chess211

I used an estimate of 45 billion lightyears, from memory, apparently slightly out of date. Apologies.

It is fine. The answer does depend on assumptions about the size of the universe anyways, as it is always possible that the actual universe is smaller than that are what is seen on the edge has circumnavigated the universe before.

Anyways, any question of exploring the universe depends on the size of the universe. Currently there is no reason to assume that the observable universe is equivalent to the size of the universe. If you just restrict it to a single galaxy, then in the lifetime of the universe exploring a galaxy is technically possible, even if it is difficult.

As for the impact of the expanding universe on the entropy of the universe, that is not something that I am familiar with. I have not dealt with cosmological aspects of anything in my research, so I am not qualified to talk about it, which trying to find some papers about it.

All well and good, but you're yet to explain how a civilisation could explore 3.817×10³² ly³ of space in under a million years, without exceeding lightspeed.

Sweeney, if you are going to give the number you might as well give the more accurate one based on the evidence we have which has a radius of about 46 billion light years, due to the wonderful expansion of space is much larger than just using the age of the universe estimate.


Coltrom: You might have misunderstood what I said. It is not that time is a product of entropy, but that the direction of time is probably found from entropy. Time itself is understood as just being the 'fourth' dimension of the 4D manifold of general relativity. The trick of time travel in this understanding of the arrow of time would be to just be in a near maximal (global) entropy state, as a state of maximum (global) entropy does not have a preferred direction of time except for the mentioned rare particle events.

Lowering entropy in one area does not allow for time travel, as any process that requires the input of heat (such as any endothermic reaction) generally involves the local decrease of entropy but none of these processes are evidence of time travel.

Dark Energy is a concept unrelated to the direction of time, and also unrelated to the concept of entropy.

Coltrom: Just as a clarification, time symmetry is not always found in the interaction of subatomic particles. While CPT symmetry is always found, there are a number of interactions that violate CP symmetry, thus T symmetry must also be broken at those levels. Thus time is not a true symmetry of the Standard Model of Particle Physics, which is currently the best model that we have. While the effect is small, this provides a slight preference for one direction of time compared to the other at the particle scale. It is also unconnected to the macroscopic idea of entropy, which is what we see as the cause of the macroscopic arrow of time.

The current belief of why we have a macroscopic arrow of time due to entropy is because for some reason the early universe was a state of very low entropy, if it had been a state of high entropy then there would be no arrow of time, as local processes could occur with little impact on the global entropy due to it already being at a high level.

It is just the rerelease from the negg miniquest. Evidently it can give out some great prizes, on the boards some people are claiming a Parasol of Unfortunate Demise (~2 mil), Hasee (if just the plushie as some suspect ~79k, else ~5 million).

My favorite thing about my GF is how much she cares.
I have a tendency to not eat when I'm super busy or super sick and she's always reminding me to take care of myself (:

Kind of sad, but I have a similar issue except that I tend to skip eating most of the time unless my girlfriend reminds me about it. I almost always have something else that I could be doing instead of eating.