——Science Videos——
Robert Frost
The Nobel Prize for physics was announced just last week.
The Nobel Prize in Physics 2011 was divided, one half awarded to Saul Perlmutter, the other half jointly to Brian P. Schmidt and Adam G. Riess "for the discovery of the accelerating expansion of the Universe through observations of distant supernovae". ¹
Saul Perlmutter
Brian P. Schmidt
Brian P. Schmidt, 44, professor at the
Australian National University elected lead of the
High-Z SN Search Team (HZT) in 1994 with the same aim as Dr. Perlmutter. His team, which included co-Nobel laureate and lead author Dr. Adam G. Riess (below), 41, first published their formal results in the paper
Observational Evidence from Supernovae for an Accelerating Universe and a Cosmological Constant.
Adam G. Riess
Adam G. Riess, 41, works at the
Space Telescope Science Institute and Krieger-Eisenhower Professor in Physics and Astronomy at The Johns Hopkins University in Baltimore. Dr. Riess was the lead author of the HZT 1998 paper that provided evidence for an accelerating expanding universe. Currently he is working with the Supernovae, H0, for the Equation of State of Dark energy (SHOES) team investigating Cepheid variable stars in conjunction with Type Ia supernovae to reduce the uncertainty in the measurement of the
Hubble Constant.
Nobel Medal for
Physics & Chemistry
The three astrophysicists will receive the $1.44 million prize (half to Dr. Perlmutter and half to Doctors Schmidt and Riess) for their work studying Class 1A Supernovas and, primarily, for deducing the implications of their studies for the future of our universe.
One of my favorite sites, Sixty Symbols, posted their own little report on the news. It is a very good summary of what Perlmutter, Schmidt, and Riess did, how they did it, why they did it, and what they found.
Essentially, they studied Type Ia supernovae and made use of the fact that these novae are similar enough that they could be considered 'standard candles' (see below the fold). With that information they could determine the SNe (supernovae) distance and how fast (because of their distance) they were moving. The surprising result is that the galaxies are farther away than expected (~15%-25% farther away).
The story of a dark, energetic universe unfolds...
The Big Crunch
As little as 15 or so years ago physicists and astronomers expected that the expansion of the universe would eventually slow down and begin to contract in what was called '
The Big Crunch'. It was (and is) known, however, that the universe is expanding based on the work of the pioneering astronomer
Edwin Hubble (someone we've met before
here and in
jim in IA's excellent
Kosmic Ladder [4] series).
The obvious question, then, given this theoretical framework is: When will the universe slow down and begin to collapse? Or, in other words...
What is the ultimate fate of the universe?
Of course, the question as to the ultimate fate of the universe has been on the mind of humankind for quite a long time. Philosophers, theologians, and religious dogma all considered the issue. It might have even crossed your mind on occasion, but it wasn't until a certain young physicist in Germany came up with a new way to think about the universe that physics had a solid testable foundation under which it could truly consider the problem.
Einstein working on his
Infinite Improbability Drive.
When the 20th century began, few people imagined that the universe was anything but a small, unchanging place. That’s why, when Albert Einstein introduced his general theory of relativity in 1917, he added a term to the equations to make sure they described a universe that was just barely static. He called it the cosmological constant and used Λ, the Greek letter lambda, to symbolize it.
²
So, like pretty much everything in cosmology, considertion of the question starts with Einstein. In 1917 he published his paper on General Relativity which gave the world a a testable theory that showed, at the very least, that answer to the Ultimate Question of Life, the Universe, and Everything was not likely to be 42 (6²+6≠6×9). However, it did leave open the possiblity in base 13 (6₁₃×9₁₃=42₁₃).
Ok, sorry, I just couldn't resist.
From 1917, when Einstein published his corrected paper on General Relativity, until Hubble's publication in 1929, scientists (and by that we mean Einstein) made a guess. There were three possibilities. The universe might be static, it might be open, or it might be closed. That is, the universe would either stay pretty much unchanged, expand forever, or collapse back in on itself. Einstein initially preferred a universe that was essentially static and assigned a value to Λ that would provide solutions in a static universe. Then along came a first class trouble maker named Hubble, an astronomer no less, who actually started measuring things. Einstein had a theory, Hubble measured. Hubble, in other words, took the first steps toward actually answering the 'question' by observing the universe as it is.
Hubble's 1929 paper A Relation Between Distance and Radial Velocity Among Extra-Galactic Nebulae introduced evidence for an expanding universe. Hubble's genius was being able to synthesize his own research with the work of others to advance our understanding of the universe (both literally and figuratively). He built on the works of Henrietta Leavitt and Vesto Slipher (see: Henrietta and the Harvard Calculators, Kosmic Ladder 4 - Expanding Universe, or The Most Important Star You've Never Heard Of). By recognizing the implications of his discovery of the huge stellar/galactic distances, the speed of light, and Doppler effect (redshift) Hubble showed that the universe was expanding and certainly not static. Hubble's work, in consequence, exposed what Einstein considered his greatest blunder.
