Here is a great simple explanation of gravitational waves and gravitons by Neil deGrasse Tyson. Gravitational waves have been predicted to exist in Physics but have never been measured until recently.
Recent advances in technology have resulted in construction of super-accurate interferometers capable of detecting extremely small changes in distance between laser detectors (1 ten thousand the diameter of a proton).
Two separate interferometers in the USA recently detected the passing of a gravitational wave past Earth. It was the result of a distant star being absorbed by a black hole that occurred long ago but only now, the resulting gravitational wave has reached earth.
Here is a great explanation by Physicist, Brian Greene of how the gravitational wave was detected.
Detection of a graviton wave is the first step toward understanding the true relationship of gravity in the universe.
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