Did Eilmer see Halley’s Comet twice?

If you’re wondering whether the medieval “flying monk” Eilmer of Malmesbury really saw Halley’s Comet twice, the short answer is: probably not. The best current reading of the sources is that Eilmer witnessed Halley’s famous 1066 return—and, years earlier, a different bright comet seen around 1018.

Why? Halley’s Comet swings by Earth roughly every 75–76 years. For Eilmer to have seen it twice, he would have needed to be a child or young adult at the previous return (989) and still alive—and observant—in 1066. That’s not impossible, but it is unusual given what we know about his life and the timing preserved in medieval chronicles. A new historical analysis instead lines up his “earlier” sighting with a well-attested non‑Halley comet in the 1018 timeframe, which fits his age and the textual clues much better.

Who was Eilmer, and why do we care what he saw?

Eilmer of Malmesbury was an 11th‑century Benedictine monk in southwest England, best known for an early attempt at human flight. According to the historian William of Malmesbury, Eilmer fashioned wings and glided from a monastery tower for some distance before crashing and injuring his legs.
Eilmer also appears in William’s history as a sharp observer of the sky. When a brilliant comet appeared in 1066—the year of the Norman Conquest—Eilmer interpreted it as a portent of upheaval, recalling an earlier, similar omen he had seen in his youth.
The 1066 comet is firmly identified as Halley’s Comet, widely recorded across Europe, the Islamic world, and East Asia. It even shows up in the Bayeux Tapestry. The open question is which prior comet Eilmer was thinking of—and whether it, too, was Halley.

Why two Halley sightings are unlikely

Halley’s schedule: The comet’s perihelion years around Eilmer’s lifetime include 989 and 1066—a gap of about 77 years.
Longevity problem: For Eilmer to have personally seen both passes, he would likely have been a teenager or young monk circa 989 and still observant in 1066. That would put him into his 80s or 90s in 1066, a plausible but rare age for the time—especially for someone who had suffered significant injuries from an earlier flying experiment.
Textual timing: William of Malmesbury characterizes Eilmer’s earlier sighting as something he saw in his youth, not early childhood. New scholarship argues that an eye‑catching comet recorded around 1018 matches that description far more naturally than 989 does.

Bottom line: It is more consistent with the biographical and textual evidence that Eilmer saw two different comets—one around 1018, then Halley in 1066—rather than Halley twice.

The new reading in plain terms

A University of Leicester historian has re‑examined the medieval accounts and aligned them with modern reconstructions of historical comets. The proposal:

1066: Undisputed appearance of Halley’s Comet, bright and notable from England in spring. Eilmer sees it and comments on its ominous significance.
Circa 1018: A separate bright comet, not Halley, is recorded in multiple traditions (including East Asian astronomical notes) around this period. This better fits Eilmer’s claim that he had seen a similar comet “earlier in life.”

This interpretation keeps Halley where everyone already agrees it belongs (1066) and replaces the assumed 989 sighting with a near‑contemporary comet that fits Eilmer’s likely age and memory.

How historians match medieval reports to real comets

Linking a passing reference in a thousand‑year‑old chronicle to a specific comet is a bit of detective work. Scholars combine:

Orbital back‑calculations: Astronomers integrate Halley’s orbit backward in time, accounting for gravitational tugs, to estimate when it would have been bright and where it would have appeared in the sky.
Cross‑cultural records: Chinese, Korean, Japanese, Arabic, and European sources often note dates, directions, tail length, and duration. Overlaps strengthen an identification.
Calendar corrections: Medieval Europe didn’t share a single “start of the year.” Dating could begin in January, March (Annunciation style), or at Christmas. Scribal copies also introduce off‑by‑one errors. Historians normalize dates across systems.
Local visibility: Weather, latitude, and horizon obstacles matter. If one region reports a bright comet for weeks and another does not, visibility models can explain the mismatch.
Language cues: Chroniclers use terms like “hairy star,” “broom star,” or “tailed star.” Descriptions of tail direction, motion against constellations, and the comet’s rising or setting help distinguish objects.

When these lines of evidence converge—timing, position, brightness, and cross‑regional corroboration—confidence in an identification rises. For 1066, the convergence strongly favors Halley. For the earlier sighting associated with Eilmer, the convergence favors a different comet around 1018 rather than Halley’s 989 return.

What we actually know about the 1066 return

Timing: Modern calculations put Halley’s 1066 pass near perihelion in early spring, with best visibility from Europe in April.
Records: The 1066 comet is mentioned in numerous European sources and richly chronicled in East Asian records. The Bayeux Tapestry depicts a blazing star and anxious onlookers.
Brightness and spectacle: Reports suggest a prominent naked‑eye object with a distinct tail visible over successive nights—exactly the kind of sky event that sparks commentary from monks, merchants, and monarchs alike.

Given that context, it’s unsurprising that a learned observer like Eilmer took note—and attached meaning to it.

So what was the “other” comet Eilmer saw?

