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Medieval Scholar Predicted Halley's Comet's Cycle Early

1/30/2026

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Summary

Story summary

Portegies Zwart argues that Eilmer of Malmesbury identified Halley's Comet's periodic orbit more than 600 years before Edmond Halley.
Historian William of Malmesbury notes that Eilmer linked two Halley's Comet sightings in the late 990s and 1066, a context that includes the Bayeux Tapestry.
This research is detailed in the book Dorestad and Everything After.
Halley's Comet has a 75-year cycle.
Halley's Comet has been recorded since 239 B.C.

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Story summary

Portegies Zwart argues that Eilmer of Malmesbury identified Halley's Comet's periodic orbit more than 600 years before Edmond Halley.
Historian William of Malmesbury notes that Eilmer linked two Halley's Comet sightings in the late 990s and 1066, a context that includes the Bayeux Tapestry.
This research is detailed in the book Dorestad and Everything After.
Halley's Comet has a 75-year cycle.
Halley's Comet has been recorded since 239 B.C.