How does the universe end?

[glenc (Glen)]

The science is much less settled on how that will happen. We're not even sure if the universe will come to a firm, defined end, or just slowly tail off. Our best understanding of physics suggests there are several options for the universal apocalypse. It also offers some hints on how we might, just maybe, survive it.
http://www.bbc.com/earth/story/20150...e-universe-end

[ZeroID (Brent)]

Survive it ? Maybe ? I really doubt mankind will exist in that unforseeable distant future.

[AlexN]

I've often pondered on This.

My minds eye likes the idea that the mass of the universe will eventually be so great that expansion will slow, then contraction will occur. Towards the end I could only imagine that the particles finally converging on each other would occur at such velocity and such a small point in spacetime that in essence an ultra-massive black hole would be the result.

I am far from a physicist however I would like to think this black hole would collapse upon itself with no matter left to feed it, possibly creating an inverse effect, possibly spewing particles out in an alternate universe on the other side of its event horizon. The end of one universe sparking the birth of another.

I'd love to hear from someone with a background in astrophysics to know if this "by the seat of my pants" hypothesis is even remotely plausible.

[astroboof (Steve McN)]

Good thing this topic is in amateur science.

[AlexN]

Steve - care to elaborate.

As I said I am far from a physicist, it's just an idea that feels like it would work in my mind. Clearly you know something I don't..... Knowledge belongs to the world. Share!

[Atmos (Colin)]

I personally believe that the big freeze is coming. One of the main things that we discovered from the 7 year WMAP data was further proof that the universe is flat by looking at it geometrically. Further evidence to this has been put forward by large scale surveys calculating the mass and size of galaxy clusters and superclusters, voids and super voids. Big job.

The universe could theoretically have been in one of three states, Open, Closed or Flat - these are all factors to do with the critical density of the universe as a whole, the amount of matter contained with its area.

If the universe is open, gravity is not strong enough to slow it and the universe continues accelerating expansion forever. This is sometimes known as the Big Rip.

If the universe is closed, gravity is strong enough to, in time, over come expansion and we end up with the Big Crunch.

If the universe is flat however, it is sitting on the Critical Density where the universe just continues the way it is. Bring on the Big Freeze.

Everything so far points to the universe being flat. In time, all galaxies outside of our local group (some 50-60 galaxies) will slowly drift away from us due to the expansion of the universe. Gravity is strong enough to hold things together if they're close enough, our local group is but nothing out side of that. Estimates put it at 10-100 trillion years before the closest galaxies outside of our local group disappear from our skies forever. After that... The universe will be black... At this point there is no new star formation, virtually every star has died, white dwarfs have cooled down into black dwarfs, every planet has died and exhausted all of the heat that it can pull from gravitational contraction. This, my friends, is the Black Hole Age. In time, even they will disappear with nothing left to absorb, they will continue to evaporate over the next trillions of years.

As it is currently considered that even protons have a half life, given enough time every particle in the universe will decay leaving no trace that it ever existed.

This is the Big Freeze....

Sleep well my friends for the universe will die in 10 million billion billion billion years...

ADDITIONAL:
Just pulled out my trusty calculator. After 10 million billion billion billion years the universe would have ~0.0001% of the amount of matter as it does now.

[AlexN]

10 million billion billion billion you say. Not concerned ;P

How do you calculate this rate of decay. Do all protons share the same half life or is it averaged? Very interesting thoughts

[Atmos (Colin)]

Originally Posted by AlexN

10 million billion billion billion you say. Not concerned ;P

How do you calculate this rate of decay. Do all protons share the same half life or is it averaged? Very interesting thoughts

At this stage it is all just theory, not actually confirmed that protons even decay! It is generally thought that they do, calculations from the most widely understood Grand Unified Theory (GUT) put proton decay (half life) at 100 thousand billion billion billion years. Due to how long it is though, it has never been observed so we therefore have no actual evidence of it happening.

Cheers,
Colin

[RB (Andrew)]

I've had to delete a number of responses to this thread (and other threads in this section).
A reminder that this section is strictly moderated please:

Discussions related to the Science of Astronomy, Amateur Contributions to Astronomy Science, Space Exploration etc. Strictly moderated - stay on-topic, serious discussions please.

RB

[g__day (Matthew)]

The computer simulations end and the advanced life forces say to each other - see I told you so, now lets try it again with the following factors changed as they all head off to the pub!

I don't think we have nearly a deep enough understanding of the true reality of our existence, time and consciousness to even remotely come close with our wildest guesses. I personally see us like floating on the sea of a lake we have never dived into or soared above trying to understand all life on Earth and its complexities. Our understanding of time, and even how many dimensions space time has might be totally wrong and these factors alone would wildly change the outcomes.

The whole shebang may be endless and/or time mightn't exist, be one dimensional, one directional or even remotely linear and then all our postulating goes totally out the window.

Until we know a lot more we don't know when we will have enough to answer that great question!