2011 Nobel Prize in Physics

This year’s Nobel Prize in physics was jointly awarded to Saul Perlmutter from Lawrence Berkeley National Laboratory, and Brian Schmidt from Australian National University and Adam Riess from Johns Hopkins University for the discovery of the accelerating expansion of the Universe through observations of distant supernovae.

In the 1990s, two teams used high redshift type Ia supernovae (SNe Ia) to determine if the universe will continue expanding forever or whether the expansion will eventually stop and contract, resulting in the ‘Big Crunch’.  Perlmutter led the Supernova Cosmology Project while Schmidt led the High-z Supernova Search Team.  SNe Ia are standard candles used by astronomers to measure extragalactic distance, and they can be used to determine the rate at which the Universe is expanding. It was assumed at the time that the universe would be decelerating due to the gravitational pull of distant galaxies after the rapid expansion of the Big Bang.

However, the results by both teams  showed the opposite!  Riess et al. (1998) found that the distances of the high-redshift SNe Ia were about 10%–15% farther than expected and their data unanimously favoured an eternally expanding and accelerating universe.  The results of Permutter et al. (1999) also showed an accelerating universe.

So what is driving this acceleration?  Astronomers don’t yet know, but they have labled this unknown force as Dark Energy.  Dark Energy is thought to constitute 73% of the composition of the Universe, the other 23% dark matter and the 4% ordinary matter.

The Nobel Prize in Physics has been awarded 104 times since 1901 to recognise people who have made a significant discovery or invention within the field of physics.

For more information, see

[Post by Catarina Ubach, Francesco Pignatale & Sarah Maddison]

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