Singularity or just a very small, massive shell?

[em370]

The nature of a black hole is that gravity attracts objects at a speed faster than light making it impossible for them to be able to escape but if the object is accelerating towards the black hole it would slow down and become more massive the close it got because it is approaching the speed of light and as such would never reach the center. Instead the mass would just form an extremely massive shell around the center but would never actually reach the center. I was just thinking about this on my own and never heard anyone mention it so I assume that there must be some flaw in my logic or that I just haven't studied enough. Can someone please enlighten me on the subject?

 

[Vorde]

Where is the basis for objects slowing down as they accelerate?

 

[em370]

Where is the basis for objects slowing down as they accelerate?

They would be approaching the speed of light due to the black hole's gravity as they accelerate inwards causing time to slow down. Please excuse my wording as they wouldn't be "slowing down" in relation to speed but instead time would go very slowly for the object compared to the rest of the universe making it take a very long time (for us) for the object to get any closer to the center. In addition the closer it got to the center the slower time would move for the object as it would have accelerated even more within that time frame.

 

[Vorde]

Thats an interesting point I've never thought of. I don't know enough Relativity to say what an object falling into a black hole would appear to look like from other reference frames, so I think someone else needs to answer you here.

My guess is this doesn't matter because even though it may appear to take infinitely long to fall into the singularity, it doesn't appear that way to anyone else (imagine a ship traveling at 99.9999...% c leaving Earth heading to the sun, while it may take infinitely long for the people on the ship to experience the time it takes to hit the sun, from an outside observer they would just smash into the sun in 8 minutes).

 

[em370]

Thats an interesting point I've never thought of. I don't know enough Relativity to say what an object falling into a black hole would appear to look like from other reference frames, so I think someone else needs to answer you here.

My guess is this doesn't matter because even though it may appear to take infinitely long to fall into the singularity, it doesn't appear that way to anyone else (imagine a ship traveling at 99.9999...% c leaving Earth heading to the sun, while it may take infinitely long for the people on the ship to experience the time it takes to hit the sun, from an outside observer they would just smash into the sun in 8 minutes).

I think you're backwards with the effects of moving near the speed of light. To the people on the spaceship it would take 8 minutes to hit the sun but for the people on Earth it would seem that it took them an extremely long time. This is due to the fact that light must be measured as traveling at the same speed from all points of reference. The people on the ship would travel at a very slow speed and be become very compact (flat) so that when they measure the speed (distance/time) of light it would still come out the same as the people on earth. The ship would also become very massive in order to have the same amount of energy without surpassing light speed.

 

[Vorde]

If that is the case then why don't we see light as motionless?

 

[em370]

If that is the case then why don't we see light as motionless?

Because light has no mass. It is pure energy making it able to travel at the fastest possible speed. That is why we measure light to be the maximum speed possible because all mass will be unable to reach that speed and therefore fall short.

 

[Vorde]

I'm getting myself confused, and it's a bit too late for me to pull out the Lorentz equations to see if I'm thinking about that correctly (if this is still unresolved tomorrow I might do that). But I'm pretty sure I'm right here, the last thought experiment I can think of is this:

The concept of accelerating to near-light speed velocities to accomplish interstellar travel within a human lifetime (for the passengers onboard the ship) is well established. If time dilation works like you are saying, this would be impossible like this:

Lets say you are moving at a speed infinitely close to c. You are traveling to a star approx. 100 ly away. If light worked the way you said it does, then it would still take 100 years for the astronauts to reach the star, and they would all be dead.

 

[em370]

I'm getting myself confused, and it's a bit too late for me to pull out the Lorentz equations to see if I'm thinking about that correctly (if this is still unresolved tomorrow I might do that). But I'm pretty sure I'm right here, the last thought experiment I can think of is this:

The concept of accelerating to near-light speed velocities to accomplish interstellar travel within a human lifetime (for the passengers onboard the ship) is well established. If time dilation works like you are saying, this would be impossible like this:

Lets say you are moving at a speed infinitely close to c. You are traveling to a star approx. 100 ly away. If light worked the way you said it does, then it would still take 100 years for the astronauts to reach the star, and they would all be dead.

Yes, this is what I'm saying. That is why even if we could accelerate close to the speed of light it would still take a very long time to reach another planet which makes people either use multi-generational space ships or the use of huge amounts of mass and energy to pull space towards them shortening the distance between the two locations.

 

[Chronos]

You are assuming black holes can arise by virtue of relativistic mass increase. This does not occur. If an object is not sufficiently dense to form a black hole in its own reference frame, it is not a black hole in any reference frame.

