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skrap1r0n
2005-Feb-02, 06:36 PM
I had a thought last night right before I fell asleep that I can't let go of, so I am going to post it here and see what you guys think. Remember, I am no physicist and College algebra almost killed me, so these thought are coming from ignorance.

How much information about the universe is permanently lost? I ask this because I had a thought triggered by an archeology show on one of the discovery channels. Basically, there was a guy chipping rocks from a spot in Australia. These are the oldest rocks know to exist on earth, around 3 billion years old.

The Archeologist was explaining that plate tectonics has recycled rocks any older than that. In other words, the earth sucked it back into the mantle.

My thought went a step further. I understand that we look back in time as we stargaze. The EM radiation we see today could be hundreds or millions of years old.

How much of this EM radiation has been lost? Wouldn't a black hole, or singularity essentially "recycle" the information? I mean if a supernova went off hundreds of thousands of years ago, could that information get trapped in a black hole on it's way to us?

Also, this kinda brought up another question. In my understanding of the Big Bang, a singularity reached some critical mass and blew all matter and energy out of it. Essentially, a big explosion. In any explosion, there is a central point and all matter radiates away from that point, like an expanding bubble.

Now we are in this expanding bubble traveling in a certain direction through space. Following this logic, there should be other systems/stars traveling in a similar direction as us. So following this line of thought, I would imagine that certain objects are traveling away from us as well as with us.

Why can't we detect objects traveling away and alongside us and track that back to a central point?

Kaptain K
2005-Feb-02, 06:47 PM
There is no central point! The Big Bang was not an explosion into space-time, it was an explosion of space-time!
As an analogy, think of an expanding balloon. the surface of the balloon has no center!
Space-time (our universe) is a four dimensional analogue of the two dimensional surface of the balloon.

Kristophe
2005-Feb-02, 06:58 PM
And as a result, when we do track the motion of other galaxies and such, they all track back to right here.

skrap1r0n
2005-Feb-02, 06:58 PM
There is no central point! The Big Bang was not an explosion into space-time, it was an explosion of space-time!
As an analogy, think of an expanding balloon. the surface of the balloon has no center!
Space-time (our universe) is a four dimensional analogue of the two dimensional surface of the balloon.

Ok thats where I have trouble conceptualizing this idea. Using your balloon analogy, then we are essentialy in the "bubble membrane" Thats not hard to visualize. Whats hard to visualize is that we are stuck IN that membrane and can't travel through it.

I guess, im my minds eye, I see the universe like an expanding fishbowl.

Also I have a question regarding curved space/time. Would this mean that energy and matter are also bound by this curvature? Where I am headed with this, is that if the speed of light is a basic constant in our universe, then wouldn't it also be bound by the curvature? Can you thoeretically go slower than stopped to approach the SoL?

skrap1r0n
2005-Feb-02, 07:01 PM
And as a result, when we do track the motion of other galaxies and such, they all track back to right here.

Ok, I understand that we detect objects travelling away from us, but can we not also detect oblets travling WITH us?

Also, following the Curved Space line of thought, wouldn't we theoretically be able to see an object by finding it then turning 180 degrees and see it as well?

Doodler
2005-Feb-02, 07:43 PM
And as a result, when we do track the motion of other galaxies and such, they all track back to right here.

Ok, I understand that we detect objects travelling away from us, but can we not also detect oblets travling WITH us?

Also, following the Curved Space line of thought, wouldn't we theoretically be able to see an object by finding it then turning 180 degrees and see it as well?

Theoretically yes. Though in practical terms, we cannot. The universe is some 80 gigalightyears across (crude term to apply here, but its all I have.) in any given direction and we can only see 13.7 gigalightyears or so. Also, as the expansion continues, it will continue to accelerate. At some point, ultradistant objects will simply disappear as the rate of expansion exceeds the speed of light. This is possible since the object in question isn't truly exceeding lightspeed, the space around it is expanding that fast. To explain, space is viewed as the surface of a balloon constantly being inflated. Using that same analogy, gravity is seen to warp space by creating indentations, so-called gravity wells. The surface of the universe is covered in 'dimples' that are the result of galaxies 'depressing' the 'surface', holding local space-time within the currently understood laws of physics. The rapid expansion is occuring in the empty space between the dimples.

