Zero rest mass particles?

Question

How is it possible to have zero rest mass particles?

Surely if a particle exists its MUST have mass?

If it did not how could it affect things around it?

Surely this doesnt make sense?

Could you also state your sources? So I can tell the guessers from the professors?

Thanks!

Answer 1

You are surrounded by zero rest mass particles. They are called photons and they transmit the light from the screen to your eye. They transmit the electrostatic force that holds the atoms in your body together. They carry momentum but have no mass if at rest - in fact, they cannot exist at rest (though their phase velociy can be slowed to be near at rest).

Any suitably modern and suitably advanced book on physics in any store in any country will give you the details, and the experimental verification that led to the conclusions. Try Eisberg and Resnick or Resnick and Halliday.

Zero rest mass particles are also affected by gravity, and this has also been measured using the mossbauer effect.

The zero rest mass particles in nature are those that carry the interactions between quarks and leptons.

Contrary to what is said elsewhere here, a charged particle cannot have zero mass because charge is a property of quarks, all of which have mass.

See ref below for more.

Answer 2

It is possible to have zero mass particles in two main ways.

The first is for the particle to exists as a point charge. In that way the particle can be defined by the charge, but because charge itself has no mass the particle has no mass.


The second is for the particle to have no charge but to exist as a travelling ‘disturbance’ in space-time. Photons and gravitons are examples of such particles. Because a disturbance is a change it can be detected by reference to past and future conditions, hence the particle exists, but the particle does not have mass itself, it simply exists as a disturbance.

So no, there is no “Surely’ that says that a particle must have mass simply because it exists. Mass is only one of numerous ways for spacetime to be interfered with. There are numerous others. Particles can exist and be detectable and measurable by virtue of their disturbance of properties of spacetime aside from the strong force.

Answer 3

altough there are some particles which we define as mass-less I personally don't think any particle has zero rest-mass. I think that some particles are just too light for us to measure them.

Photons are the usual example and they influence things through their electric/magnetic field. I think photons can also have momentum which can be seen when they are used in things like "optical tweezers" or laser cooling/trapping.

I find it hard to accept that something can carry momentum without having any rest-mass.