How does Carlos Frenk simulate the whole universe on a computer?

Carlos Frenk of Durham described four steps. Start from the tiny quantum fluctuations left by inflation, assume what the dark matter consists of, instruct the computer to solve the equations of physics including Einstein's relativity, then let it run, often for months. With the right dark matter assumption the results look like the real universe, and he shows colleagues simulated and real galaxy images side by side.

Inflation was a very rapid expansion in the first tiny fraction of a second, which seeded the irregularities that grew into galaxies.
Simulations in the 1970s found a disc of stars alone buckles into a bar unless a dark matter halo is added.

▸In their words

“And I challenge them to tell me which is which. And more often than not, they fail.” Carlos Frenk · at 30:32 — 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 →

▸More from this episode

Q1How do astronomers know dark matter exists if it gives off no light, according to In Our Time?Q2What did Anne Green say about gravitational lensing as evidence for dark matter?Q3Why do Carolyn Crawford and Carlos Frenk say dark matter cannot be ordinary matter?Q4What are WIMPs and why does Anne Green call them the best dark matter candidate?Q5Why were neutrinos ruled out as dark matter, according to Carolyn Crawford and Carlos Frenk?Q7How are scientists trying to detect dark matter particles directly, according to In Our Time?Q8When does Carlos Frenk predict dark matter will be discovered, and do the other panelists agree?

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