 

[Astro.padma]

The nature of a black hole is that gravity attracts objects at a speed faster than light making it impossible for them to be able to escape but if the object is accelerating towards the black hole it would slow down and become more massive the close it got because it is approaching the speed of light and as such would never reach the center. Instead the mass would just form an extremely massive shell around the center but would never actually reach the center. I was just thinking about this on my own and never heard anyone mention it so I assume that there must be some flaw in my logic or that I just haven't studied enough. Can someone please enlighten me on the subject?

Anyone out there ! Are there any theories stating that the matter falls exactly into the center of a black hole? Not to be rude, am just a beginner. thank yo :)

 

[em370]

You are assuming black holes can arise by virtue of relativistic mass increase. This does not occur. If an object is not sufficiently dense to form a black hole in its own reference frame, it is not a black hole in any reference frame.

What about once the original singularity forms? What will happen to other matter that falls towards the black hole? Will it ever reach the center?

 

[em370]

Anyone out there ! Are there any theories stating that the matter falls exactly into the center of a black hole? Not to be rude, I am just a beginner. thank you! :)

Matter will fall exactly toward the center of a black hole because that is where the strongest gravitational attraction is. This thread is about if the matter actually ever makes it into the center of a black hole.

 

[Astro.padma]

The nature of a black hole is that gravity attracts objects at a speed faster than light making it impossible for them to be able to escape but if the object is accelerating towards the black hole it would slow down and become more massive the close it got because it is approaching the speed of light and as such would never reach the center. Instead the mass would just form an extremely massive shell around the center but would never actually reach the center. I was just thinking about this on my own and never heard anyone mention it so I assume that there must be some flaw in my logic or that I just haven't studied enough. Can someone please enlighten me on the subject?

K...got it ! But why do you think it would ever form a "shell" like thing ? Couldn't it be "as it is" and stop at one point somewhere near the center?

 

[em370]

K...got it ! But why do you think it would ever form a "shell" like thing ? Couldn't it be "as it is" and stop at one point somewhere near the center?

Ya but I was thinking that mass would be coming in from all sides so the shell would be roughly uniform with stopped matter creating the "shell". Most of the mass making up the shell would probably be hydrogen so if a larger object fell in it would be as you described just stopping "as it is" at some point near the center.

 

[Astro.padma]

Most of the mass making up the shell would probably be hydrogen .

Being simple n straight, why hydrogen??

 

[em370]

Being simple n straight, why hydrogen??

Because that's the most common element in space. The center of the black will probably contain the heavier elements the star fused so the shell will likely contain hydrogen from space and from the part of the star that was blown away during the end of the red super giant phase. Helium will also be in the shell as well as any other matter that was brought into the black hole after the singularity formed.

 

[Ryan_m_b]

Em370 what are you basing any of this on? It is my understanding that current models predict a gravitational singularity beyond an event horizon though contemporary understanding is that this is due to a limitation of current science. There is a thread going over this https://www.physicsforums.com/showthread.php?goto=newpost&t=226671

Please note that overly speculative posts and unsubstantiated personal theories are not allowed at PF

 

[Ryan_m_b]

Matter will fall exactly toward the center of a black hole because that is where the strongest gravitational attraction is. This thread is about if the matter actually ever makes it into the center of a black hole.

Ya but I was thinking that mass would be coming in from all sides so the shell would be roughly uniform with stopped matter creating the "shell". Most of the mass making up the shell would probably be hydrogen so if a larger object fell in it would be as you described just stopping "as it is" at some point near the center.

From the perspective of an outside observer the infalling mass does not slow down, processes in the mass do. E.g.

A clock falls into the black hole
It falls at the rate and acceleration you would expect
However the rate of it's ticking keeps slowing down

From the perspective of the clock things are different e.g.

A clock falls into the black hole
It falls at the rate and acceleration it would expects
It's own rate of ticking is constant

 

[em370]

Okay reading back I realized I probably phrased this really poorly. I learned that a black hole is an object with a gravitational force faster than the speed of light which is why it is called a black hole since light can't escape. I also learned that as things approach the speed of light they experience time at a rate different from those not traveling at that speed. I just want to know if something that falls into a black hole will actually ever reach the center or if the gravity of the black hole will cause it to travel towards the center so fast that it will experience time so slow that to us outside the black hole it will seem to never reach the center. The stuff I said about the shell was just speculation as to what it would look like if we could see inside the event horizon. I apologize if this seems insubstantial I really don't know that much about what happens past the event horizon.

