Science a GoGo's Home Page Forums General Discussion General Science Discussion Forum Can anything have zero mass?

Scientists used to think a neutrino had zero mass. That was soon proved wrong. Can anything ever have zero mass?

Photons. Any particle that propagates at lightspeed is massless.

The electron neutrino's non-zero mass is demanded by observed neutrino oscillation. The amount of mass required is less than 0.1 eV/c^2.

http://hyperphysics.phy-astr.gsu.edu/hbase/particles/neutrino.html
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A particle is deeply relativistic when its kinetic energy equals its rest mass. 0.1 eV corresponds to a temperature of 11,600 kelvin. Any nuclear process (keV, MeV) that produces neutrinos will have them essentially indistinguishable from traveling at lightspeed.

But I heard a neutrino was smaller than a photon.
Anyway,
How can it be possible for anything to exist without mass? Maybe something can have a mass so small it can't be calculated, but to say that a particle has no mass is absurd- it would be nothingness.

not true.

mass and energy are phases of the same thing. like ice and steam are different kinds of water.

a photon is a packet of energy that propagates at the speed of light, has zero mass, and experiences all time between creation and absorbtion as occurring at once (or put another way, does not experience time). it has zero mass, and yet is most certainly not "nothingness."

and experiences all time between creation and absorbtion as occurring at once

That is ming-blowing - is it really true?

But what else is mind-blowing is that, in the relatively short time humanity has been undertaking serious exploration of these things, we have worked this out. It is totally counter intuitive.

I mean, if Newton had said something like that, people would have thought he was quite literally insane.

Now, putting my Dunce Hat on - can you explain how we reach the point where we knew this - or is the story too long - or would I need to know slightly more than my 12 times table?

Grab one of those Stephen Hawking books. He explains it better than I could, with cool pictures and everything.

But I read that energy was the measure of how fast a particle of mass was moving in a small area around it?s self.

Kinetic energy is the energy an object has by virtue of its motion. It's given by the formula:

K.E. = (m* v^2) / 2

(This applies to most situations you are likely to encounter, i.e. when v/c << 1; that is, when the speed of the object is much less than the speed of light.)

Energy is the ability to do Work. There are other kinds of energy: potential energy is stored energy. For example a ball at the top of a table is stored energy. The least little tap might cause the ball to roll over the edge - releasing that potential into kinetic energy.

There's a book you might find interesting:
"Understanding Thermodynamics" by H.C. Van Ness.
He starts with an example that Feynman uses in Vol I of his lectures on physics. I suspect the Van Ness book will be better for you to start with, though.

I once heard that mass was 'trapped energy' I thought this was a load of rubbish. Was I correct?

If a photon has zero mass.. then does an object emitting photons not become lighter.. conversely an object absorbing photons not become heavier?

Sincerely,

Heavy has no meaning in physics.

Use the word "mass" and your question can be answered. Energy equates with mass. Photons of a REST mass of zero.

DA, you are correct. I should have used the term "mass". UV photons are more energetic than visible photons, and so are more "massive" in this sense, a statement which confuses more than it explicates. The energy and momentum of light also generates curvature of space-time so according to theory it can attract objects gravitationally. This effect is far too weak to have been measured, yet.
Sincerely,

Mung asks:
"What else exists which we can not yet dectect?"

Intelligence in humans?

Many many things. More than we can measure no doubt.

See here.

If we ever did find something with zero mass, it wouldn't necessarily mean it had no mass. Its mass would just be so small that our machines working on an atomic level wouldn't be able to detect it.