Why lorentz contraction

Indeed, it allows you to see partly around the object and observe its reverse side. Of course, the rapidly moving Enterprise would also be subject to the Doppler effect, which would render it a different colour. Indeed, the frequency shift might even make the craft totally invisible to human eyes. All in all, these effects will make a rapidly moving object, such as the Enterprise , appear nothing like it does at rest.

The idea of length contraction was postulated by the Irish theoretical physicist George FitzGerald in and by the Dutch theorist Hendrik Lorentz in It was only in that Albert Einstein cut through the confusion when he published his special theory of relativity.

It did away with the aether altogether and proposed two postulates. The second postulate states that an observer in any inertial reference frame will measure the speed of light in a vacuum to be the same. From his theory, Einstein derived length contraction as well as time dilation, the equivalence of mass and energy, and more.

Paradoxically, an observer on that train will measure the first as shortened by the same factor. Length contraction has never been directly measured. But its effects show up in the magnetic force that acts between parallel, current-carrying wires.

Phys 29 and Eur. What both Einstein and Lorentz overlooked, however, is the fact that the photons may have been emitted by the object at a different time, especially if the object is large. For an observer looking head-on, two sides would now be visible but not seen to be of equal area.

The moving cube will thus look the same as an undistorted, rotated, non-relativistic cube of length L. Lost in history Over the years, few people paid much attention to observing Lorentz contraction. Concerning the appearance of a moving rod to an observer, his work was unfortunately largely overlooked.

Here's a table that gives the observed length for velocities of various fractions of the speed of light. Now remember that the speed of light is huge compared to any velocity you encounter in everyday life; about ,, metres per second—a thousand million kilometers per hour— million miles an hour.

You aren't likely to notice this; a big dog, one metre from slimy nose to smelly tail, sniffing at a fire hydrant, will appear shorter by less than the size of an atomic nucleus. But if street peddlers don't notice the contraction, surely our exalted spacefarers must look down upon their Earthbound brethren and see us unnaturally slim!

A satellite in low Earth orbit travels about metres per second, which is but 0. Off-duty Blue Team gawkers putting nose-prints on the mid-deck windows of the Space Shuttle will observe objects on the Earth contracted only by a factor of 0. Looking down upon Fourmilab from space station Mir, cosmonauts on board will see the entire kilometre east to west extent of Switzerland contracted by 0.

Here's a view of our ship in the foreground, stopped at rest with respect the the Lattice in the distant background. January 12, at am. Aahan Agrawal says:. April 15, at pm. Aditya says:. August 25, at am. November 25, at pm. Sorry, I can not receive E-mail. November 26, at pm. Sorry, I cannot receive E-mail. November 28, at pm.

Allow mw to rewrite previous post Nov 25 as follows. September 30, at pm. Lorentz contraction In a passenger car, a light source is placed on the floor. Sorry, I cannot receive E mail. I do not have PC. The Physicist says:. October 1, at am. Hiroji kurihara says:. April 29, at pm. Lorentz contraction Plain waves of light wavelength is constant are coming from the upper right 45 degrees.

September 24, at pm. Tranceverse Doppler effect On a plane, pararell lines are drawn. Lorentz contraction In a moving passenger car, MM experiment is being done. Leave a Reply Cancel reply Your email address will not be published. To develop an equation relating distances measured by different observers, we note that the velocity relative to the Earth-bound observer in our muon example is given by.

The velocity relative to the moving observer is given by. The two velocities are identical; thus,. Substituting this equation into the relationship above gives. If we measure the length of anything moving relative to our frame, we find its length L to be smaller than the proper length L 0 that would be measured if the object were stationary.

Those points are fixed relative to the Earth but moving relative to the muon. Figure 3. She can travel this shorter distance in a smaller time her proper time without exceeding the speed of light.

First note that a light year ly is a convenient unit of distance on an astronomical scale—it is the distance light travels in a year. For Part 1, note that the 4. To the astronaut, the Earth and the Alpha Centauri are moving by at the same velocity, and so the distance between them is the contracted length L. First, remember that you should not round off calculations until the final result is obtained, or you could get erroneous results.

This is especially true for special relativity calculations, where the differences might only be revealed after several decimal places. Since the distance as measured by the astronaut is so much smaller, the astronaut can travel it in much less time in her frame. People could be sent very large distances thousands or even millions of light years and age only a few years on the way if they traveled at extremely high velocities.

But, like emigrants of centuries past, they would leave the Earth they know forever. Even if they returned, thousands to millions of years would have passed on the Earth, obliterating most of what now exists. There is also a more serious practical obstacle to traveling at such velocities; immensely greater energies than classical physics predicts would be needed to achieve such high velocities.

This will be discussed in Relatavistic Energy.