username2752874
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Euci
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(Original post by Kyber Ninja)
Is it possible that the Big Bang is a cycle that repeatedly starts over? I imagine in the middle of our universe is a big Black hole that will eventually suck everything in, making a singularity. Once this happens, aren't the conditions the same as when the Big Bang originally started, i.e. the universe in one small spot?
If you think about it, yes, but this takes many many many years to do. - The sun is only in it's mid-life crisis. Another 5 billion years, approximatley, then it will turn into a red giant, and destroy Mercury, Venus and possibly Earth (There is a possibility that it could move to Mars' position (Mars is now in the asteroid belt and possibly dead now) and just survive the sun, but the oceans will all be sucked dry and the land burnt, so no life would survive, no matter if the sun hits Earth or not) Then the sun may turn into a Black Hole, and destroy the whole Solar System a few billion years after that.

A star's life span is billions of years longer than this.
Then think, we're in the outer rim (Star Wars reference!) of the Milky Way, so most of the other stars in the Milky Way were made before our sun, then our galaxy is more than likely, not in the centre of the universe, so thats all the galaxies before and after the Milky Way was made, so that's more than likely a few quadrillion years (or even more).
Then the universe is so huge that it would take so long for everything to collapse back in on itself, so in that time, galaxies could be born.
Then there will be no more universe and it'll be back where it started, so yes
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username2752874
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(Original post by IDOZ)
If you think about it, yes, but this takes many many many years to do. - The sun is only in it's mid-life crisis. Another 5 billion years, approximatley, then it will turn into a red giant, and destroy Mercury, Venus and possibly Earth (There is a possibility that it could move to Mars' position (Mars is now in the asteroid belt and possibly dead now) and just survive the sun, but the oceans will all be sucked dry and the land burnt, so no life would survive, no matter if the sun hits Earth or not) Then the sun may turn into a Black Hole, and destroy the whole Solar System a few billion years after that.

A star's life span is billions of years longer than this.
Then think, we're in the outer rim (Star Wars reference!) of the Milky Way, so most of the other stars in the Milky Way were made before our sun, then our galaxy is more than likely, not in the centre of the universe, so thats all the galaxies before and after the Milky Way was made, so that's more than likely a few quadrillion years (or even more).
Then the universe is so huge that it would take so long for everything to collapse back in on itself, so in that time, galaxies could be born.
Then there will be no more universe and it'll be back where it started, so yes
Thanks for the post.

The long term future of humanity seems so depressing. Can't imagine what It'd be like to live on Earth and get sucked into a red giant
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Euci
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(Original post by Kyber Ninja)
Thanks for the post.

The long term future of humanity seems so depressing. Can't imagine what It'd be like to live on Earth and get sucked into a red giant
Yeah...Lets just hope that humanity has developed long range spacecraft and can get everyone off Earth before the sun collapses.
We won't be here for that, unless we invent a time machine...
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I doubt everything will be sucked in

Black holes experience hawking evaporation
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Doones
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(Original post by Kyber Ninja)
Is it possible that the Big Bang is a cycle that repeatedly starts over? I imagine in the middle of our universe is a big Black hole that will eventually suck everything in, making a singularity. Once this happens, aren't the conditions the same as when the Big Bang originally started, i.e. the universe in one small spot?
No, afaik the current thinking by most physicists is that we aren't in cycle - the universe will continue to expand. The big bang/big crunch cycle *is* certainly a theory but the numbers don't seem to work for it to happen.

You might be interested in this book - very well written:
https://www.amazon.co.uk/Copernicus-...dp/0141974931/
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Euci
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(Original post by Doonesbury)
No, afaik the current thinking by most physicists is that we aren't in cycle - the universe will continue to expand. The big bang/big crunch cycle *is* certainly a theory but the numbers don't seem to work for it to happen.

You might be interested in this book - very well written:
https://www.amazon.co.uk/Copernicus-...dp/0141974931/
No, soon the universe will stop expanding, and be attracted to the immense gravity from the centre of the universe, so the universe will collapse in on itself
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uberteknik
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(Original post by Kyber Ninja)
Thanks for the post.

The long term future of humanity seems so depressing. Can't imagine what It'd be like to live on Earth and get sucked into a red giant
Mortality is 100%.

Average lifespan of a human in the UK is 30,000 days.

Life on Earth will be long extinct before the planet is devoured by an expanding sun. The sun's energy output will eventually increase to the point where life becomes extinct, which is estimated to be around 1 billion years from now. (At that time the energy output is estimated to be only 10% greater than the energy output today).

In other words, about 32 million human generations from now.

I don't think there is anything to lose sleep over.
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Euci
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(Original post by uberteknik)
The sun's output will eventually increase to the point where life becomes extinct, which is estimated to be around 1 billion years from now.
I thought it was 5 billion, as this stage of a stars life lasts for approximatley 10 billion years.
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(Original post by IDOZ)
No, soon the universe will stop expanding, and be attracted to the immense gravity from the centre of the universe, so the universe will collapse in on itself
Yes that's one theory. But, as I said, latest indications are that might not happen. The universe's rate of expansion is increasing not decreasing.

/awaits an astrophysicist to explain....
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Euci
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(Original post by Doonesbury)
/awaits an astrophysicist to explain....
Do you know any?
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(Original post by IDOZ)
Do you know any?
There's plenty of mathematicians and engineers on TSR, but no astrophysicists, or even physicists that come to mind
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(Original post by uberteknik)
Mortality is 100%.

