# does friction slow down the speed of light?

how fast does light travel I heard everything that travels is eventually slowed down by friction.

If this is true is light slowed down by friction or does it always keep a constant speed?Why does it always travel the same speed?is there anyway to slow down light?could this possibly be a way for time travel?How fast would light travel if there was friction affecting its speed?

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• 10 years ago

HAHAHAHAHAHAHA

buddy, your thoughts are completely wrong.

• Jared
Lv 7
10 years ago

Anybody who tells you that light can be "slowed down" is not telling you the whole truth.

Light ALWAYS travels @ the speed of light (a constant value).

On the other hand, it takes billions of years for light to go from the core of the Sun to the outter sun.

Why is this? Well it's easy, light bounces off of things. When we say that a certain material slows down light, what is REALLY happening is that the material is "dense" enough such that the light will collide with many particles (could be atoms or molecules). So it's unlikely that the light will travel through the substance unimpeded, instead it will likely collide many times meaning that the distance it needs to travel through the material is MUCH greater than just the thickness (because it's constantly being ping-ponged back and forth before it can exit the material).

So light get's "slowed" down by this effect. But you need to realize that if we look @ one bounce, the time it takes the photon to travel from atom A to atom B is still governed by the constant speed of light.

This has NOTHING to do with time travel...you can't actually slow down a photon...you can only klinko style slow it down...that is present an obstacle course that the photon has to traverse...therefore it can't just go straight through.

• 10 years ago

Light always travels at a constant speed in a vacuum, which is about 3x10^8 m/s.

Light can be slowed down when it travels through some sort of medium, such as water or a crystal, it is slowed down because its energy is quickly absorbed and then re-radiated, but the time delay between the two creates a sort of "friction" if you would like to think of it that way. however, once light is re-radiated, it returns to its standard speed of 3x10^8. The amount by which light is slowed down while traveling through a medium is largely dependent on the type of material,difference materials are given different "refractive indexes" which is a ratio of the standard speed of light to its speed in the medium. It is theoretically possible for the speed of light to be changed by extremely strong gravitational waves, such as the area surrounded a black hole. Time traveling is currently considered impossible because there is no way to exceed the speed of light for any sort of information travel, which would be necessary for time travel.

Source(s): Engineering student with quite a few physics classes.
• 10 years ago

Friction has no effect on the speed of light. The speed of light is set by the electric permittivity and magnetic permeability, which are both properties of empty space.

Just wondering, who told you that "everything that travels is eventually slowed down by friction"? This isn't true...who told you that? Only macroscopic systems created in our Earth world with practical considerations are slowed down by friction. There is no fundamental law that friction has to act, in fact quite the opposite, it is called Newton's first law. Friction is nothing more than a hidden force, which is just a challenge of which to get rid.

Why does it always travel the same speed?

It just does. All observers measure light to travel at the same speed no matter how fast said observer travels. Maxwell's equations predict that there is a wave which uses electric and magnetic fields to propagate, and that wave is light.

Is there anyway to slow down light?

Sort of. If you are wearing glasses and reading this, your glasses work because you can effectively "slow light down". Notice I used the word "effectively".

Materials which are transparent have the ability to change the effective speed of light within them, such that wavelengths get shorter and the phenomena of refraction occurs. Glass, plastic, water, diamond, and even air to a small degree are optically dense materials which can do this.

BUT, you aren't really slowing actual light down. The molecules of optically dense media function more as "stop signs" to light than the "roadway". Free space and the EM fields between molecules is its "roadway". What really happens during transmission of light is that the transparent media molecules absorb and re-emit light, making it waste time in billions of molecules. It just seems to us at the common level that light is slowed down.

Is there a way to actually slow down light in free space? No there is not. Even gravitational lensing (a phenomena of light bending in extreme gravitational fields) doesn't slow down light, it just red-shifts the light.

How fast would light travel if there was friction affecting its speed? I don't really know how friction would apply a force to light.

• 10 years ago

Light slows down when it enters a medium. This is why it looks like objects bend when they're underwater. Friction can slow down anything mass, but light does not consist of mass.

Also, not everything that travels is slowed down by friction. Friction is only present when there is something to give off friction. If you throw a baseball somewhere in space, it will keep going forever, unless it hits some object in space.

• lahne
Lv 4
3 years ago

the speedier an merchandise is vacationing the fewer effect the thrust bursts could have on increasing its velocity assuming the thrust bursts stay consistent. in some unspecified time interior the destiny the cost of the item will tournament the cost of the thrust and there will be not extra pass of momentum. At that element the only thank you to proceed to characteristic velocity is to develop the cost of the thrust.

• 10 years ago

Rephrase what you heard with "ALL MATTER that travels is eventually slowed down by resistive forces, IF it is travelling within a medium that is also composed of matter". Friction is one such resistive force.

However Light is not matter. It is not affected by friciton, or any resistive force.