How Are We Pushing the Concept of Infinity in Multiverse Theories?

[julcab12]

... I don't think is a waste of time and we shoudl wait for more data. If they theory makess prediction for the next set fo data (hopefully the B mode polarisation) and it matches that people will be far mroe impressed if the theoy is developed after the data is already out, then some might say it was fitted to meet the data we already know.

Odds are in favor(only way) with B mode due to some good features in such that we can deduced the confusion of radio signals, accuracy of weeping beam strategy and even with circular scan strategy and posses answers to uniformity of CMB, scale invariant of initial conditions and why Ω = 1? (cmb observations fit LCDM standard cosmological model) Which appears to be infinite?

One prediction is that gravity waves of all sizes might be apparent during the primordial universe.

Will the LCMD be consistent still?

I still find some interesting stuff in ekpyrotic prediction (cyclic universe) by Paul Steinhardt and Neil Turok. . Maybe the universe is infinite at all or Not but sure 'looks' that way for now.

 

[bapowell]

I think this is a cheat. Math allows the creation of all sorts of numbers but they might not have any physical significance. The minimum distance that we could ever move physically is the Planck length.

You know this? I wasn't aware there was a complete theory of quantum geometry. Do send it my way! ;)

As for an infinite Universe having a definite temperature, I don't think this is possible. An infinite Universe can have infinite volume and things like that but I think the temperature would be zero then. The temperature would tend to zero as it is diluted into an infinite volume.

But the big bang happened everywhere in the universe at once -- even if it is infinite. There should be no trouble in assigning an energy density to the resulting radiation that fills the universe, and questions about establishing thermal equilibrium notwithstanding, assigning a temperature to this radiation. The CMB is 2.7 K, whether or not the universe is infinite.

I'm sure I could be wrong but even given my blunt reasoning, what happens if you just keep traveling out into space. Assuming you can beat the rate of expansion and have A LOT of time, you should be able to overtake it? So what happens, do you hit a wall? the Universe's wall/bounds?

Nobody knows, but it's unlikely that the universe has a boundary (unlikely mostly in an aesthetic sense) A popular conception of a closed universe is a sphere, or more generally, a closed manifold without boundary. The universe could also be infinite (of course, it's important to distinguish between the observable universe, which is of finite volume and has a well-defined boundary, and *the* universe.)

We know singularities, they are at the centers of black holes.

The centers of black holes are examples of singularities -- singularities are a general feature in relativity. A gravitational singularity occurs whenever/wherever the gravitational field (metric) becomes infinite.

We can mark a definite point in space as a singularity yet the Big Bang singularity was everywhere or is it because we are inside this singularity which then became bigger and so from our perspective, it happened everywhere except that it didn't really happen everywhere but that everywhere was once the same place? correct?

The big bang singularity is not something that should be interpreted physically -- it is sign that the theory is broken at that point. Infinite densities and their associated singularities are nonphysical, and so ultimately something must replace the big bang singularity.

After all, all these documentaries start of with a tiny little light that explodes into everything.

Yes, and those producers should all be fired.

Also, one question: There is definitely a mechanism that enables the Universe/universes to form. We can agree on that. My question would then be what enables the mechanism that enables? so you see, we could keep on asking this question. Is there an ultimate? because even if these processes were circular, how would they even begin to exist? what mechanism enables circular mechanisms? if these processes are linear, the they tend to infinity in either direction?

Yes. Until we have a scientific understanding of the physics behind the origin of the universe, we can only resort to philosophy. The infinite regress is a consequence of not knowing the physical bounds of the process.

 

[osxraider]

Why would the Universe expand at all if it is an infinite Universe? Seems like there would be no reason for any mechanism to operate to expand the Universe if it wasn't expanding it to an amount that was "balanced" so to say. This might sound like a bad question because it might imply purpose and regardless of anything, the Universe has been observed to be expanding but...

Anyway, I guess I am simplifying it to a great extend. For example, heat flows only when there is difference of temperature. What purpose does the expansion fulfill. I mean sure, we can say that if this was slightly different or that was slightly different, we wouldn't be here to observe it but regardless of whether we are here or not, why is the mechanism for expansion operating? if not to fulfill a certain role.

Also, I tried looking into Cantor's infinity theory but couldn't make sense of it. It involves cardinality and powerset (which I have trouble grasping.)

Could someone please shed some light on this? (in a simplistic manner using an appropriate analogy?)

Also, could someone shed some light on the black hole- white hole theory? to me it sounds very appealing that there are other Universes through black holes and what we see as a black hole in out universe is seen as a white hole/big bang in another Universe. There is just one problem. What is the first black hole in this branching universe set (again comes in infinity.) But is this recognized as a plausible theory or is the M-Theory with branes more appealing?

Bapowell:I was able to understand all your responses except for the one about Planck length. Am I not right about that? the problem is we don't know what replaces the laws of physics below Planck length (or whether any law even exists that governs such a distance scale) because as far as I have gathered from sources, it should be the minimum physical distance (given the the physics we know today.) In that sense, it is incomplete but correct me if I'm wrong.

 

[bapowell]

Bapowell:I was able to understand all your responses except for the one about Planck length. Am I not right about that? the problem is we don't know what replaces the laws of physics below Planck length (or whether any law even exists that governs such a distance scale) because as far as I have gathered from sources, it should be the minimum physical distance (given the the physics we know today.) In that sense, it is incomplete but correct me if I'm wrong.

No, you are absolutely correct -- we don't know what happens to geometry on scales beyond the Planck length. You seemed to be suggesting a discrete spacetime in response to my earlier post regarding the fact that there are an infinite number of reals in the interval [0,1]. Now, I don't necessarily disagree with this view of a discrete spacetime, but we simply don't know yet what the nature of spacetime is at these scales: it could be discrete, or it coule be something else entirely.

 

[Hurkyl]

Why would the Universe expand at all if it is an infinite Universe?

Expansion is a local property. A loose analogy you might be able to visualize is to imagine standing on an immense sheet of rubber, to which you've attached a bunch of stickers. If the sheet of rubber started to distort so as to make your stickers move apart, you could say that the sheet of rubber is expanding here where you're standing, even though you know nothing about what is happening everywhere else.

What purpose does the expansion fulfill.

The word "purpose" has connotations irrelevant to physical law...

Also, I tried looking into Cantor's infinity theory but couldn't make sense of it. It involves cardinality and powerset (which I have trouble grasping.)

The notion of cardinality studied in set theory is mostly unrelated to the number +\infty that appears in continuous mathematics.

as far as I have gathered from sources, it should be the minimum physical distance (given the the physics we know today.)

To the best of my knowledge, this idea is still speculative -- there is not yet anything to back up the idea that there is a minimum distance, simply evidence suggesting we look for new theories having this property.