# Homework Help: A theoretical question

1. Nov 9, 2007

### transgalactic

i was told that
when we speed up a partical the closer it gets to the speed of light
the more energy you need to put in in order to increase his speed

and the closer he gets closer the heavier he gets

E=mc^2

my question is than
how does a simple electron or other partical wich can travel at the speed of
light can be so light (weighs very little)???

because the more we push the partical the heavier it gets
and still it never reaches the spedd off light only come closer
explonesioly

2. Nov 9, 2007

### cristo

Staff Emeritus
Erm.. an electron cannot travel at the speed of light. Special relativity states that massives particles can never break through the speed of light boundary (i.e. that if a massive particle is travelling slower than the speed of light, it can never go faster than the speed of light, or even equal to the speed of light) and that particles with zero mass must travel at precisely the speed of light.