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Hypothetical astrophysics question
John Griffin wrote:
Two tiny, fuzzy points of light are observed. Observations of each object indicate that it's a globular galaxy ten billion light years distant. The first one is exactly that, but the second one happens to be another entire universe. It's 100,000 times as far away as the galaxy, and it's emiting ten billion times as much light. Is there anything that would distinguish these objects from one another? Redshift. The universe is expanding, and there is more space in between us and the object 100,000 times as far away; it would appear to be more redshifted. -- -- With Best Regards, Matthew Funke ) |
#2
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Hypothetical astrophysics question
"John Griffin" wrote in message
... Two tiny, fuzzy points of light are observed. Observations of each object indicate that it's a globular galaxy ten billion light years distant. The first one is exactly that, but the second one happens to be another entire universe. It's 100,000 times as far away as the galaxy, and it's emitting ten billion times as much light. Is there anything that would distinguish these objects from one another? I'm just curious. I haven't seen anything like that, as far as I know. Well, by current theory it would be an impossible observation for several reasons. For instance, our cosmic viewing horizon is at just about 13.7BLY, so nothing can be seen that's further. Also, to judge its distance, presumably you would rely on the hubble red-shift. At the stated distance, if the cosmic horizon wasn't a factor, the red-shift would be extreme -- there'd be almost nothing left of the light energy to detect. Not to mention the fact that if you're seeing it, it's *in* our universe and not a separate universe. |
#3
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Hypothetical astrophysics question
"John Griffin" wrote in sci.astro:
Two tiny, fuzzy points of light are observed. Observations of each object indicate that it's a globular galaxy ten billion light years distant. The first one is exactly that, but the second one happens to be another entire universe. It's 100,000 times as far away as the galaxy, and it's emiting ten billion times as much light. Is there anything that would distinguish these objects from one another? Our current understanding tells us that it's impossible to look outside our own universe. It also tells us that there's at least a horizon to our view due to the age and expansion rate of our universe that is around 13 billion lightyears. -- CeeBee Uxbridge: "By God, sir, I've lost my leg!" Wellington: "By God, sir, so you have!" Google CeeBee @ www.geocities.com/ceebee_2 |
#4
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Hypothetical astrophysics question
Matthew F Funke replied to John Griffin:
Two tiny, fuzzy points of light are observed. Observations of each object indicate that it's a globular galaxy ten billion light years distant. The first one is exactly that, but the second one happens to be another entire universe. It's 100,000 times as far away as the galaxy, and it's emiting ten billion times as much light. Is there anything that would distinguish these objects from one another? Redshift. The universe is expanding, and there is more space in between us and the object 100,000 times as far away; it would appear to be more redshifted. Why would it necessarily be redshifted at all? Since it's a different universe, it didn't take part in the Big Bang. It may have had its own Big Bang a quadrillion years or so ago, in which case its near side could be moving toward us at high speed. The two universes could even be moving toward or away from each other overall. -- Jeff, in Minneapolis .. |
#5
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Hypothetical astrophysics question
Greg Neill replied to John Griffin:
Two tiny, fuzzy points of light are observed. Observations of each object indicate that it's a globular galaxy ten billion light years distant. The first one is exactly that, but the second one happens to be another entire universe. It's 100,000 times as far away as the galaxy, and it's emitting ten billion times as much light. Is there anything that would distinguish these objects from one another? I'm just curious. I haven't seen anything like that, as far as I know. Well, by current theory it would be an impossible observation for several reasons. For instance, our cosmic viewing horizon is at just about 13.7BLY, so nothing can be seen that's further. That "horizon" is imposed by the light travel time since the plasma cleared up after the Big Bang. Light from a separate universe, not involved in our Big Bang, would be temporarily blocked by the plasma, but once the plasma cleared, the light would get through. I don't know whether the geometry of the situation would allow the light to reach us in a finite time. It may depend on the size and history of our Universe. Also, to judge its distance, presumably you would rely on the hubble red-shift. Which would be completely usesless, since a separate universe would have no connection to the Big Bang which got our Universe started. No way to correlate redshift with distance. At the stated distance, if the cosmic horizon wasn't a factor, the red-shift would be extreme -- there'd be almost nothing left of the light energy to detect. Or it might be extremely blue-shifted. Or anything in between. Not to mention the fact that if you're seeing it, it's *in* our universe and not a separate universe. Under *some* definitions of "universe". Not all. Clearly, this imaginary thing had no part in our Big Bang, and existed some time before our Big Bang occurred. I think that calling it a "universe" is entirely reasonable, and I think that such other universes could very well exist-- perhaps infinitely many of them, if space is infinite. Whether we would be able to see such a distant universe is a question I'm not sure anyone can answer until we understand the nature of our own Universe a bit better. -- Jeff, in Minneapolis .. |
