Is the speed of light really constant ?

Quote from Gordon Gekko:

so you have a personal relationship with the creator of the universe?

LOL.....i find that a little hard to believe. :D
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What made you suddenly believe in God?
 
Quote from inandlong:

Aphie I don't understand your logic here. It seems that you are saying observed speed and actual speed are two different things.

A light-year is an actual measure of distance that assumes a constant speed. The distance is not covered instantly. It is covered in a year. If I am cruising at the speed of light, it will take me a year to get to something one light year away. And it will feel like a year, not an instant.
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Observed speed and actual speed are two different things, according to Einstein. The best example is a thought experiment. Imagine a man on a train that is traveling 99% of the speed of light. An stationary observer watches as the train shoots by and records the speed at 99% (he's got great reflexes).

Now, the man on the train decides to point his flashlight in the direction that the train is traveling and turns it on. To the man on the train the light travels across the train at 186,282 miles per second.

However, the stationary observer also records the speed of the light leaving the flashlight and finds that it is going precisely 186,282 miles per hour.

How can this be??

General Theory of Relativity.
 
does time exist at all in space ? is time an invention of man to make sense of the seasonal, daily cycles ? if there are no cycles--in space for instance-- does time still exist ?

surfer :)
 
In eastern thought based in Vedic text, time is thought of as an element, a force and power that gives direction to creation. Time moves constantly forward, not backward. There is a beginning in which time becomes active, and an end when time ceases to be active.

According their thought, time is but one of the forces that becomes active at the time of creation of the universe, along with many other forces that perpetuate and maintain the universe until its cycle back into sleep.

The Vedic term for time is Kal.

Here is a link: http://www.boloji.com/hinduism/038.htm

Quote from marketsurfer:

does time exist at all in space ? is time an invention of man to make sense of the seasonal, daily cycles ? if there are no cycles--in space for instance-- does time still exist ?

surfer :)
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Jem, that the speed of light is a universal constant in inertial frames of reference is the postulate that Special Relativity is built upon. In other words, to get the results of SR, you must assume this is true.

It is a good assumption to make, because experimental tests have shown it to be so.

If you ask why the speed of light is constant in all inertial frames, no one knows the answer.

Quote from jem:

aphexcoil. In school I always questioned my physics professors about the concept that two spaceships travelling at 99C shine a light at each other and the light still moves at C. No one ever answered my questions satisfactorily.
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If you want to study the effect on time due to high velocity in accordance with the Special Theory of Relativity, you need to examine the Lorenz Time Dilation Equation. This equation will theoretically show how time is distorted as velocity approaches the speed of light. It should be in any good text on modern physics.

This effect is probably the basis for the idea that velocity cannot exceed the velocity of light and also the younger twin/older twin scenario.

Regards
 
I have seen a lot of pseudo-science relativity talk in these threads... for those interested in the REAL DEAL why not try the short, easy to understand book by the MAN HIMSELF...

"RELATIVITY" by ALBERT EINSTEIN

Really, all you need is a little high school algebra to understand his exposition of Special Relativity. Also note what he does *not* talk about... "what photons see"... "what would happen if you were moving at the speed of light"... great questions, but not science...
 
That's the very point of the thread: Walter Shewart, who was a professional statistician who is the father of Industrial Quality Control, has examined the statistical distribution of the 2885 mesurements of light and said that it was doubtful that the mesurements were consistent as for the stability of the variance - that is to say there was heteroscedascity which can be due to the instrument or to real anisotropy. Since he is not a physician he couldn't say. Now Maurice Allais is a Physician that lives today - so that he can use the latest mesurement tools - and as a Nobel Prize, one cannot doubt his intelligence, if he says that the heteroscedascity is real well it's an hypothesis to be taken into account seriously. And since String Theorists from the fundamental point of view is seeing some problem also with a speed of light that is constant this is even more interesting. Now Allais only says that the speed of light varies around the known constant he didn't say that the speed of light can be say double the current constant :D.

Quote from peterfigliozzi:

Jem, that the speed of light is a universal constant in inertial frames of reference is the postulate that Special Relativity is built upon. In other words, to get the results of SR, you must assume this is true.

It is a good assumption to make, because experimental tests have shown it to be so.

If you ask why the speed of light is constant in all inertial frames, no one knows the answer.
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In fact there are already some astrophysicians who create models with varying constants:

http://www.jp-petit.com/science/f300/a301.htm

A - J.P.Petit : An interpretation of cosmological model with variable light velocity. Modern Physics Letters A, Vol. 3, n°16, nov 1988, p.1527

B - J.P.Petit : Cosmological model with variable light velocity: the interpretation of red shifts. Modern Physics Letters A, Vol.3 , n° 18, dec. 1988, p.1733

BTW apart from constant of light, there is also polemic on the very existence of ... Black Holes :D
J.P.Petit and P.Midy : Questionable black hole. Geometrical Physics A , 12, 2000
http://www.jp-petit.com/Extensions/pres_questionable_en/PQ1trad.htm

As Jean Heidmann, cosmologist at Meudon, now retired, used to say :

- When the talk turns to black holes, you have to leave your common sense in the cloakroom...

Under these conditions, if we decide to forget common sense, where is the limit to unreasonableness? How do we decide to build a "physics of the unobservable".



Quote from harrytrader:

That's the very point of the thread: Walter Shewart, who was a professional statistician who is the father of Industrial Quality Control, has examined the statistical distribution of the 2885 mesurements of light and said that it was doubtful that the mesurements were consistent as for the stability of the variance - that is to say there was heteroscedascity which can be due to the instrument or to real anisotropy. Since he is not a physician he couldn't say. Now Maurice Allais is a Physician that lives today - so that he can use the latest mesurement tools - and as a Nobel Prize, one cannot doubt his intelligence, if he says that the heteroscedascity is real well it's an hypothesis to be taken into account seriously. And since String Theorists from the fundamental point of view is seeing some problem also with a speed of light that is constant this is even more interesting. Now Allais only says that the speed of light varies around the known constant he didn't say that the speed of light can be say double the current constant :D.
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