wHAT is the aim of michelson and morley experiment?

Question

also tell weather practically experiment succeded or not?

Answer 1

To find evidence of an ether. None was found, that is, the experiment behaved the same in all directions.

Answer 2

M&M performed their famous experiment on the campus of the U.S. Naval Academy while Michelson was a professor there. USNA now has Michelson Hall as its science building in honor of its distinguished faculty member.

What they discovered was not what they set out to find. They set out to find the so-called aether that, at the time, a lot of physicists thought had to be in space to carry light. So, like a big ocean, this aether would carry light like the water carries waves.

What they expected to see was that light went faster when going into the aether (the sum of velocities) than going out of it. What they found was that v = c = a constant no matter which direction the speed of light was measured. This discovery was, of course, a fundamental stepping stone on the way to the relativity concepts.

So, to answer your question, it did not succeed in proving the existance of aether. But it did succeed in motivating and spuring Einstein to come up with his relativity theories.

Answer 3

Michelson and Morley conducted experiments to find the velocity of light.They have succeeded in their experiment .They placed lens and mirrors in two mountains of approximately equal height , they passed light from one mountain and calculated the time taken for too and fro motion . With the knowledge of time and distance he calculated the velocity of light as 2.99797*10^8m/s .

Answer 4

Here is a series of post that I wrote several years ago when sending a series on relativity. This is the section on the Michelson-Morley experiement and some of its ramifications:

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The laws of motion worked out by Newton and Galileo depended on the assumption that such a thing as absolute motion existed, but, everything is in motion, the Earth, the sun, everything (boy does that sound familiar).

By definition, ether (here, and elsewhere, I’m referring to the luminiferous ether, but I’m just going to call it ether) is motionless, no force can effect it.

If the Earth is moving through the ether, then we ought to be able to use light to calculate the absolute motion of the earth.

Now, suppose that a beam of light is sent out in the direction in which Earth is traveling, and then the light is reflected back to the source. Let us symbolize the velocity of light as c and the velocity of the earth as v, and the distance to the mirror as d. On the trip to the mirror, the velocity of beam is c+v, the velocity of light plus the velocity of the earth (it is traveling with a tail wind). The time it takes to reach the mirror is d divided by (c+v).

On the return trip however, the opposite is true, the light is now bucking a head wind that the new velocity is c-v. The time for the return trips is d divided by (c-v).

The total time for the round trip is:


(d/(c+v)) + (d/(c-v))
Combining the terms we get,

(d(c-v)+d(c+v))/(c+v)(c-v) = (dc-dv+dc+dv)/c²-v² = 2dc/c²-v²

Now, suppose that using the interferometer we send a light beam to a mirror in a direction at right angles to the earths motion.

The beam of light is aimed from S (the source) to M (the mirror) over the distance d. However, during the time it takes the light to reach the mirror, the earths motion has carried the mirror from M to M’, so the actual path traveled by the light is from S to M’. This distance, x, and the distance from M to M’ we will call y.

While the light is moving the distance x at it’s velocity c, the mirror is moving the distance y at the velocity of the earths motion. Since both the light and the mirror arrive at M’ simultaneously, the distances traveled must be proportional to the velocities, therefore:

y/x =v/c

or,

y=xv/c

We can solve for the value of x by using the Pythagorean theorem (no, I’m not going into Pythagoras). In the triangle SMM’, substituting vx/c for y:
x² = d² + (vx/c)²

x² - (vx/c)² = d²

x² - (v²x²/c²) = d²

(c²x² - v²x²)/c² = d²

(c² - v²)x² = d²c²

x² = d²c²/c²-v²

x = dc/ sqr(c²-v²)

Now, did you follow that. It is simple high school algebra, but if you have any trouble with it, ask. Do not be afraid to look dumb, but if you don’t understand that, then you will be lost for the rest of the series.

The light is reflected from the mirror at M’ to the source, which has moved to S”. Since the distance S’S” is equal to SS’, the distance M’S” is equal to x. The total path traveled by the light beam is 2x, or
2dc/sqr(c²-v²).

The time taken by the light beam to cover this distance at it’s velocity c is:

(2dc/sqr(c²-v²)) ÷ c = 2d/√c²-v² .

How does this compare with the time it takes light to travel for the round trip in the direction of earth’s motion? Let us divide the time in the parallel case (2dc/(c²-v²)) by the time in the perpendicular case

(2d/sqr(c²-v²)):

2dc/c²-v² ÷ 2d/sqr(c²-v²) = (2dc/c²-v²)(sqr(c²-v²)) /2d = c/ sqr(c²-v²) /c²-v² .

Now, any number divided by it’s square root is equal gives the same square root as the quotient
that is x/sqr(x) . Conversely, sqr(x) /x = 1/√x . So the last equation simplifies to: c/sqr(c²-v²) .

This expression can be further simplified if we multiply but the numerator and the denominator by sqt1/c² (which is equal to 1/c).

c sqr(1/c²) /sqr(c²-v²) sqr(1/c²) = c/c / sqr(c²/c² - v²/c²) = 1/sqr(1 - v²/c²) .

And there you are.


As you can see by the formulas above, the light traveling perpendicular to the earth motion should take longer then the light traveling with the earths motion to cross the same distance.

Michelson and Morley made herculean efforts to free their equipment from vibrations. They used every means at their disposal to insure that nothing would interfere with their observations. Finally, they sent a beam of light out, split it, rejoined it, and saw...Nothing.

Of course, it might be that the rays of light weren’t heading exactly upwind and downwind, but in such a direction that the ether wind had no effect. However, the instrument could be rotated. They took measurements at all angles— surely the ether wind had to be blowing in some direction. They kept talking measurements all year while the earth itself changed direction as it moved around the sun.

