# Thread: Length Contraction Question 2

1. Hi,

So, as you approach the speed of light, length contracts and volume is reduced but my understanding is that mass increases. So, if volume decreases and mass increases do we wind up with a black hold situation at the speed of light?

Thanks again!
Rusty

2.

3. Nope.
The rest mass doesn't increase, only the "relativistic mass".
(And nothing with mass can ever move at c).
Here and here.

4. Remember, length contraction is a relative measurement. If two observers have a relative speed with respect to each other, then they each measure the other as being length contracted. So while we would measure a spaceship traveling near c relative to the Earth as being length contracted, occupants in the spaceship would measure the Earth as being length contracted. So, would you expect the Earth to collapse into a black hole just because some aliens decided to do a fly by at near c? . And if the Earth doesn't collapse into a black hole as measured by its occupants, it can't do so according to the occupants of the ship or you would produce physical contradictions.

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