# Ancients Predicting Solar Eclipses **URL:** \ **Category:** Factual Questions\ **Created:** [May 28, 2025, 7:34pm UTC](https://boards.straightdope.com/t/ancients-predicting-solar-eclipses/1018917 "2025-05-28T19:34:30Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![OldGuy](https://avatars.discourse-cdn.com/v4/letter/o/3bc359/32.png) [@OldGuy](https://boards.straightdope.com/u/OldGuy)\ **Post date:** [May 28, 2025, 7:34pm UTC](https://boards.straightdope.com/t/ancients-predicting-solar-eclipses/1018917/1 "2025-05-28T19:34:30Z")
On this date (well sort of who knows exactly what calendar they were using) a solar eclipse occurred, as predicted by the Greek philosopher Thales, while Alyattes was battling Cyaxares leading to a truce. This is the earliest event of which the precise date is known. How could ancients predict solar eclipses. I realize they come with some regularity and the regularity of lunar eclipses which can be seen by half the Earth could likely be predicted. But how regular would solar eclipses that the Greeks would know about have occurred. And the timing has to be quite accurate to know where on Earth it would be seen. ---
**Author:** ![dolphinboy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dolphinboy/32/330_2.png) [@dolphinboy](https://boards.straightdope.com/u/dolphinboy)\ **Post date:** [May 28, 2025, 7:39pm UTC](https://boards.straightdope.com/t/ancients-predicting-solar-eclipses/1018917/2 "2025-05-28T19:39:34Z")
It is believed they used the **[Antikythera Mechanism](https://www.google.com/search?client=firefox-b-1-d&cs=0&sca_esv=3f2684b5ae9554a2&sxsrf=AE3TifPxe7JBlsY2un91urqSZtEaVGJQHw%3A1748461103174&q=Antikythera+Mechanism&sa=X&ved=2ahUKEwiBsdGX9caNAxUJJDQIHSTZI8EQxccNegQICxAB&mstk=AUtExfBd9hCas2zvqddb3dhRxssBwjH5-A_Q7SJ4p7HNqmxhQSA0pbuSNhfR3MuCW0F4vlyDdmBstfp8eFOLHU0rbuZsQzyOS_JIy5nrgYlSpAWYN1dxVRBdnAUCIKCKLBhuTbVOPyFG8TYjodVQGkQP6ETGRm4DjbURypFPAJOS82MfJxk&csui=3):** This intricate device, discovered in a shipwreck, was an analog computer with gears and dials that allowed for the simulation of celestial bodies’ movements, including the Moon and Sun. It could predict eclipses by tracking the Saros cycle. ---
**Author:** ![OldGuy](https://avatars.discourse-cdn.com/v4/letter/o/3bc359/32.png) [@OldGuy](https://boards.straightdope.com/u/OldGuy)\ **Post date:** [May 28, 2025, 8:01pm UTC](https://boards.straightdope.com/t/ancients-predicting-solar-eclipses/1018917/3 "2025-05-28T20:01:18Z")
I didn’t realize repeat solar eclipses in the same spot were so frequent. It sure doesn’t seem like that. ---
**Author:** ![Pleonast](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pleonast/32/1183_2.png) [@Pleonast](https://boards.straightdope.com/u/Pleonast)\ **Post date:** [May 28, 2025, 8:02pm UTC](https://boards.straightdope.com/t/ancients-predicting-solar-eclipses/1018917/4 "2025-05-28T20:02:44Z")
> [@dolphinboy](#): > > It could predict eclipses by tracking the Saros cycle. > **[Saros (astronomy)](https://en.wikipedia.org/wiki/Saros_(astronomy))** > > The saros (/ˈsɛərɒs/ ⓘ) is a period of exactly 223 synodic months, \[a\] 18 years 11 days and 8 hours, that can be used to predict eclipses of the Sun and Moon. One saros period after an eclipse, the Sun, Earth, and Moon return to approximately the same relative geometry, a near straight line, and a nearly identical eclipse will occur, in what is referred to as an eclipse cycle. Every eclipse has an associated saros series and all succeeding or preceding eclipses have a different saros series A ser... Yes, they calculated the saros cycle. I’m not sure if this was done only with mechanical computers, or if anyone used manual arithmetic. ---
