# Faster than Light Question

1. Mar 19, 2009

### Ninja Tang

Please correct me if I'm wrong, but as far as I know:

1. Photons have no mass at rest, but gain mass as they accelerate, like all objects (although it is an extremely small amount).

2. Light is composed of Photons traveling in waves.

3. It is theoretically impossible for an object to travel at the speed of light, due to the fact that all objects gain mass as they accelerate towards the speed of light.

Assuming the above is correct, in theory, wouldn't it be possible for an object whose mass is less than that of a proton to travel faster than the speed of light? What I'm proposing, is that the speed of light is not the universal speed limit, but that the photon is simply the smallest (or more specifically the "lightest") particle we have discovered, and that if there were to be an object smaller than a photon, it would have the potential to travel faster than light.

Now I may be 100% wrong, but this has been bothering me all day, so I felt the need to discuss this with somebody.

2. Mar 19, 2009

### mgb_phys

Assuming you meant photon here not proton.

Yes if something had a rest mass lower than the photon it could go faster than light, but since the rest mass of the photon is 0 it is unlikely. There are particles called Tachyons that have a negative rest mass and so can only go faster than light - but they are a mathematical game, there is no reason to believe they are real.

I think you are getting confused by a particles mass increasing as it nears the speed of light - this only applies to particles with a rest mass, the 'mass' of a photon doesn't increase - it is always zero.

3. Mar 19, 2009

### humanino

Photons are strictly massless, and can not be accelerated. The speed of light in vacuum happens to coincide with the speed "limit" you refer to in your point 3 only because photons are massless.

4. Mar 19, 2009

### buffordboy23

Nothing can travel faster than light in a vacuum (free space). However, in other mediums, where light travels at some fraction of "c", it is possible for other particles to travel faster than light, but not at speed "c". You might be interested in learning about Cerenkov radiation: http://en.wikipedia.org/wiki/Cherenkov_radiation

5. Mar 20, 2009

### Ninja Tang

Oops, that was a miss type. I did mean photon.

Thank you for the link, it helped me see the subject from a different point of view.

Another question though; Is there any method, either actual or theoretical, of reducing the mass of an object relative to it's surroundings?

6. Mar 20, 2009

### Dmitry67

Yes, a diet :)

7. Mar 20, 2009

### HallsofIvy

Staff Emeritus
This is wrong in two ways. Photons have no mass- they have momentum, but no mass. Photons do not accelerate, they always move at the same speed.

Well, light can be thought of as photons or waves. I would not say they were "photons traveling in waves".

That is one reason.

That "lightest" particle has mass 0. If you are going to postulate a particle having lower mass, you are going to have to say what you mean by "negative mass"!