Average lifespan of a human in the UK is 30,000 days.

Life on Earth will be long extinct before the planet is devoured by an expanding sun. The sun's energy output will eventually increase to the point where life becomes extinct, which is estimated to be around 1 billion years from now. (At that time the energy output is estimated to be only 10% greater than the energy output today).

In other words, about 32 million human generations from now.

I don't think there is anything to lose sleep over.
Idk, some theorists believe we can be become sentient machines and transform to become mechanical in a way - I think most people who bet on humanity living past Earth's end - if we don't, that's such a whimper.

Here's hoping for multiverse travel
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United2810
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Doonesbury is right in saying that the rate of expansion of the universe is increasing. The presence of dark matter and dark energy are 2 very mysterious quantities in space, and not much is known about either, but they are responsible for certain thing. Dark energy is the most theorized cause of the increase in rate of expansion. In the early 1900s, scientists knew that the universe was expanding however they thought the energy density was too high for it to continue expanding in the future. They thought it would eventually lead a gravitational collapse but the Hubble telescope showed in 1998 that the universe was instead accelerating in it’s expansion. Scientists therefore theorize that there is a mysterious force which we cannot see, which is accelerating the expansion of the universe. This is dark energy. It makes up around 68% of the universe.

We were only able to identify dark matter at all due to it's gravitational effect on normal matter. As galaxies spin in their orbits, they require mass in order for stars to stay in proximity to each other. Since most of the matter we observe is close to the centre of galaxies, there has to be a special type of matter which keeps the edges of the galaxies from floating out into space. We are more confident in knowing what dark matter isn’t rather than what it is. The dark nature of it means it doesn’t emit light like stars/planets. It is also not composed of normal matter (baryons), because we cannot detect the absorption radiation of any dark matter clouds. Lastly, dark matter cannot be antimatter because it does not give off gamma rays when it collides with matter particles.

In the 1920s, Edwin Hubble studied supernovae in the sky and concluded that the universe was expanding. After that discovery, the question was how long the expansion would last? This was because everyone primarily thought that the effect of gravity would outweigh this expansion and eventually stop it. However in the 1990s, we were shocked to see that the universe was actually accelerating in it's expansion. This energy which is counteracting gravity is called dark energy. We have since attempted to use quantum theory to explain dark energy. Quantum theory suggests empty space can also have energy due to temporary particles which continually form and disappear. But the value for the energy of this energy space resulted in a value of 10^120 bigger than expected.

Essentially, unless proven otherwise, or we find out what dark energy/matter is, we won't really fully understand what is happening to cause the increase. Hope this helps.
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uberteknik
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(Original post by Kyber Ninja)
Idk, some theorists believe we can be become sentient machines and transform to become mechanical in a way - I think most people who bet on humanity living past Earth's end - if we don't, that's such a whimper.

Here's hoping for multiverse travel
Of course that's a possibility. Another possibility is that humanity destroys itself along with everything else on the planet. Another possibility is that artificial life destroys humanity.

All I did was to put the timescales involved into perspective.
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DarthRoar
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(Original post by IDOZ)
No, soon the universe will stop expanding, and be attracted to the immense gravity from the centre of the universe, so the universe will collapse in on itself
Simple answer:
This is antiquated thinking from the 1990s. The rate of the universe's expansion is increasing for a yet unknown reason. The universe will most likely die a heat death after trillions of years, not in a reverse-big bang.
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Amullai
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(Original post by IDOZ)
No, soon the universe will stop expanding, and be attracted to the immense gravity from the centre of the universe, so the universe will collapse in on itself
It doesn't work like that. We orbit the black hole at the centre of the universe and therefore we have a velocity that must be moving us at 90 degrees to the black hole so yes we are attracted to it but we will never reach it. It's like spinning something that is attached to string. The tension pulls the object towards the centre but the object moves at 90 degrees to the force.
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(Original post by Amullai)
It doesn't work like that. We orbit the black hole at the centre of the universe and therefore we have a velocity that must be moving us at 90 degrees to the black hole so yes we are attracted to it but we will never reach it. It's like spinning something that is attached to string. The tension pulls the object towards the centre but the object moves at 90 degrees to the force.
Also there is nothing to collide with for us to lose momentum with so we are just stuck orbiting it until the sun expands killing us all. What a fun future that sounds like.
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(Original post by Kyber Ninja)
There's plenty of mathematicians and engineers on TSR, but no astrophysicists, or even physicists that come to mind
DrSebWilkes
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DrSebWilkes
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(Original post by Black Water)
DrSebWilkes
Cheers bro!

(Original post by Kyber Ninja)
Is it possible that the Big Bang is a cycle that repeatedly starts over? I imagine in the middle of our universe is a big Black hole that will eventually suck everything in, making a singularity. Once this happens, aren't the conditions the same as when the Big Bang originally started, i.e. the universe in one small spot?
Well actually there is something in this. Technically speaking the position of everything is a statistical phenomena. You may have heard of something called entropy which must increase, but since it is ultimately a statistical thing it is possible that all matter re-coalesces into one space (though there are some requirements on the "geometry characteristics" of the universe, but AFAIK nothing ruled out) at one instantaneous point which could result in some big-bang like event, and would look like the big-bang.
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