Did the Greeks Spot Halley's Comet First?

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Piecing together historic record and correlating it with the location of celestial objects nearly 2,500 years ago is an an epic task, but it can prove rather useful for interpreting ancient cosmic discoveries.

After some fascinating astronomical detective work, researchers have (possibly) found the first documented proof of a sighting of Halley’s Comet two centuries earlier than when Chinese astronomers first described the famous ‘dirty snowball’ around 240 BC.

So, who beat the Chinese? The Greeks.

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As reported by Physorg.com, researchers Daniel Graham and Eric Hintz from Brigham Young University at Provo in Utah have modeled the most likely path taken by the comet and found it was possibly visible around 466-467 BC for 82 days.

As they delved into ancient texts prepared by Greek astronomers around that time, it coincided with a meteorite fall and a description of a comet in the sky for a period of 75 days. The fall occurred in the Hellespont region of northern Greece, something that became quite the tourist attraction for five centuries.

But was it Halley’s comet they saw?

Graham and Hintz think so. Adding to the coincidental events, the ancient text also mentions a meteor shower. It seems logical that the Earth could have been passing through the debris field of Halley’s at the time.

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Twice a year in October and May, the Earth sweeps through the comet’s trail of expelled dust and ice, producing two distinct meteor showers, the Orionids and the Eta Aquarids respectively. This trail was left when the famous comet barreled through the inner solar system in 1986, following a similar path every 75-76 years.

But according to the researchers, this meteor shower occurred during July — the text also described strong winds that are typical during that month in the region.

This can be explained by the researcher’s model that back-dated the comet’s position in relation to the Earth, it turns out that our planet may have been passing under the comet’s tail, generating the observed meteors.

Although it might be tempting to link the Hellespont meteorite with the appearance of the comet (did the comet throw a small asteroid toward Earth as it made its passage near the Earth?), it is more likely that the two events were unrelated. “My feeling is that it was just a really cool coincidence,” Hintz said.

Of course, dating anything back to 2,500 years ago comes with huge uncertainties. The accuracy of ancient accounts of observations are debatable. Also, trying to model the path taken by a comet over millennia is fiendishly difficult.

Comets are prone to orbital deviations caused by gravitational influences by the planets and as they expel jets of gas when they get heated by the sun, they can tumble more than expected, creating uncertainty in their predicted location.

Although this research is far from conclusive, it is very interesting to think that Chinese astronomers may have been pipped to the post by their European counterparts on this particular discovery. It makes me wonder what other cosmic events are written in long-lost ancient texts.

Publication: An Ancient Greek Sighting of Halley’s Comet? by Daniel W. Graham and Eric Hintz, 2010.

Image: Halley’s Comet during its 1910 approach (The Yerkes Observatory)

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