He calculated the gravitational mass of the galaxies within the cluster and obtained a value at least 400 times greater than expected from their luminosity, which means that most of the matter must be dark.
Izračunao je gravitacionu masu galaksije unutar klastera i dobio vrednost barem 400 puta veću nego što se očekivalo na osnovu njihovog sjaja, što je značilo da je većina materije tamna.