Special thanks to String for alerting me to this amazing recent discovery:

About a week ago, a team of astrophysicists from the University of Helsinki led by Dr. Lauri Jetsu submitted research suggesting that the ancient Egyptians understood the periodicity of the star Algol, and that they incorporated its cycle into their charts for the relative auspiciousness and unluckiness of days throughout the year (in fact, not just of days, but of sections of days -- their calendars were three times more precise than simply lucky and unlucky days, breaking each day into three parts and discussing the merits of each).

Algol is the second-brightest star (designated as β-Persei) in the constellation Perseus (almost as bright as the brightest star in Perseus, Mirfak, also known as α-Persei)The constellation Perseus is shown below, with a red arrow pointing to Algol.  His position in the sky relative to nearby celestial landmarks is discussed in this previous post and this previous post, although those tend to depict Perseus as seen rising in the east, and during this time of the year he is descending in the west in the hours after sunset and before midnight.

Why would the ancient Egyptians (circa 1200 BC according to the texts examined by Dr. Jetsu and colleagues) tie their predictions as to the relative propitiousness of days (and portions of days) to Algol, and how did these modern researchers discover that they were looking at Algol based on texts discussing the merits of those days and times throughout the year?

As the article above explains, the researchers analyzed the pattern of predictions preserved in the ancient Egyptian Cairo Calendar and discovered two cycles throughout the year, one corresponding quite accurately to the cycle of the moon, and one corresponding to a period of 2.85 days.  The scholars present evidence that the Cairo Calendar's 2.85-day cycle is linked to the cycle of Algol, which dims appreciably every 2.867 days.  

This phenomenon is visible to the naked eye, and is caused by the fact that Algol is actually a system of three stars, two of which orbit one another rather closely (one of which being the star we see and the other a much larger but less massive and dimmer giant star which causes the dimming phenomenon as it eclipses the smaller brighter star) plus a third star orbiting this pair at a greater distance.  The system and the dimming phenomenon (also known as the "minima of Algol") are described here in the very informative website of Professor Jim Kaler.  The entire eclipse lasts about ten hours from start to finish, but the appreciable dimmed period is shorter than that, perhaps four to five hours. 

Some astronomers have long suspected that the ancients may have known about the antics of Algol.  For one thing, there is the Arabic name of the star, Al Ghul or "the demon" ("the ghoul"), which gives us the star's modern name.  The great H.A. Rey describes this Arabic name as meaning "the prankster" (The Stars: A New Way to See Them, 42).

There is also the fact that Ptolemy (c. AD 90 - c. AD 168) in his Almagest (which was preserved by and heavily influenced the Arabic astronomers) designates this star as representing the head of the Gorgon Medusa being carried by Perseus (who slew her with the help of Athena, Hermes, and Pegasus).

There have also been those who have denied the ancients the sophistication to have identified the periodicity of Algol, although it seems quite presumptuous to do so, particularly in light of other evidence demonstrating that their knowledge clearly surpassed anything for thousands of years afterwards (such as this evidence that they understood the atmospheric effects which cause a phenomenon called "extinction," to say nothing of the even more ancient evidence that they understood the subtle phenomenon of precession, a fact that most conventional historians continue to dispute).

Now, this intrepid team from Finland has added further evidence for the high level of precision attained at very remote dates in mankind's ancient history.  They even provide an argument that the periodicity captured in the Cairo Calendar (which is slightly shorter than the periodicity recorded in modern times, since Algol's behavior was "rediscovered" in the 1600s) was not in error, but that the observations provided by the ancient texts can help astronomers today to determine the change in the motions of the Algol system over the 3000-plus intervening years!  We should all be grateful to Drs. Jetsu, Porceddu, Lyytinen, Kajatkari, Lehtinen, Markkanen, and Toivari-Viitala for their diligent work in uncovering this amazing new window into human history and knowledge.

Left unexamined in many articles discussing this incredible new find is one other big elephant in the room.  Remember, this entire discovery by the Finnish team came about because the ancient Egyptians recorded very detailed beliefs about the relative auspiciousness of the segments of each day throughout the year.  Nobody seems to ask whether -- if they knew so much about astronomy, as well as about many other subjects (and see here as well) -- they could have actually known something we don't know about the impact of the different "arrangements of the heavens" on affairs here on our little planet.  

This previous post discusses some of the logic behind the idea that the "harmonies" created by the arrangements of heavenly bodies might have some impact on the way that we feel, just as the relative "harmonies" or "dis-harmonies" of a building's architecture (or even the arrangement of furniture inside) can have an impact on us but from a smaller scale of distance.  This post explores the idea as well.

Here is one other reference discussing the minima of Algol, and the traditions that these eclipses of the star can lead to unfortunate "losing one's head" with unpleasant results (see Medusa, above).  Note that this site contains a list of times and dates for these cycles of Algol, running all the way up to the end of 2012.  As this is published, Algol has just emerged a few hours ago from one minima, and another eclipse will take place early in the small hours of the morning just after midnight on May 11 (Greenwich Mean Time, which will still be May 10 in North America and points west, out to the International Date Line).