The universe is expanding faster than expected • Hacker News Board

Re: The universe is expanding faster than expected

#181

Post by johnnujler » Tue, Dec 22, 2020, 5:25 AM UTC

vecter wrote: post #176

johnnujler wrote: post #172

Forgive my ignorance here. What do we mean when we say the universe is expanding, expanding into what. My untrained brain is trying to look at it like the inflation of a balloon that takes up more space when it is inflated, but if the universe is all the space there is, what would it even mean for it to expand. Is there space outside our universe that is like unfilled or something?

Your balloon analogy is almost correct but it's missing one important piece. In that analogy, the surface of the balloon itself is the entire universe. It is a two-dimensional universe. Imagine that there is no other space except for that surface of the balloon. No emptiness inside and no space outside that it's "expanding into". The entire space is the infinitesimally thin surface which is the balloon surface, yet i…

Ah! That makes sense. I realise that talking about complex concepts in terms of analogy can be misleading, but is it like the fabric is elastic and long enough and is only getting stretched? Is there a way to reconcile this with the (3 dimensional) inside and outside aspect of our experiences.

Re: The universe is expanding faster than expected

#182

Post by throwaway201103 » Tue, Dec 22, 2020, 5:29 AM UTC

bouncycastle wrote: post #166

dheera wrote: post #147

Earlier quoted context omitted.

The biggest "concern" I have about the expanding universe is that although I have a lot of hope for interstellar travel at some point in the coming few millenia, intergalactic travel poses a whole another set of impossibilities to face, that I'm worried it will never be possible. The space between galaxies is pretty devoid of anything you can use as fuel, repair materials, or anything else. That space is expanding, a…

However, after the universe finishes expanding, wouldn't it start contracting again? Btw, Andromeda will collide with the Milky Way in about 4 billion years, so at least we won't need ten times the mass of Mt. Everest to get there...

If you subscribe to Roger Penrose's theory, at the point of infinite expansion, the current "Aeon" will end and a new big bang will happen. As best I understand it, at the point of infinite expansion, there are only photons. Mass no longer exists therefore scale no longer exists. So an infinitely huge universe becomes indistinguishable from an infinitely small universe.

Re: The universe is expanding faster than expected

#183

Post by brodie » Tue, Dec 22, 2020, 5:29 AM UTC

johnnujler wrote: post #181

vecter wrote: post #176

Earlier quoted context omitted.

Your balloon analogy is almost correct but it's missing one important piece. In that analogy, the surface of the balloon itself is the entire universe. It is a two-dimensional universe. Imagine that there is no other space except for that surface of the balloon. No emptiness inside and no space outside that it's "expanding into". The entire space is the infinitesimally thin surface which is the balloon surface, yet i…

Ah! That makes sense. I realise that talking about complex concepts in terms of analogy can be misleading, but is it like the fabric is elastic and long enough and is only getting stretched? Is there a way to reconcile this with the (3 dimensional) inside and outside aspect of our experiences.

I think it’s more like the balloon analogy or baking bread analogy is required because there’s no good way to explain what we observe without either analogies or math or unintuitive descriptions.

That doesn’t mean there can’t be a higher spatial dimension that our observable universe is part of; we just haven’t observed it or can’t observe it.

I guess we’re sort of like ants crawling on the surface of an opaque, seemingly-indestructible balloon. We’re pretty clever ants, but we probably aren’t gonna peer inside the balloon anytime soon.

Re: The universe is expanding faster than expected

#184

Post by r00fus » Tue, Dec 22, 2020, 5:59 AM UTC

drukenemo wrote: post #143

chanakya wrote: post #126

Can someone explain why the universe is expanding at all? I've heard it said "it's the momentum from the Big Bang". That sounds reasonable, but then we're told that it's not that the galaxies are flying apart, it's that the "basic metric of space itself is expanding". I can understand momentum from an explosion, but why would "space itself" expand because of an explosion?

I’m amazed how the God hypothesis seems to not exist amongst the modern, smart tech world. Everything is science, science one day will know...

The answer being “god” is not useful. You can’t use it to predict or measure (people have certainly tried for millennia) phenomena therefore it isn’t worthy of discussion outside the purely philosophical.

Re: The universe is expanding faster than expected

#185

Post by renewiltord » Tue, Dec 22, 2020, 6:23 AM UTC

grey-area wrote: post #9

eloff wrote: post #6

Earlier quoted context omitted.

