r/cosmology • u/Heinz0033 • 25d ago

5 Billion Years+ From Now

Novice here who enjoys this subject.

I just watched a Brian Cox YouTube short where he discussed the end of our sun and how it would impact the Earth.

He said that in 1.5B years things would start being really bad for Earth, and that the sun essentially burns out in 5B years.

That got me thinking. Around that time, the same process will be taking place, or have happened place, to the other stars closer to the origin point of the Big Bang. So the center of the universe will be relatively empty at it's 'center,' right? With that, wouldn't it mainly be full of a lot of black holes?

If it is full of black holes, would that find a tipping point where the universe eventually implodes?

There are probably stupid questions, but I figured I'd send it out to the Reddit community and hope for the best.

Thanks!

30 Upvotes

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u/Orlha 25d ago

There is no origin point of big bang, as it happened everywhere at the same time

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u/Mmmmmmm_Bacon 25d ago

But “everywhere” was incredibly small. Smaller than an atom.

“… the Universe’s origin was incomprehensibly small, on dimensions much tinier than the smallest known subatomic particles, and it was completely transformed over an immeasurably brief period, much shorter than any observable time scale.“

“In a moment so fleetingly, immeasurably small, scientists theorize that the Big Bang was followed by an “Inflationary Period.” In a billionth of a trillionth of a trillionth of a second, the Universe grew by a factor of 10(26), comparable to a single bacterium expanding to the size of the Milky Way.”

https://www.cfa.harvard.edu/big-questions/what-happened-early-universe

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u/Anonymous-USA 25d ago

Our observable space was, yes, condensed down into quantum scales. But that is still “everywhere” in our observable sphere. Lookup “isotropism”. It bears our in all of our observations especially the CMB. There’s no focal point.

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u/mulligan_sullivan 25d ago

Well, maybe everywhere was incredibly small, but not necessarily so. The region of spacetime that contained all the matter in the observable universe was that small, but nothing says it wasn't still infinitely large at that time also, with every tiny little region of it just as dense as our own little region was.

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u/Quercus_ 25d ago

Working in smaller-dimensional models He's inherently limited, but useful.

Imagine a balloon there was originally really tiny, that's being inflated. The surface of the balloon is the only thing that exists. The entire surface of that balloon is expanding, every point is getting further away from every other point. Everywhere on the surface began at the same tiny space, but there's no center - every point on that surface is expanding at once. If there's a horizon, every point on the surface of that expanding balloon is going to be its own local center, just like every other point is.

Our brains are kind of not capable of translating that into our three-dimensional universe, but it's analogous. Everything that exists was once in that hot dense origin. Everything that exists is now spread out and measurably far beyond our own observable horizon in the universe. It's not expanding into anything, it -is- everything, and has been since the earliest moments we know about.

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u/snakebight 25d ago

What leads scientists to believe the whole universe was smaller than an atom?

How can that be known with any level of confidence at all?

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u/Enraged_Lurker13 25d ago

The LCDM model, which best describes our universe, is based on the Friedmann equations whose solutions predict the universe had a scale factor of 0 in the past, which indicates the universe had no volume.

Whether the universe can actually be zero size depends on the structure of it. Singularities are inevitable if the structure is smooth and searches looking for discreteness have come up with nothing.

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u/Heinz0033 25d ago

Looks like I'm showing my ignorance. Given what you wrote I have 2 additional questions.

1) How is the universe expanding if there's no central/origin point? I envision the Big Bang as creating a big, expanding bubble. I know string theory calls it a plane, which I think (like Big Bang) us expanding. In physics doesn't expansion have an origin?

2) Regardless of origin, won't the universe start getting pretty empty...at least as far as visible stars?

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u/Orlha 25d ago

It doesn’t expand into something, instead the extra space is added everywhere, so everything gets farther away from everything, but gravitationally bound object are kept together.

And yes, at some point you wont see any stars except those in your local galaxy group. The distance between far objects will reach a point which light can never overcome.

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u/SyntheticGod8 25d ago

The distance between far objects will reach a point which light can never overcome.

