Einstein’s Theory of Gravitation Is Confirmed over Newton’s Theory Summary

  • Last updated on November 10, 2022

Measurements made during an eclipse showed that the Sun’s gravitational field bends the path of starlight.

Summary of Event

Sir Isaac Newton’s Newton, Sir Isaac law of gravitation, published in 1687, states that every mass (every object composed of matter) attracts every other mass through gravitation. Gravitation is the tendency of every particle of matter in the universe to be attracted to every other particle. The more massive the bodies, the stronger the gravitational force between them, and the farther apart the bodies, the weaker the force between them. Gravitation theories Physics;gravitation [kw]Einstein’s Theory of Gravitation Is Confirmed over Newton’s Theory (Nov. 6, 1919)[Einsteins Theory of Gravitation Is Confirmed over Newtons Theory (Nov. 6, 1919)] [kw]Gravitation Is Confirmed over Newton’s Theory, Einstein’s Theory of (Nov. 6, 1919) [kw]Newton’s Theory, Einstein’s Theory of Gravitation Is Confirmed over (Nov. 6, 1919)[Newtons Theory, Einsteins Theory of Gravitation Is Confirmed over (Nov. 6, 1919)] Gravitation theories Physics;gravitation [g]England;Nov. 6, 1919: Einstein’s Theory of Gravitation Is Confirmed over Newton’s Theory[04850] [c]Science and technology;Nov. 6, 1919: Einstein’s Theory of Gravitation Is Confirmed over Newton’s Theory[04850] [c]Physics;Nov. 6, 1919: Einstein’s Theory of Gravitation Is Confirmed over Newton’s Theory[04850] [c]Astronomy;Nov. 6, 1919: Einstein’s Theory of Gravitation Is Confirmed over Newton’s Theory[04850] Einstein, Albert Eddington, Arthur Stanley Dyson, Frank Sitter, Willem de

Although this law was extremely successful, it seemed impossible that one body could exert a force on another body some distance away. To avoid this problem, scientists began to speak of a mass modifying the space around it by establishing a gravitational field. Another mass interacted with the field at its location but not directly with the first mass. How mass could establish a field was not explained.

Albert Einstein took gravitational theory a giant step forward. Taking a hint from the well-known result that all objects—no matter how massive—accelerate at the same rate when acted upon by gravity, Einstein deduced that gravitation and acceleration are equivalent in some fashion. He thought about how a beam of light might look to someone moving upward very quickly in an elevator. If the light beam were actually parallel with the floor as it entered the elevator, it would appear to bend downward slightly as the elevator accelerated. If acceleration and gravitation are equivalent, then gravity must also deflect light rays downward. Since light has no mass, as one normally thinks of it, this result was completely unexpected.

The Sun’s gravity causes space-time to curve, which bends the star’s light and makes it appear to be located where it is not.

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Einstein was perplexed about why a light beam took a curved path when traversing a gravitational field in an otherwise empty space. After all, the path taken by a light ray in an empty space is the definition of a straight line. Yet when is a straight line also a curved line? The answer is clear when the line is drawn on a curved surface such as a globe. For example, one may travel in a straight line along the earth’s equator and eventually return to the starting point without ever turning around.

In 1915 and 1916, Einstein announced his general theory of relativity. General relativity Relativity;general This theory interpreted gravitation not as a force but as the result of curved space-time. Einstein’s idea of space-time Space-time[Space time] imagines the universe as being one unified “continuum” made up of four dimensions. These dimensions are length, width, and height—all of which are defined as “space”—and time. Within that space-time continuum, physical events occur and can be precisely located or mapped. A moving mass would produce a ripple in the curvature of space-time that would expand at the speed of light. By contrast, a weak gravitational field corresponds to almost no curvature of space-time, meaning that space-time is nearly flat.

Einstein suggested three effects that could be measured to see if his theory was accurate: the gravitational “redshift” of light, the advancement of the “perihelion” of the planet Mercury (the part of the planet’s orbit that takes it closest to the Sun), and the deflection of starlight by the Sun. Einstein calculated that a ray of starlight just grazing the Sun should be deflected by only about 1.75 seconds of arc. Stars cannot normally be seen when the Sun is out, so Einstein suggested the measurement be made during a total solar eclipse.

Sir Frank Dyson, the British Astronomer Royal, sent out two expeditions to photograph the eclipse of May 29, 1919. Charles Rundle Davidson Davidson, Charles Rundle led one expedition to Sobral in northern Brazil, while Sir Arthur Stanley Eddington, an English astronomer and physicist, headed the other expedition to Príncipe Island in the Gulf of Guinea. Eddington’s expedition took sixteen photographs of the eclipse. Comparing one of them with another photograph of the same star field taken six months earlier when the Sun was not present, Eddington was delighted to find the star images shifted by the same amount that Einstein had predicted.

