Top Physics Stories

By JoAnne Hewett | December 14, 2005 4:21 pm

It’s that time of year – lists of the best and the worst of 2005 are popping up everywhere. One of my favorites is published by the American Institute of Physics with their annual compilation of the Top Physics Stories of the year. The list contains 25 physics events which occured throughout 2005, ranging from the arrival of Cassini at Saturn to various exciting physics results to the announcement of the Nobel Prize. It’s a great read and a great way to catch up on the hot news from various physics subfields. It’s a standard reference for anyone who is on a departmental colloquium committee.

According to the AIP, this year’s most interesting results ranged from the development of lasing in silicon, the biggest burst ever recorded from a soft-gamma repeater, to the observation of geoneutrinos. The latter is cool: KamLAND (the Kamioka Liquid scintillator AntiNeutrino Detector in Japan) has observed the appearance of electron neutrinos orginating from radioactive decays inside the Earth, presumably from U-238 or Th-232.

The top story of the year was the quest to observe quark-gluon plasma at the Relativistic Heavy Ion Collider at Brookhaven National Lab. Theorists say that quarks and gluons become unconfined at high temperatures and form a plasma-like sea of free particles, consistent with conditions in the early universe. The search for this quark-gluon plasma has been long and frought with peril (CERN miraculously announced its discovery just before the turnon of RHIC – an announcement which later proved to be premature and a stretching of the truth). But now, after years of collecting and analyzing data, all 4 RHIC experiments have formed a concensus on the observation of a quark-gluon liquid. That’s right, not a plasma at all, but a liquid! So much for the theorists! When gold ions collide at RHIC, the detectors see a dense liquid which flows with very little viscosity. In fact, it flows so freely that it approximates a perfect liquid, the kind governed by the standard laws of hydrodynamics. Having discovered the surprising liquid nature of the free quark-gluon sea, the experiments next want to probe its properties, such as its heat capacity and its reaction to shock waves. However, RHIC has been subject to extensive budget cuts this year (run time is reduced by 61% fewer hours) and the collider may be terminated in the near future.

Lastly, one of the top 25 is from my homeground, SLAC! It is billed as the best measurement yet of the weak nuclear force. The experiment, known as E-158 (we sometimes have the custom in high energy physics of naming our experiments simply by the numbers, i.e., this is the 158th experiment to be conducted in the End Station at SLAC), carried out the most precise measurement of the weak mixing angle at low momentum transfer. The weak mixing angle relates the stength of the electromagnetic coupling to that of the weak coupling, and provides a sensitive test of our Standard Model of particle physics. This mixing angle has been measured extremely precisely at energies corresponding to the Z-boson resonance, but a full test of our Standard Model requires precision measurements of this quantity at different energies as well. Using the polarized 90 GeV electron beam from the SLAC linac, E-158 measured Moller scattering, which is electrons scattering off of electrons to form electrons + more electrons. It may sound a bit silly, but it is a very clean process from which we can precisely determine the properties of the particles being exchanged in this scattering (the photon, Z boson, and possible new heavy bosons). The accuracy of E-158’s measurement is roughly 0.6% and reaching this level of precision was an experimental tour de force. The End Station at SLAC has since been shut-down for HEP experiment due to budget constraints.

The bottom line from this “best of” list is that there is lots of exciting physics being produced!

  • Count Iblis

    I wonder what would have happened if the SSC hadn’t been canceled.

    Would it have become operational by now?

  • Ben L

    The other bottom line is that the US budget for exciting science is being slashed to death.

  • Belizean

    Perhaps we might be somewhat sparing in the use of word “exciting” to describe what is actually a rather routine year of physics. After all, if we exhaust that adjective in describing 2005, it will be unavailable to characterize another 1905 or even a 1974.

  • DM

    Perhaps we might be somewhat sparing in the use of word “exciting” to describe what is actually a rather routine year of physics.

    I think you have a point there: “routine physics” is exciting! I found the list quite impressive.

    About 1905, I think we can come up with another, stronger adjetive for it.

