Sorry to present such a difficult question I went looking for answers early today. It seems to be a very speculative area of thought dictated bt the observations suggesting that not only is the Universe is expanding but the expansion is speeding up. I dont agree but as it suits my purposes I will go along with it
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Here is a snip from Physicsweb this morning
"The existence of gravitationally repulsive dark energy would have dramatic consequences for fundamental physics. The most conservative suggestions are that the universe is filled with a uniform sea of quantum zero-point energy, or a condensate of new particles that have a mass that is 10-39 times smaller than that of the electron".
I knew it this could be the gravity rain particle I have imagined. Speculation only but it suits my idea of it would have to be small even in relationship to the electron.
Anyways goto go found some good leads and I cant wait to follow them.
alex