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Alan Guth
1980· Person
ProvenTested many times; part of working physics.
Alan Guth (born 1947), American theoretical physicist at MIT, who proposed and named cosmic inflation in 1980.
See it on the Science map →How it works
Trained in particle physics, Guth spent years as a postdoc at Princeton, Columbia, Cornell and Stanford's SLAC. A 1978 lecture by Robert Dicke introduced him to the flatness puzzle. In 1979, studying with Henry Tye why the early universe did not make too many magnetic monopoles, he saw that a supercooled field would inflate space. Unusually, he spelled out his model's flaw in the paper itself. Later he championed eternal inflation and, with Borde and Vilenkin, asked whether inflation needs a beginning.
Why it matters
He turned the Big Bang's unexplained starting conditions into something physics could calculate, and launched the field that links particle theory to the early universe.
How the work held up
Inflation's predictions, flat space and nearly even, slightly tilted ripples, were confirmed by COBE, WMAP and Planck (1992–2018). He shared the 2004 Gruber Prize and the 2014 Kavli Prize.
Still a mystery
His original 'old inflation' did not work: its bubbles never merged, so Linde, Albrecht and Steinhardt had to repair it. Whether inflation is eternal, as he came to believe, is untested.
Connections (2)
▸Alan Guth proposed Cosmic inflationWell supported
The relationship
Guth realized that a universe stuck in a false vacuum would grow exponentially, and that this growth would flatten space and let distant regions share one temperature. He named the idea 'inflation' and laid out its problem-solving power in one paper. His 1980 lectures spread it fast, starting a worldwide effort to make it work.
How the link was found
Alan Guth at SLAC, Stanford. His notebook entry of December 1979 is headed 'SPECTACULAR REALIZATION'. The paper, 'Inflationary universe: A possible solution to the horizon and flatness problems', appeared in Physical Review D in January 1981.
Is it proven?
His specific model failed, as he admitted in the paper, but the core idea passed later tests: flat space and the ripple pattern measured by COBE, WMAP and Planck.
Open questions and mysteries
Did inflation happen at all? It is well supported but awaits a signature no rival can mimic, such as its gravitational waves. Which of hundreds of models is right is open.
▸Alan Guth built "old inflation" on False vacuum: energy trapped in empty spaceWell supported
The relationship
In Guth's model, a grand unified field cooled but stayed stuck in its false vacuum, supercooling like water below freezing. That trapped energy drove inflation. It was meant to end when bubbles of true vacuum formed and merged, releasing heat. But bubbles formed randomly and the space between kept inflating, so they never joined, leaving a hopelessly lumpy universe.
How the link was found
Guth described the plan, and its flaw, in his 1981 paper. Guth and Erick Weinberg, and separately Hawking, Ian Moss and John Stewart, confirmed in 1982–83 that the bubbles never merge. It became known as 'old inflation'.
Is it proven?
The bubble calculations are standard. The microwave background is smooth to 1 part in 100,000, which a universe of colliding bubbles could not produce, so old inflation is ruled out.
Open questions and mysteries
The stuck false vacuum survives in eternal-inflation and string-landscape pictures, where one bubble becomes a whole universe. Whether our universe began that way is open.