Aliens: Yes Or No?

[Corinnguard]

How did a discussion on whether or not intelligent alien life exists turn into the age, size and fate of our universe?

 

[MarkB]

How did a discussion on whether or not intelligent alien life exists turn into the age, size and fate of our universe?

Because those are factors in considering the potential development of life in the universe.

 

[Corinnguard]

Because those are factors in considering the potential development of life in the universe.

One of many. There is also the issue of that intelligent life being carbon-based or being the result of some alternate biology. Hypothetical types of biochemistry - Wikipedia

 

[Umbran]

How did a discussion on whether or not intelligent alien life exists turn into the age, size and fate of our universe?

Well, part of it is that my graduate physics training was alongside some top cosmologists - so if you flash some misconceptions in front of me, I'm apt to try to dispel them.

Because those are factors in considering the potential development of life in the universe.

... and in whether or not there can be effective travel/communication between inhabited worlds.

 

[payn]

Timely this thread for my rewatch of The Outer Limits

 

[tomBitonti]

Ultimately it's semantics, but there are a couple of sensible reasons to say eternal inflation leads to a multiverse.

First of all, there is a boundary of sorts, even if a soft one. The space between two bubbles is still inflating and will do so forever, so you will never be able to travel from one bubble two the other, while in principle you could visit every region within a single bubble if you had infinite time (and no dark energy).

In addition, while the high-energy limit of physical laws will be identical for all the bubbles, we are not guaranteed that symmetries that breaks at energy lower than those of the post-inflation reheating scale (which will itself be different in each bubble) break in the same way in the various bubbles.

You might not be able to visit an entire single bubble. Non-observable regions are not reachable, if expansion continues at at least the same rate, since the distance to a non-observable region gets bigger faster than it can be traversed.
TomB

 

[briggart]

You might not be able to visit an entire single bubble. Non-observable regions are not reachable, if expansion continues at at least the same rate, since the distance to a non-observable region gets bigger faster than it can be traversed.
TomB

I admit I was implicitly assuming that other potential bubbles would be similar in composition to our own, so matter, radiation, and possibly curvature and dark energy. In this case, if there is no dark energy, the expansion rate will always be decreasing and there is no upper limit to the distance light can travel, given enough time.

I guess it's possible to have something that is not dark energy, but nonetheless with an equation of state negative enough so that the expansion rate increases with time, in which case as you said there will be regions within a single bubble that will not be reachable.

 

[tomBitonti]

I admit I was implicitly assuming that other potential bubbles would be similar in composition to our own, so matter, radiation, and possibly curvature and dark energy. In this case, if there is no dark energy, the expansion rate will always be decreasing and there is no upper limit to the distance light can travel, given enough time.

I guess it's possible to have something that is not dark energy, but nonetheless with an equation of state negative enough so that the expansion rate increases with time, in which case as you said there will be regions within a single bubble that will not be reachable.

Current evidence is that the rate of expansion is increasing.

I’m intrigued by two follow up questions: For a time-like curve that is continued indefinitely in to the past and future, for every other such curve, is there always at least one light-like path from a point of the first curve to a point of the second curve? What if the curves are continued only until the end of the early inflationary period? And, can there be points which remain un-observable even if the rate of expansion is asymptotically 0?

TomB

 

[CleverNickName]

 

[MoonSong]

I'm very late to this party, but I voted no. Maybe the universe is infinite, but short of a "basically magic" breakthorugh, we are limited to the observable universe. Anything outside is unobservable, unknowable and impossible to interact with, so it doesn't matter if there are countless civilizations in a galaxy far away many universes over, it is the same as they not being there. And well, the observable universe is finite, and within it, I think we are the only ones. Even if we aren't, short of "basically magic" advancements, we'll never meet another sentient species. And that is assuming there is anybody there. I'd bet there are none. Evolution is aimless and never guaranteed to create complex life, let alone intelligent life. So TLDR: I think the Drake Equation actually amounts to 0 and we are the rounding error.

And well, belief in "we are being visited" and stuff, well it is the same belief in witches, imps and succubi, just with another coat of paint. One that is dressed in a sci-fi coat of paint, but not fundamentally different. Heck, a lot of contactees claim aliens "are extradimensional visitors" which muddies the waters.