Is the Speed of Light always the same?

Question

Whoa, thanks. I assume the same goes for sound, like a pin dropping and a supernova?

Answer 1

Yes it is! If two spaceships approached each other at the speed of light (C) would they see each other approaching or receding? and don't say "no"cos they were both in bed at the time! That's not fair! lol.

Answer 2

depends on what it travels through the magnitude you mentioned has no effect on speed. 3.00E8m/s but the deviation would very small Im not talking thousands of miles difference/s

Answer 3

very very small variasions in the void of space it's 300 000 km/s in the athmosfere veries a little not much...

Answer 4

The speed of light is always constant no matter what medium it is traveling in.  The light appears to slow down in certain mediums because it takes a little more time for it to bounce around and reflect before it leaves the other side but as it is in there it is still moving at a constant speed.

Answer 5

mohamed mahmoud from California Institute of Technology-

the velocity of light is not constant

Answer 6

The speed varies with the medium.

The constant c is the speed of light in a vacuum. The speed of light in air is very slightly less than c, so c is generally used for simple calculations in air.

Answer 7

The speed of light depends on the medium through which the light travels.

Speed of light in a medium = (Speed of light in a vacuum)/(index of refraction of the medium)

In fact, the index of refraction depends on the frequency of light too, this phenomenon is called dispersion. So, if your christmas light was blue and the star you were comparing it to was a red giant, then the blue light would move slightly slower through air or water than the star light.

So it is not the size of the light that matters but it is the color.

(My question is why do people answer these questions when they have no idea what they are talking about? "Dude, light is light. Thanks for asking such an enlightening question."  The Internet needs less c**p being written by ignoramuses.)  

Answer 8

Contrary to popular belief, the speed of light is not the same all the time.

The speed of light can be different, this is why there is a red shift in stars that are further away, because red light travels faster (so ironically red IS faster!!!).

Light also changes speed in different mediums, light is slightly slower when going through glass then in water, and slower in water than in air.

This difference in speed is such a small amount that to the casual person it is irrelevant. It is only important to physicists and astronomers.

Answer 9

yes

appx 186,000 mi/sec

Answer 10

It's not as simple as a yes or no. If the medium through which they travel is the same temperature, then their speed is the same to a stationary observer. However, since the speed of light is relative, a second observer who has a different velocity (is moving) would see the light travelling at a different speed than the stationary observer would see it travelling relative to the second observer.

To explain it another way:

Say you travel through space at the speed of light. You would still see the light travelling away from you at the speed of light; and to account for this, time would slow down.

To me on the ground, I would see you travelling as fast as light and you would return immediately. For you, it would take much longer. Years may have gone by for you, while on Earth, it was only seconds.

The speed of light is constant and relative, in that it will constantly be the same speed for each observer, no matter how fast that observer moves. Light doesn't speed up; time slows down.

Answer 11

The speed of light never changes. Its always constant. However, if you want to multiply the light in a vacuum to the index of refraction of the medium. That's the speed of light in a MEDIUM. The speed of light will only change when your adding/multiplying something to it, like water or air for instance, otherwise the speed of light stays constant.

Speed of light in a medium = (Speed of light in a vacuum)/(index of refraction of the medium)

And yes, a small christmas light from a strand would travel fast as a large spotlight...Same goes for sound.

Answer 12

Yes, the light from the christmas light would travel as fast as light from a spotlight.  And sound from a pin dropping would travel as fast as sound from a supernova, IF they were both in the same medium (which is unrealistic because supernovas are in space and no sound can travel in space).

Light is said to travel at different speeds in different mediums, but technically it's travelling the same speed always.  When light is in a medium instead of a vacuum, say glass for example, it is bumping into particles.  This means it doesn't get to travel in a perfectly straight line, but instead has to zig-zag.  The actual waves aren't slowing down, it's just they have to travel a bigger distance just to get from point A to B, because the path the light is taking is longer than a straight line.

As for relativity, light is the only thing that has the same relative speed no matter how fast you are travelling relative to it.  If you're travelling toward a lightbeam and you're going half the speed of light, the light still appears to be going at the regular speed of light toward you, not half the speed of light like one might expect.

Answer 13

yes the speed of light is a constant.

Answer 14

The technical speed of light is, in fact, relative. For instance, it goes slower through glass or bouncing off of something reflective. The official speed of light is its speed in space.

Answer 15

No it does not. When taking on an obstacle, to say, or medium it can be slowed not significantly but minutely. In fact, in 1999, a team of scientists led by Lene Hau were able to slow the speed of a light pulse to about 17 metres per second. However, the speed of light is constant when not facing and opposing obstacles.

For more information read this article:

http://en.wikipedia.org/wiki/Speed_of_li...

Answer 16

It depends on the medium.

Light can go fastest at vacuum in 3 * 10^8 m/s.

It will go slower when it passes through water or other translucent materials.  

Answer 17

The speed of light is only constant through a vacuum.

Through other media, its speed is attenuated but not observable to our senses.

The same goes for sound but, sound won't travel through a vacuum so, a Supernova won't be heard anyway. Sound travels well through air, better through liquids and better still through solids.

Answer 18

The speed of light in a vacuum, 299,792,458 m/s (scientific abbreviation "c"), is the universal speed limit. Nothing can go faster than that. However, the speed of light through a medium can be much slower. For example, in glass it's 0.67c.

Jazz Hands has it the other way around. Time dilation is given by the equation:

∆t' = ∆t √(1-v²/c²))

If you travel at .95c, time slows down for you by:

∆t' = ∆t √(1-v²/c²)

∆t' = ∆t √(1-.95²c²/c²)

∆t' = ∆t √(1-.95²)

∆t' = ∆t 0.31225

So, if you were traveling at .95c, time as you measure it goes by slower than someone left on Earth. This has been verified several times using atomic clocks, and is factored into GPS satellites to compensate for the time dilation effect.

See the example applet in the following link:

http://www.walter-fendt.de/ph11e/timedil...

Answer 19

yep, its fast too.

Answer 20

yes the speed of light is constant.

Answer 21

Yea its all the same just the christmas lights would dissipate faster.

Answer 22

The speed at which light travels is a constant 299,792,458 meters per second.

Omg... lala said that the sun is brighter then a star...  The sun is a star!!!

Answer 23

Yes, all light travels at a constant rate. However, the intensity depends on the source. (which is why the sun is brighter than a star)

Answer 24

Red light does not travel faster.  

Answer 25

speed of light is constant in a vacuum. It slows down in other substances, It does not depend on the brightness of the light. It does not depend on relative motion. Everyone, always will measure the same speed of light. It is possible to travel faster than the speed of light in a different medium, like water or plastic, but information can't travel faster. Good question.