Saturday, January 8, 2011

The Graviton 
Goel Andres Velazquez Rosa      
There are four forces that hold the universe together.  First, we have strong force which is carried by the particle gluon.  Then we have the electromagnetic force carried by the photon particles.  The weak force carried by the W and Z bosons.  And finally we have the gravitational force which is believed to be carried by the graviton.  I state that it is believed to be the particle carrier of the gravitational force because it has not yet been observed or discovered.
The graviton is believed to be a particle with specific properties.  If a particle without mass that has a spin of 2 is discovered, automatically it will be known as the graviton. The reason the graviton has to be a particle without mass is because Newton’s law of universal gravitation states that two objects with mass are going to be attracted to each other by a force which is proportional to the product of the two masses and inversely proportional to the square of the distance between the two objects.  The law then infers that no matter the distance, even if it is immense, there will always be an irrelevant attraction; the range is unlimited, so the particle must not have mass.  As to the spin of 2, it is because the graviton is associated with the second-rank tensor gravitational field, thus a spin-2 is needed.  
Then, if we know the specific particle and the properties it needs to have, why is the graviton not yet discovered or approved as the quantum of the gravitational force?  The detection of gravitons is not prohibited by any physical or fundamental law, but at least with the technology we count on, it seems impossible to build a physically reasonable graviton detector because of the graviton’s low interaction with matter (if it exists).  An example of what is thought to be a functional detector, though not reasonable, is one that possesses the mass of Jupiter and is located around a neutron star.  Even with those extreme favorable conditions and 100% efficiency, this ideal detector would only be expected to observe one graviton every 10 years.  So at least for now, we can scratch off the idea of detecting individual gravitons.  Still, there are another detectors like LIGO (Laser Interferometer Gravitational-Wave Observatory) and VIRGO, which is a gravitational wave detector in Italy, that observe and study gravitational waves, which may be a possible coherent state of the gravitons.  One important achievement is that it would be discovered if the gravitons have mass due to the speed at which the gravitational waves travel.  If the waves travel slower than c, the speed of light, this would infer that the gravitons have mass. 
In the Standard Model of elementary particles are present three different categories: quarks, leptons and bosons.  We are interested in the classification of bosons, since these are the carriers of the different four forces.  If the gravitons do exist, the particle would have to be added to the Standard Model of elementary particle as a gauge boson.

1 comment:

  1. Well, the graviton has been discovered. I found it in 2,002. You can detect gravitons using something called a Graviton Sphere....Alfred Schrader May 26, 2011

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