
Rømer's Diagram
1676 CE
The Hesitation of Light
For most of history, light was assumed to be instantaneous. If you opened your eyes, you saw the world as it was right now. In 1676, Ole Rømer noticed a glitch in the clockwork of the solar system. The eclipses of Jupiter's moon Io happened 'late' when Earth was far from Jupiter, and 'early' when Earth was close.
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For most of history, light was assumed to be instantaneous. If you opened your eyes, you saw the world as it was right now. In 1676, Ole Rømer noticed a glitch in the clockwork of the solar system. The eclipses of Jupiter's moon Io happened 'late' when Earth was far from Jupiter, and 'early' when Earth was close.
He realized this wasn't an irregularity in the moon's orbit, but a delay in the signal itself. Light took time to cross the extra distance. The universe was not a single, simultaneous 'now', but a patchwork of delayed signals.






























































