- Person
- Adam Riess
- Lived
- b. 1969
- Field
- Astrophysics
- From
- American
The story
In the mid-1990s two teams of astronomers were racing to measure how fast the expansion of the universe was slowing down. Adam Riess, a young astrophysicist from a Jewish family in New Jersey, was a key member of the High-z Supernova Search Team led by Brian Schmidt; the rival Supernova Cosmology Project was led by Saul Perlmutter. Both used type Ia supernovae, exploding white dwarf stars that are bright and uniform enough to serve as cosmic yardsticks. Riess’s Harvard doctoral thesis had developed ways to correct their light for dust and for the stars’ natural variations, making the yardsticks much more reliable.
Finding very distant supernovae meant photographing the same patches of sky weeks apart, spotting new points of light and racing to large telescopes, including the Hubble Space Telescope, before each one faded. Riess later recalled that the Hubble institute’s director, Bob Williams, gave both teams time from his own discretionary allocation because he thought the experiment so important.
When Riess carried out the final analysis, the answer had what he took to be the wrong sign. The distant supernovae were fainter than expected, meaning the expansion was not slowing but speeding up. He told the Nobel Foundation that he thought he had made a terrible mistake and spent weeks looking for it. When he could not find one, colleagues checked each step, and Schmidt replied to the last calculation with an email: “Well, hello Lambda,” the symbol for Einstein’s cosmological constant.
The team published its result in the Astronomical Journal in 1998, with Riess as lead author, and Perlmutter’s team found the same thing. Science magazine named the accelerating universe its Breakthrough of the Year. The cause, now called dark energy, makes up about three quarters of the universe according to the Nobel committee, which awarded Riess, Schmidt and Perlmutter the 2011 Nobel Prize in Physics. Riess has since led the SH0ES team’s precise measurements of the universe’s present expansion rate.
Why it matters
The discovery revealed that most of the universe consists of dark energy, reshaping cosmology and guiding the telescopes and space missions now built to understand it.
About Adam Riess
Johns Hopkins astrophysicist who co-discovered that the universe’s expansion is speeding up, revealing dark energy, and now leads precise measurements of how fast the cosmos grows. Nobel Prize 2011.
Sources
- Popular information: The Nobel Prize in Physics 2011 NobelPrize.org
- Adam G. Riess, Interview NobelPrize.org
- Discovering dark energy and the Hubble tension: extended interview with Adam Riess GBH, Particles of Thought
- Adam Riess Wikipedia
Another act of tikkun olam. This is part of tikkun olam, the Jewish idea of repairing the world, and every one of us can add to it.