On November 6, 1919, Dyson reported on the eclipse expeditions to a joint meeting of the Fellows of the Royal Society and the Fellows of the Royal Astronomical Society held at the Burlington House in London. Sir Joseph John Thomson, Thomson, Joseph John credited with the discovery of the electron and then president of the Royal Society, called Einstein’s theory “one of the greatest achievements in the history of human thought.”

Significance

After the confirmation of Einstein’s general theory of relativity, the public was eager to learn more about him and his theory. Within one year, more than one hundred books on the subject had been published. Leopold Infeld, Infeld, Leopold who cowrote a book with Einstein on relativity, suggested that the intensity of the public reaction was a result of the timing—World War I had just ended. “People were weary of hatred, of killing. . . . Here was something which captured the imagination . . . the mystery of the Sun’s eclipse and of the penetrating power of the human mind.” The general theory of relativity was a great achievement in which all of humankind could take pride.

Einstein’s theory of gravitation will continue to be tested under any circumstance that can be devised, for that is the nature of science. The general theory of relativity has passed the three tests (gravitational redshift, perihelion advance of Mercury, and bending of starlight) Einstein suggested as well as many more tests using radar, radio telescopes, pulsars, and quasars.

Einstein has shown that space is not simply an empty place. Space and time are not independent but must be considered together; furthermore, they are curved by mass. Perhaps most exciting is the picture of the universe that the theory predicts. Ironically, when Einstein’s theory led to the conclusion that the universe was expanding, he rejected it at first, until 1929, when the American astronomer Edwin Powell Hubble Hubble, Edwin Powell offered experimental evidence to show that the universe is, in fact, expanding. Although the properties of the universe as a whole are not yet known, there is every reason to suppose that they will be consistent with the general theory of relativity. Gravitation theories Physics;gravitation

Further Reading
  • citation-type="booksimple"

    xlink:type="simple">Bergmann, Peter G. The Riddle of Gravitation. Rev. ed. Mineola, N.Y.: Dover, 1993. A clear, full presentation of gravitation from the ancient Greeks through special and general relativity and the consequences of quantum mechanics. Many illustrations and diagrams. Helpful bibliography, glossary, and index.
  • citation-type="booksimple"

    xlink:type="simple">Clark, Ronald W. Einstein: The Life and Times. 1971. Reprint. New York: Avon Books, 1984. Among the hundreds of books published on the subject, this one remains a classic. Offers a comprehensive story of Einstein’s life interwoven with his scientific theories. Accessible to lay readers. Includes many historical photographs.
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    xlink:type="simple">Eddington, A. S. Space, Time, and Gravitation. 1920. Reprint. Cambridge, England: Cambridge University Press, 1995. This delightful classic has been reprinted numerous times. Eddington was one of the original researchers of general relativity and was one of the first to understand it. For the well-informed reader, this book gives as much insight into general relativity as can be had without mastery of the mathematics of tensor calculus.
  • citation-type="booksimple"

    xlink:type="simple">Goldsmith, Maurice, Alan Mackay, and James Woudhuysen, eds. Einstein: The First Hundred Years. Elmsford, N.Y.: Pergamon Press, 1980. Collection of various papers on Einstein by experts. Contributions address Einstein the man as well as his impacts on science, society, world affairs, and the arts. Useful for the general reader.
  • citation-type="booksimple"

    xlink:type="simple">Hoffmann, Banesh, and Helen Dukas. Albert Einstein: Creator and Rebel. New York: Viking Press, 1972. Presents “the essential flavor of the man and his science.” Dukas was Einstein’s personal secretary for many years, and she offers some interesting insights. Includes many historical photographs.
  • citation-type="booksimple"

    xlink:type="simple">Pais, Abraham. Subtle Is the Lord: The Science and the Life of Albert Einstein. 1982. Reprint. New York: Oxford University Press, 2005. Meticulously referenced biography of Einstein. Features detailed chronology of Einstein’s life, good subject index, and exhaustive name index.
  • citation-type="booksimple"

    xlink:type="simple">Schilpp, Paul Arthur, ed. Albert Einstein: Philosopher-Scientist. 2 vols. Evanston, Ill.: Library of Living Philosophers, 1949. Collection of essays about Einstein and his work, most of which should be useful to the well-informed layperson. Of special interest are the autobiographical notes by Einstein in volume 1 and the extensive bibliography of Einstein’s works in volume 2.
  • citation-type="booksimple"

    xlink:type="simple">Will, Clifford M. Was Einstein Right? Putting General Relativity to the Test. 2d ed. New York: Basic Books, 1993. Fascinating work, geared for the informed layperson, reviews the classic three tests of relativity.

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