# Q & A: accelerating past c?

Most recent answer: 10/22/2007
Q:
if you accerated a particle, in a vacuum, and kept accelerating it for ages, would it eventualy reach the speed of light (assuming no E is los through friction/air resistance). If so, why now continue the acceleration (with more E) and go faster than light speed.
- billy (age 15)
oundle, england
A:
If the particle were to keep feeling a constant force, its acceleration with respect to non-accelerating observers who happen to be traveling along with the particle at the moment would be constant. However, its acceleration with respect to an observer initially at rest with respect to it would keep decreasing. Velocities turn out not to add up in the way we intuitively expect them to. The resulting speed would never reach c.

Now you might wonder, why not add some oomph to that push and make the particle keep a constant acceleration with respect to the initial observer. One problem with that is that it turns out that an INFINITE amount of work would have to be done on the particle to get it to speed c.

Mike W.

(published on 10/22/2007)