# Neutrinos and mass

Discussion in 'Physics & Math' started by Hypnogog, Aug 16, 2001.

1. ### HypnogogRegistered Member

Messages:
29
I was just reading a little about the neutrino and noted somethiing interesting.
1) neutrinos travel at close to c
2) neutrinos have a small amount of mass.

So how do we justify that the mass of the neutrino does not seem to be approaching infinite. I'm gonna have to find the equation but doesn't it state that as v approaches c the closer to infinite mass becomes? If a neutrino does have mass and suddenly jumped to c[I/] would there be a massive increase of ..er.. mass?
I know there's probably an expl. but I don't gitit.

3. ### Chagur.Seeker.Registered Senior Member

Messages:
2,235
Hi, Hypnogog ...

It could be that its 'at rest' mass is almost zero and it travels at only ... lets say ... 96% of the speed of light.

Just a thought.

As for the equation, I believe it's that as Velocity approaches the speed of light, relativistic mass approaches infinite and time approaches zero.

Last edited: Aug 16, 2001

5. ### HypnogogRegistered Member

Messages:
29
NO mass

Even if it's mass were near 0 isn't that irrelevant? The equation doesn't state that objects bigger than a breadbox approaching the speed of light gain inifinite mass the requirement is only that it has mass. My main conundrum is if a single neutrino made the universal mistake of suddenly jumping to the speed of light would that tiny particle drastically increase, or the other way, if it cuts speed by point ohohohohohohohoh1 percent does it become massless?

7. ### CrispGone 4everRegistered Senior Member

Messages:
1,339
Mass vs. relativistic mass

Hi Hypnogog,

This is a classical flaw of reasoning with relativity, mainly caused by bad naming conventions in the physical community

.

When scientists talk about the neutrino mass, it is always assumed to be the restmass (that is the mass in a classical sense, when the particle is at rest). In the special theory of relativity, the term "mass" should be read as "relativistic mass" and not "restmass". Relativistic mass includes both the particle's restmass and its (kinetic) energy. Perhaps formula's will help to clarify this:

Restmass = m0
(Relativistic) mass m = m0 + kinetic energy.

A more accurate way of formulating this would be to use the mass/energy equivalence:

E = mc^2

Here m is the relativistic mass. In terms of the restmass this equation becomes:

E = m0*c^2 + p^2*c^4.

As you can see, the (relativistic) mass of a particle at rest (p = 0) is the restmass m0.

The correct formulation would then be: "A particle with a non-zero restmass would get an infinite relativistic mass if its velocity approaches the speed of light."

This basically expresses that you would need an infinite amount of energy to reach lightspeed. Since no object with a restmass can acquire an infinite amount of energy, no object with a restmass can ever reach the speed of light. Since the neutrinomass has been confirmed (see e.g. Superkamiokande detector) a neutrino would never be able to reach the speed of light, or even go faster.

But that is only if you believe the theory of special relativity ofcourse

.

Bye!

Crisp

8. ### Chagur.Seeker.Registered Senior Member

Messages:
2,235
Thanks for popping in Crisp ...

Really, really rusty.