**Author:** ![markn\_1](https://avatars.discourse-cdn.com/v4/letter/m/f9ae1b/32.png) [@markn\_1](https://boards.straightdope.com/u/markn_1)\ **Post date:** [May 28, 2025, 8:22pm UTC](https://boards.straightdope.com/t/ancients-predicting-solar-eclipses/1018917/5 "2025-05-28T20:22:10Z")
The Antikythera mechanism is dated to sometime between about 200 BC and 100 BC. Thales died around 550 BC. He certainly did not use the Antikythera mechanism. Probably nothing like it existed in his time. But the mechanism was designed based on an understanding of various astronomical cycles, and perhaps some of that theory was developed by Thales hundreds of years earlier. The claim that Thales predicted an eclipse which later took place and interrupted a battle between the Median king Cyaxares and the Lydian king Alyattes comes from Herodotus. However, this claim is suspect for several reasons, the most obvious being that Herodotus himself says that Cyaxares died ten years before the date of the eclipse. I believe many, if not most, modern historians do not accept that Thales predicted this particular eclipse, and many believe that he probably did not predict eclipses at all. ---
**Author:** ![74westy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/74westy/32/3950_2.png) [@74westy](https://boards.straightdope.com/u/74westy)\ **Post date:** [May 28, 2025, 8:57pm UTC](https://boards.straightdope.com/t/ancients-predicting-solar-eclipses/1018917/6 "2025-05-28T20:57:14Z")
According to [Cicero](https://en.wikipedia.org/wiki/Antikythera_mechanism#Roman_world), Thales had a similar device. > [@](#): > > I had often heard this celestial globe or sphere mentioned on account of the great fame of Archimedes. Its appearance, however, did not seem to me particularly striking. There is another, more elegant in form, and more generally known, moulded by the same Archimedes, and deposited by the same Marcellus, in the Temple of Virtue at Rome. But as soon as Gallus had begun to explain, by his sublime science, the composition of this machine, I felt that the Sicilian geometrician must have possessed a genius superior to any thing we usually conceive to belong to our nature. Gallus assured us, that the solid and compact globe, was a very ancient invention, and that the first model of it had been presented by Thales of Miletus. That afterwards Eudoxus of Cnidus, a disciple of Plato, had traced on its surface the stars that appear in the sky, and that many years subsequent, borrowing from Eudoxus this beautiful design and representation, Aratus had illustrated them in his verses, not by any science of astronomy, but the ornament of poetic description. He added, that the figure of the sphere, which displayed the motions of the Sun and Moon, and the five planets, or wandering stars, could not be represented by the primitive solid globe. And that in this, the invention of Archimedes was admirable, because he had calculated how a single revolution should maintain unequal and diversified progressions in dissimilar motions. When Gallus moved this globe, it showed the relationship of the Moon with the Sun, and there were exactly the same number of turns on the bronze device as the number of days in the real globe of the sky. Thus it showed the same eclipse of the Sun as in the globe [of the sky], as well as showing the Moon entering the area of the Earth’s shadow when the Sun is in line … [missing text] [i.e. It showed both solar and lunar eclipses.] That was written long after the fact so I don’t know what current historians think. ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [May 29, 2025, 11:29am UTC](https://boards.straightdope.com/t/ancients-predicting-solar-eclipses/1018917/7 "2025-05-29T11:29:38Z")
You don’t need something as complicated as an Antikythera Mechanism to predict eclipses. As Gerald Hawkins pointed out in 1966 in **Decoding Stonehenge** , you can simply use the Aubrey Holes at Stonehenge and a couple of markers to calculate when eclipses will occur. Astronomer Fred Hoyle rebutted a critic of the idea and gave detailed instructions on how to do it. > **[Stonehenge – Eclipse Predictor?](https://blog.stonehenge-stone-circle.co.uk/2017/01/04/stonehenge-eclipse-predictor/)** > > Astronomer Prof. Gerald Hawkins wrote two articles for “Nature” in 1963 and 1964 in which he pointed out several new Stonehenge alignments to the Sun and Moon and proposed that the 56 Aubrey Holes … ---
