Changing speed of light

  • #1
iScience
466
5
If the speed of light is changing, does this mean that the permattivity and/or permeability are dynamically changing quantities? are these "constants" derivable yet or are they still only experimentally measured quantities?
 

Answers and Replies

  • #2
mathman
Science Advisor
8,077
547
If the speed of light is changing, does this mean that the permattivity and/or permeability are dynamically changing quantities? are these "constants" derivable yet or are they still only experimentally measured quantities?

What makes you think the speed of light (in vacuum) is changing?
 
  • #3
Dale
Mentor
Insights Author
2021 Award
33,446
10,899
If the speed of light is changing, does this mean that the permattivity and/or permeability are dynamically changing quantities? are these "constants" derivable yet or are they still only experimentally measured quantities?
The speed of light, vacuum permettivity and vacuum permeability are all determined by the system of units. In natural units they are all equal to 1, and in CGS the vacuum permeability and permittivity do not even exist.

What you should really be asking is if the fine structure constant is derivable or only experimentally measured. That is a dimensionless number and so is independent of the system of units. It characterizes the physics rather than the units.

The answer is that the fine structure constant is experimentally measured, not yet derivable.
 
  • #4
CWatters
Science Advisor
Homework Helper
Gold Member
10,545
2,317
Has there been a follow up to..

http://www.newscientist.com/article...t-may-have-changed-recently.html#.U6_HJ2cU91M

Now, Lamoreaux, along with LANL colleague Justin Torgerson, has re-analysed the Oklo data using what he says are more realistic figures for the energy spectrum of the neutrons present in the reactor. The results have surprised him. Alpha, it seems, has decreased by more than 4.5 parts in 108 since Oklo was live (Physical Review D, vol 69, p121701).

That translates into a very small increase in the speed of light (assuming no change in the other constants that alpha depends on), but Lamoreaux's new analysis is so precise that he can rule out the possibility of zero change in the speed of light. "It's pretty exciting," he says.
 
  • #5
iScience
466
5
What makes you think the speed of light (in vacuum) is changing?

I just assumed he was referring to vacuum

The speed of light, vacuum permettivity and vacuum permeability are all determined by the system of units. In natural units they are all equal to 1, and in CGS the vacuum permeability and permittivity do not even exist.

what's CGS?
 
  • #7
athosanian
67
8
the speed of light will be changed when the light goes from the vacuum into the media due to the change of the permability and permittivity. the speed of the light is related to these material properties by checking the wave equations in the medias.
 

Suggested for: Changing speed of light

Replies
19
Views
791
Replies
15
Views
1K
  • Last Post
Replies
2
Views
356
  • Last Post
Replies
2
Views
638
Replies
25
Views
553
Replies
12
Views
1K
  • Last Post
Replies
25
Views
2K
Replies
4
Views
2K
Replies
14
Views
1K
  • Last Post
Replies
4
Views
8K
Top