This discovery is why Einstein was history’s greatest physicist

Although many people struggle to name even one living scientist, practically everyone around the world knows who Einstein was. Perhaps the most famous person of the 20th century, Einstein revolutionized the sciences of physics and astronomy, making important contributions that taught us: among many other discoveries that are still relevant today. Einstein’s work continues to endure on a number of other fronts as well, including on paradoxes in quantum entanglement (the EPR paradox), on connecting two well-separated points in spacetime through wormholes (Einstein-Rosen bridges), and in describing the statistics of integer-spin particles (Bose-Einstein statistics).

That would have been enough for a remarkable career and a place among the all-time greats in physics. But the crown jewel of Einstein’s achievements was his revolutionary new theory of gravity — general relativity — which was somehow put forth all the way back in 1915 and has succeeded in every prediction it’s made in all the time since. No other physical theory has endured, without failing and needing to be superseded, for nearly as long in all of modern science.

It’s this success, above all others, that explains why physicists revere and esteem Albert Einstein so highly. This illustration shows the precession of a planet’s orbit around the Sun. A very small amount of precession is due to general relativity in our Solar System; Mercury precesses by 43 arc-seconds per century, the greatest value of all our planets.

Although the total rate of precession is 5600 arc-seconds per century, 5025 of them are due to the precession of the equinoxes and 532 are due to the effects of the other planets in our Solar System. Those final 43 arc-seconds per century cannot be explained without general relativity or some other alternative form of novel physics, beyond the predictions of Newtonian gravity. Although Newton’s gravity was first put forth way back in the 1600s, it seemed to explain absolutely everything we observed — in the heavens and on Earth — for around the next 200 years.

For a while, it looked as though something was odd with Uranus’s orbit, as it wasn’t quite obeying Kepler’s laws of planetary motion as expected, from its discovery in 1781: While some suspected a flaw with Newton’s gravity, the culprit turned out to be an eighth, more distant planet gravitationally tugging on Uranus: Neptune. Its 1846 discovery quieted any critics that Newton had out there. But a new problem wasn’t so easy to get rid of: the orbit of Mercury, whose perihelion was precessing at a slightly greater rate than Newton’s law of universal gravitation could account for.

Additionally, Newton’s laws of motion couldn’t account for behaviors that arose near the speed of light, such as length contraction and time dilation. Newton’s laws, including the laws of motion and the law of gravitation, appeared to work very, very well under nearly all circumstances, but these exceptions were perhaps a hint of something new, exciting, and revolutionary that would take us beyond Newton’s conception of the Universe. If you split light into two perpendicular components and bring them back together, they will produce an interference pattern.