Among the four fundamental forces of nature, only gravity has not had a basic unit, or quanta, detected. Physicists expect that gravitational force is transmitted by an elementary particle called a graviton, just as the electromagnetic force is carried by the photon.
While there are deep theoretical reasons why gravitons should exist, detecting them may be physically impossible on Earth.
For example, the conventional way of measuring gravitational forces – by bouncing light off a set of mirrors to measure tiny shifts in their separation – would be impossible in the case of gravitons. According to physicist Freeman Dyson, the sensitivity required to detect such a miniscule distance change caused by a graviton requires the mirrors to be so massive and heavy that they'd collapse and form a black hole.
Because of this, some have claimed that measuring a single graviton is hopeless. But what if you used the largest entity you know of – in this case the universe – to search for the telltale effects of gravitons. That is what two physicists are proposing.
Read more at: http://phys.org/news/2014-03-elusive-graviton.html#jCp
While there are deep theoretical reasons why gravitons should exist, detecting them may be physically impossible on Earth.
For example, the conventional way of measuring gravitational forces – by bouncing light off a set of mirrors to measure tiny shifts in their separation – would be impossible in the case of gravitons. According to physicist Freeman Dyson, the sensitivity required to detect such a miniscule distance change caused by a graviton requires the mirrors to be so massive and heavy that they'd collapse and form a black hole.
Because of this, some have claimed that measuring a single graviton is hopeless. But what if you used the largest entity you know of – in this case the universe – to search for the telltale effects of gravitons. That is what two physicists are proposing.