Do photons, phonons and electrons have mass?

  • #1
56
12
Poster has been reminded to always show their efforts and links to their reading when asking for help understanding a concept.

Summary:

Do photons, phonons and electrons have mass?

Main Question or Discussion Point

These articles have energy but do they have mass?
 

Answers and Replies

  • #2
berkeman
Mentor
57,510
7,534
Summary:: Do photons, phonons and electrons have mass?

These articles have energy but do they have mass?
What does ##m_e## usually refer to?
 
  • Like
Likes Vanadium 50
  • #4
berkeman
Mentor
57,510
7,534
?
Copy/paste your thread title into a Google search. Then do some reading in the search results. That should answer the ##m_e## part. You will likely still have a few questions about the mass of a photon and phonon, so reply with links to your reading and ask *specific* questions about that reading so that we can help you. Thank you.
 
  • Like
Likes TeethWhitener, Joshy, jim mcnamara and 3 others
  • #5
berkeman
Mentor
57,510
7,534
{crickets}...
 
  • Like
Likes jim mcnamara, Daanh, jbriggs444 and 2 others
  • #6
chemisttree
Science Advisor
Homework Helper
Gold Member
3,424
455
Phonons? You mean lattice vibrations?
 
  • #7
56
12
{crickets}...
It means electron rest mass. But an electron can't be at rest so how it has rest mass?
 
  • Skeptical
Likes PeroK
  • #8
berkeman
Mentor
57,510
7,534
It means electron rest mass. But an electron can't be at rest so how it has rest mass?
You are confusing electrons and photons. Can you post links to the reading you've been doing? That will help us to help you. :smile:
 
  • #9
56
12
You are confusing electrons and photons. Can you post links to the reading you've been doing? That will help us to help you. :smile:
I know the differences between electrons and photons. I just replied about the symbol 'me'. So the correction is: A photon can't be at rest so how it has rest mass? Is 0 considered mass?
 
  • #10
berkeman
Mentor
57,510
7,534
A photon can't be at rest so how it has rest mass?
Where are you reading that?
 
  • #11
56
12
Where are you reading that?
I have yet read at many websites and watched you tube videos.
 
  • #12
berkeman
Mentor
57,510
7,534
I have yet read at many websites and watched you tube videos.
Please post a link to such a source and highlight where they say a photon has rest mass...
 
  • #14
56
12
Electrons don't come at rest. Electron rest mass is the mass of an electron as measured when its speed is zero relative to an observer. A photon never comes at rest thus its rest mass is 0. But why can't be the rest mass of a photon be measured when its speed is zero relative to the observer?
 
  • #15
berkeman
Mentor
57,510
7,534
But why can't be the rest mass of a photon be measured when its speed is zero relative to the observer?
Because photons move at velocity c (the speed of light) relative to all observers. They never appear at rest to any observers. There are probably some Insights articles that we can point you to. Back in a minute...
 
  • #17
38
3
Because photons move at velocity c (the speed of light) relative to all observers.
Not always i.e. inside glass they are moving slower,and inside heavy water of a nuclear reactor very slow.
 
  • Skeptical
Likes weirdoguy
  • #18
Borek
Mentor
28,447
2,842
and inside heavy water of a nuclear reactor very slow.
You've made that up, probably mixing and confusing several unrelated concepts. For most practical purposes the difference between the speed of light in water and heavy water is negligible, close to 0.75c.
 
  • Like
Likes nasu
  • #19
38
3
For most practical purposes the difference between the speed of light in water and heavy water is negligible, close to 0.75c.
You have right,might be inside the core,not in heavy water.
 
  • #20
543
347
Not always
Electromagnetic waves move slower in medium, but that says nothing about photons which are particular states of quantum electromagnetic field. Viewing EM waves as stream of bullet-like particles that slow down in medium is not a good idea.
 
  • Like
Likes dextercioby, etotheipi and phinds
  • #21
Borek
Mentor
28,447
2,842
You have right,might be inside the core,not in heavy water.
You are still making that up.
 
  • Like
Likes nasu
  • #22
38
3
Electromagnetic waves move slower in medium, but that says nothing about photons which are particular states of quantum electromagnetic field. Viewing EM waves as stream of bullet-like particles that slow down in medium is not a good idea.
A static EM field is practicaly not extending to infinite (math function has a definition field);how can EM waves do it,except viewing them as traveling particles? Moreover,you know that pair production is of one gamma-photon,not of a quantum EM field.
 
  • Skeptical
Likes weirdoguy
  • #23
543
347
A static EM field is practicaly not extending to infinite (math function has a definition field);how can EM waves do it,except viewing them as traveling particles?
How EM waves can do what? In your first sentence you wrote about static EM fields, EM waves are not static. Anyways, there are plenty of threads on PF about what photons are, and what they are not. For example this one: https://www.physicsforums.com/threads/what-is-a-photon.879128/ Take your time because it's not an easy topic and a lot of misconceptions circle around.

Moreover,you know that pair production is of one gamma-photon,not of a quantum EM field.
I'm sorry but I don't understand this sentence. Besides, pair production involves at least two photons.
 
Last edited:
  • Like
  • Informative
Likes bhobba and binis
  • #24
34,395
10,479
A static EM field is practicaly not extending to infinite (math function has a definition field);how can EM waves do it,except viewing them as traveling particles? Moreover,you know that pair production is of one gamma-photon,not of a quantum EM field.
I'm not sure what you mean here, but I'm sure it won't help OP understand the concept of mass, so I don't think it's a good idea to continue that.
 
  • Like
Likes bhobba
  • #25
PeterDonis
Mentor
Insights Author
2019 Award
29,718
8,973
Moderator's note: Thread moved to quantum physics forum.
 

Related Threads on Do photons, phonons and electrons have mass?

  • Last Post
Replies
13
Views
7K
  • Last Post
Replies
18
Views
4K
  • Last Post
Replies
2
Views
1K
  • Last Post
Replies
15
Views
823
  • Last Post
Replies
2
Views
139
Replies
5
Views
6K
  • Last Post
Replies
5
Views
456
  • Last Post
Replies
3
Views
3K
  • Last Post
Replies
3
Views
3K
Replies
10
Views
1K
Top