Volkov

This common theory is outdated. There is a newer one, but I don't know much about it.

Time is always around, whether we observe it or not. To think that the universe just came out of nothing like that would require the external impulse of God, and therefore, this older theory is nothing more than a secular creation myth. See http://www.marxist.com/science/bigbang.html in order to find out just how asurd the old Big Bang Theory is.

epepke

Sorry; it was sloppy writing. I was tired. I should have written more precisely that spacetime can easily be modeled using quaternions.

In the normal formulation, there are three spatial dimensions and one time dimension, but the time dimension works differently from the spatial dimensions. The difference can and has been modeled in several ways. There's Minkowski space. There's using standard real 4-vectors and changing the formulas to have minus signs. There's pretending that time is imaginary and just using standard vector math. There's pretending that the three spacial dimensions are imaginary. Those are quaternions. There's some overlap between the different ways, and there's some leeway to where you want to put the difference between time and space, but they are all equivalent in the sense that they all work and produce the same results.

While quaternions get used a lot with spinors and stuff like that, for some reason they are not too popular in GR. I think that's a shame, as they work beautifully, and the rules of i, j, and k give you the right-hand rule for free. Some other people like them too: http://world.std.com/~sweetser/quate...ex/qindex.html .

Now, it's my gut feeling and my experience, though of course I cannot show evidence that it is always this way, that when a physical phenomenon fits a natural mathematical structure this well, that exploring the mathematical structure can provide clues to the physical phenomenon which often turn out to be correct. It's the idea that particle physicists use when they look at symmetry groups. Something like this has already happened with quaternions. Unit quaternions can model orientations in 3-space, and they do so rather nicely, but there are two quaternions for each obvious orientation. It turns out that this is consistent with geometry; if something is attached by a ribbon to something fixed, rotating the object 360 degrees in any direction twists the ribbon, and then rotating it again 360 degrees in any direction untiwsts it. (The ribbon may have to be passed around the object to untwist it, but this does not require additional rotation.) So I think that at least it's a worthwhile way of generating hypotheses or guesses.

Quaternions belong to a family of numbers mostly discovered/invented by Hamilton, and they include real numbers (1 coefficient), complex numbers (2 coefficients), quaternions (4 coefficients), octonions (8 coefficients), sedenions (16 coefficients), and I forget what (32 coefficients), and there aren't any more. There doesn't seem to be a fixed name for these things, so I'll call them Hamiltonian hypercomplex numbers. One thing to notice is that they only come in these numbers of coefficients and don't come with 5 or 64 or 37 coefficients. There are some other numbers that hang off of these. I think we can ignore the Davenport hypercomplex numbers because they don't work with spatial rotations. (Even though it's nice for restoring commutativity.)

So, assuming that quaternions work, what would that imply about Hawking's imaginary time? It has time along one real access and suggests that close to the big bang, the timeline shoots up vertically into an imaginary axis. This avoids a sudden stop at year dot. But what exactly would this imaginary axis be? If spacetime is modelable as a quaternion, then the spatial dimensions are already complex, and you can't just tack on an extra dimension to take care of time without making it not work in an algebra. So where does time go (or ungo, as we're going backward in time)?

One could guess that the time dimension bleeds over into all three spatial dimensions. But that happens already in SR, and the photon is the ultimate example of this, and that's mundane. OK, so maybe spacetime isn't really a quaternion; maybe it's a biquaternion, that is, a quaternion with complex rather than real coefficients. These still work, because complex multiplication is commutative. So maybe time and space bleed off into the imaginary values of their coefficients.

Or maybe there's another way of going about it. The best string theories I've seen so far fit in nicely with sedenions, which are also Hamiltonain hypercomplex numbers. The extra dimensions are presumed to be quite small and looped like the dimensions of a torus. But, go back far enough, and the universe is quite small. Maybe there was a kind of breaking of symmetry between all of these dimensions, and time bleeds over into some or all of them.

I find the questions fascinating, but I don't have easy answers.

Iacchus

With respect to time, there's nothing to say it didn't exist, just that there was no material yardstick by which to measure it. As for existence itself, it would have to be immaterial (some form of latent energy?) and brings to mind the notion of cosmic consciousness. Well, heck you asked ... Of course has anyone ever considered the possibility that the structure we find within thought is what gave rise to everything else?

Answerer

There are several theories on it but here we goes:

1) A cyclic universe theory-There is another universe just like ours before the Big Bang, it met its end and universe exists as a result.

2) Multiverse theory- Our universe might just be one of the many universes "born" in an infinite cosmic ocean due to quantum fluctation

3) Baby universe theory- Our universe was originated from an evaporated black hole found in another universe (note that the physics in the "parent" universe might not be the same as ours)

4) Parallel universe theory- Our universe was one of the various existing unverses found across the multiverse and each universe's natural laws was almost similar to each other and they existed because of multiples probablity results of the wave function.

5) Creationist theory- Well, you know the myth...........................

epepke

This one's particularly interesting. If the physics in the parent universe affected the child universe to some degree, something a lot like evolution would take place. Universes that were good at making black holes would come to predominate. It wouldn't exactly be the same as biological evolution, because there would be no competition amongst universes for resources, but there would be some kind of natural selection. Universes that destroyed themselves too early to form black holes would not reproduce.

Tom Sawyer

The problem with this idea is that physics (as we know it) breaks down at the level of the singularity. That's why we can't say what came before the Big Bang. Regardless of what the physics were in the parent universe, there's no way that information, including laws of physics, could come through the singularity, so there's no reason to suspect that laws of physics in the parent universe would have any relation to laws of physics in the child universe.

Jesse

Many physicists think that our final theory of quantum gravity, whatever it is, will get rid of the infinities (singularities) which appear in classical general relativity, in much the same way that quantum physics eliminated the prediction from classical physics that a blackbody would eliminate radiation with infinite power, a problem known as the ultraviolet catastrophe.

show_no_mercy

This is what boggles my mind. If there was no "time" before the big bang, then how could there have been enough time to create time via the big bang? (I realize that I stole that line from another thread, but it's the same premise )

Autonemesis

It's like what's North of the North Pole.

Plastic Jesus

Agreed. Time is the measurement of change. If there was no time, no change in the universe, then it is impossible for the status of the universe (and time) to go from non-existant to existing (unless the universe had an uncaused cause, such as the divine, which is a theory that is a bit hard to accept). If there was change that ushered in our universe, then there was time, and we'd have to search even further and further back for our origins.

But, then again, I haven't read the other thread, so if my stand has already been argued away, just ignore me.