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Gravity Probe B

Testing Einstein's Universe

Special & General Relativity Questions and Answers

What the ding dang are gravitons?

They are hypothetical particles that are responsible for transmitting the force of gravity from place to place in space-time. They, presumably, travel at the speed of light, have no rest mass, have an unlimited range of influence, and have a quantum spin of 2. Photons are the carriers of the electromagnetic force, but because they carry 10^42 times as much punch per quantum compared to gravitons, we can easily study them in excruciating detail. Gravitons, if they exist at all, are far too weak to study individually. This is a major problem for verifying that they even exist.

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All answers are provided by Dr. Sten Odenwald (Raytheon STX) for the NASA Astronomy Cafe, part of the NASA Education and Public Outreach program.