skrap1r0n
2005-Feb-02, 08:08 PM
Theoretically yes. Though in practical terms, we cannot. The universe is some 80 gigalightyears across (crude term to apply here, but its all I have.) in any given direction and we can only see 13.7 gigalightyears or so. Also, as the expansion continues, it will continue to accelerate. At some point, ultradistant objects will simply disappear as the rate of expansion exceeds the speed of light. This is possible since the object in question isn't truly exceeding lightspeed, the space around it is expanding that fast. To explain, space is viewed as the surface of a balloon constantly being inflated. Using that same analogy, gravity is seen to warp space by creating indentations, so-called gravity wells. The surface of the universe is covered in 'dimples' that are the result of galaxies 'depressing' the 'surface', holding local space-time within the currently understood laws of physics. The rapid expansion is occuring in the empty space between the dimples.

Ok I can see how that makes sense. But it raises other questions. Can a mass be so dense that it causes a DEEP well? Is this the Wormhole theory?

Additionally, could a mass be large enough to break through the "membrane" like a drop of water so to speak? Any thought as to what would happen if it did preak through?

Doodler
2005-Feb-02, 11:03 PM
Theoretically yes. Though in practical terms, we cannot. The universe is some 80 gigalightyears across (crude term to apply here, but its all I have.) in any given direction and we can only see 13.7 gigalightyears or so. Also, as the expansion continues, it will continue to accelerate. At some point, ultradistant objects will simply disappear as the rate of expansion exceeds the speed of light. This is possible since the object in question isn't truly exceeding lightspeed, the space around it is expanding that fast. To explain, space is viewed as the surface of a balloon constantly being inflated. Using that same analogy, gravity is seen to warp space by creating indentations, so-called gravity wells. The surface of the universe is covered in 'dimples' that are the result of galaxies 'depressing' the 'surface', holding local space-time within the currently understood laws of physics. The rapid expansion is occuring in the empty space between the dimples.

Ok I can see how that makes sense. But it raises other questions. Can a mass be so dense that it causes a DEEP well? Is this the Wormhole theory?

Additionally, could a mass be large enough to break through the "membrane" like a drop of water so to speak? Any thought as to what would happen if it did preak through?

Not sure on the wormhole thing, most of it beyond that one visual I described is so far over my head, I don't even feel the draft as it passes by.

mickal555
2005-Feb-02, 11:39 PM
thats what I thought of a balck hole to be a gavity so strong it breaks through and makes a kinda bottemless hole....

Russ
2005-Feb-03, 12:01 AM
Ok I can see how that makes sense. But it raises other questions. Can a mass be so dense that it causes a DEEP well? Is this the Wormhole theory?

Additionally, could a mass be large enough to break through the "membrane" like a drop of water so to speak? Any thought as to what would happen if it did preak through?

On the theory that difference of opinion is what makes for a horse race, I am going to give you some explantions that "I" think are more clear. :roll: ;)

I don't like the "Balloon" analogy for universe expanssion but prefer the "Raison Bread" analogy. The reason is the balloon only gives you 2 dimentions and you have to visualize it as a shadow of reality, the same as if you see the shadow of a cube or sphere pojected on a wall depicting the 3D object.

If you take a super giant sphere of raison bread dough and let it rise, while you stand on one of the raisons, it will appear that all other raisons are moving away from you no matter which raison you are standing on. The farther away the other raison is, the faster it will appear to move. This is what we see galaxies doing in the universe. They are relatively stationary, relative to local space, but moving quite quickly in the billion odd lightyear distance.

Regardng the questions above, I think you have a pretty good grasp of the concepts. Yes, huge masses do create huge gravity wells. Neutron stars are one example of this concept. Because it is possible (hypothetically) to escape their gravitational grip, they would not constitute a point for a worm hole.

Black holes(BH) would be a more likely candidate for creating worm holes (WH) and piercing the "membrain" as you put it. There is still a great deal of discussion going on about these ideas. I have an Audiobook (book on tape) of 8 Steven Hawking lectures, in which he talks about these very things. While I have listened to it several times, I'm not sure I have a sufficient grasp of his ideas that I can correctly echo them back to you.

The concepts I don't get are how BH's might cause points where space curves back on itself in 11 multiverses of which 7 are of sub quark scale....???? Like I said, I don't get it yet. He talks about this in terms of quantum mechanical equations the solutions of which can't be depicted in our universe!!?? Whatever that means! I gather it means only 4 or 5 partials from the equations can be depicted at a time. From the way he talks, I get the impression that he has a picture in his head and he is struggling to describe it in english.