The case for 1018 rests on a few pillars:

Documentary footprints: Non‑Halley comets are recorded around the late 1010s and early 1020s in East Asian chronicles, some bright enough to attract attention. A sighting in or near 1018 lines up with the “earlier in life” window Eilmer references.
Plausible age: If Eilmer was a younger monk or middle‑aged observer around 1018, and an elderly monk in 1066, the timeline is far more natural than bridging 989 to 1066.
Monastic memory: Medieval authors often linked disasters and rulers’ fortunes to sky omens. Eilmer’s recollection of a prior ominous comet need not have been Halley specifically—only a similarly striking apparition.

Could the earlier comet have been in 1017 or 1019 instead? Possibly. Year‑start conventions and copying errors can nudge dates by a year either way. The key point isn’t the exact month—it’s that there was a bright, non‑Halley comet in that neighborhood of time that Eilmer could have seen.

Why this matters beyond a medieval trivia dispute

How we know what we know: The question showcases how historians and astronomers corroborate each other. Medieval texts aren’t just stories; they’re data—messy, subjective, but often surprisingly precise.
Calibrating confidence: Untangling Eilmer’s sightings clarifies which parts of the 1066 narrative are ironclad (it was Halley) and which parts are interpretive (what he saw decades before).
A better biography: Getting the comet chronology right gives a more realistic portrait of Eilmer’s lifespan and intellectual world, connecting early European skywatching, technology curiosity (his glider), and the politics of omen reading.
Public understanding of comets: Many people encounter Halley’s Comet in a historical anecdote first. Showing how evidence is weighed helps demystify both science and history.

Key takeaways

Eilmer almost certainly observed Halley’s Comet in 1066.
His “earlier” comet was very likely not Halley’s 989 return but a different bright comet around 1018 (give or take a year, depending on calendrical conventions).
Seeing Halley twice would have required Eilmer to span a 77‑year gap between returns, which strains the biographical evidence.
Cross‑checking medieval texts with modern orbital models is how historians reach these conclusions.

Halley’s Comet at a glance

Nature: A periodic comet with an orbital period averaging about 75–76 years.
Famous medieval returns: 837, 912, 989, 1066, 1145, 1222, 1301.
Modern era: 1758/59 (the return predicted by Edmond Halley), 1835, 1910, 1986.
Next visit: 2061. If you’re planning ahead, mid‑century observers should get a good show from the Southern Hemisphere, with visibility for many in the North as well.

How sure can we be? A quick look at uncertainty

Orbits are certain; observers are not. Astronomers can retrodict Halley’s past positions with high confidence. The fuzziness lies in human records—what was seen, when, and by whom.
Calendars shift. An event “in 1018” in one source can land in late 1017 or early 1019 after conversion.
Copying errors happen. Many chronicles survive only in later manuscripts, sometimes centuries after the events they describe.
Overinterpretation is tempting. Famous names (like Eilmer) invite us to stitch their stories into neat arcs. Good scholarship resists tidy narratives when the evidence points elsewhere.

Who this guide is for

Readers curious about medieval science and skywatching.
Students and educators looking for a clean explanation of how Halley’s past appearances are identified in texts.
Anyone who has heard the “flying monk saw Halley twice” claim and wants to know what the sources really support.

Common myths and better answers

Myth: Eilmer definitely saw Halley in both 989 and 1066.
- Better answer: He almost certainly saw Halley in 1066; the earlier sighting fits a different comet near 1018.
Myth: Medieval people were too superstitious to be reliable observers.
- Better answer: While they often attached meanings to sky events, many recorded precise, consistent details that modern astronomers find useful.
Myth: We can’t know anything certain about comets from a thousand years ago.
- Better answer: Orbital mechanics plus cross‑cultural records let us identify many historical comets with surprising confidence.

FAQ

Did Eilmer really try to fly?
- Yes. William of Malmesbury describes Eilmer’s gliding attempt from a tower at Malmesbury Abbey, covering a notable distance before crashing. It’s one of Europe’s earliest recorded human‑flight experiments.
How do we know the 1066 comet was Halley’s?
- Multiple independent records across Europe and Asia align with modern orbital calculations for Halley’s 1066 return. The timing, duration, and visibility all fit.
Was there definitely a bright comet around 1018?
- Several independent traditions record comets near that period. Exact dates can differ after calendar conversion, but the cluster of reports supports a prominent non‑Halley comet in the late 1010s.
Could Eilmer have lived long enough to see Halley in 989 and 1066?
- It’s not impossible, but it’s unlikely given the narrative details. The 1018‑plus‑1066 pairing fits his likely age and William’s phrasing better.
Why do some books still say he saw Halley twice?
- The older interpretation linked his “earlier” memory to Halley’s 989 pass. As historians revisited the dating and cross‑records, the 1018 identification became more persuasive. Publishing cycles and summaries often lag behind scholarship.

If you want to go deeper

Look up how Edmond Halley used historical comet records in 1705 to argue that the bright comets of 1531, 1607, and 1682 were the same object returning. His prediction of the 1758/59 return became a landmark in science.
Explore East Asian astronomical annals (e.g., Chinese Song‑dynasty records) and how their systematic sky notes are used today to cross‑validate European chronicles.
Read about medieval calendars and why “what year is it?” can be a surprisingly hard question for historians to answer.

Source & original reading: https://arstechnica.com/science/2026/06/did-a-medieval-flying-monk-spot-halleys-comet-twice-its-complicated/

Did the “flying monk” Eilmer see Halley’s Comet twice? Here’s what the evidence says