The gen on Newtonmas

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What is Newtonmas?

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Newtonmas is an informal holiday, celebrating the birthday of Sir Isaac Newton. It is "celebrated" on the 25th of December in the Julian calendar, since Sir Isaac was born on 1642-12-25, in the Julian calendar that was still in force in the United Kingdom at the time.

In the Gregorian calendar of the time, as was used outside of the U.K., he was born on 1643-01-04. Newtonmas actually falls on two days of the year in the Gregorian calendar: Legal Newtonmas and Astronomical Newtonmas. It does not, however, despite some people mistakenly celebrating it then, fall on the 25th of December in the Gregorian calendar.

Several people in the age of Internet claim to have invented Newtonmas. Michal E. Marotta, for example, claimed in a post to the Usenet newsgroup sci.physics on 2005-12-17 that he had been sending out Newtonmas cards to his friends and relatives for 20 years, after he had read a (now deleted) Wikipedia article where it was claimed that it had been invented by someone called Gordon Worley (whose WWW page is here). Marotta made a radio broadcast on the subject in 2001, a transcript of which can be found here.

In fact, both claimants are roughly 100 years too late in staking their claims. Celebration of Newtonmas can be traced back to at least 1890, possibly even to 1882 when physicist Tanakadate Aikitu was an undergraduate at Tokyo Imperial University. An 1891 article in The Japan Weekly Mail records it thus:

Instead of Christmas, these natural religionists hold what might be called a Newtonmas. They style themselves the Newton-kai, and form a society unique alike in name and character. In the assembling of themselves together, they are governed by as rhythmic a law as that which governs the return of any anniversary. […]

The Society was, we believe, launched as an undergraduate one by Messrs. FUJISAWA, TANAKA, and TANAKADATE, the first brilliant triumvirate of mathematical graduates which the Tokyo University gave to the world. In its early days, it met in the Students' Dormitory; but […] a more suitable assembly hall was found in the University Observatory in Kaga Yashiki. […] The other night for the first time the Newton-kai came together in the Physical Laboratory of the Imperial University; and here we hope it will find a permanent abode. Thus met, on Christmas 1890, or Newtonmas 248, the members of the Newton-kai, to hear each other talk, to view a magic lantern exhibition, to distribute appropiate gifts, and to lengthen out the small hours with laughter and good cheer.

The Society has no President : a portrait of the august Sir Isaac Newton presides over the scene. […]

"A New Sect of Hero Worshippers". The Japan Weekly Mail. Yokohama. 1891-01-31. Volume 15, number 5, page 125.
(also reported, in edited form, a year and a half later on page 459 of an 1892 issue of Nature)

Contrary to the belief of some people, celebration of the birthday of Sir Isaac, in the same way that one would celebrate Christmas (with cards and gifts and so forth), is not a new thing that the science-oriented denizens of Usenet science newsgroups invented. It's something that science-oriented people have been doing, here and there, for fun, for almost 120 years now.

Of course, with the hokey nature of the World Wide Web, the idea has blossomed, far more than it did 120 years ago. One can send Isaac Newton cards, sing Newtonmas carols, and give Newtonmas gifts. Richard Dawkins even got in on the act, writing this article for New Statesman in 2007. So, too, did Olivia Judson, writing about Newtonmas on a The New York Times web log in 2008.

Tracy Gordon writing in Religion News in 2011 erroneously reported the Newtonkai members as English. They were, of course, Japanese (as the "-kai", 会, suffix gave away).

Ironically, people justify this celebration with the observation that "since Jesus wasn't born on December 25, we should celebrate the birthday of someone who was". Indeed, most biblical scholars agree that Jesus wasn't born on December the 25th. That date can only be traced as far back as the writings of Clement of Alexandria (circa 155–220), and doesn't appear in the text of the Christian Bible at all. Moreover, what does appear in the text of the Bible is inconsistent with events occurring in Winter. (Shepherds don't put their flocks to pasture at night in the depths of Winter, for example.) Even Clement of Alexandria doesn't support the date himself, but merely lists it as one of several possible dates.

But the irony is that the same problem of it not being the right date exists for Newtonmas as for Christmas. It's exactly the same problem that had quite a lot of people in the United State celebrating what they called "Ole Christmas" (Old Christmas) on January the 5th/6th/7th, as late even as the 1930s. It's the problem of the switch from the Julian to the Gregorian calendars. Newton was born on the 25th of December according to the Julian calendar then in force in England. But that's (currently) January the 7th in the Gregorian calendar.

One could argue in favour of using the original day of the year, rather than observing the exact anniversary. But there are three major problems with that:

Thus we have two Newtonmases in the Gregorian calendar:

So not only wasn't Newtonmas invented recently by the people who are now popularizing it on the World Wide Web, it isn't even being celebrated on the correct day.

But then they didn't get that part right in 1890, either. Although in 1890 they at least spotted their error, unlike Dawkins, Judson, et al.. As is pointed out later in the same article in The Japan Weekly Mail:

Some years ago it was pointed out by a European member of the Kai that in holding the "Newtonmas" on Christmas Day the members were guilty of a chronological crime hardly to be excused in men trained in the accurate school of Newton. For although he was registered as being born on Christmas Day 1642, it was Christmas Day, old style. In all strictness he was born on January 5th, 1643.

— ibid.

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