Please excuse my rambling and any typos I missed.

Maddad
2005-Feb-03, 01:22 AM
Also I have a question regarding curved space/time. Would this mean that energy and matter are also bound by this curvature? Where I am headed with this, is that if the speed of light is a basic constant in our universe, then wouldn't it also be bound by the curvature?When you say that a gravity field curves space, there is less of the space near the massive object than there is further away. Without the mass, space would be a series of evenly spaced concentric shells about the center of the object. Because of gravity, those shells are closer together the closer you get to the object. Since not only matter, but light also travels through space, compressing space near a massive object bends the path of both passing matter and light.

A black hole would be a special case of a massive object. The gravity is so strong that it removes all the space near it.

Toutatis
2005-Feb-03, 03:34 AM
A black hole would be a special case of a massive object. The gravity is so strong that it removes all the space near it.

As a 'workaday’ analogy I offer the following:

Think of spacetime as a trampoline deck fabricated of any substance having a rather high modulus of elasticity (as, for instance, unvulcanized latex) and transversely oriented with respect to a gravitational field.

The deck will be deflected, to varying degrees, by the mass of any object placed thereon (the magnitude of said deflection dependant upon object density [ignoring 'frictional' losses and otherwise non-elastic proprieties of the elastic sheet]) --- Very dense objects will deflect the deck to or beyond the point of invagination – thus forming a closed 'pocket'…

GRANTED!!! My analogy leaves much to be desired (Prominent among its shortcomings being that it all but ignores the transdimensional nature of spacetime, erroneously equates elastic force (i.e. potential energy/’force’) to reaction - and, in so doing, fails to address the fact that gravitation is reaction (i.e. a 'mass force', if you will) -- as opposed to force, and, perhaps worst of all, uses gravitation in an analysis of another manifestation of itself (circular analogy) -- Ok so it SUX! :( --- Still... it has been useful to some, even if I do say so myself :D

Well I tried! --- Dodgson (Carroll) said it better (with his Cheshire Cat :D )

Best
Sarandon

thkaufm
2005-Feb-03, 06:14 AM
I don't like the "Balloon" analogy for universe expanssion but prefer the "Raison Bread" analogy. The reason is the balloon only gives you 2 dimentions and you have to visualize it as a shadow of reality, the same as if you see the shadow of a cube or sphere pojected on a wall depicting the 3D object.


but a raison bread has a center point of expansion that lies in the same 3 dimensions as the raisons do, while the points on the balloon have a center that lies in an additional dimension from the points, the same way that the universe has a center that lies in an additional dimension to the 3 we live in.

Tom

Lance
2005-Feb-03, 02:12 PM
For the first time, some of this is actually beginning to make sense to me.

But then it raises the question, if galaxies are all moving away from each other, how can they ever collide?

Bad jcsd
2005-Feb-03, 02:18 PM
I don't like the "Balloon" analogy for universe expanssion but prefer the "Raison Bread" analogy. The reason is the balloon only gives you 2 dimentions and you have to visualize it as a shadow of reality, the same as if you see the shadow of a cube or sphere pojected on a wall depicting the 3D object.


but a raison bread has a center point of expansion that lies in the same 3 dimensions as the raisons do, while the points on the balloon have a center that lies in an additional dimension from the points, the same way that the universe has a center that lies in an additional dimension to the 3 we live in.

Tom

Actually I don't believe raison bread has a centre of expansion (i.e. the expansion in rasio bread is approximately homogenous and isotropic which is the whole point of the analogy, though rasion breda does have a geomertical cnetre.

Bad jcsd
2005-Feb-03, 02:19 PM
For the first time, some of this is actually beginning to make sense to me.

But then it raises the question, if galaxies are all moving away from each other, how can they ever collide?

Not all galaxies are mving away from each other, for neraby galxies the effects of their random movemtn are much gretare than the effects of expansion.

Argos
2005-Feb-03, 02:22 PM
I think it´s better to say that groups, or clusters, of galaxies (the clusters are the raisins) are drifting apart from each other. Galaxies can collide within the groups, as they actually do.

geokstr
2005-Feb-06, 01:34 AM
And occasionally even colossal galactic clusters collide, rather spectacularly too, it seems:

http://www.astronomy.com/asy/default.aspx?c=a&id=2476