**Author:** ![Schnitte](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/schnitte/32/9033_2.png) [@Schnitte](https://boards.straightdope.com/u/Schnitte)\ **Post date:** [May 29, 2025, 12:20pm UTC](https://boards.straightdope.com/t/ancients-predicting-solar-eclipses/1018917/8 "2025-05-29T12:20:01Z")
I suppose that with all these stories about ancient predictions of astronomical events, there could be a fair amount of ex post validation at work. Suppose Thales predicted that an eclipse would occur on 28 May 585 BC. But the Greeks used an entirely different calendar. How do we know, then, that the date Thales wrote about was the day we’d designate as 28 May 585 BC in our calendar? The only reason we know that is that we can calculate that a solar eclipse took place on that day, and it’s the only one that matches the description in terms of place, visual effect, and Thales’ approximate birth and death dates. But this is circular reasoning: We’re assuming that Thales correctly predcited the eclipse of that day in order to determine the day he predicted the eclipse for. As soon as you’re doubting the accuracy of the written event, the entire story breaks down. ---
**Author:** ![markn\_1](https://avatars.discourse-cdn.com/v4/letter/m/f9ae1b/32.png) [@markn\_1](https://boards.straightdope.com/u/markn_1)\ **Post date:** [May 29, 2025, 3:31pm UTC](https://boards.straightdope.com/t/ancients-predicting-solar-eclipses/1018917/9 "2025-05-29T15:31:11Z")
BTW, even Herodotus does not say that Thales predicted the exact day of the eclipse, only the year that that it occurred. ---
**Author:** ![Peter\_Morris](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/peter_morris/32/359_2.png) [@Peter\_Morris](https://boards.straightdope.com/u/Peter_Morris)\ **Post date:** [May 29, 2025, 3:44pm UTC](https://boards.straightdope.com/t/ancients-predicting-solar-eclipses/1018917/10 "2025-05-29T15:44:58Z")
> [@CalMeacham](#): > > you can simply use the Aubrey Holes at Stonehenge and a couple of markers to calculate when eclipses will occur. But they must have known how to predict eclipses in order to build Stonehenge in the first place. ---
**Author:** ![yendis](https://avatars.discourse-cdn.com/v4/letter/y/ed8c4c/32.png) [@yendis](https://boards.straightdope.com/u/yendis)\ **Post date:** [May 29, 2025, 3:49pm UTC](https://boards.straightdope.com/t/ancients-predicting-solar-eclipses/1018917/11 "2025-05-29T15:49:52Z")
> [@Peter\_Morris](#): > > But they must have known how to predict eclipses in order to build Stonehenge in the first place. That’s equivalent of saying that you can’t make a stopwatch without knowing the speed of sound. Just because a suitably knowledgeable person can use a stopwatch to calculate the distance to a lightning strike. ---
**Author:** ![OldGuy](https://avatars.discourse-cdn.com/v4/letter/o/3bc359/32.png) [@OldGuy](https://boards.straightdope.com/u/OldGuy)\ **Post date:** [May 29, 2025, 4:31pm UTC](https://boards.straightdope.com/t/ancients-predicting-solar-eclipses/1018917/12 "2025-05-29T16:31:53Z")
> [@yendis](#): > > That’s equivalent of saying that you can’t make a stopwatch without knowing the speed of sound. Just because a suitably knowledgeable person can use a stopwatch to calculate the distance to a lightning strike. Certainly if the 56 holes were dug to mark 3 18.61 (Actually 55.83) years on the lunar eclipse cycle, then they must have known of the cycle before they decided how many holes to dig. In any case, most thinking these days is they were not used to mark lunar eclipses. They never would have been used to mark solar eclipses, which don’t repeat at a given location in anything like 18 years. ---
**Author:** ![Chefguy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chefguy/32/138_2.png) [@Chefguy](https://boards.straightdope.com/u/Chefguy)\ **Post date:** [May 29, 2025, 4:50pm UTC](https://boards.straightdope.com/t/ancients-predicting-solar-eclipses/1018917/13 "2025-05-29T16:50:41Z")
> [@dolphinboy](#): > > It is believed they used the **[Antikythera Mechanism](https://www.google.com/search?client=firefox-b-1-d&cs=0&sca_esv=3f2684b5ae9554a2&sxsrf=AE3TifPxe7JBlsY2un91urqSZtEaVGJQHw%3A1748461103174&q=Antikythera+Mechanism&sa=X&ved=2ahUKEwiBsdGX9caNAxUJJDQIHSTZI8EQxccNegQICxAB&mstk=AUtExfBd9hCas2zvqddb3dhRxssBwjH5-A_Q7SJ4p7HNqmxhQSA0pbuSNhfR3MuCW0F4vlyDdmBstfp8eFOLHU0rbuZsQzyOS_JIy5nrgYlSpAWYN1dxVRBdnAUCIKCKLBhuTbVOPyFG8TYjodVQGkQP6ETGRm4DjbURypFPAJOS82MfJxk&csui=3)** Wait. . .that’s _real?_ I just watched the last of the Indiana Jones movies and assumed that it was something they made up for the story. ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [May 29, 2025, 5:11pm UTC](https://boards.straightdope.com/t/ancients-predicting-solar-eclipses/1018917/14 "2025-05-29T17:11:19Z")