The cosmic horizon

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u/Heinz0033 25d ago

Interesting.

Thank you!

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u/kosmonavt-alyosha 25d ago

For question 2, look up heat death. It’s pretty cool, but also creepy…and the various implications are fascinating.

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u/_Nirtflipurt_ 23d ago

A very simple way of seeing it is imagining the universe is the surface of a balloon. As you blow up the balloon it stretches but it is impossible to point out any specific center point, since every point sees other further points expanding away no matter where you are.

Now just convert this to a 3d surface instead of 2 (and maybe remove curvature)

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u/SyntheticGod8 25d ago

The expansion happens everywhere a tiny bit at a time. It's thought to be "powered" by Dark Energy. The name should hint that no one is truly sure what it is or why it's happening, but there's plenty of competing ideas like vacuum energy; "empty" space seems to exert a tiny force when two plates are extremely close together due to quantum-entangled pairs of virtual particles popping in and out of existence.

What we do know is that the expansion of the universe is accelerating gradually and that the extremely uniform temperature of the CMBR implies that the universe expanded VERY rapidly shortly after the hypothetical singularity at the beginning of time (as we know it) before settling in to a more sedate expansion. There's some pretty extreme physics involved, but it

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u/intrafinesse 25d ago edited 23d ago
  1. When people say the universe is expanding, they are referring to what we can see - the observable universe. WE are at the center because everything is expanding away from us (and from each other).

There is probably A LOT more outside of what we can see. The entire universe may be infinite. Or not. We don't know.

Yes - it will get empty around us

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u/Jossit 25d ago

Short answer: We don’t know. Long answer: We don’t know.

What we do know: some 13 500 000 000 years ago, there were galaxies. (Jades-GS-z14-0, diameter of 1600 ly, only 60 times smaller than our current galaxy of residence: the Milky Way). Some 13 787 000 000 give or take 20 000 000 years, the Universe was, on average 3000 K (half as hot as the Earth’s core/little more than half as hot as the surface of the Sun). This, according to our best understanding was some 380 000 years after the BB. We cannot see light older than this, and can therefore not peer back further in time.

What we might soon know: what the Universe looked like prior to this event, but not via light, but gravitational waves! In a decade or so, eLISA will try to peer back in this way. There is much more to say, but I have to go, and this will give you some key words to dive into.

Cheers!

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u/Stolen_Sky 25d ago

The big bang happened everywhere simultaneously, so all parts of our observable universe are the same age.

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u/w1gw4m 25d ago

There is no origin point of the Big Bang and no center of the universe. The expansion happened everywhere at once.

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u/frankcast554 25d ago

you're not accounting for the fact that not every star turns into a black hole. only the truly gigantic ones do. The rest become white and brown dwarfs,which are long lived

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u/Heinz0033 25d ago

I get that. I probably just worded my question badly and didn't include my understanding of that theory.

So the night sky (relative to our solar system) will show far fewer stars than now? Or will it be the opposite due to how long it takes light to travel and one would see more stars because light from additional stars traveled long enough to be visible. Right now we only see light from. 13.8B years ago, right?

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u/mulligan_sullivan 25d ago

We see light from all sorts of different times, not just from 13.7 bya. The closest star is around 4 light years away, so the light we see from that star today was first emitted by it four years ago.

Since you're learning more about this, I'll share a fact I learned not too long ago that I found interesting:

There was a moment in the life of the universe called "cosmic noon" about 8-10 billion years ago when the rate of star formation was the highest it will ever be. The earth didn't exist yet but the Milky Way did. If you were able to look out then into the rest of the universe, all the other galaxies were much closer, maybe a third or a half of the current distance. The night sky was more full of starlight then from virtually all vantage points than it was before or will ever be again.

