is it conceivable that light has variable speeds?

Question

I am sure I improperly phrased the question but o well.

This is a qustion about time and space. Can time become denser? If so would the speed of light not be affected?

Answer 1

You have to be very careful when dealing with questions along this line to make sure you say who the observer is. In special relativity (which does not deal with gravity), the speed of light is the same for all observers and for all times.

However, in general relativity, it is possible for an observer to see light moving at slower than the local speed of light. Here's the situation: An observer far from a black hole sends a beam of light into the black hole. As the light approaches the event horizon, it appears to slow down according to that distant observer. However, an unfortunate observer close to the light and the event horizon would see the light as going the usual speed of light.

For general relativity, the local speed of light is always the same, but an observer far from the light can measure a different speed. This is because of curvature effects of space-time (which are vaguely like your dense time).

Answer 2

Time is a dimension, and as such cannot be considered to have a density. According to General Relativity, time is stretched or compressed in accordance with the observer's speed, in order that the observed speed of light remain constant from all points of view. Furthermore, varying the speed of light would ruin the concept of mass/energy equivalence by E = MC^2. So, as far as speed of light in a vacuum is concerned, the answer to your question is a pretty resounding NO. That said, the speed of light is only precise up to the limits imposed by Heisenberg's uncertainty principle- a principle in quantum theory, which places a physical limit on the precision of any determination, including velocity. But within this very narrow uncertainty, the speed can still be considered essentially constant.
Of course, while speed of light in a vacuum doesn't change, its speed in air, water etc can be reduced considerably- due to its interaction with matter. That is however, irrelevant to Relativity Theory.

Answer 3

I don't think time can become denser. It is just a measurement.
Speed of light changes if the ray of the light passes through a different dense medium. For example, light travels faster in air(less dense) than in water or in glass(denser). Refraction of light occurs due to the change of speed of the light.

Answer 4

I believe that since nobody has actually computed nor calculated the actual speed of light, there might be some slight variance to it, especially when different lights are used or in a different environment. There are just too many variables to consider before actually getting the actual speed. One more thing to consider is that the actual composition of light is still a mystery.

Answer 5

I recently read about this ... http://edition.cnn.com/TECH/ptech/9902/19/slow.light.01/

Don't know if this is the answer you are looking for. Don't know what the implications of this are to time....