Thread: the speed of light in relativity.

in relativity theory, why did Einstein says that the speed of light is constant for every thing, and is independent of the speed of the object.
and what is the proof of it?

Michelson–Morley experiment

Astronomers began by observing binary stars (pairs of stars that orbit each other) that were very far away. If the light from the star moving away from us in its orbit traveled even a little slower than the light from the star moving toward us in its orbit, at distances of hundreds of light years away..... then we'd expect there'd be a delay in seeing the light from the star that's moving away, and the orbit wouldn't look right.

They found the orbit looked exactly right, so the light couldn't really be getting delayed, or the delay would have to have been a very small delay. (And the delay wouldn't have been small if there were one)

http://galileo.phys.virginia.edu/cla.../spedlite.html

Prior to Einstein, everyone thought that time was a constant. Einstein figured out that the speed of light, or rather the speed of electromagnetic propogation, was constant. If it were not, then you would see objects moving toward you sooner than you would see something moving across your line of sight.

Originally Posted by JaneBennet

Michelson–Morley experiment

May be their concept of aether was wrong.
What if the aether is attracted by the earth's gravity. i think then we wont be able to detect any aether wind. or with very less speed.

Originally Posted by kojax

Astronomers began by observing binary stars (pairs of stars that orbit each other) that were very far away. If the light from the star moving away from us in its orbit traveled even a little slower than the light from the star moving toward us in its orbit, at distances of hundreds of light years away..... then we'd expect there'd be a delay in seeing the light from the star that's moving away, and the orbit wouldn't look right.

They found the orbit looked exactly right, so the light couldn't really be getting delayed, or the delay would have to have been a very small delay. (And the delay wouldn't have been small if there were one)

the speed of light emitted by the star moving away from us is not expected to be slowed down. Example is the speed of sound of an object moving away is not slowed down, but it is red shiffted.

Originally Posted by Arch2008

Prior to Einstein, everyone thought that time was a constant. Einstein figured out that the speed of light, or rather the speed of electromagnetic propogation, was constant. If it were not, then you would see objects moving toward you sooner than you would see something moving across your line of sight.

No in that case also we are not supposed to see any thing moving towards us sooner.
since we r not moving the speed of light w.r.t. us is same for both cases.
If we move towards the object coming towards us, than we will see it sooner.

Basim, you asked:
“in relativity theory, why did Einstein says that the speed of light is constant for every thing, and is independent of the speed of the object.
and what is the proof of it?”

We are telling you that people wrongly thought there was an aether, that they didn’t know about light red shifting and that they failed to recognize that moving objects do not add there velocity to the speed of light for obvious reasons.
This is the proof.

Originally Posted by Arch2008

We are telling you that people wrongly thought there was an aether, that they didn’t know about light red shifting and that they failed to recognize that moving objects do not add there velocity to the speed of light for obvious reasons.
This is the proof.

still i dont think there is any reason the speed of any object will not be added.
Suppose there is a source of light at a distance of 3x10^8m away from an observer. And when the light is emitted, observer starts moving away from the source.
will that light move towards him with the speed of c relative to observer?
If so what ever is the speed of the observer, he should be able to detect the light in 1s.

If he moves 1.5x10^8m in 1s, then he will observe the light in 1s and second observer there will detect the light in 1.5s???

Originally Posted by basim

Originally Posted by Arch2008

We are telling you that people wrongly thought there was an aether, that they didn’t know about light red shifting and that they failed to recognize that moving objects do not add there velocity to the speed of light for obvious reasons.
This is the proof.

still i dont think there is any reason the speed of any object will not be added.
Suppose there is a source of light at a distance of 3x10^8m away from an observer. And when the light is emitted, observer starts moving away from the source.
will that light move towards him with the speed of c relative to observer?
If so what ever is the speed of the observer, he should be able to detect the light in 1s.

If he moves 1.5x10^8m in 1s, then he will observe the light in 1s and second observer there will detect the light in 1.5s???

The speed of light is independent of the observer and the objects being observed as it's properties are governed by space itself; specifically, the permittivity and permeability of space. Hence, all observers will measure the speed of light at c, and all other objects moving as a percentage of c.

With objects moving at large percentages of c relative to one another, we use velocity additions and apply the Lorentz transformations.

http://hyperphysics.phy-astr.gsu.edu...iv/einvel.html

Originally Posted by basim

Originally Posted by Arch2008

We are telling you that people wrongly thought there was an aether, that they didn’t know about light red shifting and that they failed to recognize that moving objects do not add there velocity to the speed of light for obvious reasons.
This is the proof.

still i dont think there is any reason the speed of any object will not be added.
Suppose there is a source of light at a distance of 3x10^8m away from an observer. And when the light is emitted, observer starts moving away from the source.
will that light move towards him with the speed of c relative to observer?
If so what ever is the speed of the observer, he should be able to detect the light in 1s.

If he moves 1.5x10^8m in 1s, then he will observe the light in 1s and second observer there will detect the light in 1.5s???

Well, at the quantum mechanical level of small-ness it seems that matter is a wave, not an object. It looks like an object, but it moves kind of like a wave. (It's said that it's kind of both particle and wave, but leaning toward wave)

Certain illusions are created by the way we experience matter that make it seem like objects are moving very differently than they really are "under the hood".

Albert Einstein was one of the briliant minds of our comunity , some say he lied in some of his theorys deliberately other say it was rong , but i say it was not understood, by some of your so called great minds with your spaceship cartoons and storys that are only for explaing "the neanderthal" man what is a train.
Some part of true does not make all real ... oh forget it you will never get it ...
Like the Professor sayed :
"I can wire anything directly into anything! I'm a professor!"
That is Albert Einstein.

Originally Posted by basim

in relativity theory, why did Einstein says that the speed of light is constant for every thing, and is independent of the speed of the object.
and what is the proof of it?

There were two answers for the michelson/morley experiment. The shrinkage of matter in the direction of travel is an alternate solution. A Doppler space time solution is also possible. However Einsteins solution is an excellent first order approximation to the complexity of non-liner fourier series type space time.

In general we have a constant light speed galaxy. Each galaxy is an independent inertial system. When you move toward a photon field, the light turns blue while when you move away the light turns red.

However the red shift does not mean the universe is expanding. Each inertial system carries its own reference plane. Energy flow from our galaxy big bang causes the field to move near zero outward here but at light speed C 15.9 billion light years from here.
When light from a far galaxy impinges upon our independent inertial sytem, the result is the redening of the light. Halfway out, the light sees our system moving at C/2 and the result is photons of half the wavelenght coming toward us. At the end of our galaxy field, the photons have zero energy.

Ya but light is speed down and pulled back near black holes right?
because of that light cant escape??