Do electrons really have zero mass?

  • Context: Undergrad 
  • Thread starter Thread starter Cosmo16
  • Start date Start date
  • Tags Tags
    Electrons Massless
Click For Summary

Discussion Overview

The discussion revolves around the concept of whether electrons are truly massless or if they possess mass, particularly in the context of their behavior in different physical scenarios. Participants explore the implications of this characterization in both theoretical and educational settings.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • Some participants question the description of electrons as "massless," suggesting that they must have mass, similar to approximations made in ideal gas laws.
  • One participant cites a source indicating that electrons have a rest mass of 0.511 MeV and are not massless, contrasting their mass with that of protons.
  • Another participant mentions that under certain conditions, such as in graphene, electrons can behave as if they are massless, highlighting a context-dependent nature of their mass.
  • Several participants express frustration with educational terminology, particularly in high school settings, where electrons are referred to as massless, suggesting this may lead to confusion.
  • There is a discussion about gamma rays and their classification, with some participants expressing uncertainty about whether they should be considered massless or possessing mass.
  • One participant introduces the concept of wave-particle duality, noting that photons (associated with gamma rays) exhibit both particle-like and wave-like properties, leading to further confusion regarding their mass.

Areas of Agreement / Disagreement

Participants do not reach a consensus on whether electrons are massless or not, with multiple competing views presented regarding the mass of electrons and gamma rays, as well as the implications of these classifications in educational contexts.

Contextual Notes

There are limitations in the discussion regarding the definitions of mass in different contexts, the conditions under which electrons may behave as massless, and the educational framing of these concepts, which may not fully capture the complexities involved.

Cosmo16
Messages
140
Reaction score
0
Electrons are "massless"?

Why are electrons described as "massless". It seems to me that they would have to have mass. Are they truly massless or is this the same kind of aproximation that is made with ideal gas laws?
 
Physics news on Phys.org
http://hyperphysics.phy-astr.gsu.edu/hbase/particles/lepton.html#c2

An electron is a lepton with rest mass of 0.511 MeV (or 9.11 x 10-31 kg).

Compared to a proton of rest mass 938.27 MeV (1.6726231 x 10-27 kg), the electron is light, but not massless.

Perhaps the article cited by ZapperZ indicates that electrons in certain conditions behaves as massless particles.

From the article on PhysicsWeb -
Two teams of physicists have discovered previously unseen exotic behaviour in sheets of carbon atoms. The teams have shown that electrons move through the sheets as if they have no rest mass. They have also observed a minimum value of conductivity for the sheets and an unusual form of the quantum Hall effect (Nature 438 197 and 201).

Further investigation has revealed
that the electrons in graphene behave like relativistic particles that have no rest mass and travel at about 106 metres per second. Although this is a factor of 300 slower than the speed of light in vacuum, it is still much faster than the speed of electrons in an ordinary conductor. Moreover, the electrons in most conductors can be described by non-relativistic quantum mechanics, whereas the electrons in graphene need to be treated as relativistic particles called massless Dirac fermions.
Go to Zz's thread https://www.physicsforums.com/showthread.php?t=99223
 
Last edited:
well, my chem teacher calls them masssless, which annoys me, which is why asked.
 
Cosmo16 said:
well, my chem teacher calls them masssless, which annoys me, which is why asked.

Chemistry people are nuts :P

Is this high school? College professors wouldn't make such a mistake...
 
ya its HS. Cool guy, really good teacher , I think he just doesn't want to confuse the rest of the class when were doing atomic mass. At least, I'm assuming that what is was.
 
Yah that is probably the reason. When i was in high school, i was like "wait wait wait, you didn't add in the electrons :(". He still shouldn't say they are massless however, he should just say they are too small to be considered in weighing masses at a high school level.
 
he might have said they were negligible once.
While I'm on the topic- gamma rays (edit:particles not rays) have mass- correct?
Cause he did say that those were massless.
 
There is no such thing as a gamma particle. Gamma rays are massless however.
 
ok, maybe it is gamma rays I am thinking of then, we were doing radiation, he was talking about it like it was a particle, but then he called it a ray, left me kinda confused.
 
  • #10
Well it's an electromagnetic wave as far as i know :)
 
  • #11
about gamma-rays... They shouldn't be the electromagnetic waves with the most corpuscular behaviour? The great deal of particle aspect of light (i.e. see Compton effect: a photon come to act like a ball that on a pool table matches another one, the electron, which is a really material particle despite gamma-ray!) is to attribute to them!
It is a strange dualism, for which some people have never come out!


Sorry for my spit-joint english

airman:shy:
 
  • #12
Cosmo16 said:
ok, maybe it is gamma rays I am thinking of then, we were doing radiation, he was talking about it like it was a particle, but then he called it a ray, left me kinda confused.
Well, there's alpha particles, beta particles, and gamma particles/rays. Gamma rays, are photons, electromagnetic radiation. Wave-particle duality. And photons kind of have mass and kind of don't... rest mass they do have.
 
  • #13
Mk said:
Well, there's alpha particles, beta particles, and gamma particles/rays. Gamma rays, are photons, electromagnetic radiation. Wave-particle duality. And photons kind of have mass and kind of don't... rest mass they do have.

Whoa! Since when?

Zz.
 

Similar threads

Undergrad Trying to understand the inner workings of a solar cell
  • · Replies 2 ·
Replies
2
Views
2K
Undergrad How Can Photons Be Massless Yet Have Energy According to Einstein's Equations?
  • · Replies 3 ·
Replies
3
Views
2K
Graduate Properties of Degenerate Electron Gas
  • · Replies 5 ·
Replies
5
Views
2K
Undergrad Issues in understanding screening effects in the Jellium model
  • · Replies 0 ·
Replies
0
Views
3K
Undergrad Are the electrons in the conduction band completely free?
  • · Replies 11 ·
Replies
11
Views
5K
Undergrad Do electron orbitals ever change?
  • · Replies 13 ·
Replies
13
Views
2K
Undergrad Do electrons have a net motion when a DC voltage is applied?
  • · Replies 7 ·
Replies
7
Views
3K
Undergrad Focus Problem for Entropy Change in Irreversible Adiabatic Process
  • · Replies 60 ·
3
Replies
60
Views
11K
High School Gravitational Force acting on a massless body
  • · Replies 67 ·
3
Replies
67
Views
6K
Undergrad Why can you not describe massive neutrinos with a temperature?
  • · Replies 3 ·
Replies
3
Views
2K