Yes - the Einstein topic was a digression meant to make it clear what a theory is in scientific method/natural sciences. The big bang expansion rate was far, far greater than the current expansion rate - the rate has not been constant. One actually has to measure today's expansion rate. The size of the observable universe today depends on today's expansion rate. If the expansion rate were to change, we would be able to observe more (or less) of the total universe. What we can observe is everything between Earth and the distance where the expansion of the universe becomes faster than the speed of light. Since the speed of light is a hard core limit, even light that is emitted from stars beyond that point can never, ever get to Earth. It's my understanding that there are several ways to measure the expansion of the universe. And unfortunately, there is room between the results of the various measurement methods that is a little bit more than what can be written off as measurement error - a serious issue in astrophysics today.
I can't. The numbers I quoted were calculations made by scientists. I have no reason or knowledge to question them.
Current measurements of the expansion rate of the universe are about 72 kilometers per second per ~3.3 million light years. The radius of the observable universe is measured to be 46.5 billion light-years. Anything farther away that that can't be seen, because the expansion of the universe at that distance is faster than the speed of light. Light from beyond that radius can not ever reach us. Stars, galaxies, etc. are flying from the observable portion of the universe into the portion that we can not observe - never to be seen again.
Only if you can keep going for infinity will you discover if there are any boundaries. Anyway, the onus is on you to prove your claim since you made the initial statement "It has to have a limit. Infinity doesn't exist in nature"
You have that backward. I said there is no evidence of infinity in nature. And there isn't any. The fact that someone else can't prove their side is immaterial. Common sense tells one that infinity is nowhere to be seen. Logic doesn't lead to it either.
Wrong! You said that "It has to have a limit". That is a definite statement. You were the first one to give a definite statement.
You have argued that the universe is finite. You haven't given any actual evidence, but that has been your cliam. I've pointed out that astrohysicists do not support that claim. They tend to hold that it is UNKNOWN whether the universe is finite or infinite. I don't know of any post on this thread where the universe is claimed to be infinite.
Suppose that we existed a billion years later, how little we would be able to see...........nothing much but darkness. I wonder how that would have changed our appreciation of the universe.
Yes - this universe seems headed toward darkness, and then further falling apart from there. It's weird to contemplate. On the one hand, it's so ridiculously far in the future as to be irrelevant. On the other hand, it looks like there will be an end to absolutely everything.
It's difficult to know where it will all end. The data seems to show that the rate of expansion is increasing, hence dark energy; but it's hard to accept that as we don't know what it is. There are theories that postulate a series of cyclical universes, a big bounce instead of a big bang, but that would require our universe to start contracting at some point. At any rate, I won't be around to find out.
Yes, it's hard to come up with a force that would overcome the current expansion. But, there are models of the universe where the expansion reverses to contraction - at least as I understand it.. I'm glad there are people looking at these issues, as it might just lead to a better understanding of the problem of Einstein gravity not matching quantum mechanics. In my wildest dreams it might lead to a revolution like the one from Newton to Einstein, where today's physics is intact, but that there is an important generalization that opens vast new possibility.
Yes, you provided the size of the observable universe. You will remember that I agreed with you on that. But, there is NO PHYSICIST who thinks that is the limit of the size of the universe. It is just the size of the portion that is observable. Beyond that limit, the expansion of the universe is faster than the speed of light, so there is no possiility of us observing anything beyond that distance. Beyond that distance, light from stars or galaxies will never reach us. You may hear physicists and others talk about the size of the universe when they actually mean the size of the observable portion. That's a reasonable shorthand for many discussions, as there are a lot of astrophysical issues that can be discussed without qualifying by repeatedly saying "observable".
There really is a lot that nobody knows yet - certainly not for sure. Can you imagine how boring science would be if humans had figured out all the answers?