I appreciate your optimism. I tend to be optimistic about the future myself. But there is no law of the universe that everything will work out ok. Only if we make the right decisions as a species and we don't get unlucky. I'm quite apprehensive that the great filter lies ahead - that technology accelerates too rapidly compared to our wisdom and we end up nearly destroying ourselves. We're getting the ability to progr…

I believe the OP said 0K, not OK. There may not be a universal law which says everything will be OK, but there is one which says everything will be 0K in the end.

Not zero, just zero potential.

Re: The universe is expanding faster than expected

#186

Post by eurasiantiger » Tue, Dec 22, 2020, 6:50 AM UTC

est31 wrote: post #154

atomi wrote: post #151

Earlier quoted context omitted.

There is also one of my favorite talks tangentially related by Lawrence Krauss. He explains that eventually a civilization exploring the universe around them will only see it's own galaxy and likely believe that's all there is. We are living in an extraordinary time where we are still able to see other galaxies. https://www.youtube.com/watch?v=7ImvlS8PLIo

I can imagine scientists in a couple billion years debating whether the historic records of other galaxies existing should be believed or whether one should dismiss them as crazy religious texts someone faked a couple million years ago... (obviously by then we'll probably uploaded ourselves to computers and turned into totally different beings from what we are now, but the problem of trusting historic data still exis…

Finally, an actual use case for a blockchain!

Re: The universe is expanding faster than expected

#187

Post by 867-5309 » Tue, Dec 22, 2020, 6:55 AM UTC

dave_sid wrote: post #93

yokem55 wrote: post #4

Earlier quoted context omitted.

Don't worry too much about it. In the end, everything will be nearly 0k.

I don’t think this joke quite got the credit it deserves.

> The Big Freeze (or Big Chill) is a scenario under which continued expansion results in a universe that asymptotically approaches absolute zero temperature.

https://en.m.wikipedia.org/wiki/Ultimate_fate_of_the_univers...

absolute zero == zero kelvin == 0K

Re: The universe is expanding faster than expected

#188

Post by Razengan » Tue, Dec 22, 2020, 7:03 AM UTC

vecter wrote: post #176

johnnujler wrote: post #172

Forgive my ignorance here. What do we mean when we say the universe is expanding, expanding into what. My untrained brain is trying to look at it like the inflation of a balloon that takes up more space when it is inflated, but if the universe is all the space there is, what would it even mean for it to expand. Is there space outside our universe that is like unfilled or something?

Your balloon analogy is almost correct but it's missing one important piece. In that analogy, the surface of the balloon itself is the entire universe. It is a two-dimensional universe. Imagine that there is no other space except for that surface of the balloon. No emptiness inside and no space outside that it's "expanding into". The entire space is the infinitesimally thin surface which is the balloon surface, yet i…

But what's filling the space between the dots?

Is it new space?

If I have a long ass string, is the string gradually getting longer, or will it break apart?

Re: The universe is expanding faster than expected

#189

Post by lisper » Tue, Dec 22, 2020, 7:08 AM UTC

User23 wrote: post #168

lisper wrote: post #159

Earlier quoted context omitted.

> Astronomy is a phenomenology OK, again this would come as a surprise to most astronomers. Are you aware that we have sent spacecraft to other planets, and that humans have walked on the moon?

I think you might want to review the site guidelines[1]: "Please respond to the strongest plausible interpretation of what someone says, not a weaker one that's easier to criticize. Assume good faith." [1] https://news.ycombinator.com/newsguidelines.html

Except that you have given me evidence that you are not dealing in good faith. You have chosen to be cagey about your beliefs, so I am making as few assumptions about them as possible. I don't know if you're a YEC, a flat-earther, or a lunar landing denialist. People exist who subscribe to all of these positions, so unless you tell me otherwise, I'm perfectly justified in considering the possibility that you might be any of these things.

Re: The universe is expanding faster than expected

#190

Post by vecter » Tue, Dec 22, 2020, 7:17 AM UTC

Razengan wrote: post #188

vecter wrote: post #176

Earlier quoted context omitted.

Your balloon analogy is almost correct but it's missing one important piece. In that analogy, the surface of the balloon itself is the entire universe. It is a two-dimensional universe. Imagine that there is no other space except for that surface of the balloon. No emptiness inside and no space outside that it's "expanding into". The entire space is the infinitesimally thin surface which is the balloon surface, yet i…

But what's filling the space between the dots? Is it new space? If I have a long ass string, is the string gradually getting longer, or will it break apart?

More space. It's pretty nuts. Imagine you were stretching a rubber band. What's in-between two points on that rubber that was stretched? Just rubber, albeit thinner and less dense.

In our universe, however, the space that's created is the same as the space that was just there. It'd be like if the rubber band stretched, but didn't lose any density while it did so.

Insane, I know.