
The Nobel Prize in Physics 2011 - aarghh
http://www.nobelprize.org/nobel_prizes/physics/laureates/2011/
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hugh3
This is an excellent choice, and (of course) congratulations to the
recipients. Their work really did add an extremely significant chunk to our
understanding of the universe. And I think it has now been long enough to
confirm that their observations really were accurate.

It was also, I think, the first scientific paper I actually read -- I did an
assignment on it as a callow young undergraduate, and I still remember sitting
in Fisher library poring through the text copy of the journal and trying to
figure out what was going on.

Since the page doesn't actually explain the work, I'll have a go. I'm doing
this from memory, so someone correct me if I get something wrong. Basically,
they set out to study how the distance of a receding galaxy relates to its
redshift (ie the speed at which it's receding). Up to this point we could
easily measure the redshift of a galaxy, but not its actual distance.

How do you measure the distance to a galaxy? What they did was to look for
Type 1a supernovae. This is a particular subclass of supernovae which always
have the same luminosity, because they occur when a previously-stable neutron
star goes _just_ over the mass limit and becomes unstable. There's a
sufficient number of these going off in the universe in any given week that
they make a good "standard candle", so by measuring their brightness you can
estimate their distance.

What these guys found was extremely surprising: the relationship between
distance and speed was _not_ what we would have expected based on a universe
which has been evolving only under the influence of gravity since its birth --
there was an extra term which appears to be accelerating the expansion of the
universe over time.

And that, right there, is an amazing fact about the universe which nobody knew
fifteen years ago.

~~~
lutorm
Hugh is right. A few more details:

SNIa are not _quite_ standard candles, not good enough to by themselves make
this measurement. However, experimentally it has been observed that their
brightness correlates with how fast they brighten and then fade. This
relationship, which is not well understood theoretically, makes it possible to
measure how fast they brighten and fade and use this to know how bright they
are. The difference between an accelerating and a decelerating universe is too
small to be seen without this correction.

Second, what these guys did that no one had done before was to figure out how
to _find_ the supernovae. Up until then, the way it was generally done was
that someone (generally an amateur astronomer) would notice a bright dot in
some galaxy and report it. Then the professional astronomers would use large
telescopes to observe it in detail and follow it as it brightened and faded.
However, this only works for nearby galaxies that amateurs look at.

The problem is that professional telescopes are scheduled months in advance,
but you of course can't _know_ that there will be a SN in a few months time so
you can apply for telescope time. What they did was sort of the opposite - by
surveying a large number of galaxies with a smallish telescope they would be
guaranteed to find a number of actual supernovae. They wouldn't know exactly
where, of course, but with a large enough number of surveyed galaxies there
would always be a few in _some_ galaxies. They managed to convince the time
allocation committees on the large telescopes that it was not a waste of
telescope time to give them the time just based on the expectation that they
would have something to look at. (I think this was the first time where
telescope time was awarded to look at something that would happen in the
future... ;-) With this method in place, the number of observed high-redshift
supernovae skyrocketed.

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flyingdutchman
Robert Kirshner advised both Schmidt and Riess at Harvard and was an integral
member of the High-Z Search Team. His book The Extravagant Universe is worth
reading if you are interested in the topic.
[http://www.amazon.com/dp/069111742X/?tag=googhydr-20&hva...](http://www.amazon.com/dp/069111742X/?tag=googhydr-20&hvadid=8524560924&ref=pd_sl_9fhdfr287q_b)
Many thought that Kirshner himself would get the Nobel for his work in the
field, and I am sure it is a little bitter-sweet (if mostly sweet) for his
team members to be among the winners.

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scythe
Up until the '50s, there were mostly single winners; now, there hasn't been a
single winner since 1992.

~~~
Panoramix
Martin Rees just commented on that: "I think, however, that this is one of the
increasingly frequent instances when the Nobel Committee is damagingly
constrained by its tradition that a prize can't be shared between more than
three individuals. The key papers recognised by this award were authored by
two groups, each containing a dozen or so scientists. It would have been
fairer, and would send a less distorted message about how this kind of science
is actually done, if the award had been made collectively to all members of
the two groups."

More here: [http://www.guardian.co.uk/science/blog/2011/oct/04/nobel-
pri...](http://www.guardian.co.uk/science/blog/2011/oct/04/nobel-prize-
physics)

~~~
hugh3
Yeah, but once you relax that rule you'll wind up devaluing, pretty quickly,
the Nobel Prize. If every one of those 24 authors can equally claim to be a
Nobel Prize winner on their CVs, then you've just significantly increased the
number of living Nobel laureates in physics.

The real problem would arise a few years down the road, though, next time the
Nobel gets awarded for some high-energy experimental work (discovery of the
Higgs boson?). Those papers can typically have _hundreds_ of authors, listing
everyone involved with the project (the most extreme example I've seen has
2512 authors). Now all of a sudden pretty much _everyone_ in high-energy
physics is a Nobel laureate, and the _proper_ Nobel laureates are a tiny
minority.

I think the constraint that no more than three people can share it is fair. It
just means the committee needs to look into it and find out who the _real_
brains behind the operation were.

~~~
lutorm
_It just means the committee needs to look into it and find out who the real
brains behind the operation were._

But the problem is that this is _impossible_. Who are the real brains? The
person who had the idea, but didn't do anything about it? The person who
organized the project and got funding for it but didn't do any real science?
The person who build the hardware without which nothing would have been
possible? The person who wrote the software, without which nothing would have
been possible? The person who wrote the paper that explained the results? The
grad student who found a crucial error in the analysis without which the
results would have been wrong?

In many (most?) fields of science these days, progress is made by huge
projects. Clearly there are wide differences between how crucial different
people are to the success of the project, but to cut it down to 1-3 "winners"
to the detriment of everyone else hardly seems fair. It seems more reasonable
to say that if there are 200 people on the paper that's awarded the prize,
everyone is a 0.5% Nobel Laureate....

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A-K
Adam Riess! One of my friends took "Stars and the Universe" with him last
semester here at Hopkins and really enjoyed the class (perhaps corroborating
the claim that the most capable researchers tend to also be great educators).

~~~
epo
Erm, at the risk of being (equally) trite, one data point doesn't corroborate
anything except for the somewhat fluffy claim that some good researchers are
also good educators.

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micah63
So, can we put the oscillating universe theory to rest now?

~~~
hugh3
Well, we can never fully bury a theory like that, but it's looking pretty
unlikely.

------
unwind
The Nobel committee is awesome, since they can split a prize in three and
still give one half to each winner. :)

~~~
jgrahamc
"The Nobel Prize in Physics 2011 was awarded "for the discovery of the
accelerating expansion of the Universe through observations of distant
supernovae" with one half to Saul Perlmutter and the other half jointly to
Brian P. Schmidt and Adam G. Riess."

Seems clear to me. Perlmutter gets 50%, Schmidt and Riess each get 25%.

