Tikalon Blog by Dev Gualtieri

The 2011 Nobel Prize in Physics

October 6, 2011

Alfred Nobel was the inventor of dynamite . His invention was transformative, since it allowed the safe and routine use of the powerful explosive , nitroglycerin . As a result, Nobel became a wealthy man, and his wealth funded the Nobel Prizes .

The Nobel Prizes, which were endowed with the equivalent of about $250 million in today's money, were effectively Nobel's sin offering for the unintended consequences of his life's work. His explosives were important for large civil engineering projects, but they were also useful in weapons of war.

It's interesting that this year's Nobel Prize in Physics , funded by explosives technology, relates to the Big Bang theory of the Universe. The Big Bang theory (not to be confused with the eponymous television series ), posits that the universe began as an extremely compact state that expanded to the vast expanse that we now know.

This universal expansion was derisively named the Big Bang by the prominent astronomer, Fred Hoyle , a proponent of a "steady state " cosmological model.[1] The name was embraced by even the proponents of the expansion theory, and the Big Bang was effectively proven by the Penzias and Wilson discovery of the cosmic microwave background radiation .

Knowing that the universe is expanding leads to the further question of whether it will expand forever; or whether the expansion will slow, eventually coming back to a contraction symmetrically named, the Big Crunch . To discover this observationally, astronomers need to compare the expansion rate in the distant universe, which corresponds to times at the start of the expansion process, with the rate observed today. Such work resulted in the award of this year's Nobel Prize in Physics "for the discovery of the accelerating expansion of the Universe through observations of distant supernovae."[2-11]

The 2011 Nobel Prize in Physics was awarded to Saul Perlmutter of the Supernova Cosmology Project at Lawrence Berkeley National Laboratory , Brian P. Schmidt of the High-z Supernova Search Team at the Australian National University , and Adam G. Riess of the High-z Supernova Search Team at Johns Hopkins University and the Space Telescope Science Institute (Baltimore, MD). Perlmutter will get half of the $1.5-million monetary award, with the other half shared equally by Riess and Schmidt.[2] All three are Americans (Schmidt was born and raised in the United States, but he is also a citizen of Australia),[7] so the American physics hegemony is still intact, at least for the present.

Their observations involved a newer sort of "standard candle " for cosmology , the rare type Ia supernova , the explosion of a white dwarf that can emit as much light as an entire galaxy . Type Ia supernova were found to be extremely uniform. Their spectra match closely, as do their light curves, the change in brightness as a function of time after explosion. They could be used as a standard across the breadth of the universe.

Supernova 1994ae in NGC 3370 . The left image is the discovery image, taken on Nov. 14, 1994. The right image is from the Hubble Space Telescope nine years later, long after the supernova had declined in brightness. (Image: NASA/A. Riess, STScI).

The research teams studying these found more than fifty of these distant supernovae and discovered that their light was weaker than expected. This indicated that the universal expansion was accelerating.[2] It's now thought that the expansion is driven by an enigmatic dark energy that makes up about 73% of the Universe. The rest of the universe is composed of dark matter (23%) and visible matter (4%).[3]

The result was so unexpected that the scientists initially thought there was some error.[3] Schmidt, in teleconferences after the Nobel Prize was announced, said the following:

"It was with a fair bit of trepidation that we ended up telling our group and eventually telling the world that we had this crazy result."[10]

"It seemed too crazy to be right and I think we were a little scared."[9]

Observation of these type Ia supernovae was no mean feat. In a 2003 article, Saul Perlmutter listed these difficulties:[12]

•  They are rare. There are only a few type Ia explosions per galaxy per millennium.

•  They are random. There is no advance warning, and no way to schedule time on the few telescopes that are powerful enough for these observations.

•  They are fleeting. After a star explodes into a type Ia supernova, it must be measured many times within the first few weeks. Otherwise, it will have passed its peak brightness, which is essential for calibration.

Perlmutter, Schmidt and Riess are relatively young recipients of the physics prize. Perlmutter is 52, Schmidt is 44, and Riess is 41.[7] William Lawrence Bragg , the youngest physics laureate, was just 25 at the time of his award; Ray Davis , the oldest, was 88. The three shared the 2006 Shaw Prize in Astronomy ,[3] and the Peter Gruber Foundation 2007 Cosmology Prize .[4]

The path to the prize started for Perlmutter in 1988 when he became leader of the Supernova Cosmology Project. Years later, in 1994, Schmidt and Riess started working on the High-z Supernova Search Team.[5] Having two teams was beneficial, since they announced their results within a few weeks of each other, which added credence to the idea of accelerated expansion.[5]

On the occasion of the award, Frank Wilczek , a 2004 Nobel Physics Laureate, had this to say,

"As far as fundamental significance for the foundations of physics and how we view the world, I think it's absolutely one of the major discoveries of the 20th century."[3]

The 2011 Nobel Prize in Physics

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