What is the subatomic particle with the smallest mass?

Answer 1

electron

No, wrong.

The electron neutrino has the least nonzero mass, it is so small the exact value has not been determined. The photon and graviton both have zero mass.

Answer 2

I'd be willing to bet the farm that this question is only inquiring about protons, neutrons, and electrons, but I'll be more thorough anyways. First off, out of the previously mentioned particles; electrons are the lightest, having a mass of 9.109 X 10-31 kg or 511 keV/c2; followed by protons, with a mass of 1.672 X 10-27 kg or 938.3 MeV/c2; and finally ending with neutrons, having a mass of 1.675 X 10-27 kg or 939.6 MeV/c2.

Now, as for all of the other subatomic particles out there, we have a tie for the lightest: photons and gluons; both weighing in at a paltry 0. Both particles are members of the larger group of particles known as gauge bosons, which means that they are force mediating particles. Photons mediate the electromagnetic force, and are found in such atomic processes as gamma decay and X-ray emission. Gluons mediate the strong nuclear force, and are the guys responsible for keeping quarks confined within protons and neutrons.

As a side note, there are actually 8 types of gluons, meaning that there's actually a 9-way tie for lightest subatomic particle. However, explaining the what's, why's, and how's for there being 8 gluons is WAY beyond the scope of this answer, especially considering that I've probably already gone too far.

That being said:

There may be another massless particle out there called the graviton. Gravitons are the proposed gauge bosons that would mediate the force of gravity. Also, the graviton's existence is a necessary condition for pretty much all of the most promising "Theories Of Everything" to be correct. However, they thus far remain unobserved.

Answer 3

It depends, in part, on the definition of mass used. Nowadays, physicists often use what was traditionally called the "rest mass", now sometimes called the "invariant mass", because it is the same for all frames of reference. A photon has a rest mass of zero.

Of objects that move at LESS than the speed of light, the neutrino has an extremely small rest mass. Since the neutrino moves so extremely fast, it was believed for some time to travel at the speed of light, but it seems its speed is actually slightly less.

It depends, in part, on the definition of mass used. Nowadays, physicists often use what was traditionally called the "rest mass", now sometimes called the "invariant mass", because it is the same for all frames of reference. A photon has a rest mass of zero.

Of objects that move at LESS than the speed of light, the neutrino has an extremely small rest mass. Since the neutrino moves so extremely fast, it was believed for some time to travel at the speed of light, but it seems its speed is actually slightly less.

It depends, in part, on the definition of mass used. Nowadays, physicists often use what was traditionally called the "rest mass", now sometimes called the "invariant mass", because it is the same for all frames of reference. A photon has a rest mass of zero.

Of objects that move at LESS than the speed of light, the neutrino has an extremely small rest mass. Since the neutrino moves so extremely fast, it was believed for some time to travel at the speed of light, but it seems its speed is actually slightly less.

It depends, in part, on the definition of mass used. Nowadays, physicists often use what was traditionally called the "rest mass", now sometimes called the "invariant mass", because it is the same for all frames of reference. A photon has a rest mass of zero.

Of objects that move at LESS than the speed of light, the neutrino has an extremely small rest mass. Since the neutrino moves so extremely fast, it was believed for some time to travel at the speed of light, but it seems its speed is actually slightly less.

Answer 4

what you mean to say is what subatomic particle has the lowest mass? Which would be by far the neutron

You probably meant to say the neutrino.

Although note that the photon has zero mass, which is even less than that of a neutrino.

EDIT: I struck out the wrong answers. The photon and gluon have the smallest mass of all particles, both of which have zero mass; however, the photon does have momentum (recall that, traditionally, momentum is proportional to velocity and mass) and I am unsure if the gluon does (in fact, nobody knows because gluons have never been directly observed and tested.)

Answer 5

It depends, in part, on the definition of mass used. Nowadays, physicists often use what was traditionally called the "rest mass", now sometimes called the "invariant mass", because it is the same for all frames of reference. A photon has a rest mass of zero.

Of objects that move at LESS than the speed of light, the neutrino has an extremely small rest mass. Since the neutrino moves so extremely fast, it was believed for some time to travel at the speed of light, but it seems its speed is actually slightly less.

Answer 6

Photons and gluons have no mass and neutrinos have a small but nonzero mass.

Answer 7

the quark has the smallest mass in an atom, but there are lighter subatomic particles

Answer 8

the quark ;)

The above answer is wrong. Photons and gluons have no mass and neutrinos have a small but nonzero mass.

Answer 9

Electrons has the least mass. Protons and neutrons are almost equal mass.

Answer 10

This particle is the electron.