 

[em370]

From the perspective of an outside observer the infalling mass does not slow down, processes in the mass do. E.g.

A clock falls into the black hole
It falls at the rate and acceleration you would expect
However the rate of it's ticking keeps slowing down

From the perspective of the clock things are different e.g.

A clock falls into the black hole
It falls at the rate and acceleration it would expects
It's own rate of ticking is constant

Really? My teacher said that its speed would appear to decrease, not just the speed of its functions. Sorry about my misconceptions. Also I type my previous post before you posted this one, thanks for answering my question.

 

[Vorde]

Okay reading back I realized I probably phrased this really poorly. I learned that a black hole is an object with a gravitational force faster than the speed of light which is why it is called a black hole since light can't escape. I also learned that as things approach the speed of light they experience time at a rate different from those not traveling at that speed. I just want to know if something that falls into a black hole will actually ever reach the center or if the gravity of the black hole will cause it to travel towards the center so fast that it will experience time so slow that to us outside the black hole it will seem to never reach the center. The stuff I said about the shell was just speculation as to what it would look like if we could see inside the event horizon. I apologize if this seems insubstantial I really don't know that much about what happens past the event horizon.

I believe it has been shown that all matter that falls into a black hole will ultimately reach the singularity (though I forget who showed it), I think your misconceptions comes from your teacher telling you that the speed of an object undergoing significant time dilation would appear to decrease from the reference frames of other objects, which is not the case.

 

[em370]

I believe it has been shown that all matter that falls into a black hole will ultimately reach the singularity (though I forget who showed it), I think your misconceptions comes from your teacher telling you that the speed of an object undergoing significant time dilation would appear to decrease from the reference frames of other objects, which is not the case.

Ya my teacher told me that when an object approaches light speed it would contract, time would move slower for that object making it appear to move slowly, and that its mass would increase so that it would take more energy to make the object accelerate. So just to clear things up if you went near light speed time People would see you as moving near light speed but things such as a watch on you would appear to be moving slower?

 

[Vorde]

If you are moving close enough to light speed for time dilation to kick in (I've heard 30% is where it starts becoming noticeable), time slows down for the object moving at the given speed. An outside observer would see no difference in speed, but would notice that time on board the object would be moving slower. For an observer on the object (lets call it a ship), time would be moving normally, and its speed would be normal.

 

[Ryan_m_b]

Ya my teacher told me that when an object approaches light speed it would contract, time would move slower for that object making it appear to move slowly, and that its mass would increase so that it would take more energy to make the object accelerate. So just to clear things up if you went near light speed time People would see you as moving near light speed but things such as a watch on you would appear to be moving slower?

Remember movement must be relative, there is no preferential frame of reference. But if you observe something traveling at near light speed relative to you yes they appear slow and contracted etc yet still traveling at near light speed.

For the travellers everything seems slow and they measure their length and mass to be exactly the same as usual. If you are interested I suggest posting questions in the relativity forums.

 

[Max™]

Em370, you're conflating reference frames, relative motion, and numerous other concepts.If a clock large enough for you to read from a great distance flew past you at 99% of the speed of light, on a path that took it across the face of the moon from your perspective, here is what you would observe.

Compared to your own clocks, the hands on the moving clock would be at a virtual standstill, but if you calculated how long it took to transit the moon (which would of course take a pretty impressive camera/timing system) you could work out that it was traveling at nearly the speed of light relative to you.

Additionally, the clock would appear distorted as it passed you, due to a phenomenon known as Terrel Rotation.

http://newport.eecs.uci.edu/~dblack/backlightsoftware.htm

From the perspective of an observer riding the clock, YOUR clock would appear to be at a standstill as the Earth and Moon flew past at nearly the speed of light, undergoing Terrel Rotation (as well as the distortion of their color/brightness due to the searchlight and doppler effects).

If the clock started on Earth beside you, flew out into space, and whipped past the moon before returning to your side, it would show that from the perspective of the clock the journey took a fraction of the duration you observer.

Note that this isn't just a mechanical effect, if you think of a clock as being similar to an odometer for time, it crossed a shorter "distance" through time during the highly accelerated journey than your clock did in your less accelerated frame on Earth.

 

[DNMock]

The shell is a neat idea, and if I may chime in on it a bit at a different angle possibly.

