Harumi Shibukawa

Japanese: 渋川春海 - しぶかわ・はるみ

Year of death: 6th October 1715 (1st November 1715)
Year of birth: Kanei 16, leap year 11 (1639)
A mid-Edo period astronomy and calendar scholar. Born in Kyoto as the son of the shogunate's Go official Yasui Santetsu (first generation). His childhood name was Rokuzo, but he changed it to Sukezaemon in 1692. His pen name was Junsei, and his given name was Miyako and Shinashi. Upon his father's death, he took on the family name and worked at the Go office, calling himself the second Santetsu. He later changed his surname to Yasui and then Shibukawa. His given name is apparently pronounced "Harumi," but is commonly known as "Shunkai." Japan had been using the Chinese calendar since ancient times, but he is known as the first person to create an original calendar system (the Jokyo calendar) created by a Japanese person. Due to his achievements, he became the first astronomy official in 1684. Although it was original, it was not a big deal, and most of it was a copy of the original Shoji calendar. Although some adjustments were made to the central differences of the sun and the moon, it is difficult to say whether they were improvements or deteriorations. The adjustments were not based on any theoretical basis. In the Shushi calendar, the central difference is expressed by a third-order algebraic formula for each quadrant, but the Jokyo calendar followed the Shushi calendar, only changing the coefficients to smooth the curves at the joints of the quadrants. Nevertheless, the maximum central difference based on observation is closer to the current value than the Shushi calendar, so it can be said to be an improvement. If there is anything original about it, it would be that the longitude difference between China and Japan was taken into account when predicting solar eclipses. Since the longitude and latitude of China and Japan are different, it is natural that the method of the Shushi calendar had to be adjusted. Harumi adjusted the longitude by shifting the time accordingly, but although he said that the latitude also had an effect, he did not know how to adjust it. Why was Shibukawa Harumi, who was not necessarily a first-rate theorist, able to realize the first calendar reform in Japan? In the first place, calendar reform is more of a political issue than a scientific one. Especially when it comes to being the first in Japan, there is opposition simply because it is not customary. It was necessary to resist the arguments of Confucian scholars of the Chinese school, who said that since the Chinese calendar had been used up until that point, it was fine to continue as it was. Having succeeded his father, who worked at the Shogunate's Go Office, he knew important people in the Shogunate, learned Tsuchimikado Shinto and other schools of Shinto from Abe no Yasutoshi, the head of the Onmyo clan in Kyoto, and was close to the Imperial Court. This political undertaking was only accomplished by making full use of his personal connections. It is not something that an ordinary scholar could have done.

(Shigeru Nakayama)

Source: Asahi Japanese Historical Biography: Asahi Shimbun Publications Inc. About Asahi Japanese Historical Biography

Japanese:

没年：正徳5.10.6(1715.11.1)
生年：寛永16.閏11(1639)
江戸中期の天文暦学者。幕府碁方安井算哲(初代)の子として京都に生まれた。幼名は六蔵といったが,元禄5(1692)年助左衛門と改めた。字を順正,諱は都翁,新葦と号した。父の死に当たり,襲名して家職を継いで碁所に勤め,2代目算哲と称している。のち保井,さらに渋川と姓を改める。名の方は「はるみ」と読むらしいが,ふつうには「しゅんかい」で通っている。日本では古来中国の暦を採用していたが,初めて日本人の手になる独自の暦法(貞享暦)を作った人物として著名。その功により貞享1(1684)年初の天文方となる。独自といっても大したことはなく,大部分は元の授時暦の引き写しである。太陽や月の中心差などに多少の手直しを行ったが,はたして改良か改悪かいちがいにいえない。その手直しも,あまり理論的根拠のあるものではない。授時暦では中心差を各象限ごとに3次の代数式で表現するが,貞享暦も授時暦を踏襲し,ただ係数だけ変えて,象限のつなぎ目のカーブを滑らかにしただけである.それでも観測に根拠を持つ中心差の最大値は,授時暦よりも現在値に近いものをつかっているから,改良であったといえる。あえて独自なものといえば,日食の予報のときに,中国と日本の経度差を考慮に入れたことだけであろう。中国と日本では経度,緯度が違うから,当然授時暦のやり方を修正しなければならない。春海は経度についてはそれだけ時間をずらして修正したが,緯度についてはそれも影響するといいながらも,修正の仕方が分からなかった。理論的には必ずしも一流ではなかった渋川春海が,本邦最初の改暦を実現できたのは,なぜか。そもそも改暦というものは科学上の問題よりも政治的問題である。特に本邦最初ということになると,慣例にないからという理由だけで反対される。これまで中国の暦を採用していたのだから,そのままでよい,という中国派の儒者のいうことを押さえねばならない。彼が幕府の碁所に勤める父のあとを継いで碁所に勤め,幕府の要人を知っており,また京都の陰陽頭安倍泰福から土御門神道その他の流の神道を学び,朝廷とも近かった,という人間関係をフルに使って,初めて達成された政治的事業である。並みの学者でできることではない。

(中山茂)

出典　朝日日本歴史人物事典：（株）朝日新聞出版朝日日本歴史人物事典について　情報

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