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Gravity has an analogue to magnetism called gravitomagnetism.

Is it always attractive?

Could "dark matter" or MOND be explained as gravitomagnetism?

i.e if gravitomagnetism is always attractive and additive, what is its strength galaxy-side

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- Thread starter ensabah6
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Gravity has an analogue to magnetism called gravitomagnetism.

Is it always attractive?

Could "dark matter" or MOND be explained as gravitomagnetism?

i.e if gravitomagnetism is always attractive and additive, what is its strength galaxy-side

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mathman

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Jonathan Scott

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Gravity has an analogue to magnetism called gravitomagnetism.

Is it always attractive?

Could "dark matter" or MOND be explained as gravitomagnetism?

i.e if gravitomagnetism is always attractive and additive, what is its strength galaxy-side

Gravitomagnetism is extremely weak. As could be guessed from the analogy with electromagnetism, the strength of a gravitomagnetic source moving at speed v is of the order of v/c times its usual gravitational field, and the strength of the acceleration effect on an object moving at speed V is of the order of V/c times the effect of the usual gravitational field, so overall the effect is of order vV/c

This is much too weak to explain MOND effects, where the acceleration of stars at the edge of a galaxy appears to be significantly greater than the usual gravitational field.

The effects of gravitomagnetism on the path of an object are somewhat ambiguous anyway, as there are other effects of the same order due to the curvature of space which may or may not be considered part of "gravitomagnetism" depending on the point of view.

The effects of gravitomagnetism on rotation are more distinct, in that a body in the vicinity of a massive rotating body experiences tiny rotational effects, such that when local tests appear to show no rotation, there is a very slight rotation relative to the fixed stars, or vice versa. This effect was being investigated by Gravity Probe B, which gave results reasonably consistent with theory but unfortunately failed to achieve the expected accuracy because of unexpected effects of residual charge in the experimental apparatus.

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