ABSTRACT
The history of MRS (magnetic resonance spectroscopy) began with natural magnets. In China more than 3,000 years ago, vehicles called shinan-sha (south-pointing cart) were mounted on a figure whose hand pointed south because of the nature of magnets.l Natural magnets were also known in ancient Greece in about 600 B.C. In those days, there was a town called Magnesia in Asia Minor, and there was a town by the same name also in Macedonia. Since both towns produced natural magnets, the word "magnet" was coined from the name of the towns2 In China, the phrase "magnet invites iron or attracts it" seen in Roshi Shunju compiled in the third century B.C. is the first mention of magnetism. In Japan in the sixth year of Wado (713 A.D.) the people of the Ohmi region presented a "magnet" to the Emperor. This incident recorded in Book 6 of Shoku Nihongi is the first reference to magnets in Japan. Interestingly, the character g& was used in those days instead of l& to denote the word magnet as in the present time. This character, g j i means to give loving care, to be affectionate, and to have mercy as is still used in expressions such as jiai (affection), g$& jihi (mercy), and gm jiu (beneficial rain). A magnet is called g& Jishaku, because a magnet and iron attract each other just as an affectionate mother and her child are attached to each other by the mystic love between them. It may be the Oriental intuition and wisdom that made our ancestors feel mercy, which is the
Toshiro Fujimoto
cal phenomenon of magnetism. Here, we make a great leap to Europe in the
early 20th century, where quantum mechanics and physics were coming into bloom. At that time, physicists were struggling to establish the concept of spin. According to Tomonaga and SegrZ, the struggle was as follow^.^*^ It started with the discovery of the Zeeman effect (1896) by the Dutch physicist, Zeeman. He found that a spectral line splits into several lines when a light is placed in a magnetic field. The reason for this splitting of the spectral line was unknown. To explain this phenomenon, Uhlenbeck and Goudsmit of the Netherlands proposed the concept of spinning electrons in 1925. However, as this concept was so unconventional and contradictory to experimental findings, the two investigators lost confidence in their theory after contributing their paper to a journal and even asked the journal to return the manuscript. The manuscript, however, was already in ~ r i n t . ~ ~ ~ The concept of spinning electrons was promoted by Kronig, an American physicist in his 20s, about half a year before the paper of Uhlenbeck and Goudsmit. Unfortunately, the idea was refuted by Pauli, who was an influential figure in physics in those days, and publication of Kronig's theory was abandoned. Pauli maintained his opposition to the theory of spinning electrons even after the appearance of Uhlenbeck and Goudsmit paper. Ironically, however, Dirac noted that Pauli's exclusion principle agrees exactly with the concept of spinning electrons with a minor supplementation. Pauli's exclusion principle has since been linked closely to imaging of spin. This concept of spinning was called spin by the Danish
12 Chapter l History of MRS
Stern measured the nuclear magnetic moment of the proton (1933), and Rabi published a theoretical paper about nuclear magnetic resonance in a molecular beam. And in 19 1 1, Kamerlingh Onnes discovered the phenomenon of superconductivity.
