Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: gem on 23/01/2010 15:53:42
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Has any experiment's ever been done along the lines of the Mitchell/Cavendish to see if the temperature of the mass has any effect on the value of big G
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The equation F = ma requires no constant because we know that every time we use it in the local environment it works. If an equation does not fully understand a phenomena then it requires a constant to make it work. Case in point is gravity, we don't have a clue as to it's mechanism. None the less I don't have an answer for your question since all calculations even on far off galaxies appear to be correct except for galaxy rotation and the pioneer anomaly.
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Experiments have been done at different temperatures and no change has been detected but from the nature of the force, gravity would not be expected to vary with temperature because it is far more fundamental than the concept of temperature. However as temperature is a measure of the atomic agitation of matter the temperature of a gas cloud has a very significant effect on its ability to condense into a compact object like a star or a planet. if the temperature of a gas cloud is too high its atoms can escape from the gravitational field of the condensing object and cause it to loose mass and stop condensing. That is why stars are formed in clouds of cold gas and dust and eventually as stars begin to shine they heat up the cloud and it blows away and evaporates creating beautiful nebulae like the Orion nebula. This is also why "dark matter" cannot condense into dark stars because the only mechanism that allows it to cool down is gravitational radiation and that is incredibly weak.
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Dark matter, is that the thing for which no one has devised a test?
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If I walk across a dark room and stub my toe on something, I don't need any further test to know that it's there.
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How silly of me. That is a very convincing test. Because we can see some anomalies that means it can not be anything but dark matter. No possibility of another explanation?
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I've measured big G between a two masses; one at 18C and one at -270C. The result is close to the world average (which has an uncertainty of +-0.01%). Though an ideal test would compare G between two warm masses to big G between two cold masses, this suggests that if there is a dependence on temperature, it would be very very small. (see http://physics.uci.edu/gravity).
Eric
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Thanks for the reply and the link provided Eric.
I have been studying some of what is posted on the link and i am struggling to understand how the G cryostat pendulum mass interacts with the two 59 KG source masses,it seems that the pendulum mass is central between the two source masses in which case they would just equal each other with no net effect or are the source masses moving in some way?.Can you please explain.
Also what was the diameter and width of the source masses and at what range of distance centre to centre from source mass to pendulum mass were tested?
[it looks from the diagram that there was a fixed limit due to the container as to how close the centres of mass could be] And what was the weight/mass of the pendulum.
Also can you please tell me what material was used for the pendulum mass and what known effects does this reduced temperature have on the movement of the components of its atomic mass. thanks GEM