How Mercury and Starlight Overthrew Newton
#5752·Isaac NewtonHistorical profile, July 5, 1687·AI-assistedEvery object pulls on every other object. The pull grows with their masses and weakens with the square of the distance between them. This one law explains the orbits of the planets and why things fall on Earth.
The orbit of the star S2 around the black hole at the center of the Milky Way turns by about 12 arcminutes each time around, as general relativity predicts. Newton’s law predicts no such turning for a single star orbiting a single mass.
#5759·Albert EinsteinHistorical profile revised November 18, 1915·AI-assistedGravity isn’t a force pulling across empty space. It’s the bending of space and time by matter and energy. Planets and light follow the straightest possible paths through this bent spacetime. Starlight passing the edge of the Sun is bent by about 1.7 arcseconds.
General relativity can’t be the whole truth about gravity. Together with quantum theory, it implies that gravity can’t be measured precisely in tiny regions of space. So the smooth spacetime of general relativity must break down there.
#5763·Frank Watson DysonHistorical profile, March 1917·AI-assistedEinstein’s prediction that the Sun bends starlight by 1.7 arcseconds hasn’t been tested yet. The eclipse of May 29, 1919, can test it, since the Sun will be among the many bright stars of the Hyades.
The eclipse photos of 1919 show starlight bent by between about 1.6 and 2.0 arcseconds at the edge of the Sun, as general relativity predicts.
#5752·Isaac NewtonHistorical profile, July 5, 1687·AI-assistedEvery object pulls on every other object. The pull grows with their masses and weakens with the square of the distance between them. This one law explains the orbits of the planets and why things fall on Earth.
Starlight passing the Sun is bent about twice as much as Newton’s law allows.
#5759·Albert EinsteinHistorical profile revised November 18, 1915·AI-assistedGravity isn’t a force pulling across empty space. It’s the bending of space and time by matter and energy. Planets and light follow the straightest possible paths through this bent spacetime. Starlight passing the edge of the Sun is bent by about 1.7 arcseconds.
Einstein’s prediction that the Sun bends starlight by 1.7 arcseconds hasn’t been tested yet. The eclipse of May 29, 1919, can test it, since the Sun will be among the many bright stars of the Hyades.
#5761·Albert EinsteinHistorical profile, November 18, 1915·AI-assistedGeneral relativity has to explain the extra movement of Mercury’s perihelion, which Newton’s law can’t.
General relativity explains it. It makes Mercury’s perihelion move 43 arcseconds per century more than Newton’s law does, with no hidden matter needed.
#5759·Albert EinsteinHistorical profile revised November 18, 1915·AI-assistedGravity isn’t a force pulling across empty space. It’s the bending of space and time by matter and energy. Planets and light follow the straightest possible paths through this bent spacetime. Starlight passing the edge of the Sun is bent by about 1.7 arcseconds.
General relativity has to explain the extra movement of Mercury’s perihelion, which Newton’s law can’t.
Gravity bends light. Starlight passing the edge of the Sun is bent by about 0.83 arcseconds.
Gravity isn’t a force pulling across empty space. It’s the bending of space and time by matter and energy. Planets and light follow the straightest possible paths through this bent spacetime. Starlight passing the edge of the Sun is bent by about 1.7 arcseconds.
#5756·Albert EinsteinHistorical profile, June 1911·AI-assistedGravity bends light. Starlight passing the edge of the Sun is bent by about 0.83 arcseconds.
My calculation of 1911 only counted how gravity slows time. It left out how gravity bends space, which bends light just as much again. So starlight passing the edge of the Sun is bent by about 1.7 arcseconds, not 0.83.
#5756·Albert EinsteinHistorical profile, June 1911·AI-assistedGravity bends light. Starlight passing the edge of the Sun is bent by about 0.83 arcseconds.
Clouds covered the Sun during the eclipse, so we couldn’t measure how much the starlight was bent.
Gravity bends light. Starlight passing the edge of the Sun is bent by about 0.83 arcseconds.
#5754·Urbain Le VerrierHistorical profile, September 12, 1859·AI-assistedNewton’s law isn’t wrong. Unseen matter inside Mercury’s orbit, a planet or a ring of small bodies, would explain the difference. That’s how the unseen Neptune explained the odd motion of Uranus.
Photographs from the eclipses of 1901, 1905, and 1908 show no planet inside Mercury’s orbit big enough to explain its motion. Whatever moves Mercury’s perihelion, it isn’t a planet, or anything else bright enough to photograph.
#5753·Urbain Le VerrierHistorical profile, September 12, 1859·AI-assistedMercury’s perihelion moves about 38 arcseconds per century more than Newton’s law predicts from the pull of the known planets.
Newton’s law isn’t wrong. Unseen matter inside Mercury’s orbit, a planet or a ring of small bodies, would explain the difference. That’s how the unseen Neptune explained the odd motion of Uranus.
#5752·Isaac NewtonHistorical profile, July 5, 1687·AI-assistedEvery object pulls on every other object. The pull grows with their masses and weakens with the square of the distance between them. This one law explains the orbits of the planets and why things fall on Earth.
Mercury’s perihelion moves about 38 arcseconds per century more than Newton’s law predicts from the pull of the known planets.
Every object pulls on every other object. The pull grows with their masses and weakens with the square of the distance between them. This one law explains the orbits of the planets and why things fall on Earth.