# Will object with speed near the speed of light become black holes?

The theory of general relativity predicts that a sufficiently compact mass will deform spacetime to form a black hole.
.

http://en.wikipedia.org/wiki/Black_hole

and we know that when object travels near the speed of light it gains infinite mass, so does it means that it becomes a black hole?

Related Special and General Relativity News on Phys.org
HallsofIvy
Homework Helper
"Travels near the speed of light" relative to what? Speed is always relative to a given observer. Are you saying that wheter or not a star is a black hole depends upon the observer?

I am saying that when object travels near the speed of light (300'000 km/s relative to the point where it started to move), it gains infinite mass (from Einstein's formula E = mc2). So object with infinite mass will become a black hole (wikipedia link in my first post). If it is NOT true than tell me why?

Doc Al
Mentor
phinds
Gold Member
2019 Award
I am saying that when object travels near the speed of light (300'000 km/s relative to the point where it started to move), it gains infinite mass (from Einstein's formula E = mc2). So object with infinite mass will become a black hole (wikipedia link in my first post). If it is NOT true than tell me why?
You yourself, RIGHT NOW, are moving at 99.99999% of the speed of light relative to some frame of reference. Are you a black hole?

CERN would have done it by now if it were that easy :P

You yourself, RIGHT NOW, are moving at 99.99999% of the speed of light relative to some frame of reference. Are you a black hole?
Yes you are true but I am NOT moving with the speed of light relative to my starting location. This is very important. Object can't move faster than speed of light relative to it's starting position.

CERN would have done it by now if it were that easy :P
None is telling you that it is easy

first of all, a black hole does not have infinite mass.

furthermore, anything with a definite rest mass can never reach the speed of light.

photons, with zero rest mass, have a definite momentum.

phinds
Gold Member
2019 Award
Yes you are true but I am NOT moving with the speed of light relative to my starting location. This is very important. Object can't move faster than speed of light relative to it's starting position.
I take it you either did not bother to read, or else did not understand, the explaination given at the link provided.

Yes you are true but I am NOT moving with the speed of light relative to my starting location. This is very important. Object can't move faster than speed of light relative to it's starting position.

Can't move faster than light relative to ANY position. So why is the starting position important?

Last edited by a moderator:
Here is a nice trick to resolve such difficult comparisons:

Any situation involving a rapidly moving massive body's gravitational effect and a 'stationary' inertial observer can be transformed to an equivalent question about the interaction between a rapidly moving inertial observer and a 'stationary' massive body.
Your 'starting location', whatever that means is irrelevant, the above works for ALL observers.

The quote above is a generalized statement relating to phinds post:

You yourself, RIGHT NOW, are moving at 99.99999% of the speed of light relative to some frame of reference. Are you a black hole?

So object with infinite mass will become a black hole (wikipedia link in my first post). If it is NOT true than tell me why?
is impossible to realize because no mass can travel at speed 'c'....

Dale
Mentor
You yourself, RIGHT NOW, are moving at 99.99999% of the speed of light relative to some frame of reference. Are you a black hole?
Yes you are true but I am NOT moving with the speed of light relative to my starting location. This is very important. Object can't move faster than light with respect to it's starting position
Please reconsider phinds' point here. As he said, there are reference frames where you are moving at .9999999 c. Furthermore, your objection is both irrelevant and wrong. It is irrelevant because the speed wrt the starting location is not important in physics and wrong because you can move faster than c away from your starting location in any frame where your starting location is moving. (assuming that by starting location you are thinking of an object rather than a coordinate).

i think no,black holes create when a star dies,in this case there will be no formation of black holes

I am saying that when object travels near the speed of light (300'000 km/s relative to the point where it started to move), it gains infinite mass (from Einstein's formula E = mc2). So object with infinite mass will become a black hole (wikipedia link in my first post). If it is NOT true than tell me why?
This has already been explained in several ways, but here's one more try: a black hole is assumed to form when the proper mass (also called rest mass, or just mass) reaches a critical value. Many laws/descriptions are only valid for an object "in rest" and this is one of them.

Indeed initial mass is important here. When an object gaines speed we might say it gaines mass, but only because mass is calculated as force/accelleration. Also the extra mass is only measured in the direction of the moving object. Happily at the LHC the protons become 700 times heavier (at 99.9999*c) to get them around but not heavier relative to earth.
Another remark I like to make is that when an object travels near the speed of light the fysical laws do not change. It does not become smaller or heavier. Only to some external observer it is an object with high kinetic energy and very hard to push any further.

There is no such thing as 'infinite mass', which is why it's impossible for an object with nonzero invariant (rest) mass to accelerate to light speed in the first place. You can't pour unending amounts of energy into a system to make it move at c, because unending amounts of energy don't exist.

Also, only a bit unrelated to your question is bringing the quantum fluctuations of the type associated with virtual particles into the argument. Because, even if an infinite amount of energy could manifest due to such fluctuations (it can't, as far as I know), the energy would have to be 'repaid' to the vacuum within the limit of uncertainty of the measurement, which is a very short interval. In other words, it's not "usable" energy.

Your 'starting location', whatever that means is irrelevant, the above works for ALL observers.
Quite right. That's basic SR, which states that "The laws of physics are the same in all inertial frames of reference." It's also an integral part of GR in the (generalized) form of the equivalence principle, which boils down to the postulate that the laws of physics are the same in ALL frames of reference, inertial or not.