纸上谈兵不好，纸上“发现”美洲还是了不起的

武夷山

李兆良博主（http://blog.sciencenet.cn/home.php?mod=space&uid=1674084）关于中国人发现美洲的大量讨论，未能引起足够的重视，令人遗憾。其实，“到底谁发现了美洲？”这个话题，世界上很多人都有兴趣。

在2014年6月20日出版的Science杂志上，记者报道了生活在1000年前的撒马尔罕（现乌兹别克境内）一代的科学家Abū Rayḥān al-Bīrūnī（973－1048）在纸上“发现”美洲的情况。

早在一千年前，他就精确地计算了地球的周长；提出了比重的概念；拒绝创世论，认为时间既无起点也无终点；比哥白尼早500年提出太阳也许是太阳系的中心。

为了准确地确定麦加的方向，他不厌其烦地搜集了他去过的每个地方的坐标，也汇集了欧亚大陆数以千计的人类定居点的方位数据。据说他制作了一个5米高的大“地球仪”，然后将所有已知定居点标记在球面上，结果发现，地球表面还有五分之三是未知的。

到那时为止，大家普遍接受的解释是，欧亚大陆块被海洋包围着，那些海洋就是五分之三。Abū Rayḥān al-Bīrūnī却认为，作用于地表五分之二的陆地的力，也一定对另外五分之三发生作用。他的结论是，在欧洲和亚洲之间一定还有一个或多个大陆块，“决不能否定有人类定居的其他大陆存在的可能性”。

S. Frederick Starr先生（1940－ ）是约翰霍普金斯大学高级国际研究学院的中亚－高加索研究所的负责人，具有考古学专业背景，俄语很好，还是著名的音乐家。去年10月，他出了一本书，题为Lost Enlightenment:  Central Asia's Golden Age from the Arab Conquest to Tamerlane （被遗忘的启蒙：从阿拉伯征服到帖木儿的中亚黄金时代），书中有对Abū Rayḥān al-Bīrūnī科学成就的叙述。

该报道的原文见http://www.sciencemag.org/content/344/6190/1331.full。

Science 20 June 2014: 
Vol. 344 no. 6190 pp. 1331-1332 
DOI: 10.1126/science.344.6190.1331

· IN DEPTH

HISTORY OF SCIENCE

1. Richard Stone*

Al-Biruni's diagram of the moon's phases.

PHOTO: REPRODUCTION FROM SEYYED HOSSEIN NASR, ISLAMIC SOCIAL SCIENCE: AN ILLUSTRATED STUDY (WORLD OF ISLAM FESTIVAL PUBL. CO., 1976)

He was a Renaissance man long before the Renaissance. Abu Rayhan al-Biruni, born a thousand years ago in this region of Central Asia, calculated Earth's circumference with astounding accuracy and invented specific gravity, the measure of a substance's density compared to that of water. He rejected creationism, accepted that time has neither a beginning nor an end, and—5 centuries before Copernicus—argued that the sun might be the center of the solar system. Now, an influential scholar has proposed adding another laurel to that list: inferring the existence of America.

The discovery of America is bitterly contested, with vying claims on behalf of prehistoric peoples who crossed over Beringia or the Pacific Ocean, Norse seafarers who landed in Newfoundland around 1000 C.E., and the 15th century explorers Christopher Columbus and John Cabot. Biruni, who never laid eyes on any ocean, also deserves “to wear the crown of discovery,” averred S. Frederick Starr, chair of the Central Asia-Caucasus Institute of the Johns Hopkins School of Advanced International Studies in Washington, D.C., at a conference on medieval Central Asia held here last month. “His tools were not wooden boats powered by sail and muscular oarsmen but an adroit combination of carefully controlled observation, meticulously assembled quantitative data, and rigorous logic.”

Some experts are not persuaded. “There is a tendency these days to read too many modern discoveries into the works of the medieval scientists,” says Jan Hogendijk, an authority on Biruni at Utrecht University in the Netherlands. “We don't say that Copernicus ‘discovered’ that the Earth moves around the sun simply based on the fact that he hypothesized that it does,” adds Nathan Sidoli, a science historian at Waseda University in Tokyo, “so I don't see why we should say that al-Biruni ‘discovered’ the American continent.”