They made thousands of observations, and in July of 1887 they were ready to make their report. The results were negative. They had tried to measure the Earth’s absolute velocity and they failed.

There had to be an explanation of this failure and no less then five of them can be considered for the moment.

1.)The experiment can be dismissed. Perhaps something was wrong with the equipment or the procedure or the reasoning behind it. Lord Kelvin and Oliver Lodge took that point of view.

However, this point of view is not tenable. Since 1887, numerous physicists have repeated the experiment, in 1960, masers were used for this purpose and an accuracy of one part in a trillion was achieved. But, always, the failure was repeated.

2.)Well, the experiment is valid and there is no ether wind for the following reasons.

a)The Earth is not moving. It is the center of the universe and everything revolves around it.

Let’s get real, ok. This would throw everything we ever learned about astronomy out the window.

However, in the interest of proving beyond any doubt that this is wrong, there are plans to duplicate the experiment on the moon as soon as it is feasible.

b)The Earth does move, but in doing so it drags the neighboring ether with it so that it seems motionless compared with the ether at the earths surface.

British physicist George Stokes suggested this, but, this implies that there is friction between the Earth and the ether, and this would raise the question as to why the motions of heavenly bodies weren’t slowing down due to “ether drag”. Stokes’ notion died a quick and painless death.

There are, however two suggestions that survived.

c)The Irish physicist George FitzGerald suggested that all object (and therefore all measuring apparatus) grew shorter in the direction of motion in accordance to a formula which was easily derived.

This is going to be the crux of my next post or two.

The FitzGerald contraction (derived from the Michelson-Morley experiment) was one of the formulas that Albert Whatzname used in formulating his general theory of relativity.

d)The Austrian physicist Ernst Mach went right for the heart of the matter. He said there was no ether wind because there was no ether. What could be simpler?

This still doesn’t explain how light could cross a vacuum. (I could say more about Mach, but I have very little good to say about a man who believed that atoms were a convenient fiction.)

All right, a fairly long post, but it is dealing with an important subject matter. (Notice, not one bit of math) An understanding of Michelson and Morley’s experiment is crucial to understanding what I’m going to start on next.


As I said in the last post, FitzGerald conceived a way to solve the dilemma. He suggested that all objects decrease in length in the direction in which they are moving by an amount equal to: sqr(1-v²/c²).

Thus: L’ = L sqr(1-v²/c²)

Where L’ is the length of a moving object in the direction of it’s motion and L is what the length would be at rest.

The foreshortening fraction sqr(1-v²/c²) is just enough to cancel the ratio 1/sqr(1-v²/c²), which related the maximum and minimum velocities of light in the Michelson-Morley experiment. The ratio would become 1, and the velocity would of light would seem to out foreshortened instruments and senses to be equal in all directions, regardless of movement of the source of light through the ether.

Lets take a close look at this ratio for a minute. As you can see, in order to have any noticeable foreshortening you have to traveling at an appreciable fraction of the speed of light. Let us work this out for an object traveling at .1c (one tenth of the speed of light or 186,282 miles per second).

L’ = L sqr(1 - 0.1/1)²

L’ = L sqr(1-/0.001)

L’ = L sqr(0.99)

L’ = .995L

So, as you can see, even moving at 0.1c, you only have a foreshortening of about half of 1 percent. For moving bodies, velocities such as this only exist in the realm of subatomic particles. The foreshortening of an airplane traveling at 2000 miles per hour would be inconsequential, as you can calculate yourself.

The FitzGerald contraction, while explaining the lack of success in the Michelson-Morley experiment, did, at the time, seem like an excuse and not the major breakthrough it was. He seemed to be saying that nature is conspiring to keep us from measuring absolute motion by introducing an effect that just cancels out any differences we might try to use to detect that motion.

The Dutch physicist, Hendrik Lorentz carried the FitzGerald contraction a bit farther, and used it to show that the mass of an object increases with the motion.

Lets talk mass.

Soon after FitzGerald advanced his equation, the electron was discovered, and scientist began to study the properties of the tiny particle.

Hendrik Lorentz worked out a theory that the mass of a particle with a given charge is inversely proportional to its radius. In other words, the smaller the volume into which a particle crowds it charge, the greater the mass.

Now if a particle is foreshortened because of its motion, its radius in the direction of motion is reduced in accordance with the FitzGerald equation. Substituting the symbols R and R’ for L and L’, we could write the equation:

R’ = R sqr(1-v²/c²),

or:
R’/R = sqr(1-v²/c²).

Now, the mass of a particle is inversely proportional to its radius, or:

R’/R = M/M’

where M is the mass of the particle at rest and M’ is its mass in motion.

Substituting M/M’ for R’/R in the preceding equation, we get:


M/M’ = sqr(1-v²/c²)

or:
M’ = M/sqr(1-v²/c²)

All this means is that the faster a particle travels, the more mass it has, you have the same proportions that FitzGerald worked out or:

vL’M’
.01c-0.995+0.005



Now, lets look at what happens when v=c,
M’ = M/sqr(1-c²/c²) = M/sqr(1-1) = M/0

Now, as the denominator of any fraction with a fixed numerator becomes smaller, the value of the fraction becomes larger. In other words, from the preceding equation it would seem that mass of any object traveling at a velocity approaching that of light becomes infinitely large. Again, the speed of light would seem to be the maximum limit.

All this led Einstein to recast the laws of motion and of gravitation. He considered a universe, in other words, in which the results of the Michelson-Morley experiment would be expected.