Gravitons

[Aki]

Why do gravitons and waves travel at the speed of light? Why not at another speed?

[Tormod]

I am not aware that gravitons have been discovered yet, but I think they are expected to travel at the speed of light because a) they are massless and b) are predicted to have similar properties to the photon.

I assume you mean "gravitational" waves (because obviously not all waves travel at the speed of light) but again the reason would be that gravity and light share some properties, and one of them is speed. I am not a physicist so I assume that there is a better explanation...

[Bo]

All massless particles travel at the speed of light. and as it turns out that the graviton is massless, it travels at the speed of light.
the handwaving argument why massless particles travel with the speed of light:
- To accalarate a particle, you need some energy, proportional to it's mass.
- Special relativity says that the faster a particle moves,the higher it's 'effective' mass becomes.
- at the time you want to give the particle the speed f light: the mass becomes infinite, therefore the energy required to do this is infinite. This basicly means that it is impossible.
- so the only way to have a particle move at the speed of light, would mean to give it mass 0.

Bo

[lindagarrette]

Whatever happened to the notion that gravity is a spacial displacement? Why is gravity sometimes referred to as consisting of waves, or particles when it iss not at all similar to light except for its speed. (And why is that?) Light is just the energy generated when electrons move to a higher orbit in theer atomic structure. Right? And according to recent theories, at least the ones that attempt to explain the universe being created by crashing "branes," gravity can cross the void between these phenomena but photons (or light waves) cannot. If there is no graviton, are we comparing macro with micro concepts like apples and oranges? This is all so confusing it's hard to ask about it coherently. A little help, please.

I'm still stuck on the concept of mass. I think I've asked about under every topic in this forum.

[Tormod]

Linda, good questions. I guess one reason why you have to keep asking is that few of us do understand what mass is.

[Uncle Martin]

Tightly bundled energy?

[lindagarrette]

Originally posted by: Uncle Martin
Tightly bundled energy?

Granted, mass is potential energy, by definition. I guess the question is, what is <b>matter?</b> matter is composed on particles which are composed of something else. Whenever you jump off a tall building and land on concrete, it isn't your particles smacking intoh the concrte particles, but the electromagnetic fields of energy colliding. Right?

Back to gravity and mass. Gravity acts on matter (mass) and on photons which have zero mass at rest. Except that photons are never at rest, so they also have mass. Does this have anything to do with Higgs Bosons?

[wazzuuup]

How can photons be massless when at rest, since intuitively it seems like nothing can be massless if it is made up of something. How could gravity act upon massless things, I always thought that masses attract each other, so how can massless photons be attracted?
Is it correct that when photons move at high speeds, the energy is the mass, so when they are at rest, there is no mass? I am so confused…

[Tormod]

Energy IS mass. That is the basis of relativity theory. E=mc^2 describes how much energy you get from a given mass multiplied with the speed of light in vacuum squared. So while a particle may be massless the equation is NOT E = zero x c^2. Why? Because if an object has *both* zero energy AND zero mass, then it does not exist. So turn it over and you'll find that m=(c^2)/E. That will never give 0.

[Freethinker]

Originally posted by: Tormod
Energy IS mass. That is the basis of relativity theory. E=mc^2...So turn it over and you'll find that m=(c^2)/E. That will never give 0.

Er Tormod

E=m(C^2)

divide (C^2) out of both sides

E/(C^2)=m(C^2)/(C^2)

(C^2)/(C^2) cancel and leave

E/(C^2)= m

or:

m=E/(C^2)

NOT

m=(C^2)/E

You shouldn't post math this late at night! :-)