Follow Jan Oort through 1 dated historical records for Netherlands.
A chronological timeline drawn from matching World History Database records.
Oort was studying stellar motions in the local galactic neighbourhood and found that the mass in the galactic plane must be greater than what was observed. Dark matter is postulated by Jan Oort based upon insufficient evidence, to account for the orbital velocities of stars in the Milky Way
These dates and descriptions come from the historical_events database. Exact duplicate records have been collapsed. Names are grouped by the country, Name 2 and Name 1 fields; records with missing Name 2 cannot be reliably assigned to an individual biography. Check the underlying sources before formal citation.