(1947–) American physicist and cosmologist
Born in New Brunswick, New Jersey, Guth was educated at Massachusetts Institute of Technology, where he obtained his PhD in 1969. After holding postdoctoral appointments at Princeton, Columbia, Cornell, and Stanford, Guth returned to MIT in 1980, becoming professor of physics in 1986.
Initially Guth worked as a theorist in elementary-particle physics, but, stimulated by the work of Steven Weinberg, he began to consider some of the outstanding problems of cosmology. These included a number of difficulties raised against the standard interpretation of the big-bang account of the origin of the universe. Many had found the apparent isotropy of the universe puzzling while James Peebles and Charles Misner had discovered the flatness and horizon problems. The big-bang was clearly in need of revision.
Consequently Guth in 1980 first proposed the inflationary universe model. Guth's theory agrees with the standard model after the first 10–30 second. Within the initial brief period, he proposed that the universe had undergone an extraordinarily rapid inflation. During this period the diameter of the universe would have increased by a factor of about 1050. An increase of this size would expand a centimeter to 1032 light-years.
Thus as the region from which the present universe emerged was so small, thermal equilibrium could have been achieved before the inflation. An observer today would, therefore, detect an isotropic cosmic-background radiation. He would also detect a flat universe – an observer on a globe that had increased 1050 times in diameter would have seen his universe flattened.
Guth has conceded that even if the inflationary model is correct “it will be difficult for anyone to ever discover observable consequences of the conditions existing before the inflationary phase transition.” He has also pointed out that the grand unified theories of physics allow that the observed universe could have evolved from nothing. The inflationary model comes close to this by providing a mechanism by which the observable universe could have evolved from an infinitesimal region: “They say that there is no such thing as a free lunch – but the universe is the ultimate free lunch!”