Abstract
In 1898, respectable physicists were permitted to speculate in Nature to an extent that would never be allowed today. Schuster's conjectures about "antiatoms" predate Dirac's prediction of "a new kind of particle, unknown to experimental physics, having the same mass and opposite charge to an electron" by 30 years. This new particle was needed to explain certain additional solutions of Dirac's relativistic version of quantum mechanics. Since them antielectrons (positrons), antiprotons and antineutrons have all been produced and detected. Today there is no known particle for which a corresponding antiparticle has not been observed, although in some cases, such as the photon, particle and antiparticle are identical. Almost a century after Schuster wrote to Nature, it at last appears feasible to synthesise the simplest antiatom, the positron-antiproton bound state known as antihydrogen. The prospect of applying high-precision spectroscopic techniques, perfected on hydrogen, to antihydrogen to test fundamental physical principles, makes antihydrogen much more interesting to the physicist than antigold.