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A few years ago I learned the fate of the universe, and my exact place in it - hit me pretty hard. Anyone else share similar experiences?

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I don’t let it bother me as it’s something that may happen or not and would be billions of years after I’m gone and theories on the subject come and go so the fate of the universe is unknown as far as I’m concerned anyway. 

Edited by johninderby

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5 hours ago, Atlas629 said:

A few years ago I learned the fate of the universe, and my exact place in it - hit me pretty hard. Anyone else share similar experiences?

Why don’t you share a bit more about what you found out and why it’s bothering you? 

Personally I have always found that contemplating the universe is comforting as it puts my every day problems into perspective. But I have been into astronomy since I was 14 and so I probably never went through the process of contemplating the wider questions such as the reasons, significance, context and impact of the universe on our human existence. For me, it’s just there to be discovered! 

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I'm not personally bothered by the fate of the universe of even our solar system. The Milky Way and Andromeda galaxies are on a collision course in about two million yrs. They will crash into each other and form one combined Galaxy. Not sure how the universe will end, if it does. Surely it will just keep expanding.

I have faith in humanity and technology, that we will be travelling interstellar by then. Generational ships or colonies on suitable exo planters.

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1 minute ago, LukeSkywatcher said:

I'm not personally bothered by the fate of the universe of even our solar system. The Milky Way and Andromeda galaxies are on a collision course in about two million yrs. They will crash into each other and form one combined Galaxy.

 

4 to 5 BILLION, not million actually.

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6 minutes ago, Xilman said:

4 to 5 BILLION, not million actually.

I thought it was millions. I know the Sun will die in about 4 billion yrs and take out all the planets between itself and Jupiter.

Sure none of us will be around either way.

Edited by LukeSkywatcher

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Acutally there won’t be any crashing as galaxies are mostly empty space so will pass through each other and gravity will make them form one bigger galaxy.

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4 minutes ago, johninderby said:

Acutally there won’t be any crashing as galaxies are mostly empty space so will pass through each other and gravity will make them form one bigger galaxy.

Symantics. You know what I mean. People living on Earth probably wont feel a thing. The night sky will change. I'm not saying overnight. I'd love to be here to see it.

Best example of two galaxies colliding and passing through each other are the LMC and SMC.

Edited by LukeSkywatcher

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Just now, johninderby said:

Acutally there won’t be any crashing as galaxies are mostly empty space so will pass through each other and gravity will make them form one bigger galaxy.

Although very few stars will collide directly, the ISM (gas and dust) surely will.  It will set off a burst of star formation.  We can see this happening in other galaxies.

As you note, the galaxies (treated as units, not their individual stars), will merge after the collision.

Both sound like a reasonable description of "crash" to me.

 

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Blending might be a better term but crash or colliision sounds  better I suppose. 🤔

 

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Back to original topic - what will the actual fate of universe be?

As far as I remember - "Big rip" is not certain to happen (even with current accelerated expansion of universe) or is it?

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Just now, LukeSkywatcher said:

Symantics. You know what I mean. People living on Earth probably wont feel a thing. The night sky will change. I'm not saying overnight. I'd love to be here to see it.

Unfortunately people won't be living on Earth in 4-5 billion years unless we do something to prevent it (a) becoming uninhabitable for life as we know it in about 1-2 billion years through increased solar luminosity and (b) being swallowed up by a red-giant Sun in the 4-5 billion year time scale.

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1 minute ago, johninderby said:

Blending might be a better term but crash or colliision sounds  better I suppose. 🤔

 

Combining is a good term. Any word is fine really.

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1 minute ago, vlaiv said:

Back to original topic - what will the actual fate of universe be?

As far as I remember - "Big rip" is not certain to happen (even with current accelerated expansion of universe) or is it?

Back to original Q.

I've read a theory that the universe will expand as far as it can before retracting in on itself again. Explosion and implosion. It will be like a YoYo.

Who knows.

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Just now, vlaiv said:

Back to original topic - what will the actual fate of universe be?

As far as I remember - "Big rip" is not certain to happen (even with current accelerated expansion of universe) or is it?

No-one yet knows.

