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Author | Topic: The infinite space of the Universe | ||||||||||||||||||||||||
New Cat's Eye Inactive Member |
By Universe you mean space, right? Not just space. I mean space and time, or spacetime, if you will.
So what's the difference between unbounded space and infinite space? Unbounded space can be finite while not having an "end" to it. The two dimensional surface of the Earth is finite and unbounded. You can go in the east direction forever while remaining on a finite surface.
What evidence is there to support this theory? The CMBR and also this:
quote: Let me guess... You never googled "evidence for a finite universe", did you?
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Agobot Member (Idle past 5530 days) Posts: 786 Joined: |
quote: There is no 2-dimensional surface in a 3 dimensional material world. Anything out there and around us is 3 dimensional. 2-dimensional could only be something imaginary.
quote: I did. This theory is refuted in more web sites than you'll find it being promoted. Regardless, what's the meaning in the English language of: "Unbounded but finite, spherical empty 3 dimensional space" ? English is my third language and I can't really grasp it. I can't even picture it. Edited by Agobot, : No reason given. Edited by Agobot, : No reason given. Edited by Agobot, : No reason given. Edited by Agobot, : No reason given.
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New Cat's Eye Inactive Member |
There is no 2-dimensional surface in a 3 dimensional material world. Anything out there and around us is 3 dimensional. 2-dimensional could only be something imaginary. 3-dimensional could only be something imaginary Anyways, the 2d surface is helpful in picturing how the three dimensional material world is a 'surface' of 4d spacetime, much like the 2d surface is the surface of the 3d globe. The 2d surface of Earth is finite but you can travel east forever because it is unbounded. In a similar way, 3d space is also finite but unbounded. And, "Anything out there and around us" is no less 4d than it is 3d.
I did. This theory is refuted in more web sites than you'll find it being promoted. Links?
Regardless, what's the meaning in the English language of: "Unbounded but finite, spherical empty 3 dimensional space" ? English is my third language and I can't really grasp it. I can't even picture it. I'm sorry but I doubt I could help much with that. Edited by Catholic Scientist, : No reason given.
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Libmr2bs Member (Idle past 5727 days) Posts: 45 Joined: |
My idea of universe is not space. Space is dimensional and might have edges or possibly turn back on itself. The universe includes that which is unknown. Light generated by objects at the edge of space (or if you prefer the most remote object) will travel outside that space into what? If light was generated during the big bang, photons would be traveling far beyond the confines of space and would have escaped the influence of gravity.
Before and after are relative terms. That which is before is also after and that which is after is also before. Without cyclical recurrance time would have no meaning. One second must be the same as all others or it is irrelevant as a measurement and we insist on defining time as the fourth dimension. My perception of infinite is beyond the ability to reasonably understand - much like the square root of a negative number.
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Agobot Member (Idle past 5530 days) Posts: 786 Joined: |
quote: Correct me if I am wrong, but I think they are talking about the material universe being finite(galaxies), which is vastly different to space being finite or not.
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Agobot Member (Idle past 5530 days) Posts: 786 Joined: |
quote: quote: LOL. You said the space in the Universe if finite but unbounded/I quoted that/. Then you gave an example with the spherical shape of the Earth as being finite and unbounded. And now you don't know what you have meant by "finite but unbounded spherical 3-dimensional empty space"? BTW, you have a wrong idea about the theory of the unbounded but finite universe. It only applies to the material portion of the universe(galaxies). It does not apply to the seemingly infinite empty 3-dimension space of the Universe(of which we talk about here and which is beyond the last, farthest galaxies). Edited by Agobot, : No reason given. Edited by Agobot, : No reason given. Edited by Agobot, : No reason given.
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cavediver Member (Idle past 3643 days) Posts: 4129 From: UK Joined: |
Correct me if I am wrong Ok
I think they are talking about the material universe being finite(galaxies), which is vastly different to space being finite or not. You are wrong - they are talking about space being finite - in the manner that Catholic Scientist has described to you. Travel in any direction in the Universe, and without deviating from your straight path, you will eventually return to where you started. This is almost certainly practically impossible, because the expansion of the Universe will outpace your attempt to reach your starting point. If the expansion should slow and halt, then it may be possible. The actual topology of the Universe that wraps it into a finite shape is not totally certain - in all likelihood it is spherical (as in the topology of the three-dimensional spherical surface of a four-dimensional ball) ALternatively, it could have the topology of a torus, or something more complex. It is possible that future detailed examination of the CMBR will reveal clues to the actual topology, should the Universe be spatially finite (still an open question) .
