以a visit to the farm为题的英语作文
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and other galaxies, there should be a lot of "dark matter", that is we cannot see directly, but due to the influence of its gravitational attraction on the orbits of stars in the galaxy, we know it must exist. Moreover, it is found that most galaxies are of a group.. Similarly, by the effect of its motion on galaxies, we can infer that there is more dark matter between the galaxies and the clusters.. Adding all these dark matter together, we can only get 1/10 of the
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