Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: acecharly on 27/08/2015 15:51:07

Title: Do gravitons exist, and how we can we detect them?
Post by: acecharly on 27/08/2015 15:51:07

Is it known weather Gravitons exist or are just a theoretical? and if it is theoretical could you not use the height of the tides as an experiment to detect them? When the Moon is above the sea it directly affects the height of the tide whereas when its the opposite side of the Earth it has to work through the mass of the Earth and so could you see a lower tide as some of the Gravitons were absorbed by the Earths mass in a similar way to how they try to detect dark matter deep under ground.

Title: Re: Detecting Gravitons
Post by: jeffreyH on 27/08/2015 18:09:32

You have to appreciate just how weak gravity really is. Gravity is 10^-36 times weaker than the electromagnetic force. Trying to detect individual gravitons will be impossible with the tools we have at hand. That is why scientists are trying to detect gravity waves generated during the early stages of the universe. The effect of gravity on mass is independent of the size of the mass unless the masses involved are of roughly equivalent size. If one mass is very much smaller than the other then its influence is negligible. The tides, whilst involving a substantial amount of mass are a very bad choice. Firstly, they are composed of liquids which are not only reacting to the gravitational force, but to the kinetic energy of the molecules that constitute the oceans. Secondly, overall they compose only a fraction of the mass of the whole earth.

Title: Re: Detecting Gravitons
Post by: acecharly on 27/08/2015 18:16:57

thankyou for the reply very concise :)

Title: Re: Do gravitons exist, and how we can we detect them?
Post by: evan_au on 28/08/2015 01:22:17

Individual gravitons are impossible to detect, with current methods.

However, closely orbiting neutron stars or black holes should emit massive numbers of gravitons with coherent phase. The effects of this on orbiting pulsars  (https://en.wikipedia.org/wiki/PSR_B1913%2B16)has been measured, providing indirect evidence that gravitational waves exist, which is indirect evidence that gravitons exist.

With some upgrades, gravity wave detectors like LIGO (https://en.wikipedia.org/wiki/LIGO#Mission) might just be able to detect some nearby spiralling binary pairs, if they are within 1000km of each other. But we really need space-based detectors, as Earth is too shaky (and too small for a good baseline).

Title: Re: Do gravitons exist, and how we can we detect them?
Post by: lightarrow on 28/08/2015 08:25:14

Detecting gravitons? It's not even sure if they exist (a quantum theory of gravity hasn't been elaborated yet) and you talk of detecting them? Very optimist!  [:)]

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lightarrow