By the 1930s a completely different picture had emerged from observations with big telescopes. The universe was vast, and innumerable galaxies were moving outward in every direction; many believed that space and time and all they contained had originated in an incredibly hot, dense instant, later called the big bang. Faced with this evidence of a dynamic universe, Einstein berated himself for introducing a term that now seemed unnecessary, and cheerfully abandoned his cosmological constant.
²
“A candle loses nothing by lighting another candle”
Proverbs
How could one begin to investigate such a question as the ultimate fate of the universe? Nobody even knew the universe’s shape or dimensions. For decades astronomers had been hoping to find a way to use brightness to measure distance. If a regular relationship between a particular kind of astronomical object’s brightness and its distance could be found, such objects could be used as “standard candles.”
²
A standard candle in astronomy is a stellar object with a known luminosity. It is an intuitive concept. The further away you get from a light the dimmer it gets by an inverse square law (∝ 1/r²).
Hubble's research depended on the use of Cepheid variable stars as standard candles from which he determined the vast size of the universe. As mentioned above, that discovery implied that the universe was not static, but that it was expanding. This left two possible alternatives, an open universe or a closed one. From Hubble's time until 1998 scientists assumed we lived in a closed universe.
Not surprisingly Perlmutter, Reiss, and Schmidt lit their candle with Edwin Hubble's, so to speak. The Nobel laureates were, essentially, trying to measure the expansion of the universe and the acceleration of deep stellar objects to determine when the universe would slow down and begin to collapse. The two teams (SCP and HZT) were using Type Ia supernovae as standard candles to measure the acceleration of high redshift (very old) supernovae and the galaxies they lived in. They ran into a bit of an oops, however, they weren't finding what they expected to find. What they found is an open universe, dark energy, and ultimately a Nobel Prize.
At the time of their work, astrophysicists believed that the rate of expansion of the universe — set in motion by the Big Bang 13.7 billion years ago — would be slowing down as matter was pulled together by gravity. The goal at the time was to figure out how rapid the deceleration was.
What the two teams found instead was that the expansion of the universe was accelerating — an observation that could best be explained by the existence of a mysterious "dark energy" that pushes matter farther and farther apart.⁴
KQED produced a short film describing the discovery of dark energy, featuring Dr. Perlmutter.
Dr. Alex Filippenko was a member of the SCP before moving over to the HZT program. Here is his
TEDx talk on dark energy and the universe from December of 2010. TEDx is an offshoot of the
TED conference series.
In 2000 Nova produced the documentary film Runaway Universe that chronicles some of the events, methods, theory, and people which lead to the discovery of dark energy. I recommend it if you find this subject interesting; I think I might be able to find you a copy if so. Nova and PBS have a web site associated with the program here. It is quite the slick multimedia site.
Addendum on Edwin Hubble...
Hubble spent much of the later part of his career attempting to have astronomy considered an area of physics, instead of being its own science. He did this largely so that astronomers — including himself — could be recognized by the Nobel Prize Committee for their valuable contributions to astrophysics. This campaign was unsuccessful in Hubble's lifetime, but shortly after his death the Nobel Prize Committee decided that astronomical work would be eligible for the physics prize.³
The Nobel Prize is not usually awarded posthumously. Dr. Ralph M. Steinman, who passed on September 30, 2011, will receive the award. From the Nobel Committee's press release concerning this unusual event...
As announced earlier, Ralph Steinman – one of this year’s three Nobel Laureates in Physiology or Medicine – died on September 30. This information reached the Nobel Assembly at Karolinska Institutet via the president of Rockefeller University, where Steinman worked, at 14.30 CET on October 3, 2011. Earlier the same day, at 11.30 CET, the Nobel Assembly had announced the 2011 Nobel Laureates in Physiology or Medicine without knowing of Ralph Steinman’s death.
The events that have occurred are unique and, to the best of our knowledge, are unprecedented in the history of the Nobel Prize. In light of this, the Board of the Nobel Foundation has held a meeting this afternoon. According to the statutes of the Nobel Foundation, work produced by a person since deceased shall not be given an award. However, the statutes specify that if a person has been awarded a prize and has died before receiving it, the prize may be presented.
Footnotes
- Nobelprize.org
- Dark Energy’s 10th Anniversary - Part I, Announcing the accelerating universe
- Hubble and the Nobel Committee
- Los Angeles Times - Physics 'error' leads to Nobel Prize
Links
I hope you've enjoyed this little diary as much as I had putting it together.