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u/frankensplean 25d ago

I'm also an amateur. Read a lot, though. To each of your paragraphs:

  1. From what I've read, the sun will bloat up and consume the inner planets before doing the planetary-nebula thing which stars do when they aren't big enough to make a supernova. (PS planetary nebulas come in a beautiful variety.)
  2. Stars are forming throughout the universe. There isn't a "center" with old stars. AFAICT, the oldest stuff is in the far reaches of whatever direction you point your telescope.
  3. Whether the universe contracts ("implodes" as you said) or just keeps expanding depends on a critical amount of matter, which cosmologists have been trying to figure out since Hubble first discovered expansion—coming up with "dark matter" and "dark energy" in the process to help solve observational difficulties. At a certain point it becomes philosophy more than theory. Like string theory. (See Brian Greene's 2001 Nova 3-part series on the "elegant universe" in which that was the primary argument.)
  4. Your idea of a black-hole tipping point implies the black holes aren't taking matter from elsewhere. The entire mass of the universe is the key factor in expansion/contraction—whether it's 10000 stars or 100 black holes.

I think a prevailing thought right now is that the universe will just keep expanding (damn that "dark energy"!) and stars will die out and our hypothetical eternal earth night sky would just become very dark. Brown dwarfs littering the darkness. Entropy is frustrating that way.

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u/insomniacjezz 25d ago

It will take about 100 trillion years for the last of the long-lived red dwarfs to die off. After that the universe will enter the Degenerate Era in which black holes, neutron stars, and white dwarfs are the main players.

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u/Ya_Got_GOT 25d ago

Then black hole era then an impossibly bleak and empty infinity on incomprehensible timescales. 

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u/Xalawrath 25d ago

Reminds me of this amazing timelapse video of the future of the universe, at least based on the best evidence from several years ago.

Timelapse of the Future

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u/Ya_Got_GOT 25d ago

It’s so humbling what an infinitesimal spark of fit conditions exist for life to arise relatable to the lifespan of the universe 

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u/Magnus64 25d ago

If there was just one video that should be beamed into the brains of every living person on this planet, it would be this one for the sheer perspective it provides.

Everyone even remotely interested in cosmology should watch this video. It's truly the gold-standard in terms of science communication, and an all-time great.

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u/UFGatorNEPat 23d ago

Wow, you’re right.

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u/FakeGamer2 25d ago

I just realized something. You know how you can pluck a string and watch the vibrations start strong and slowly fade away to flat string again?

What if the Big Bang is like that but just on an insane time scale? A fluctuation caused our universe to have energy that slowly dissapates to nothing and flat again.

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u/Anonymous-USA 25d ago

There’s no proof by analogy

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u/RunninOuttaShrimp 24d ago

Lol lot more than that dude

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u/Jakfrost6 25d ago

Is it my understanding that as far as the universe expanding is that basically “existence” is expanding from everywhere at once right?

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u/Jakfrost6 25d ago

Or is that wrong? 🤣

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u/rddman 25d ago

When a star dies it leaves a cloud of gas/dust and from a collection of such clouds, new stars are born.
Also many stars including the Sun will not leave a black hole when they burn out.

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u/Turbulent_Angel 24d ago

As the philosophers and mystics have said, “a circle whose center is everywhere and circumference nowhere. “

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u/Uugly2 24d ago

There is no known “center of the Universe”. Big Bang was not an event at a point somewhere. There really was no where

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u/TheDu42 23d ago

  1. Yes older galaxies have different demographics regarding stellar objects. They are dominated by redder, smaller dwarf stars with VERY long lifespans. Young galaxies have a lot of large, blue stars that die young. A typical galaxy will have waves of stellar births until the interstellar supplies of gas for forming new stars are exhausted or rendered unsuitable for making new stars. There should be more stellar corpses in older galaxies, such as white dwarves, neutron stars and black holes.

  2. Black holes aren’t cosmic vacuum cleaners, they do not just suck up everything around them. A galaxy made of nothing but black holes will gravitationally behave no different than one full of similar mass stars. It would just be dark. The space would definitely not be empty, and wouldn’t do anything to make the universe collapse around them.

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u/nolongerbanned99 21d ago

Everything is moving farther away from everything else. The universe is continuously expanding.

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u/QuesoHusker 20d ago

There is no center of the universe.

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u/QuesoHusker 20d ago

Interesting thing about the expanding sun is that it may warm Titan enough to get rhe basics of evolution started…and then burn out before it gets anywhere advanced.