But others think Biruni deserves credit for his prediction. “Assuming that the key passages in Biruni's texts have been correctly read, I see no reason to exclude al-Biruni from the list of early ‘discoverers’ of America,” says Robert van Gent, a specialist on the history of astronomy at Utrecht University who attended Starr's talk here.

Biruni was one of a constellation of Central Asian scholars who led an “Eastern Renaissance” spanning 7 centuries, from about 800 to 1500 C.E. These scholars include some of the greatest minds you've never heard of, and their achievements include the principles of algebra and trigonometry, the invention of the algorithm and the astrolabe, and the foundations of modern medicine. “These were tremendous figures,” Starr says. Yet, he says, “This incredible effervescence in science has largely escaped our attention in the West.”

Starr, an archaeologist by training who has made dozens of trips to Central Asia, is at the vanguard of a scholarly movement to document the Eastern Renaissance and the factors that nurtured it. At the crossroads of the vibrant cultures of China, India, the Middle East, and Europe, Central Asians became traders non-pareil, and for that they had to know how to calculate. “The Chinese were amazed that young boys in Samarkand were learning mathematics when they were 8 years old,” Starr says.

Biruni boldly sorted scientific fact from fantasy.

PHOTO: COURTESY OF THE ACADEMY OF SCIENCES OF UZBEKISTAN

The brightest star in the Central Asian firmament may have been Biruni. “He was really a universal genius,” versed not only in the hard sciences and anthropology, but in pharmacology and philosophy as well, says Jules Janssens, a specialist on medieval Central Asia at the Catholic University of Leuven in Belgium. Biruni authored at least 150 texts, although only 31 have survived—and these are virtually unknown outside a small circle of scholars.

Born in 973 C.E. near the Aral Sea in present-day Khiva, Uzbekistan, Biruni used the height of the midday sun to calculate the latitude of his hometown when he was just 16. He traveled widely as an adult, and at a hilltop fortress near present-day Islamabad he devised a technique for measuring Earth's circumference using an astrolabe, spherical trigonometry, and the law of sines. (Like the ancient Greeks, Biruni was aware that Earth is round.) His calculation was a mere 16.8 kilometers off the modern value, Starr says. “I don't know where he became a data freak, but he's the real thing. His was an original kind of mind.”

In a massive tome called the Masudic Canon completed in 1037 C.E., Biruni analyzed classical Greek, Indian, and Islamic astronomy and used “bold hypothesizing” to sort out credible claims from fantasy, Starr says. In another treatise, Biruni introduced the concept of specific gravity and applied it to scores of minerals and metals, making measurements accurate to three decimal points that Starr says Europeans could not match until the 18th century.

Most sensational of all may be Biruni's “discovery” of America. For the purpose of precisely determining the qiblah—the direction of Mecca during Islamic prayers—Biruni meticulously recorded coordinates of the places he visited, and compiled data on thousands of other Eurasian settlements from other sources. After plotting out the known world—possibly on a 5-meter-tall globe he is said to have constructed—he found that three-fifths of Earth's surface was unaccounted for.

“The most obvious way to account for this enormous gap was to invoke the explanation that all geographers from antiquity down to Biruni's day had accepted, namely, that the Eurasian land mass was surrounded by a ‘world ocean,’” Starr relates in Lost Enlightenment: Central Asia's Golden Age from the Arab Conquest to Tamerlane, a book published last October. Biruni rejected that notion in a passage flagged by the Indian scholar Sayyid Hasan Barani in the mid-1950s but overlooked in the decades since, Starr says. Biruni argued that the same forces that gave rise to land on two-fifths of our planet must have been at work in the other three-fifths. He concluded that one or more landmasses must lie between Europe and Asia, writing, “There is nothing to prohibit the existence of inhabited lands.”

In the December 2013 issue of History Today, Starr wrote that Biruni's “modus operandi strikes one as astonishingly modern, a voice of calm and dispassionate scientific enquiry sounding forth from the depths of the irrational and superstitious medieval world.” The Eastern Renaissance wound down, Starr says, when “a pall of suspicion fell on science” in Central Asia. For centuries, Biruni and other scholars of that era—like America—awaited rediscovery.