Is the universe going to die?


by jacksdvds
Tags: black hole, universe
Drakkith
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#19
Mar15-12, 07:32 PM
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Quote Quote by GeorgeDishman View Post
As I said, some will be ejected from the galaxy but those that aren't will eventually become part of Sag A*. Item 13 on the list is valid, nobody said it would be quick.

Stars that are ejected from the galaxy will quantum tunnel to iron stars in perhaps 10^1500 years and to black holes in 10^(10^26) years or more after which Hawking Radiation is again their fate so 10^23 years is the proverbial blink of an eye.

http://en.wikipedia.org/wiki/Future_...cays_into_iron

http://math.ucr.edu/home/baez/end.html
Unless Hawking radiation is real, in which even supermassive black holes will decay in about 2x10^99 years.

Also, per wiki: Since encounters are more frequent in the denser galaxy, the process then accelerates. The end result is that most objects are ejected from the galaxy, leaving a small fraction (perhaps 1% to 10%) which fall into the central supermassive black hole.

So no, number 13 is not accurate, as much of the galaxy will be thrown out, not sucked into the black hole.
Chalnoth
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#20
Mar16-12, 01:42 AM
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Quote Quote by Drakkith View Post
Unless Hawking radiation is real, in which even supermassive black holes will decay in about 2x10^99 years.
Hawking radiation is real. It is a feature that any horizon must have, and has been observed for those horizons which we can create in laboratories (sound horizons).
GeorgeDishman
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#21
Mar16-12, 02:57 AM
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Quote Quote by Drakkith View Post
.. after which Hawking Radiation is again their fate ..
Unless Hawking radiation is real, ...
Yep, I said that.

Also, per wiki: Since encounters are more frequent in the denser galaxy, the process then accelerates. The end result is that most objects are ejected from the galaxy, leaving a small fraction (perhaps 1% to 10%) which fall into the central supermassive black hole.

So no, number 13 is not accurate, as much of the galaxy will be thrown out, not sucked into the black hole.
1% to 10% is still 3 to 30 billion stars, or 1000 to 10,000 times its present mass, and that ignores dark matter. We can nitpick estimates but compared to the other items on the list, IMHO it is not that far out. YMMV.
Chalnoth
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#22
Mar16-12, 03:21 AM
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Quote Quote by GeorgeDishman View Post
Stars that are ejected from the galaxy will quantum tunnel to iron stars in perhaps 10^1500 years and to black holes in 10^(10^26) years or more after which Hawking Radiation is again their fate so 10^23 years is the proverbial blink of an eye.
Proton decay is likely to get rid of most matter long before this.
Drakkith
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#23
Mar16-12, 09:46 AM
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Quote Quote by GeorgeDishman View Post
Yep, I said that.



1% to 10% is still 3 to 30 billion stars, or 1000 to 10,000 times its present mass, and that ignores dark matter. We can nitpick estimates but compared to the other items on the list, IMHO it is not that far out. YMMV.
So 90-99% incorrect is "nitpicking"? Ok. We'll agree to disagree.
Cosmo Novice
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#24
Mar16-12, 10:36 AM
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Quote Quote by Chalnoth View Post
Hawking radiation is real. It is a feature that any horizon must have, and has been observed for those horizons which we can create in laboratories (sound horizons).
It is theoretically real but for obvious reasons has not been observed in nature. You cannot qualify this statement as fact and you should not present it as such. Hawking radiation is a prediction of prevailing theory.