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Hypothetical astrophysics question
CeeBee replied to John Griffin:
Two tiny, fuzzy points of light are observed. Observations of each object indicate that it's a globular galaxy ten billion light years distant. The first one is exactly that, but the second one happens to be another entire universe. It's 100,000 times as far away as the galaxy, and it's emiting ten billion times as much light. Is there anything that would distinguish these objects from one another? Our current understanding tells us that it's impossible to look outside our own universe. Maybe. The plasma of our Universe early in its history may have blocked the light from anything outside it. Maybe. It also tells us that there's at least a horizon to our view due to the age and expansion rate of our universe that is around 13 billion lightyears. But that only applies to light originating from some object which took part in OUR Big Bang. It doesn't apply to any other universe. -- Jeff, in Minneapolis .. |
#7
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Hypothetical astrophysics question
"Jeff Root" wrote in message
om... Greg Neill replied to John Griffin: Two tiny, fuzzy points of light are observed. Observations of each object indicate that it's a globular galaxy ten billion light years distant. The first one is exactly that, but the second one happens to be another entire universe. It's 100,000 times as far away as the galaxy, and it's emitting ten billion times as much light. Is there anything that would distinguish these objects from one another? I'm just curious. I haven't seen anything like that, as far as I know. Well, by current theory it would be an impossible observation for several reasons. For instance, our cosmic viewing horizon is at just about 13.7BLY, so nothing can be seen that's further. That "horizon" is imposed by the light travel time since the plasma cleared up after the Big Bang. Light from a separate universe, not involved in our Big Bang, would be temporarily blocked by the plasma, but once the plasma cleared, the light would get through. I don't know whether the geometry of the situation would allow the light to reach us in a finite time. It may depend on the size and history of our Universe. Also, to judge its distance, presumably you would rely on the hubble red-shift. Which would be completely usesless, since a separate universe would have no connection to the Big Bang which got our Universe started. No way to correlate redshift with distance. At the stated distance, if the cosmic horizon wasn't a factor, the red-shift would be extreme -- there'd be almost nothing left of the light energy to detect. Or it might be extremely blue-shifted. Or anything in between. Not to mention the fact that if you're seeing it, it's *in* our universe and not a separate universe. Under *some* definitions of "universe". Not all. Clearly, this imaginary thing had no part in our Big Bang, and existed some time before our Big Bang occurred. I think that calling it a "universe" is entirely reasonable, and I think that such other universes could very well exist-- perhaps infinitely many of them, if space is infinite. Whether we would be able to see such a distant universe is a question I'm not sure anyone can answer until we understand the nature of our own Universe a bit better. The usual definition applied to our universe is that it contains everything. If the BB scenario is taken to describe it, space itself was created and began evolving at the moment of the BB. If so, there is no space for this other universe to pre-exist in, in our frame of reference. Certainly it could not exist in our universe and be a universe itself. There can be no connection betwixt or between, so no path for light to follow. The plasma haze you refer to encompassed all of space existing at the time, and before it things just get worse. Even if anything were "outside" and shining in, our universe is likely immensely larger than our teensy drop-in-the-ocean cosmic horizon. Light entering our universe after the decoupling of matter and light would have unimaginable numbers of light years to travel to get to us, all of it in space that is moving away from us at more that the speed of light outside the horizon; it simply could not get here. |
#8
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Hypothetical astrophysics question
Jeff Root wrote:
Matthew F Funke replied to John Griffin: Two tiny, fuzzy points of light are observed. Observations of each object indicate that it's a globular galaxy ten billion light years distant. The first one is exactly that, but the second one happens to be another entire universe. It's 100,000 times as far away as the galaxy, and it's emiting ten billion times as much light. Is there anything that would distinguish these objects from one another? Redshift. The universe is expanding, and there is more space in between us and the object 100,000 times as far away; it would appear to be more redshifted. Why would it necessarily be redshifted at all? Since it's a different universe, it didn't take part in the Big Bang. It may have had its own Big Bang a quadrillion years or so ago, in which case its near side could be moving toward us at high speed. The two universes could even be moving toward or away from each other overall. To be honest, I took the OP's "another entire universe" to be a poetic description of its scale. If it were, in fact, another universe, we wouldn't be able to see it as a fuzzy point of light -- or anything else, for that matter. The entire question would be irrelevant; information (including light information) doesn't go between universes. Not to mention that spacetime is a function of being within a universe (assuming it's one like ours); speaking of universes moving "toward or away from each other" would be nonsensical. -- -- With Best Regards, Matthew Funke ) |
#9
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Hypothetical astrophysics question
"Matthew F Funke" wrote in message ... Jeff Root wrote: Matthew F Funke replied to John Griffin: Two tiny, fuzzy points of light are observed. Observations of each object indicate that it's a globular galaxy ten billion light years distant. The first one is exactly that, but the second one happens to be another entire universe. It's 100,000 times as far away as the galaxy, and it's emiting ten billion times as much light. Is there anything that would distinguish these objects from one another? Redshift. The universe is expanding, and there is more space in between us and the object 100,000 times as far away; it would appear to be more redshifted. Why would it necessarily be redshifted at all? Since it's a different universe, it didn't take part in the Big Bang. It may have had its own Big Bang a quadrillion years or so ago, in which case its near side could be moving toward us at high speed. The two universes could even be moving toward or away from each other overall. To be honest, I took the OP's "another entire universe" to be a poetic description of its scale. If it were, in fact, another universe, we wouldn't be able to see it as a fuzzy point of light -- or anything else, for that matter. The entire question would be irrelevant; information (including light information) doesn't go between universes. I was thinking of a universe as another collection of galaxies and stuff, with its own origin (big bang or whatever) occupying another part of the infinite space this one is in. It seems to me that you're saying light emitted by a universe stops or vanishes at some kind of boundary. (A universal event horizon?) I don't know if that's a consequence of the big bang theory, common sense, or just a conjecture. If it has to do with the curvature of space, can the path of a photon that doesn't collide with another object in the galaxy be described? I don't understand why this universe wouldn't be visible from "outside." Not to mention that spacetime is a function of being within a universe (assuming it's one like ours); speaking of universes moving "toward or away from each other" would be nonsensical. If photons don't stop at "the edge of the universe," what would prevent them from entering another one when they encountered it? Can you refer me to a website or some literature that addresses those questions? |
#10
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Hypothetical astrophysics question
John Griffin wrote:
I was thinking of a universe as another collection of galaxies and stuff, with its own origin (big bang or whatever) occupying another part of the infinite space this one is in. This universe isn't just "in" space. Space was created during the Big Bang. Space doesn't "surround" the universe; space is *part of* the universe. It seems to me that you're saying light emitted by a universe stops or vanishes at some kind of boundary. (A universal event horizon?) I don't know if that's a consequence of the big bang theory, common sense, or just a conjecture. AIUI, it's common sense. If the Big Bang created space, then outside the universe, there's no space for light to travel in. I don't understand why this universe wouldn't be visible from "outside." What would the light travel through? What allows the light to perpetuate outside the universe? There's also the problem that universes can have radically different natural laws, so we have no idea how EM waves would behave in that "other universe", even if one ignores what happens to it when it tries to get from one universe to another. Can you refer me to a website or some literature that addresses those questions? Try the Cosmology FAQ as a starting point: http://www.astro.ucla.edu/~wright/cosmology_faq.html It even has a good bibliography. And it's written by people you can take much, much more seriously than me. -- -- With Best Regards, Matthew Funke ) |
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