> [@Peter\_Morris](#): > > But they must have known how to predict eclipses in order to build Stonehenge in the first place. What you you mean “but”? I didn’t say that they used Stonehenge to figure out how to predict eclipses. I was pointing out that you didn’t need a complex geared mechanism to do the predicting. In either case, you constructed your calculating device already knowing how to do the calculation. ---
**Author:** ![DrDeth](https://avatars.discourse-cdn.com/v4/letter/d/b487fb/32.png) [@DrDeth](https://boards.straightdope.com/u/DrDeth)\ **Post date:** [May 29, 2025, 5:34pm UTC](https://boards.straightdope.com/t/ancients-predicting-solar-eclipses/1018917/15 "2025-05-29T17:34:23Z")
> [@Chefguy](#): > > Wait. . .that’s _real?_ I just watched the last of the Indiana Jones movies and assumed that it was something they made up for the story. Yes, it is real, but of course the one in the film was the fantasy version. Just like no doubt Jesus drank wine at the last Supper, and thus there was a chalice or cup, vs a grail that can cure all wounds and make you live forever. ---
**Author:** ![Peter\_Morris](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/peter_morris/32/359_2.png) [@Peter\_Morris](https://boards.straightdope.com/u/Peter_Morris)\ **Post date:** [May 29, 2025, 6:19pm UTC](https://boards.straightdope.com/t/ancients-predicting-solar-eclipses/1018917/16 "2025-05-29T18:19:55Z")
> [@yendis](#): > > That’s equivalent of saying that you can’t make a stopwatch without knowing the speed of sound. Come again? Sounds like a total non-sequitur. ---
**Author:** ![Hari\_Seldon](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hari_seldon/32/5173_2.png) [@Hari\_Seldon](https://boards.straightdope.com/u/Hari_Seldon)\ **Post date:** [May 29, 2025, 7:11pm UTC](https://boards.straightdope.com/t/ancients-predicting-solar-eclipses/1018917/17 "2025-05-29T19:11:01Z")
You might enjoy seeing this video: [![](https://img.youtube.com/vi/ML4tw_UzqZE/maxresdefault.jpg "Building The World's First Computer - Greeks, Clocks and Rockets - Antikythera Mechanism Episode #1") ](https://www.youtube.com/watch?v=ML4tw_UzqZE) ---
**Author:** ![Marvin\_the\_Martian](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/marvin_the_martian/32/2898_2.png) [@Marvin\_the\_Martian](https://boards.straightdope.com/u/Marvin_the_Martian)\ **Post date:** [May 29, 2025, 7:34pm UTC](https://boards.straightdope.com/t/ancients-predicting-solar-eclipses/1018917/18 "2025-05-29T19:34:40Z")
> [@Schnitte](#): > > We’re assuming that Thales correctly predcited the eclipse of that day in order to determine the day he predicted the eclipse for. We also don’t know how many times he incorrectly predicted an eclipse. Nobody would bother writing that down. “That Thales guy - always with the eclipses…” ---
**Author:** ![dolphinboy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dolphinboy/32/330_2.png) [@dolphinboy](https://boards.straightdope.com/u/dolphinboy)\ **Post date:** [May 30, 2025, 1:24am UTC](https://boards.straightdope.com/t/ancients-predicting-solar-eclipses/1018917/19 "2025-05-30T01:24:48Z")
> [@Chefguy](#): > > Wait. . .that’s _real?_ I just watched the last of the Indiana Jones movies and assumed that it was something they made up for the story. Yes, the Antikythera Mechanism is real. Did you really think the Indiana Jones movies were made up stories? ---
**Author:** ![MikeS](https://avatars.discourse-cdn.com/v4/letter/m/919ad9/32.png) [@MikeS](https://boards.straightdope.com/u/MikeS)\ **Post date:** [May 30, 2025, 11:59am UTC](https://boards.straightdope.com/t/ancients-predicting-solar-eclipses/1018917/20 "2025-05-30T11:59:52Z")
They’re all made up except for _Crystal Skull_, which is 100% true. [Next page](https://boards.straightdope.com/t/ancients-predicting-solar-eclipses/1018917.md?page=2)