The Naked Scientists

The Naked Scientists Forum

Author Topic: Speed of light always the same  (Read 12523 times)

Offline syhprum

  • Neilep Level Member
  • ******
  • Posts: 3820
  • Thanked: 19 times
    • View Profile
Re: Speed of light always the same
« Reply #25 on: 31/08/2006 19:31:31 »
David sparkman ask "why does light travel more slowly in a dielectric medium", the answer is that it does not!
What happens is that the photons are absorbed and then re emitted by the atoms of the intervening medium each time this happens there is a small delay but between atoms the photons travel at their normal speed

syhprum
 

Offline syhprum

  • Neilep Level Member
  • ******
  • Posts: 3820
  • Thanked: 19 times
    • View Profile
Re: Speed of light always the same
« Reply #26 on: 06/09/2006 15:54:01 »
It is understood that the apparent slowing down of light in a dielectric medium is due to the absorption and remission of photons by the intervening atoms, could something similar be happening when light moves through 'empty' space where the photons move at infinite speed between the the spontaneously occurring particle/anti particle pairs that quantum theory postulates but interacts with them?

syhprum
 

Offline lightarrow

  • Neilep Level Member
  • ******
  • Posts: 4586
  • Thanked: 7 times
    • View Profile
Re: Speed of light always the same
« Reply #27 on: 07/09/2006 07:57:55 »
It's an interesting idea. Infact, I had thought about it too.

In the Casimir effect http://en.wikipedia.org/wiki/Casimir_effect two plane metal plates very close together produce an "higher quantum void" in the space between, because not all the virtual photons can "fit" inside, so there is a net force pushing the two plates together, due to virtual photons radiation pressure, higher outside the plates than inside of them.

Maybe the electric properties inside this "higher quantum void", specifically the dielectric permittivity epsilon(0), are different, so that even the speed of light is different? If epsilon(0) were lower, c would be higher!
« Last Edit: 07/09/2006 08:00:13 by lightarrow »
 

Offline syhprum

  • Neilep Level Member
  • ******
  • Posts: 3820
  • Thanked: 19 times
    • View Profile
Re: Speed of light always the same
« Reply #28 on: 07/09/2006 08:45:22 »
In the twenties and thirties when electronics were less sophisticated 'Lecher lines' see

http://en.wikipedia.org/wiki/Lecher_lines

Were used to measure the frequency/wavelength of radio frequency generators.
Perhaps this technique could be used with a Casimir system as an experiment.
Sounds so simple someone must of done it already!

syhprum
 

Offline jhaworth562

  • First timers
  • *
  • Posts: 1
    • View Profile
Re: Speed of light always the same
« Reply #29 on: 24/09/2006 21:58:52 »
quote:
Originally posted by darksat

E=MC times pie or pie inverted
Just a thought.


 

Offline ScouseLad

  • Jr. Member
  • **
  • Posts: 16
    • View Profile
Re: Speed of light always the same
« Reply #30 on: 25/09/2006 06:43:59 »
you can say all this mind bogglin stuff......
but how can u actually physically measure the speed of light??? you can't.... its all just made up numbers haha
 

Offline lightarrow

  • Neilep Level Member
  • ******
  • Posts: 4586
  • Thanked: 7 times
    • View Profile
Re: Speed of light always the same
« Reply #31 on: 25/09/2006 14:13:11 »
There isn't the need to measure light's speed anylonger, now c = 299,792,458 m/s by definition.
 

Offline Sandwalker

  • Full Member
  • ***
  • Posts: 83
    • View Profile
Re: Speed of light always the same
« Reply #32 on: 27/09/2006 03:27:25 »
E=MC^2 this formula gives the energy 'tied' up in mass, a joule=1Nm, c=3*10^8 m/s (approx) so the energy in 1kg of mass = 1 x 3*10^8 m/s^2 so thats 9*10^16 joules, thats a lot of energy in a bag of sugar! or enougth energy to accelerate 1 kg of mass to the speed of light in one second in Classical Newtonian Mechanics ((F=MA) and a vacuum), Now this you need to ponder!!

I could not join any group that would have me as a member!
 

Offline bostjan

  • Sr. Member
  • ****
  • Posts: 107
    • View Profile
Re: Speed of light always the same
« Reply #33 on: 28/09/2006 07:40:29 »
Hey, it's pretty simple to measure the speed of light.  Very simple, in fact, as long as you assume light bounces instantly off a mirror.  Set a mirror into regular rotation with a known frequency.  (You can use an elctric drill and an electronic tuner to set the speed).  Bounce a laser from the rotating mirror to a stationary mirror, back to the rotating mirror and you can measure the deflection of the beam.  Knowing the frequency gives you the time of travel and using the measured distances, you can easily calculate the speed.  If you are careful enough, you can get 3.0*10^8 m/s to +/- 5% or so.

The speed of light was calculated from maxwell's equations to be the inverse of square root mu times epsilon (permiability and permitivity).  This has been measure many times since the late 1800's.
 

The Naked Scientists Forum

Re: Speed of light always the same
« Reply #33 on: 28/09/2006 07:40:29 »

 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums
 
Login
Login with username, password and session length