We know there is matter that cannot be seen by any means available to us, including the different wavelengths of the electromagnetic spectrum. Yet we know this so-called "dark matter" exists. How?
A. Black holes have consumed much of the matter that once existed.
B. At the origin of the universe, there was a large amount of antimatter that became hidden.
C. Einstein's equation shows us the equivalence of energy that could also be considered matter.
D. The spins of galaxies cannot be explained by the amount of known, ordinary matter.

Dark matter is an invisible form of matter that significantly influences the gravitational effects on visible matter. It is necessary to explain the rotational speeds of galaxies and other cosmic phenomena that cannot be accounted for with known ordinary matter. Thus, option D is correct as it highlights the unexplained spins of galaxies by ordinary matter alone. ;

Answered by GinnyAnswer | 2025-07-06

Dark matter is an invisible substance believed to make up about 27% of the universe's mass, inferred mainly from its gravitational effects on visible matter. The spins of galaxies, which cannot be explained by the amount of visible matter alone, are one of the primary pieces of evidence for dark matter. Therefore, option D correctly identifies that the spins of galaxies cannot be explained by the known ordinary matter.
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Answered by Anonymous | 2025-07-09