When does light slow down?

Answer 1

Yes, light is always slowed down when it goes through a medium. All media have an empirical index of refraction which is essentially how much they slow light. A vacuum like space has an index of refraction of 1, which means that light is going it's normal (fastest) speed. Water has an index of refraction of 1.333 so it slows light about 25%. Air is slightly above 1 but less than water.

Light is slowed because its electromagnetic field interacts with that of the atoms and electrons it is passing by.

Answer 2

The speed of light is slowing down simply because we are speeding up. We are speeding up because our galaxy is being pulled towards the intergalactic mass located towards the sagitarius constellation.

See, the common mis-conception is that when our velocity increases, time slows down... but with applied skepticism, we can tell that the only proof we have for time dilation is that light-waves slow down... NOT time itself. In fact, if time were to slow down as well, then there would be no measured difference of alleged "time dilation". This is because (v=d/t) which means that velocity is equivalent to distance (traveled) over time (passed). Now we know from basic algebra, if you increase one side of the equation (by assuming that time slows, therefore providing MORE passage of time) then the other side MUST be increased to remain equivalent as well. That means that if time slows, velocity actually increases... to the effect that there is no measured difference in the overall equation.

Scientist's try to deny this logic because they want to hold on to the fact that 'c' is a constant... (which it is) but they don't understand that applying velocity (a variable) to a constant (light-speed) renders the outcome as another variable... even though 'c' is still in fact constant. For example: '5' is a constant. it is always less than 6 but more than 4. but if we subtract a varibale (x) from 5 (5-x) the answer itself becomes another variable (5-x=y) even though 5 is still constant. For purposes of this explanation, 5 is 'c', 'x' is velocity(v) and y is the modified speed of light dependent of the current velocity. Therefore over time as we are pulled faster and faster towards sagittarius, light will only (and contiuously) slow down.

My question is that if everything is 'relative', how is it that we are apparently able to take a constant measurement of light without a stationary universal point of reference. Whether we are at rest on the surface of the planet or in orbit, we are moving through the solar system, which is moving through the galaxy, which is moving through the universe! Therefore any measurement that we may make on or even around the planet is tainted with are own relative velocities.

Answer 3

The speed of electromagnetic radiation is determined by the electrical characteristics
of the material it's traveling through ... specifically, the electrostatic permittivity and
the magnetic permeability. Those numbers are different for every material. The speed
of light in the material is 1/(the square root of their product). It's slower in any material
than it is in vacuum.

Answer 4

Light slows down when it passes into a denser medium, e.g. when it goes from air to glass.