How do astronomers detect dark matter in the universe?
Quick Answer
They look for its gravitational effects, such as galaxy rotation, lensing, and the way galaxy clusters hold together. Dark matter does not emit or absorb light, so it must be inferred indirectly.
The Full Story
Dark matter was proposed because visible matter alone could not explain how galaxies and clusters move. Stars in galaxy outskirts orbit too quickly to be held together by visible mass alone, and light from distant objects can bend more than expected around massive structures. The cosmic microwave background also shows patterns that fit a universe containing much more dark matter than ordinary matter. Current estimates suggest dark matter makes up about 27% of the universe’s energy content.
Key Facts
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