What are WIMPs and why does Anne Green call them the best dark matter candidate?

Anne Green described weakly interacting massive particles, or WIMPs, as the most popular and best motivated dark matter candidate. They barely interact with each other or with normal matter, which explains why none has been seen, and they would weigh from a few to a thousand times a proton. They would be produced just after the Big Bang in the right amount, and they appear in particle theories proposed to unify the fundamental forces.

• The name answers MACHOs, massive astrophysical compact halo objects, the rival ordinary-matter explanation.
• Carolyn Crawford named the axion as another hypothetical particle outside the mainstream.

▸In their words

“Particle physicists are very creative. We're very good at inventing particles.” Anne Green · at 30:57 — open in the transcript →

Source: our own transcription of the episode. The full conversation is on In Our Time (2026-10-26). Read the whole episode summary →

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