Sound horizons are an entirely different thing.
Cosmo Novice
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#25
Mar16-12, 10:37 AM
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Quote Quote by Chalnoth View Post
Proton decay is likely to get rid of most matter long before this.
This statement can also not be qualified - proton decay is a hypothetical scenario and has never been observed due to its nature.
GeorgeDishman
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#26
Mar17-12, 07:56 AM
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Quote Quote by Drakkith View Post
So 90-99% incorrect is "nitpicking"? Ok. We'll agree to disagree.
What I meant is that we agree that some is ejected and some falls to the centre, it is a question of degree, whereas other points on his list were simply wrong. I'm not really disagreeing with you.
Chalnoth
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#27
Mar17-12, 12:57 PM
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Quote Quote by Cosmo Novice View Post
Sound horizons are an entirely different thing.
They're really not. The only difference is there is a horizon in sound waves as opposed to light waves. In either case, the horizon produces radiation just because it is a horizon. The exact same mathematical argument leads to radiation in either situation. So the observation of this radiation on a sound horizon is an observation of Hawking radiation.
Chalnoth
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#28
Mar17-12, 01:03 PM
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Quote Quote by Cosmo Novice View Post
This statement can also not be qualified - proton decay is a hypothetical scenario and has never been observed due to its nature.
Except protons were produced in the early universe. This fact alone proves that proton decay must occur.
jacksdvds
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#29
Mar17-12, 01:11 PM
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Just because we can't see it doesn't mean there is not a speed faster than light!
Chalnoth
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#30
Mar17-12, 01:17 PM
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Quote Quote by jacksdvds View Post
Just because we can't see it doesn't mean there is not a speed faster than light!
Objects that move faster than light would cause the universe to be unstable. That is, reality would explode. That doesn't happen, so it's pretty clear that nothing is likely to ever move faster than light.
jacksdvds
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#31
Mar17-12, 01:21 PM
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And you know this how?
Chalnoth
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#32
Mar17-12, 02:01 PM
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Quote Quote by jacksdvds View Post
And you know this how?
Anything that moves faster than light emits radiation. If it's a charged particle, it emits Cherenkov radiation. This is observed, for example, when high-energy particles move through mediums faster than the speed of light in those mediums. If it uncharged, there are other, similar processes (they're slower, but still occur). So not only would anything moving faster than light be very much observable, it would rapidly cease to move faster than light as it loses energy.

That, or it's a tachyon, in which case the extra emission will just cause it to gain speed and emit more radiation, which would cause the universe to explode. As I mentioned.
bill alsept
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#33
Mar17-12, 02:45 PM
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Quote Quote by jacksdvds View Post
Just because we can't see it doesn't mean there is not a speed faster than light!
I always wondered if there was nothing faster than light then why do we have black holes? What does it mean need an escape velocity faster than light?
alexg
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#34
Mar17-12, 03:13 PM
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Quote Quote by bill alsept View Post
I always wondered if there was nothing faster than light then why do we have black holes? What does it mean need an escape velocity faster than light?
It means once you check in, you don't get out.
jacksdvds
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#35
Mar17-12, 06:36 PM
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Quote Quote by Chalnoth View Post
Anything that moves faster than light emits radiation. If it's a charged particle, it emits Cherenkov radiation. This is observed, for example, when high-energy particles move through mediums faster than the speed of light in those mediums. If it uncharged, there are other, similar processes (they're slower, but still occur). So not only would anything moving faster than light be very much observable, it would rapidly cease to move faster than light as it loses energy.

That, or it's a tachyon, in which case the extra emission will just cause it to gain speed and emit more radiation, which would cause the universe to explode. As I mentioned.
Hence, it has been observed "when energy particles move through mediums faster that the speed of light", supposes that there is a speed FTL. Your very words!

Secondly, energy moving through a medium, perhaps a flash light beam through a fish tank, the speed of the light beam on the emerging beam would then be slower than light speed due to the lost energy. Now we have a second argument and a second speed of light.

It strike me as though you are arguing both sides of the issue. Correct me if I mistook your words.
alexg
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#36
Mar17-12, 06:41 PM
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Hence, it has been observed "when energy particles move through mediums faster that the speed of light", supposes that there is a speed FTL.
Light moves through mediums other than the vacuum at less than c.

the speed of the light beam on the emerging beam would then be slower than light speed due to the lost energy.
When the beam emerges from the medium back into the vacuum, it travels at c. Lost energy shows up as a lowering of the frequency.


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