# Speed of light

It is a stated fact that, as an object is accelerated to the speed of light;
A- it’s weight increases to infinity,
B-It flattens out…size shrinks to zero,
C-time slows down to zero

This also sounds like the formation of a black hole.

Lets say you take an object (a solid sphere, one kilometer in diameter, and one million metric tons) and start accelerating it towards the speed of light. At what point does the sphere’s weight overcome the electromagnetic force
(The electrons’ repelling each other, separating the atomic nuclei), thus creating a neutron star?
And at what further velocity is required for the conversion to go all the way to black hole formation?

At no point. Relative to the sphere, there is no contraction and if you travelled with it your watch would still tick at the same rate as far as you could tell. The contraction and time effects are what would be measured by an observer not moving. As to what happens at the speed of light, you cannot say; You can’t reach the speed of light, you can only approach it.

I’m not sure, but I don’t see how a black hole could form this way.

No…it’s MASS increases. Big difference.

And if it’s mass was infinate, it would have to have infinate energy, which of course, not possible. It may be possible to get an object close to ‘c’, but not TO ‘c’.

Never heard this before…(But I am far from a Physics Major.)

It only appears that way to the person outside observing.

I think you will have to reword the question given the above info.

I think it’s “Black Hole” theory that you would want to read up on…

http://www.ncsa.uiuc.edu/Cyberia/NumRel/BlackHoles.html

(I couldn’t the the ‘link’ thing to work…sorry.)

DrMatrix has got it, but there’s a few points to clear up. First of all, it’s not completely accurate to say that the mass of an object increases as it approaches the speed of light. Its energy increases, but when physicists say “mass”, they usually mean “rest mass”. Saying that mass increases is just a fudge to make the the formula for momentum look the same in relativity and Newtonian mechanics.

Secondly, the flattening effect does, indeed, occur: Length along the direction of motion is decreased, which will cause a flattening. Dimensions perpendicular to the motion are unaffected.

The best way to think about problems like this is to remember that there’s no absolute zero of velocity, and any velocity less than light is just as good as any other. If I see an electron pass me at .999999 c, then from the electron’s point of view, I’m travelling at .999999 c, but I don’t seem to be turning into a black hole.

Chronos sez: Saying that mass increases is just a fudge to make the the formula for momentum look the same in relativity and Newtonian mechanics.

Someone said something similar to this not too long ago (but I couldn’t find the thread). So in other words, relativistic “mass” is not the same as the mass that gives a body a gravitational pull?

You know…I never thought of it that way. That is very profound. I mean no disrespect by questioning, but - is that an accurate way to think of it? I sure hope so, because I can get my mind around that example!

Fierra and I were just discussing what happens as an object approaches c - if it’s mass increase would allow it to turn into a black hole. I guess not - so the gravitational attraction of the heavy object moving at near-c conditions does not increase then?

Relativistic mass is the mass that generates gravity. It’s just that the contraction and relativistic mass increase are not there relative to its frame. As the sphere pass me, I observe a contraction in the direction of its travel. If it carries a clock, it appears to me to run slow; its relativistic mass increases and it does have a stronger gravitational field than it would if it were not moving.

However, according to its frame of reference, its shape is unchanged, its mass is unchanged and its clocks run just fine. An observer on the sphere would say that I was moving and I was contracted. It will not collapse, because in its frame there is no increase in its relativistic mass. The increase in attraction between us would be attributed to my increase in relativistic mass.

Photons have no rest mass, but they do have momentum and relativistic mass. They do exert a gravitational field. Enough of them could create a black hole.