Since, as an object approaches the speed of light it gets more massive, the stream of atoms and subatomic particles stream toward the singularity, they will eventually reach a point where their mass reaches an equal level to the singularity itself. The two singularities, being of similar mass, should orbit each other like a binary star system for a moment before the tiny particle slows down a little bit and gets gobbled up. The dance would be constantly going on as matter is sucked in and every single particle should theoretically reach critical mass. Thus, as long as matter is falling into a black hole the singularity shouldn't be a point but appear as a shell of millions of singularities in a complex orbital pattern all with infinite mass until they slow down enough to be overcome by the original.

Oh, and OP, think about it in terms of vectors, the whole speed of light thing, helps me understand it personally.

 

[Vorde]

The shell is a neat idea, and if I may chime in on it a bit at a different angle possibly.

Since, as an object approaches the speed of light it gets more massive, the stream of atoms and subatomic particles stream toward the singularity, they will eventually reach a point where their mass reaches an equal level to the singularity itself. The two singularities, being of similar mass, should orbit each other like a binary star system for a moment before the tiny particle slows down a little bit and gets gobbled up. The dance would be constantly going on as matter is sucked in and every single particle should theoretically reach critical mass. Thus, as long as matter is falling into a black hole the singularity shouldn't be a point but appear as a shell of millions of singularities in a complex orbital pattern all with infinite mass until they slow down enough to be overcome by the original.

Oh, and OP, think about it in terms of vectors, the whole speed of light thing, helps me understand it personally.

Huh, interesting idea. But two things pop out at me.
1) Neither singularities nor particles within the event horizon of a black hole reach infinite mass. Singularities have infinite density, but a finite and discoverable mass. Particles are similar.
2) I'm struggling with thinking about a singularity forming within an event horizon. The way I think about it (and this hasn't been verified by anyone else, but I've never had anyone show me why not), is that within the event horizon of a black hole, any objects with a lesser radius than you (i.e. closer to the singularity) will be accelerating faster and therefore will always be going away from you. Likewise, any object with a greater radius will be going away from you because you are accelerating. So based on that, within a black hole, a particle will never be able to interact with any other particle that does not have the exact same radius as it (and I'm not sure about that, because I'm not sure how to add perpendicular velocities within the confines of general relativity).

It seems to me that not only will this prevent singularities from forming (or any clump of mass for that matter), but this will in fact work in the opposite direction. But I have to think about this more.

 

[Ryan_m_b]

The shell is a neat idea, and if I may chime in on it a bit at a different angle possibly.

Since, as an object approaches the speed of light it gets more massive, the stream of atoms and subatomic particles stream toward the singularity, they will eventually reach a point where their mass reaches an equal level to the singularity itself. The two singularities, being of similar mass, should orbit each other like a binary star system for a moment before the tiny particle slows down a little bit and gets gobbled up. The dance would be constantly going on as matter is sucked in and every single particle should theoretically reach critical mass. Thus, as long as matter is falling into a black hole the singularity shouldn't be a point but appear as a shell of millions of singularities in a complex orbital pattern all with infinite mass until they slow down enough to be overcome by the original.

Oh, and OP, think about it in terms of vectors, the whole speed of light thing, helps me understand it personally.

This is not the case. No matter how fast something goes its mass will never reach that density because in its own reference frame nothing has changed.

Also gravitational singularities are artefacts of incomplete theory and are not necessarily a true representation of these conditions.

 

[em370]

Are singularities actually finitely dense? The basis of the singularity is that gravity is so strong that the object contracts without stopping and will never slow down as their is nothing to stop it( I could be wrong in this as shown by my previous immense lack of understanding). Will it really become infinitely dense or do we just say that because it will continue getting denser and denser to the point where it would no longer make any sense or even matter to measure the density? I read something on the internet about the Schwarzschild radius but I think it was talking about the size of the event horizon instead of the actual singularity.

 

[Vorde]

The easy way out is to say that a singularity has a finite mass and an infinite density.

However we don't have a good mathematical description of a singularity, so we don't really know.

 

[Ryan_m_b]

Are singularities actually finitely dense? The basis of the singularity is that gravity is so strong that the object contracts without stopping and will never slow down as their is nothing to stop it( I could be wrong in this as shown by my previous immense lack of understanding). Will it really become infinitely dense or do we just say that because it will continue getting denser and denser to the point where it would no longer make any sense or even matter to measure the density? I read something on the internet about the Schwarzschild radius but I think it was talking about the size of the event horizon instead of the actual singularity.

The easy way out is to say that a singularity has a finite mass and an infinite density.

However we don't have a good mathematical description of a singularity, so we don't really know.

I refer you both to this thread https://www.physicsforums.com/showthread.php?t=226671