IF:

Expansion continues indefinitely;

Black holes evaporate into radiation through the Hawking process;

Protons decay, if only because their constituent quarks very, very occasionally approach each other closely enough to lie within their gravitational event horizon and collapse into a proton-mass black hole

THEN

the universe ends up made up of ever more red-shifted photons, neutrinos and electron-positron pairs which are too far apart to mutually annihilate before cosmic expansion drags them even further apart.  Each pair forms an atom of positronium parsecs in diameter.

Our current knowledge of physics is so pitifully crude that this is at best a plausible guess.

 

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Just now, LukeSkywatcher said:

Back to original Q.

I've read a theory that the universe will expand as far as it can before retracting in on itself again. Explosion and implosion. It will be like a YoYo.

Who knows.

According to this:

https://en.wikipedia.org/wiki/Ultimate_fate_of_the_universe

We have a few competing theories: Big Freeze or heat death, Big Rip, Big Crunch, Big Bounce, Big Slurp and Cosmic uncertainty

I did not know about Big Slurp which is pretty interesting as it says everything could disappear in an instant (due to Higgs Field and true/false vacuum thing - not going to pretend I understand it), and Cosmic uncertainty which basically means that we have no clue (well educated guess of not having a clue :D ).

I vote Big Freeze as being most realistic from current data.

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4 minutes ago, LukeSkywatcher said:

Back to original Q.

I've read a theory that the universe will expand as far as it can before retracting in on itself again. Explosion and implosion. It will be like a YoYo.

Who knows.

I don't think that idea holds water anymore. Current "best guess" is that it'll continue to expand at an ever-increasing rate and eventually just become, essentially, a vacuum. Gravity will have lost. At least, that's my understanding of the current ideas.

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28 minutes ago, LukeSkywatcher said:

The Milky Way and Andromeda galaxies are on a collision course in about two million yrs.

 

21 minutes ago, LukeSkywatcher said:

I thought it was millions

It couldn't be 2 millions years since the Andromeda galaxy is about 2.537 million light years away, so it would have to move faster than the speed of light to get here in 2 million years.

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4 minutes ago, LukeSkywatcher said:

Back to original Q.

I've read a theory that the universe will expand as far as it can before retracting in on itself again. Explosion and implosion. It will be like a YoYo.

Who knows.

Current observations suggest otherwise. The universe appears to be expanding ever faster (look up "dark energy" or "cosmological constant") rather than slowing down ahead of a big crunch.

What *might* happen is a quantum fluctuation temporarily creates enough energy in a small enough volume of space-time for a new inflationary epoch to occur.  A good search term is "eternal inflation", and specifically "bubble nucleation" as used within that context.

 

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I believe the human race will be already wiped out by then. Either by killing each other or by us ruining the planet we live on. 

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1 minute ago, Bartman said:

I believe the human race will be already wiped out by then. Either by killing each other or by us ruining the planet we live on. 

Given that very few species last more than a few million years, you are almost certainly correct in your belief.

If we hang on for another century or so, AIs may well prove to have a longer lifetime than primates.

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24 minutes ago, Louis D said:

 

It couldn't be 2 millions years since the Andromeda galaxy is about 2.537 million light years away, so it would have to move faster than the speed of light to get here in 2 million years.

I know. I dont understand it either if the universe is all expanding at the same speed.....how can the Milky Way and Andromeda "collide,merge". I suppose maybe size and gravitational pull play a part.

Edited by LukeSkywatcher

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2 minutes ago, LukeSkywatcher said:

I know. I dont understand it either if the universe is all expanding at the same speed.....how can the Milky Way and Android "collide,merge". I suppose maybe size and gravitational pull play a part.

My understanding is that locally (e.g., within gravity groups), gravity can overcome the general expansion of space-time at this point in the age of the universe.  If it continues to accelerate its expansion, this would no longer be true at some point in the distant future.

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18 hours ago, Atlas629 said:

A few years ago I learned the fate of the universe, and my exact place in it - hit me pretty hard. Anyone else share similar experiences?

I figure it's so far in the future, that humans probably won't even be around anyway, so no worries here.  I'm more concerned about paying for retirement in a few years. 😉

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