Light travels "faster" through vacuums and "slower" through other mediums?

Question

This doesn't make any d**n sense. Lets assume a beam of light traveled through 4 consective points in space.

A. In a Vacuum

B. Through water

C. Back through a Vacuum

D. In air

According to the accepted theory on light travel - That beam of light would have

A. Accelerated to (c)

B. Slowed down considerably

C.Accelerated to (c).

D. Decelerate again.

What it just speeds down and slows up according to the medium? Does anything else accelerate/decelerate like that? Do bullets speed up after exiting corpses?

Wait, thats right - light is massless. Then how in the h**l does it have speed F=Ma?

Isn't it obvious that its our "Minds eye" causing the perceived flucations in light-peed?

Vacuum = No atmospheric density

Air/Water = Dense

It takes "longer" to see light in denser mediums.

Lightspeed = 186,000 kps?

The information has to be there in order for us to register it.

Is lightspeed the speed of registration?

Sunlight 8min from earth = Dist\Reg speed = Time interval

Answer 1

Yeah, I hear what you're saying, when you start talking about light and relativistic velocities, it starts to get dicy, so you really sort of have to step away from classical Newtonian principles because they start to break down when you're talking about quantum phenomena.  First you have to assume that the photon has particle-wave duality.  Mass is irreleveant, so forget f=ma.  Second, you'd really have to carefully study Einsteinian postulates concerning the absolute speed of light in a vacuum.  This is where it gets really difficult to conceptualize since we can even begin to grasp in our everday lives what 300 million m/s is.  It's just a ridiculous speed.  But anyway, if you can accept Einsteinian postulates that light has both particle and wave properties, then you begin to accept that certain phenomena do take place, e.g. refraction of different wavelengths of light as it goes from air and into a prism or a swimming pool, Snell's law and so forth.  The concepts are difficult to intuitively grasp, but they have such significant practical implications on the things we use everyday, that one can only conclude that it has to be right, since after all this time no one has been able to prove that light travels faster in a medium other than a vacuum.

Answer 2

1) light is not massless,

2) wave particle duality is not needed, all the results

can be calculated by wave forms,

3) particle calculations do not return this favour

4) as rule one obtains, it (light) is affected by mass, gravity, etc, the presence of mass in an experiment will have a determinable effect on it's velocity, it will cause drag, as the air does on a car, ( the figure represents the coefficient of drag) , and differing drags (materials) will have different coefficients of drag,

5) the bullet moves by kinetic energy, it loses some of that energy, after passing through a victim, but it is still able to move through air at a higher velocity, because of the lower drag ( resistance) while it first air passage will remain higher , the body passage will slow it overall, the lower resitance, on exit will allow it to lose speed at a slower rate, as well, depending on the amount of resistance (this time caused by the viscosity/resistance of the solid mass, and its thickness the apparent velocity can be observed, in some circumstances to increase, not because of increased energy in the system, but because of lower resistance to it's pathway.

     There is a PS to all this, the fact that we view light speed as  a fixed (for practical purpose)  phenomena, it actually is variable to a degree, (see quantum theory, the theory that Einstein originally came up with, and went on to dismiss, saying it was his one greatest regret, as a scientist, and also that he did not believe god played dice with the universe)but the real stinger is that there are objects in space, that we are aware of, as having far higher velocities than that of light, they are known as "hypervelocity objects" but if you want to have fun, consider this problem , does a shadow move faster than "c", if we have a super powered flashlight, and we point it at an object, it throws a shadow, if we move the flashlight very fast, from one side to another the shadow passes across the geometry of space at increasing speeds depending on how far we are from the object, so a shadow on a wall ten feet away moves far faster than one at two feet, far enough away and the shadow will move across space at what speed, ? and we have these cosmic flashlights in space, so just how fast can a shadow move when the viewer is at cosmic distances, of the receiving end ?