Oldness/Flatness Problem

[otseng]

This has been mentioned a couple of times in different threads: Anthropic Principle and Intelligent Creation (God) as opposed to Evolution. But, I'd like to put this in its own thread.

So for debate. Why is the universe flat? That is, why does it have Euclidean geometry?

[Viridis]

Since the main point of this thread seems to be to provide evidence for intelligent design, I think it would be interesting to consider some points in that light. It appears that the line of reasoning for I.D. is that God created the perfect conditions in the universe to give rise to life and eventually to humans. However, this begs the question: if we have an omnipotent deity with the ability to manipulate the laws of physics in any way He sees fit to create the exact universe He wants, and if humans are the ultimate goal of that creation, why bother with the universe at all? Why not just create the Earth and the Sun? What's the point of everything else?

Another thing to consider is where the universe is ultimately headed. Correct me if I'm wrong, but I believe the current measurements of the universe and its geometry lead to an ever-expanding universe, one in which all stars will eventually die out, all life will cease and temperatures will ebb to near absolute zero. For the rest of eternity. Is this part of the intelligent design? I guess the Christian answer might be that all "saved" humans would be in heaven with God at that point, but then that kind of makes me wonder what the purpose of physical creation was. Why not just create humans in spiritual form in heaven and completely cut out the physical universe?

[QED]

Somewhere along the line I'm sure I already mentioned that the observable universe must be a subset of space-time if space has expanded.

Flatness implies a critical density which is neither too large to avoid a re-collapse or too small to avoid an exponentiating separation. The critical density is one which has given life a chance to appear before everything is squashed together again or is blown too far apart for stellar formation. We can only expect to find things like ourselves present in such particular circumstances.

Knowing that we lie on this critical line and knowing that the universe is expanding does indeed imply a great deal of universe existing outside our light-cone. Chaotic inflation provides a very compelling explanation for this situation and the greater (meta) universe enables our existence through the Weak Anthropic Principle. Who said there was a mystery about our origins

[otseng]

Since the main point of this thread seems to be to provide evidence for intelligent design, I think it would be interesting to consider some points in that light.

Interesting questions, but not really relevant to this topic. Please start separate threads to address your questions.

Somewhere along the line I'm sure I already mentioned that the observable universe must be a subset of space-time if space has expanded.

Yes, you have. But, I'd like to see some evidence (rather than arguments) to support the claim.

The age of the universe is around 13.7 billion years. The farthest observable object is currently around 13 billion light years away. To me, this points to the observable universe close to the size of the actual universe. (Of course, this assumes that objects can not travel faster than the speed of light)

[QED]

Somewhere along the line I'm sure I already mentioned that the observable universe must be a subset of space-time if space has expanded.

Yes, you have. But, I'd like to see some evidence (rather than arguments) to support the claim.

That's rather ironic! I'm quite sure you're aware that we can only get the sort of evidence you're asking for (information -- generally in the form of electromagnetic radiation) within a certain range over time. In the rapidly expanding universe (an extreme understatement doubling as it was at least once every 10E-43 Seconds according to our best understandings) the expansion of space overtakes photons travelling at light speed towards us so none will have arrived here yet from regions further away than 13 billion light years. Only if space had never expanded would it be possible for us to "see" its full extent. This is only like saying that a dog running at 10MPH couldn't catch-up with a car travelling at 50MPH. Sure it's an argument, but would it not persuade you on its merits alone?

[otseng]

That's rather ironic! I'm quite sure you're aware that we can only get the sort of evidence you're asking for (information -- generally in the form of electromagnetic radiation) within a certain range over time. In the rapidly expanding universe (an extreme understatement doubling as it was at least once every 10E-43 Seconds according to our best understandings) the expansion of space overtakes photons travelling at light speed towards us so none will have arrived here yet from regions further away than 13 billion light years. Only if space had never expanded would it be possible for us to "see" its full extent. This is only like saying that a dog running at 10MPH couldn't catch-up with a car travelling at 50MPH. Sure it's an argument, but would it not persuade you on its merits alone?

