# Speed of Light

1. Aug 18, 2008

### km90

I am new to this forum, so forgive me if this question has already been asked. Also forgive me if this is a seemingly simple question, as I am just now starting my undergrad and am relatively new to a lot of physics topics.

I understand that it is generally considered that anything with an intrinsic mass cannot travel at the speed of light. As an object's speed comes closer to c, its mass (and so kinetic energy) increases and it is therefore harder to accelerate it to a speed even closer to c. I understand that traveling at c would give the object an infinite mass and an infinite energy of motion and thus such travel is not allowed. However, how can the object have a finite mass and finite energy while approaching a finite number (c), only to have an infinite mass and an infinite energy when it finally gets there? What makes c so special?

2. Aug 18, 2008

### Staff: Mentor

Think of c as a universal speed limit. The total energy of a particle as a function of its speed is given by:

$$E = \frac{mc^2}{\sqrt{1 - v^2/c^2}}$$

So, while the speed remains finite, the total energy of a particle approaches infinity as v approaches c.

Last edited: Aug 18, 2008
3. Aug 18, 2008

### km90

Ah, fantastic. Thanks a lot.