# relativity and black holes

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#### optimisticcynic

• 2200
##### relativity and black holes
« on: November 21, 2011, 02:37:40 PM »
So the other day I had a random thought that I think is has not been asked on this forum before.
so the faster you go the denser you get according to relativity.( you gain mass but your length shrinks) so if you are going fast enough shouldn't you collapse into a black hole? and since it is all relative isn't there a reference frame where we all collapse into a black hole? does anyone know how relativity deals with this? I am probably missing something obvious...
You can't outrun death forever
But you can sure make the old bastard work for it.

#### Lorddave

• 16451
##### Re: relativity and black holes
« Reply #1 on: November 21, 2011, 02:55:03 PM »
I think you gain apparent mass but none of the gravitational effects since it's not really mass.
I am a terrible person and I am a typical Blowhard Liberal for being wrong about Bom.

#### Rushy

• 8971
##### Re: relativity and black holes
« Reply #2 on: December 04, 2011, 09:42:02 AM »
So the other day I had a random thought that I think is has not been asked on this forum before.
so the faster you go the denser you get according to relativity.( you gain mass but your length shrinks) so if you are going fast enough shouldn't you collapse into a black hole? and since it is all relative isn't there a reference frame where we all collapse into a black hole? does anyone know how relativity deals with this? I am probably missing something obvious...

It would depend on what you are trying to move so quickly. The only known objects dense enough to collapse into singularities are stars. There is no reference frame where we all collapse into singularities, I think you are defining reference frame incorrectly.

The only time relativistic mass truly becomes a problem is when the object you are moving approaches the speed of light (rather than reach the speed of light, all energy it receives will simply make it more massive, rather than increase its velocity.). This means something would have to be giving you an infinite amount of energy that exponentially increases as it gives it to you. Therefore, say we are actually moving momentously fast, but we don't know it since we have no "slow object" to reference ourselves to, we would never have to worry about becoming too massive. If we were receiving infinite amounts of energy at an exponential rate, the universe would have collapsed itself billions of years ago.

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• 3
##### Re: relativity and black holes
« Reply #3 on: December 13, 2011, 05:47:53 PM »
There is no need to post for black holes flat earths just might think black holes are also flat or just a hole that that makes new planes who knows what they  might imagine to say

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#### jraffield1

• 697
##### Re: relativity and black holes
« Reply #4 on: December 13, 2011, 05:58:05 PM »
There is no need to post for black holes flat earths just might think black holes are also flat or just a hole that that makes new planes who knows what they  might imagine to say

what?
You, sir, can't comprehend the idea of bottoms.

#### optimisticcynic

• 2200
##### Re: relativity and black holes
« Reply #5 on: December 22, 2011, 12:13:12 PM »
So the other day I had a random thought that I think is has not been asked on this forum before.
so the faster you go the denser you get according to relativity.( you gain mass but your length shrinks) so if you are going fast enough shouldn't you collapse into a black hole? and since it is all relative isn't there a reference frame where we all collapse into a black hole? does anyone know how relativity deals with this? I am probably missing something obvious...

It would depend on what you are trying to move so quickly. The only known objects dense enough to collapse into singularities are stars. There is no reference frame where we all collapse into singularities, I think you are defining reference frame incorrectly.

The only time relativistic mass truly becomes a problem is when the object you are moving approaches the speed of light (rather than reach the speed of light, all energy it receives will simply make it more massive, rather than increase its velocity.). This means something would have to be giving you an infinite amount of energy that exponentially increases as it gives it to you. Therefore, say we are actually moving momentously fast, but we don't know it since we have no "slow object" to reference ourselves to, we would never have to worry about becoming too massive. If we were receiving infinite amounts of energy at an exponential rate, the universe would have collapsed itself billions of years ago.
sorry it has taken me so long to respond to this, graduate applications and finals took way more of my time then I thought they would. anyway we wouldn't need infinite energy because we wouldn't need infinite mass. also even a if we are using the reference frame of say a neutrino shot out by the sun some things should collapse into a black hole  that wouldn't collapse in our reference frame.
also a quick comment on Lorddave
I think you gain apparent mass but none of the gravitational effects since it's not really mass.
even ignoring the apparent gain in mass you still decrease in length, which increase density, granted that effect wouldn't increase density as quickly but wouldn't it eventually increase enough to collapse if viewed from the right reference frame?
You can't outrun death forever
But you can sure make the old bastard work for it.

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#### EireEngineer

• 1205
• Woo Nemesis
##### Re: relativity and black holes
« Reply #6 on: December 23, 2011, 06:28:41 PM »
Its moot anyway since no object with mass can ever achieve the speed of light, since the energy required reach the next highest speed logarithmically approaches infinity.
If you are not part of the solution, you are part of the precipitate.

#### Raist

• The Elder Ones
• 30590
• The cat in the Matrix
##### Re: relativity and black holes
« Reply #7 on: December 25, 2011, 04:33:55 PM »
So the other day I had a random thought that I think is has not been asked on this forum before.
so the faster you go the denser you get according to relativity.( you gain mass but your length shrinks) so if you are going fast enough shouldn't you collapse into a black hole? and since it is all relative isn't there a reference frame where we all collapse into a black hole? does anyone know how relativity deals with this? I am probably missing something obvious...

Time dilation, length changing, and changes of mass are only apparent to an outside observer. In your frame of reference you feel completely normal.

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#### NASA_Lies

• 75
• <3
##### Re: relativity and black holes
« Reply #8 on: December 29, 2011, 12:00:44 PM »
So the other day I had a random thought that I think is has not been asked on this forum before.
so the faster you go the denser you get according to relativity.( you gain mass but your length shrinks) so if you are going fast enough shouldn't you collapse into a black hole? and since it is all relative isn't there a reference frame where we all collapse into a black hole? does anyone know how relativity deals with this? I am probably missing something obvious...

The problem is that you're not defining your reference frame correctly. Think about the problem of one of a pair of twins going on a rocket and taking a short trip at close to the speed of light. They were both moving close to the speed of light relative to one another, yet when the rocket brother comes back, he finds a world where his twin is much older than he is. He experienced time dilation, but the earth-bound brother did not.

The reason is acceleration. The rocket brother was in the accelerating reference frame and the earth bound brother was not. Acceleration is not relative, it is absolute. Therefore, in order for everything in the universe to gain mass due to relativity, the universe would have to accelerate. Then you could define a non-accelerating reference frame in which relativistic effects such as time dilation and increased mass effect all bodies in the universe.