‘T Hooft, Gerardus, << tuh hohft, gay RAHR dus >> (1946-…), a Dutch physicist, won a share of the 1999 Nobel Prize for physics for his mathematical work on the characteristics of subatomic particles and the forces between them. He shared the prize with his colleague in this work, Martinus J. G. Veltman, also a Dutch physicist.
‘T Hooft and Veltman dealt with elementary particles, objects that are not made up of smaller units of matter. There are three kinds of elementary particles: (1) quarks, (2) leptons, and (3) fundamental bosons. Quarks combine to make up various composite particles, including the protons and neutrons that form the nuclei of atoms. Leptons include electrons, which whirl about atomic nuclei; two similar particles called muons and taus; and three kinds of neutrinos. Fundamental bosons, also known as gauge bosons, transmit forces between the other kinds of particles.
Two of these forces are known as the electric force and the magnetic force. The two are so closely related that physicists often refer to them together as the electromagnetic force. Another force, known as the weak force, is involved in many high-energy particle reactions in which new particles are created. The weak force is also responsible for certain kinds of radioactivity.
In the 1960’s, three physicists combined theories of the electromagnetic and weak forces into a theory of electroweak interaction. The three, Sheldon L. Glashow and Steven Weinberg of the United States and Abdus Salam of Pakistan, shared the 1979 Nobel Prize in physics for their work.
The electroweak theory stated that there exist subatomic particles called the W+, W–, and Z0. But these particles had not yet been discovered when the theory was developed. Furthermore, the theory did not provide a way to calculate the particles’ characteristics precisely. For example, physicists could not make precise calculations of the particles’ mass (amount of matter).
By the late 1960’s, Veltman had developed a computer program that could be used to test different mathematical approaches to the calculation problem. In 1969, ‘t Hooft—then a 22-year-old student—joined Veltman’s effort to solve this problem. By the mid-1970’s, ‘t Hooft and Veltman had succeeded: they had produced a detailed mathematical method for making precise calculations of the characteristics of the W and Z particles.
In 1983, scientists produced W and Z particles in a large machine called a particle accelerator. Measurements of the particles’ characteristics agreed closely with values that had been calculated as a result of the work of ‘t Hooft and Veltman. In 1995, physicists announced the discovery of the top quark, also known as the t quark, or simply the t. The measured mass of this particle was also in close agreement with calculations based on the work of ‘t Hooft and Veltman.
Gerardus ‘t Hooft was born in Den Helder, the Netherlands. In 1972, he obtained a Ph.D. in physics at the University of Utrecht in the Netherlands. He has been a professor of physics at that university since 1977.
