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Q:
Has the graviton been discovered yet? If it has not, then how can it be detected?
- Bobby (age 16)
Austin, TX, US
A:
Not yet, and I suspect it will be a long time before direct observation of a single graviton will occur. The graviton is a hypothetical quantum mechanical mass-less particle associated with the gravitational field, just as a photon is associated with electromagnetic fields. Unlike the photon, which can be very energetic and detected with off-the-shelf hardware, gravitons carry extremely small amounts of energy, interact only weakly, and carry minute amounts of detectable energy.
The one thing you can look for, however, is the presence of gravitational waves. Indirect evidence for this has been seen in certain binary star orbital decay.
See:
http://www.people.carleton.edu/~jweisber/binarypulsar/First-Binary-Pulsar.htmland
http://en.wikipedia.org/wiki/Gravitational_wave.
Direct searches for gravitational waves are ongoing in several laboratories around the world such as LIGO in the USA and VIRGO in Europe.
See:
http://www.ligo.caltech.edu/ and
http://www.ego-gw.it/virgodescription/pag_1.htmlLeeH
(published on 01/04/2010)
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