Alex Filippenko

10/5/11

I have received many inquiries regarding the significance 
of the 2011 Nobel Prize in Physics, and what my role may 
have been in the research for which the prize was awarded. 
Let me explain here briefly.

Yesterday (Oct. 4), the Royal Swedish Academy of Sciences 
announced that the 2011 Nobel Prize in Physics is being 
awarded to Dr. Saul Perlmutter (UC Berkeley), Dr. Brian 
Schmidt (Australian National University), and Dr. Adam Riess 
(Johns Hopkins University), for their discovery of the 
accelerating expansion of the Universe. By measuring the
expansion history of the Universe through observations
of exploding stars known as a "Type Ia supernovae," they 
found that the expansion is currently speeding up with time, 
rather than slowing down as would have been expected under 
the influence of attractive gravity alone! The phenomenon 
has been confirmed by other techniques, and there is now
little doubt that it's true. But the cause is unknown;
either mysterious, repulsive "dark energy" pervades all
of space and makes up 73% of the total matter/energy content 
of the Universe, or there's a problem with Einstein's general 
theory of relativity on large scales. Many scientists
think this is currently the number-one observationally 
motivated problem in all of physics, and it provides
crucial clues to the long-sought quantum theory of gravity.

This discovery was made by two teams in 1998 -- the Supernova 
Cosmology Project (led by Perlmutter) and the High-Redshift 
Supernova Search Team (led by Schmidt). I was initially on 
Perlmutter's team, but later switched to Schmidt's team, and I 
was the only person to have been a coauthor of both of the 
discovery papers. My main role on both teams was to obtain
spectra of the supernova candidates with the mighty Keck
telescopes in Hawaii, verifying that they really were Type Ia 
supernovae and determining their "redshifts" (i.e., how much 
the light has stretched on its way to us). Adam Riess was a 
young postdoctoral scholar working with me at UC Berkeley in 
1996-1999, as part of Schmidt's team; he led the analysis 
of our data, and was the first (on Schmidt's team) to 
realize the implications of our observations.

All together, the two teams had 51 scientists, each of whom
contributed significantly (and in some cases, a large amount)
to the research. But according to the rules of the Swedish
Academy, the Nobel Prize can be shared by at most 3 individuals.
Thus, the two team leaders were recognized (Perlmutter and 
Schmidt), as well as Adam Riess (who was the lead author on 
the research paper announcing the results of Schmidt's team).
This isn't entirely fair, because it doesn't give credit
to the many other hard-working scientists, and it gives the
misleading impression that science is done largely by 
individuals... but that's the way it goes.

I am enormously happy that our work led to fundamental 
breakthroughs in physics that were worthy of the Nobel Prize, and 
I wholeheartedly congratulate the three winners. I'm very proud
that much of the work was done at UC Berkeley, by both teams;
the Nobel Prize brings great honor and recognition to our
University. And I could not have imagined, decades ago, that 
I would be involved in such important research; it has truly 
been a rare and amazing privilege, and I feel extremely
fortunate.

With best wishes,

Alex

ps. For the UC Berkeley press release on the 2011 Nobel Prize
in Physics, see
http://newscenter.berkeley.edu/2011/10/04/saul-perlmutter-awarded-2011-nobel-prize-in-physics/