Changes

*Another is the ''Shapiro effect'', involving time delay in radio signals passing through the gravity well of the Sun or a planet.  Various spacecraft have confirmed this.

*Another is the ''Shapiro effect'', involving time delay in radio signals passing through the gravity well of the Sun or a planet.  Various spacecraft have confirmed this.

*Another is ''gravitational time dilation''.  This is an effect separate from the time dilation of special relativity.  It was tested by the Pound-Rebka experiment in 1959.  No Nobel Prize was was awarded for this.  Professor Pound had previously shared in the 1952 Nobel for his contributions to Nuclear Magnetic Resonance imaging.

*Another is ''gravitational time dilation''.  This is an effect separate from the time dilation of special relativity.  It was tested by the Pound-Rebka experiment in 1959.  No Nobel Prize was awarded for this.  Professor Pound had previously shared in the 1952 Nobel for his contributions to Nuclear Magnetic Resonance imaging.

*Later in the 20th century, even more subtle phenomena were tested.  One was the phenomenon of ''gravitational radiation'', or "gravitational waves".  These waves are incredibly difficult to observe, and had never been observed until 2015.  But extremely dense binary pulsars radiate gravitational waves with sufficient energy loss that, even though we can't detect the waves from Earth, we can see the effect of the energy loss from the radiation.  The extreme precision of the timing of pulses from pulsars makes it possible to observe their energy loss with great accuracy.  Observations by Hulse and Taylor of the pulsar pair known as B1913+16, if assumptions are made,<ref>Similar to the way Kepler chose orbital parameters to fit observed planetary motion to his theory</ref> could make the energy loss appear consistent with the predicted radiation.  The rotating pulsars have moved such that Earth is now out of the beams, so those observations have been discontinued.

*Later in the 20th century, even more subtle phenomena were tested.  One was the phenomenon of ''gravitational radiation'', or "gravitational waves".  These waves are incredibly difficult to observe, and had never been observed until 2015.  But extremely dense binary pulsars radiate gravitational waves with sufficient energy loss that, even though we can't detect the waves from Earth, we can see the effect of the energy loss from the radiation.  The extreme precision of the timing of pulses from pulsars makes it possible to observe their energy loss with great accuracy.  Observations by Hulse and Taylor of the pulsar pair known as B1913+16, found the energy loss to be consistent with the predicted radiation.  This required choosing orbital parameters to be consistent with observation, in the same way that Kepler chose orbital parameters to fit observed planetary motion to his theory.  The rotating pulsars have since moved such that Earth is now out of the beams.  The assumptions required for this, in addition to those listed above, were that pulsars behave consistently.  The 1993 Nobel Prize in physics was awarded for this.

*In late 2015 (and announced in 2016), the LIGO instruments directly detected gravitational waves allegedly from colliding [[black hole]]s.  See [[Gravitational waves]].  Unlike the waves from orbiting pulsars, that could only be detected by the loss of rotation energy, the waves from colliding black holes were strong enough to be detected directly.  There is inherent circularity in this approach, however, because it relies on assumptions about the existence and nature of black holes which cannot be verified independently.

*In late 2015 (and announced in 2016), the LIGO instruments directly detected gravitational waves allegedly from colliding [[black hole]]s.  See [[Gravitational waves]].  Unlike the waves from orbiting pulsars, that could only be detected by the loss of rotation energy, the waves from colliding black holes were strong enough to be detected directly.  The assumptions required for this, in addition to those listed above, were that the objects emitting the radiation (generally believed to be black holes, of course) satisfy the Schwartzschild solution to relativistic mechanics.  The 2017 Nobel Prize in physics was awarded for this.

*In 2018 an observation of the 3-body system PSR J0337+1715, consisting of 2 white dwarfs and a pulsar, was consistent with (and hence tended to confirm) general relativity under conditions of extremely high gravity, to enormous precision.  The assumptions made were the same as those listed above for the 1919 eclipse analysis.  One of the researchers stated "If there is a difference [between observation and the prediction of the Equivalence Principle], it is no more than three parts in a million."<ref>https://www.nbcnews.com/mach/science/einstein-s-theory-relativity-passes-its-toughest-test-yet-ncna889021</ref>

*In 2018 an observation of the 3-body system PSR J0337+1715, consisting of 2 white dwarfs and a pulsar, was consistent with (and hence tended to confirm) general relativity under conditions of extremely high gravity, to enormous precision.  The assumptions made were the same as those listed above.  One of the researchers stated "If there is a difference [between observation and the prediction of the Equivalence Principle], it is no more than three parts in a million."<ref>https://www.nbcnews.com/mach/science/einstein-s-theory-relativity-passes-its-toughest-test-yet-ncna889021</ref>

*In 2018, observations of a star orbiting the supermassive black hole "Sagittarius A*" at the center of our galaxy, showed that the light was stretched from the black hole's gravity just as relativity predicted.  The star orbits Sagittarius A* at speeds of up to 16 million miles per hour.  This was the first observation of such intense gravity.<ref>https://www.nbcnews.com/mach/science/einstein-s-theory-relativity-aces-its-first-black-hole-test-ncna896641</ref>

*In 2018, observations of a star orbiting the supermassive black hole "Sagittarius A*" at the center of our galaxy, showed that the light was stretched from the black hole's gravity just as relativity predicted.  The star orbits Sagittarius A* at speeds of up to 16 million miles per hour.  This was the first observation of such intense gravity.<ref>https://www.nbcnews.com/mach/science/einstein-s-theory-relativity-aces-its-first-black-hole-test-ncna896641</ref>