Correct me if I'm wrong. But, in order for the unobservable universe to be significantly larger than the observable universe is for those unseen objects to have travelled faster than the speed of light.

From what I read, it seems like the "work-around" for this is that it is the space-time fabric itself that is moving faster than the speed of light, rather than the objects on the space-time fabric. And I'm having a hard time wrapping my head around this.

Wouldn't it still appear that the objects are travelling FTL relative to another objects? Isn't FTL speed impossible? Further, if they are moving FTL, then how would it ever be possible for any light to reach us from them? Also, I cannot understand the concept of objects being "moved" by space-time fabric being stretched. Would not the objects occupying the space-time fabric also be stretched?

[Galphanore]

[center][/center]If two objects are traveling away from eachother at very high speeds, for instance both at .75 C, they are still both going below the speed of light, and they are technically traveling away from eachother faster then light, but neither is exceeding the speed of light, but at the same time any light that emits from one of those objects would only travel at 1C, so if the two objects are going away from eachother at .75C and after traveling for 1000 years one emits light, it will actually take much longer then 1000 years for that light to reach the second object.

[Goat]

That's rather ironic! I'm quite sure you're aware that we can only get the sort of evidence you're asking for (information -- generally in the form of electromagnetic radiation) within a certain range over time. In the rapidly expanding universe (an extreme understatement doubling as it was at least once every 10E-43 Seconds according to our best understandings) the expansion of space overtakes photons travelling at light speed towards us so none will have arrived here yet from regions further away than 13 billion light years. Only if space had never expanded would it be possible for us to "see" its full extent. This is only like saying that a dog running at 10MPH couldn't catch-up with a car travelling at 50MPH. Sure it's an argument, but would it not persuade you on its merits alone?

Correct me if I'm wrong. But, in order for the unobservable universe to be significantly larger than the observable universe is for those unseen objects to have travelled faster than the speed of light.

From what I read, it seems like the "work-around" for this is that it is the space-time fabric itself that is moving faster than the speed of light, rather than the objects on the space-time fabric. And I'm having a hard time wrapping my head around this.

Wouldn't it still appear that the objects are travelling FTL relative to another objects? Isn't FTL speed impossible? Further, if they are moving FTL, then how would it ever be possible for any light to reach us from them? Also, I cannot understand the concept of objects being "moved" by space-time fabric being stretched. Would not the objects occupying the space-time fabric also be stretched?

Think of a string with an ant walking along it. As the ant walks from one side of the string to the other, the string keeps on getting pulled so it is longer. As the ant proceeds down the string, it walks a certain distance, but the length of the string is longer than the distance that the ant walked.

[otseng]

Basically I'm questioning how inflation can cause things to move faster than light.

The expansion of the Universe is a "growth" of the spacetime itself; this spacetime may move faster than the speed of light relative to some other location, as long as the two locations can't communicate with each other (or, in terms of light rays, these two parts of the Universe can't see each other). According to the theory of inflation, the Universe grew by a factor of 10 to the sixtieth power in less than 10 to the negative thirty seconds, so the "edges" of the Universe were expanding away from each other faster than the speed of light; however, as long as those edges can't see each other (which is what we always assume), there is no physical law that forbids it.

How can the Universe expand faster than the speed of light during inflation?

Even if the space-time fabric was stretching faster than the speed of light, wouldn't it still mean the objects would be moving FTL?

[otseng]

Think of a string with an ant walking along it. As the ant walks from one side of the string to the other, the string keeps on getting pulled so it is longer. As the ant proceeds down the string, it walks a certain distance, but the length of the string is longer than the distance that the ant walked.

Analogy is not quite right because objects in the universe are not independent of the space-time fabric. Whereas the ant is independent of the string.

The typical description is dots painted on a balloon. Then as the balloon expands, the dots get farther apart. But, the dots are also expanding. If space-time stretches, then all objects would also experience stretching. I would guess even atoms would experience stretching.

[QED]

Well just electrostatically "glue"some dots on the balloon. The point you're missing, I think, is that particles aren't "travelling through" space at FTL speeds, they're travelling with space.