Special relativity

All three variables—length, time, mass—are covered by the same Lorentz contraction [ .

— Special relativity

The speed of light can never be reached. If it were reached, the outside observer would find that the ship had shrunk to zero length, had acquired an infinite mass, and was exerting an infinite force with its rocket motors. Astronauts inside the ship would observe no changes in themselves, but they would find the cosmos hurtling backward with the speed of light, cosmic time at a standstill, every star flattened to a disk and infinitely massive.

— Special relativity

I. Redefine the foot.VII. Don’t bother with the spacetime Lorentz transformation.

— Special relativity

The views of space and time which I wish to lay before you have sprung from the soil of experimental physics, and therein lies their strength. They are radical. Henceforth, space by itself, and time by itself, are doomed to fade away into mere shadows, and only a kind of union of the two will preserve an independent reality.

— Special relativity

The whole world appears resolved into such world-lines. And I should like to say beforehand that, according to my opinion, it would be possible for the physical laws to find their fullest expression as correlations of these world-lines.

— Special relativity

The word postulate of relativity... appears to me very stale... I should rather like to give this statement the name Postulate of the absolute world (or briefly, world-postulate).

— Special relativity

Poincaré came very close to inventing special relativity in the years 1900-1904, showing in particular that Lorentz transformations form a group; hence in the case of the Poincaré group, the name is accurate.

— Special relativity

The speed of light in an unobtainable limit; when this is reached the formula becomes which reduces to 0. ...In other words, if an object could obtain the speed of light, it would have no length at all in the direction of its motion!

— Special relativity

FitzGerald's theory was put into elegant mathematical form by the Dutch physicist Hendrick Antoon Lorentz, who had independently thought of the same explanation. ...The theory came to be known as the Lorentz-FitzGerald contraction theory.

— Special relativity

Lorentz made an important addition to his original theory. He introduced changes in time. Clocks, he said, would be slowed down by the ether wind, and in just such a way as to make the velocity of light always measure 299,800 meters per second.

— Special relativity

Einstein, following the steps of Ernst Mach... said... There is no ether wind. He did not say that there was no ether; only... [that the ether] is of no value in measuring uniform motion.

— Special relativity

The special theory of relativity carries the classical relativity of Newton forward another step. It says that in addition to being unable to detect the train's motion by a mechanical experiment, it is also impossible to detect its motion by an optical experiment.

— Special relativity

It is not possible to measure uniform motion in any absolute way.

— Special relativity

In the special theory of relativity, the speed of light becomes... a new absolute. ...Regardless of the motion of its source, light always moves through space with the same constant speed.

— Special relativity

There is no absolute time throughout the universe by which absolute simultaneity can be measured. Absolute simultaneity of distant events is a meaningless concept.

— Special relativity

If an astronaut traveled as fast as light his clock would stop completely.

— Special relativity

If two spaceships are in relative motion, an observer on each ship will measure the other ship as contracted slightly in the direction of its motion. ...The theory does not say that each ship is shorter than the other; it says that astronauts on each ship measure the other ship as shorter.

— Special relativity