If the Earth is moving at a fraction of the speed of light, does light move slower in the same direction?

Question

Let's just say the Earth is moving at 185,999 miles per second, and you shoot a laser in the same direction the Earth is already traveling, at what speed does the light from the laser move away from Earth?

Answer 1

This is one of the biggest questions in physics. In fact, because of this question, it kept many scientists busy for quite a while(including Albert Einstein). When physicists did find the answer to this question, Newtonian Mechanics was almost at a collapse.

According to Newtonian Mechanics, two objects moving moving relative to each other at the exact same velocity will see each other as "still", or stationary. For example, two cars moving next to each other at a velocity of 55 km/hr. When one driver(any driver) looks outside the window, the other car will appear to be at rest.

For light, or any electromagnetic wave, this does not apply. The speed of an electromagnetic wave is always constant. In a vacuum, it will be 3*10^8 meters per second. An electromagnetic wave(visible light in this case) does not travel relative to anything. You can be travelling at .99 the speed of light and it will still be moving 300 million meters per second. This is an odd phenomena, but this can be explained through what Einstein called his theory of special relativity.

One part of this relativity theory that explains the speed of light is time dilation. This states that as an object reaches speeds that are comparable to light, time begins to slow down. This only works for speeds that are comparable to light speed. So if you are going 100 mph in a car, there will be almost no change in time. Because the slowing down of time, the light has time to travel that 300 million meters.

Answer 2

It moves away at whatever speed light has in the medium the Earth is traveling in at the time.

However, the situation does not have no effect at all on the light of the laser. The frequency of the light, as it appears from the Earth in this example, will be MUCH lower than it would be if emitted from that laser if shot from an Earth moving at a more normal velocity.

Although, from an observer's (at a lower velocity that the Earth and laser) standpoint, the laser's frequency will be shifted some amount, based upon the observer's velocity. And so on, in general.

Note that a lower frequency means a lower energy. Since this is relative to the observer, you can think of it as being lower in inverse proportion to energy/mass of the observer. Note also that nothing about the laser actually depends on the Earth's energy/mass, except to observers that are part of the Earth system as it trucks along.

It is that relativeness that is the fascinating, vexing and perhaps brilliant aspect of Einstein's theory.

Answer 3

It's these types of questions that helped motivate Einstein to develop the theory of relativity. The light from the laser would move away from earth at the speed of light.
In addition, if somebody was at rest and watching this whole thing, they would measure the laser moving at the speed of light as well (even though intuitively it seems like they should measure it as faster).
So the answer to your question is that light always moves at the speed of light, regardless of the relative velocities of the light source and the observer.

Answer 4

No...I think the standard explanation is that light propogates
like a wave in all directions and would still move at the same
relative speed for all observers in all frames of reference
without respect to position or velocity.

In other words, light does not move in the same manner as
a bullet from a gun(a bullet shot from a moving platform
will move faster than one shot from a stationary platform.

However, a beam of light propogates from it's point of
origin like a wave at the speed C.

If you have time to read about Einstein's "thought experiments," this conclusion is what leads him to de-
clare that the speed of light(C) is a universal constant

If you were traveling at the speed of light and did the
same thing, you would still see that the wave is propogated
at speed C(not 2C or zero)

Answer 5

A couple guys named Michelson and Morley, thinking along those lines, tried to measure the speed of the earth through the lumineferous ether--the stuff in which light travels at light speed.

They failed to detect any change in the velocity of light. Ever. Light traveled at the speed of light no matter what they did. So the answer is always c=300 million m/s no matter what.

Answer 6

The fundamental axiom of special relativity is that the speed of light is the same from the perspective of *all* observers, regardless of their relative motions, and regardless of the speed of the light source. The important thing to keep in mind is that this makes no sense whatsoever according to Newton's laws of motion and one's usual intuition about the absolute nature of space and time where the velocity of forward thrown projectile is simply added to that of the thrower from the perspective of someone standing still. That is the source of your confusion. Special Relativity allows this sort of thing, however, by posing that the space contracts and time dilates in such a way as to make it so.

Answer 7

the value of sunshine is a relentless for an observer in each reference physique. this is the consumer-friendly theory at the back of the (specific) concept of relativity. on condition that this is the (axiomatic) beginning factor additionally for the final concept of relativity (this is an theory of gravitation), of direction all calculations to be certain the value of sunshine for an observer in yet another reference physique will continually finally end up restoring the "enter": the value of sunshine is a relentless in each reference physique. if so it truly is an around reasoning: c =const. => a lot of mathematical gymnastics => c = const. (whilst performed proper) So, to objective to tutor that the value of sunshine isn't a relentless, employing the thought of relativity (and gravitation is a relativistic result) is a ineffective attempt. in certainty, in case you stumble on that the value of sunshine is *no longer* consistent, is a good evidence which you made some errors on your calculations, maximum probable blended up some reference frames. do no longer difficulty, that still happens to expeirenced physicist on occasion.

Answer 8

Light always moves at 186,000 miles per second in a vacuum.