Is Infinity Real?

Why? Do you have a problem with future time being infinite? If not, and you believe in CPT, then where's the issue?

Intuitive or not, we have to. The one theory we have that teaches us the nature of "time" has no concept whatsoever of "passage of time" - we have time as a dimension and proper time as a distance measure. There is no universal clock that ticks away some universal time, by which we all move forward through time, our conciousnesses all sharing the same "now". "Passage of time" is, as far as I can tell, simply conciousness itself - and hence wholely individual and subjective.And so there is no concept as having to wait an infinite amount of time for "now" to arrive in a Universe with an infinite past. You experience "passage of time" at your place in the Universe, and no where else. This place begins around your birth and ends around your death.

Perhaps you could list these processes so that we can check the veracity of your claim?

Sure, there's nothing odd about the entropic arrow of time (well, there is, but not in this context) - a slope on a hill has a direction of steepest descent defined at each point, but that still does not suggest that anything is "moving" - there is still no dynamics. The Universe is still a static four dimensional object, just with a low entropy end and a high entropy end.Penrose's latest ideas suggest an eternally expanding, repeatedly "Big Banging" Universe, where the heat-death approaching end-state actually creates the conditions for the next generation Big Bang... a bit like the old cyclical universe but without any big crunch.Rrhain's mistake is to assume that there are processes that can reach a real equilibrium - in a suitably expanding eternal universe, there are not. Think of our earlier discussion about the lack of thermal equilibrium/maximul entropy in a universe with accelerating exapansion.Edited by cavediver, : No reason given.

Ah, but we don't get heat death with a past-infinite cosmology, only with past-finite cosmologies: so for example, classic FRW open and flat space-times are past-finite (they have a Big Bang) and they have heat death; but de-Sitter, which is past-infinite, does not. The exponential expansion driven by the Cosmological Constant ensures that there is no state of thermal equilibrium, hence no heat death. The Universe simply gets colder and colder. Sure, in a spatially infinite universe. I'm not sure about "perfect system" but this is in danger of the fallacy of composition - which is relevant in this topic given the tired old argument of "there's nothing in the Universe that is infinite, therefor the Universe cannot be infinite." Exactly Which is why we are all about the evidence... Try here...Edited by cavediver, : No reason given.

No, but I have plenty of extensions of de-Sitter that do... This isn't relevant. The point is that I have plenty of examples of past infinite space-times that do not reach any point of equilibrium. I'm not sure what you mean by "de-Sitter status". Yes, under certain behaviours of dark energy, the Universe will approximate de-Sitter behaviour, but that is not the point. I raised de-Sitter, as stressed above, simply to give an example of a past-infinite cosmology that does not approach equilibrium, not because our Universe maybe approaching the *future* state of de-Sitter. If we did live in a de-Sitter-type cosmology, which we probably don't based on evidence, then we would exist at some finite time following the de-Sitter "pinch", the pinch being what we think of as the Big Bang. The bulk of the infinite past would be the collapsing phase of de-Sitter, prior to the pinch. Distributed over a spatially infinite Universe. You just need to start thinking of densities rather than absolute quantities. Can never be recovered? There's that equilibrium again that doesn't necessarily exist. I would be careful about trying to use conventional concepts of thermodyanamics in a cosmological setting. Most need careful revision. Yes, I appreciate that. That is why I stressed that my comment was relevant to the topic, rather than our own particular discussion.

Ok, fair enough. As long as you realise that this is not the defining characteristic of de-Sitter space... Jesus, Rrhain, do you really think so? Do you not think for a moment that maybe I know a little bit about this subject and maybe I'm not wrong? Did you not read my description of de-Sitter space? I would have thought that given you are so comfortable with the term, you would understand it. Read what I said again, go and study de-Sitter space, and hopefully the light-bulb will ping on.Here's my text again: Before making a fool of yourself by telling me I'm wrong, make sure you understand the above. If you don't know what I mean by the "pinch", you should not be using the term de-Sitter at all, other than in the context of asking questions. And if that goes for de-Sitter, it goes a million times for "instanton". Fucking Wikipedia and pop science articles. Just because they use a technical term doesn't mean that when you use it, you'll magically look knowledgeable.I'm sat here face-palming, trying to work out how to explain the role of instantons in quantum cosmology to someone who thinks I don't understand something as relatively trivial as de-Sitter space!!!Screw you guys, I'm going home...[ABE]not that you deserve it, so it's really for everyone else, but here's an image of what the de-Sitter space-time looks like - time vertical and only one space-dimension shown. Hopefully that will sufficiently illuminate what I'm saying... Edited by cavediver, : No reason given.Edited by cavediver, : 'cos no matter how pissed-off I get with incompetent students, I'm still helplessly driven to teach them... grrr...