the most part appears to be black at night. It was important to add the 'at night' before some smart @@@ tells me its blue. :) I am of coarse referring to that time of the night when you the observer is in Earths shadow.
Sigh... sorry its been a long day. Now please tell me again why you think I am wrong about these facts...
and does non infinite not mean finite.

Some times a wall of misunderstanding stands between us. Could you please help me understand why my explanation of diminished light because of distance has no bearing on our dark sky?

Michael Noonan
2007-Oct-19, 06:57 AM
Some times a wall of misunderstanding stands between us. Could you please help me understand why my explanation of diminished light because of distance has no bearing on our dark sky?

You are not alone. I have trouble with the idea that the depths of the ocean are pitch black at midday because all that light on the surface just has to go somewhere doesn't it?

Neverfly
2007-Oct-19, 07:01 AM
RELEVANCY.

I may be wrong about this as being wrong seems to be the other thing I am really good at. The universe is finite. Is there any argument with that?

The sky for the most part appears to be black at night. It was important to add the 'at night' before some smart @@@ tells me its blue. :) I am of coarse referring to that time of the night when you the observer is in Earths shadow.
Sigh... sorry its been a long day. Now please tell me again why you think I am wrong about these facts...
and does non infinite not mean finite.

Some times a wall of misunderstanding stands between us. Could you please help me understand why my explanation of diminished light because of distance has no bearing on our dark sky?

With no desire to cause further confusion...

Your existing confusion may be related to the fact that I was responding to Svemir, not you:p


Michael Noonan, good question. I started to answer it but then decided that my ignorance was greater than my brilliance and shut my trap like a box.:neutral:

normdowling
2007-Oct-25, 12:35 PM
With no desire to cause further confusion...

Your existing confusion may be related to the fact that I was responding to Svemir, not you:p


Michael Noonan, good question. I started to answer it but then decided that my ignorance was greater than my brilliance and shut my trap like a box.:neutral:

neverfly , i just noticed how many times u have posted , and am thinking u should get out more???????????????????????/

normdowling
2007-Oct-25, 12:38 PM
neverfly , i just noticed how many times u have posted , and am thinking u should get out more???????????????????????/

Kaptain K seems to have a problem as well???????????????????

Kaptain K
2007-Oct-25, 02:04 PM
Kaptain K seems to have a problem as well???????????????????
1) Please note my Join Date: (Oct 2001)! :) And, that is actually the date that the Bad Astronomy discussion board became a multi-forum board. Before that, it was a single threaded board and I was there too. :)
2) I'm retired! :whistle: You should be so lucky.