czeslaw
Speed of light is = 1/ (e u)^1/2
where e - is the electrical permittivity of the material
u - is the magnetic permeability of the material

http://en.wikipedia.org/wiki/Maxwell's_equations

We know the Vacuum is not perfect empty. There are virtual particles and Vacuum could be polarised.

What is the speed of light in a perfect empty space ?
If permittivity goes to zero the speed of light goes to infinity.

What is the speed of light close to Black Hole in a dense Vacuum ?
Dense plasma has very high permittivity and speed of light slows down.
Is it a Time Dilation ?
Zephir
QUOTE (czeslaw+Jul 30 2007, 11:33 AM)
Speed Of Light Depends On Vacuum Permittivity

Yes, under strong gravitational or electromagnetic field the vacuum foam becomes birefringent, it means the refraction index, speed of light and vacuum permittivity depends on light wave polarization. Such phenomena leads even to the double event horizon of rotating black holes. This is the manifestation of paired time arrow inside of our Universe generation.

czeslaw
I do not know if the speed of light was considered according to this context on the Forum.
I found an interestin link :

RECONSIDERING LIGHT-SPEED

It is at this point in the discussion that a consideration of light-speed becomes important. It has already been mentioned that an increase in vacuum energy density will result in an increase in the electrical permittivity and the magnetic permeability of space, since they are energy related. Since light-speed is inversely linked to both these properties, if the energy density of the vacuum increases, light-speed will decrease uniformly throughout the cosmos. Indeed, in 1990 Scharnhorst [48] and Barton [20] demonstrated that a lessening of the energy density of a vacuum would produce a higher velocity for light. This is explicable in terms of the QED approach. The virtual particles that make up the "seething vacuum" can absorb a photon of light and then re-emit it when they annihilate. This process, while fast, takes a finite time. The lower the energy density of the vacuum, the fewer virtual particles will be in the path of light photons in transit. As a consequence, the fewer absorptions and re-emissions which take place over a given distance, the faster light travels over that distance [49, 50].

However, the converse is also true. The higher the energy density of the vacuum, the more virtual particles will interact with the light photons in a given distance, and so the slower light will travel. Similarly, when light enters a transparent medium such as glass, similar absorptions and re-emissions occur, but this time it is the atoms in the glass that absorb and re-emit the light photons. This is why light slows as it travels through a denser medium. Indeed, the more closely packed the atoms, the slower light will travel as a greater number of interactions occur in a given distance. In a recent illustration of this light-speed was reduced to 17 metres/second as it passed through extremely closely packed sodium atoms near absolute zero [51]. All this is now known from experimental physics. This agrees with Barnett's comments in Nature [11] that "The vacuum is certainly a most mysterious and elusive object...The suggestion that the value of the speed of light is determined by its structure is worthy of serious investigation by theoretical physicists."

http://www.ldolphin.org/setterfield/vacuum.html
Nick
QUOTE (czeslaw+Jul 30 2007, 08:33 AM)
Speed of light is = 1/ (e u)^1/2
where e - is the electrical permittivity of the material
u - is the magnetic permeability of the material

http://en.wikipedia.org/wiki/Maxwell's_equations

We know the Vacuum is not perfect empty. There are virtual particles and Vacuum could be polarised.

What is the speed of light in a perfect empty space ?
If permittivity goes to zero the speed of light goes to infinity.

What is the speed of light close to Black Hole in a dense Vacuum ?
Dense plasma has very high permittivity and speed of light slows down.
Is it a Time Dilation ?

If virtual particles are appearing everywhere and at all times they ought to form at every point a sludge that would slow down matter.

What is the proof of virtual particles?

What if virtual particles don't get their energy from empty space rather they get their energy from the immediate energy field surrounding matter?
Mitch Raemsch
LearmSceince
QUOTE (czeslaw+Jul 30 2007, 08:33 AM)

What is the speed of light in a perfect empty space ?
If permittivity goes to zero the speed of light goes to infinity.

The virtual particles only have an effect when the light has a high enough frequency (short wave length) to "see" them. You can ignore it for radio frequency and even visible light.

I think e and u can be measured using static effects, or at least sub-Hz effects.
czeslaw
QUOTE (LearmSceince+Jul 31 2007, 06:58 AM)
The virtual particles only have an effect when the light has a high enough frequency (short wave length) to "see" them.  You can ignore it for radio frequency and even visible light.

I think e and u can be measured using static effects, or at least sub-Hz effects.

The effect you write about is because of the Microwave Background Radiation and Compton scattering on real particles.
The space (Vacuum) doesn't contain the real particles and EM radiation. There are Virtual Particles only. Virtual particles exist according to uncertainty principle of Heisenberg and represent the energy of the field. See: Casimir force.
In our Observable Universe doesn't exist an empty space.
Permittivity "e" and permeability u are measurable constants.
czeslaw
QUOTE (Nick+Jul 30 2007, 08:03 PM)
If virtual particles are appearing everywhere and at all times they ought to form at every point a sludge that would slow down matter.

What is the proof of virtual particles?

What if virtual particles don't get their energy from empty space rather they get their energy from the immediate energy field surrounding matter?
Mitch Raemsch

The virtual particles are well known in science.
I wrote many examples of the virtual particles existence - http://www.blackholes.int.pl/

I agree with you that the virtual particles are created in the energetic field of the real matter. The virtual particles represent a potential energy and if it is absorbed by a rest mass matter it is transformed in a kinetic energy of the rest mass particle. If the rest mass particle oscillate faster (higher kinetic energy) it emits the oscillations in the space and it creates the potential energy in the space.
There is a simultaneously absorption and emission of the energy.
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