  • Garrett

    Evidently, producing results is a sure fire way to get your budget slashed.

  • JoAnne

    Count Iblis: The SSC was on schedule to become operational in 1998. It was 25% finished when it was cancelled, so it was well on its way to being completed. Even with inevitable delays in its budget profile, it would have been running by now. And then Belizean would have been correct – we would have needed better superlative adjectives to describe the top physics stories of 2005.

    On a personal note – I was supported by an SSC Fellowship when the project was cancelled. I remember watching the congressional vote on CSPAN on that fateful day in October 1993. I went in to work that afternoon, spent most of the time crying in the ladies locker-room, and at the end of the day, called SLAC to accept my current position. I probably would have come to SLAC no matter what happened to the SSC, but I was fortunate to have a nice alternative career path to turn to on that day.

    Ben L: You are absolutely correct. It took all I had to not include that comment in my bottom line and to end the post on an upbeat note.

  • Belizean

    At the time of the SSC vote, I remember wondering about what would happen if, having failed to obtain the necessary funds by taxation, SSC advocates simply asked the public for it.

    I wonder how much money an SSC telethon would have raised. 1%? 10%? 30%?

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  • Dissident

    Belizean, are you a closet libertarian…? :)

  • Jenny Attiyeh

    What about Lisa Randall and her new book “Warped Passages: Unravelling the mysteries of the universe’s hidden dimensions” ?? Does this not merit inclusion in your ‘top story’ list?
    Also … anybody want to suggest some good questions to ask her? I’m interviewing Lisa shortly, and would appreciate some input. FYI my audience (see is a mainstream one. Not a bunch of scientists, and I confess I have to lump myself in there as well!
    Thanks very much,

  • Dissident

    #10: No.

  • Sean

    Jenny, I would say that Lisa’s book (which we talked about here a bit) is a great story about physics, but not a physics story, if you know what I mean — the stories in the AIP list are really about actual physics discoveries. The high point of the book is the physics of “warped compactifications” of extra dimensions, which Lisa and Raman Sundrum discovered in 1999; it certainly would have been among the top stories that year. This year, it’s conceivable that in retrospect Lisa’s work with Andreas Karch on relaxing to three dimensions will be thought of as a major breakthrough, but for the moment it’s an interesting idea that is extremely speculative.

    Lots of good questions to ask — from “what first got you interested in physics”” and “why did you decide to write a book?” to “how do you think we will experimentally test the idea of extra dimensions?” and “how close are we to connecting particle physics to the Big Bang?” There is widespread interest in these big questions about cosmology and extra dimensions and particle physics and quantum gravity, the real goal should just be to bring them to life and convey some of the excitement that physicists themselves are feeling.

    Your show sounds like a lot of fun; good luck with the interview.

  • Jenny Attiyeh

    Hey Sean! I’m going to ask about “how close are we to connecting particle physics to the Big Bang?” Geat question, and thank you. What do you think the answer is? What do you think her answer will be?
    And yes, the program is a lot of fun, especially the bit about going broke putting it on…!

  • Sean

    Anything worth doing is worth going broke over.

    I think we have a chance of connecting particle physics to the Big Bang, although at the moment our ideas are still very speculative. But just the fact that we can intelligently debate different answers to the question “Why does spacetime appear four-dimensional?” is a remarkable feat.

    You might also want to ask about the prospects for different experimental inputs in the near future — from particle accelerators like the Large Hadron Collider at CERN, from searches for dark matter and dark energy, from gravitational wave observatories, etc. The next 10-20 years hold remarkable promise for surprising new discoveries that will reveal important parts of the big picture, and it would be interesting to see what Lisa thinks those prospects are.

  • Amara

    There might be some confusion on the AIP Physics top story site. Cassini-Huygens arrived at Saturn in July 2004. However the Huygens probe landing on Titan in January 2005 was remarkable and deserving its listing for 2005.

    IMO an even more remarkable feat in planetary science in 2005 than the Huygens landing was Hyabusa’s collection of asteroid material from the S-type asteroid Itokawa:

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