# Limit = C why?

1. Jul 16, 2010

### travwg33

Why is the speed of light the fastest anything travwling through space can move?

2. Jul 16, 2010

### Staff: Mentor

Objects with mass essentially gain more mass as they accelerate, which makes it progressively harder and harder to accelerate them (as viewed by an outside observer).

3. Jul 17, 2010

### travwg33

Now do objects actually gain mass or is it just the way it appears due to the acceleration?
Also, while understanding that object gain mass and as a result acceleration becomes more and more difficult, but why can it not surpass the speed of light. Is it just a fact of reality such as force of gravity?

4. Jul 17, 2010

### planethunter

Light is the universal limit that has been put in place in our universe. Who put it there? Who knows. Call the who God if you want...

5. Jul 17, 2010

### cragar

When they collide particles in an accelerator , when the particles collide some of their kinetic energy can be turned into mass , so after the collision you can have heavier particles then
what you started with , but energy is conserved .

6. Jul 17, 2010

### Staff: Mentor

To an outside observer, they really have gained mass - mass and energy are equivalent.
You're asking the same question that I just answered again. What kind of answer are you looking for?
Yes, it is a reality.

7. Jul 17, 2010

### Janus

Staff Emeritus
Try looking at it this way. Mass and energy are two sides of the same coin. As such, they have a common characteristic; they both affect the inertia of an object. Inertia is that property that makes an object want to maintain its present velocity.

So if you speed up a 1 kg object up to 1 m/s, its kinetic energy has increased by some small amount. But increase in kinetic energy carries it own inertia, which you have to overcome, in addition to the object's initial inertia, if you want to increase the object's speed any more. This means that you have to add more energy to increase the speed by a certain amount than you would if you were only dealing with the initial inertia.

In other words, it takes energy to accelerate the object, but adding energy makes the object harder to accelerate further. Its a viscous cycle where more of the energy you add goes to overcoming the inertia of the energy the object already has, and less and less goes to increasing the speed.

The reason the speed of light becomes the limit is that c, the speed of light, is a special speed; it is invariant. This means that everyone measures it to have the same value with respect to themselves. One of the consequences of having an invariant speed is that it automatically leads to that speed also being the speed limit of the universe.