Albert Einstein TLS on Precursors to his Special & General Theories of Relativity, Kepler and Quantum Law - One of the Finest Scientific Letters in English We Have Seen!
Typed Letter Signed, "A. Einstein", 1p, on letterhead of The Institute for Advanced Study, School of Mathematics, 8.5" x 11", Princeton, New Jersey, November 3, 1942. Expected light wear includes folds and creasing. In near fine condition.
Einstein writes to Felix W. Cartier, of Laconite, Minnesota, in full: "Since the times of Kepler one has found approximation formulaes for the mean distances of the planets from the sun. It is sure that there are not precise laws behind those approximate relations. It may be possible to understand regularities of this kind with the methods of statistical mechanics. But hitherto nobody seems to have been able to do so. In any case there is no analogy between such regularities and the quantum laws in molecular physics."
Early in the 17th century, Johannes Kepler (1571-1630) discovered that planets orbit the sun in ellipses rather than perfect circles. This great discovery paved the way for Isaac Newton's laws of gravity, and for Albert Einstein's general and special theories of relativity, which turned the scientific world upside down. Previous to Einstein's time, people believed in real distances and absolute time, and showed that instruments could not objectively measure the distances between planets. Einstein's theories, which hypothesized that light and space curve near a massive object, revolutionized scientific thought and gave man an exciting new perspective of his universe.
Einstein's letter reflects on some of the most important scientific revelations in the history of physics and astronomy. Kepler defined three laws of planetary motion, however the one specifically referred to in this letter is that all planets move about the Sun in elliptical orbits, having the Sun as one of the foci. If the Universe then consisted only of two point masses - the Sun and a planet - the orbit of that planet would make a perfect, closed ellipse that returned the world to its starting location with each trip around the Sun. But in a Universe governed by Newtonian gravity, with a plethora of massive bodies in our Solar System, that ellipse will precess, or rotate slightly in its orbit.
In the mid-1800s, orbital deviations of Uranus from its predicted motions led to the discovery of Neptune, as the outermost world's gravitational influence accounted for the excess motion. But in the inner Solar System, the nearest planet to the Sun, Mercury, was experiencing a similar problem. With detailed, accurate observations going back to the late 1500s, thanks to astronomer Tycho Brahe, we could measure how Mercury's perihelion, its closest orbital point to the Sun, was advancing. The number we came up with was 5,600" per century, which is incredibly slow: just over 1.5 degrees over a 100 year period! But of that, 5,025" came from the precession of Earth's equinoxes, a well-known phenomenon, while 532" was due to Newtonian gravity.
But 5,025" plus 532" does not equal 5,600"; it comes up short by a small but significant amount. The big question, of course, is why? There were, of course, a number of possibilities put forth. Perhaps the data was wrong; an error of less than one percent hardly seems like a reason to panic. And yet, the errors at the time were less than 0.2%, meaning the data was significant. Perhaps there was an extra inner planet, one even interior to Mercury. This explanation was put forth by Urbain Le Verrier, the scientist who predicted the existence of Neptune. Yet after an exhaustive search, including of modifications to the Sun's corona, no planet was found. Or perhaps the Newtonian force law needed a slight tweak.
But after Einstein's special theory of relativity came out in 1905, mathematician Henri Poincare showed that the phenomena of length contraction and time dilation contributed a fraction, between 15-25%, of the needed amount towards the solution, dependent on the error. That, plus Minkowski's formalization of space and time as not separate entities, but as a single structure bound together by their union, spacetime, led Einstein to develop the general theory of relativity. On November 25, 1915, he presented his results, computing the spectacular figure that the contribution of the extra curvature of space predicted an additional precession of 43" per century, exactly the right figure needed to explain this observation. The shockwaves through the astronomy and physics communities were tremendous. Less than two months after this, Karl Schwarzschild found an exact solution, predicting the existence of black holes. The deflection of starlight and gravitational redshifts/blueshifts were realized as possible tests, and finally the solar eclipse of 1919 validated general relativity as superseding Newtonian gravity. An incredible letter, scarce in its important content!
This item comes with a Certificate from John Reznikoff, a premier authenticator for both major 3rd party authentication services, PSA and JSA (James Spence Authentications), as well as numerous auction houses.
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