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Agobot Member (Idle past 5530 days) Posts: 786 Joined: |
quote: quote: How do you know space is finite(even if the universe has a spherical shape - which is just a hypotesis by all means now)? The material universe is expanding for sure. So if the empty space of the universe is finite, as you claim, when do we reach the boundery(and ultimately what evidence is there that proves empty space beyond the last galaxies is finite)?
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Agobot Member (Idle past 5530 days) Posts: 786 Joined: |
The universe is not spherical but flat, according to NASA:
"Recent measurements (c. 2001) by a number of ground-based and balloon-based experiments, including MAT/TOCO, Boomerang, Maxima, and DASI, have shown that the brightest spots are about 1 degree across. Thus the universe was known to be flat to within about 15% accuracy prior to the WMAP results. WMAP has confirmed this result with very high accuracy and precision. We now know that the universe is flat with only a 2% margin of error." WMAP- Shape of the Universe Edited by Agobot, : No reason given.
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cavediver Member (Idle past 3643 days) Posts: 4129 From: UK Joined: |
The universe is not spherical but flat, according to NASA Fortunately NASA is not THE authority on reality The Universe looks flat because of inflation - these measurements are far more an indication of the extent of inflation, than a determination of the open/flat/closed status of the Universe. Take a beach ball, and look at a small patch to see how curved it is. Now blow the ball up to the size of the Milky Way. How curved does your small patch look now? Say you can look as far as 100 miles away across the surface - can you determine whether this surface is flat or part of a ball?
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Agobot Member (Idle past 5530 days) Posts: 786 Joined: |
This is how NASA measured that the universe is flat:
http://www.astronomybuff.com/...we-know-the-universe-is-flat
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cavediver Member (Idle past 3643 days) Posts: 4129 From: UK Joined: |
Yes, exactly. The trouble is the CMBR (actually the surface of last scattering) is not that far away in terms of the size of the Universe, so the triangle used is just not that large. In the same way that we can use a triangle on our beach ball, but if our triangle is only 100 miles per side, and the ball happens to be the size of the Milky way, we are going to conclude that our patch of balloon is flat. This is very simple.
Edited by cavediver, : No reason given.
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onifre Member (Idle past 2951 days) Posts: 4854 From: Dark Side of the Moon Joined: |
and the ball happens to be the size of the Milky way, we are going to conclude that our patch of balloon is flat. Is this the same analogy as just standing at any point on our planet and believing it to be flat, as was once thought long ago? Also, is spacetime considered to be flat and it is gravity that curves it? This is what GR says right? All great truths begin as blasphemies
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cavediver Member (Idle past 3643 days) Posts: 4129 From: UK Joined: |
Is this the same analogy as just standing at any point on our planet and believing it to be flat, as was once thought long ago? Yes, except the Universe is far flatter than the Earth.
Also, is spacetime considered to be flat and it is gravity that curves it? This is what GR says right? GR says that the matter/energy content of the Universe curves space-time - the natural motion of an object following this curvature is what we perceive as a "force" pulling the object towards mass, and we call this "force" gravity.
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onifre Member (Idle past 2951 days) Posts: 4854 From: Dark Side of the Moon Joined: |
Yes, except the Universe is far flatter than the Earth. Got it.
GR says that the matter/energy content of the Universe curves space-time - the natural motion of an object following this curvature is what we perceive as a "force" pulling the object towards mass, and we call this "force" gravity. So it is mass that curves spacetime through the percieved forces of gravity. Got that too. Now, just for my understanding, if you don't mind answering, if we traveled in one direction of spacetime we could technically end up in the same place we started from however, do to the universe expanding at a rate faster that the speed of light this is impossible because we could never reach that speed? Is this what is meant by infinite spacetime? The fact that it could never be caught up with so its basically an infinite journey? Also, this maybe off topic but, how exactly is the expantion rate measured, and what is it in terms of matter(?) in the space that grows? This is what I read,
quote: Would you mind giving a clearer explanation on it if you don't mind? All great truths begin as blasphemies
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