Person

Ole Rømer

1644–1710 · 17th century · Also known as Ole Roemer

Ole Rømer was a Danish astronomer who in 1676, working at the Paris Observatory, showed from the timing of eclipses of Jupiter's moon Io that light travels at a finite speed and made the first estimate of it. Back in Copenhagen he was royal mathematician and chief of police, and he reformed Danish weights and measures and the calendar.

Ole Rømer
Image: Jacob Coning · Public domain · Wikimedia Commons

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Denmark-NorwayImpact

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Cite this entry
APA
The Epoch Institute. (2026). Ole Rømer. In The Epoch Institute Encyclopedia. https://the-epoch-institute.org/encyclopedia/ole-romer
MLA
“Ole Rømer.” The Epoch Institute Encyclopedia, The Epoch Institute, 2026, https://the-epoch-institute.org/encyclopedia/ole-romer. Accessed .
Chicago
The Epoch Institute. “Ole Rømer.” The Epoch Institute Encyclopedia. 2026. https://the-epoch-institute.org/encyclopedia/ole-romer.
Harvard
The Epoch Institute (2026) ‘Ole Rømer’, The Epoch Institute Encyclopedia. Available at: https://the-epoch-institute.org/encyclopedia/ole-romer (Accessed: ).

Last reviewed October 2026Random entry ↻