# Why is accelerating a spacecraft at the speed of light is impossible (in terms of energy)

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1. Oct 15, 2014

### pstir2

1. The problem statement, all variables and given/known data
In terms of the energy involved (using formulas provided), explain why accelerating a spacecraft to the speed of light is impossible.

2. Relevant equations
time, mass and length dilation formulas, and a few astrophysics formulas, E = Ek + mc2, projectile motion formulas

3. The attempt at a solution
I have solve this mathematically by using the mass dilation formula to prove that mass would be infinite and then subbed that value into E = Ek + mc2 to prove that energy would be infinite.

I don't think this is a good way to explain/solve this question. Can anyone else please explain this using the formulas provided?

2. Oct 18, 2014

### PcumP_Ravenclaw

$E = mC^2$ is the mass-energy conversion equation. when a body is moving it is supplied with kinetic energy E = 0.5mv^2. When speed becomes close to speed of light, kinetic energy cannot cause acceleration according to F = ma. (I don't know the answer to why this happens) Energy is converted to mass and the mass of the body keeps increasing so that now Force needed is for a bigger m. this way all the kinetic energy put in will turn into mass. I wonder why we need to smash atoms to discover fundamental particles when we can accelerate particles to close to speed of light and try to observe the accumulation of extra mass which may be in very small magnitudes.