One of the biggest scientific findings in recent years is the discovery that the universe is not only expanding, but it is also accelerating in its expansion. Under the influence of a mysterious dark energy, the universe will eventually thin out to nothingness and die a cold death. For the Insights story, "Dark Forces at Work," appearing in the May 2008 Scientific American, David Appell talked with Saul Perlmutter of the University of California, Berkeley, and one of the leaders of the group that came to the astonishing conclusion. Here is an edited excerpt of that interview.

In finding that the universe is on a path to runaway expansion, you had to find type Ia supernovae, which can act as distance markers. How did you get involved with supernova searching?
I was at the University of California at Berkeley for graduate school. One of the heroes here at Berkeley is Luis Alvarez. The tradition that he started is looking for interesting science no matter where it is and then finding tools to do those things. For example, he invented one of the first steady cams.

One of his protégés was my professor, Richard Muller. There was a project to do a superautomated supernova search that Luis Alvarez had suggested to Rich. They had just done one of the first adaptive-optics experiments.

So, as a grad student, you began developing the techniques for a robotic supernova search. But you also found that they could be used for other kinds of targets.
I had gotten interested in a theory that had been put forward by Rich Muller and Marc Davis and Piet Hut—namely, that you could explain periodic mass extinctions on the earth by a possible companion star around the sun. They called this star Nemesis. We realized that with the most common kind of star in the sky, the red dwarfs, you wouldn't know if it were orbiting around our sun. You could assume it was a much farther away red giant, just because it would have very little motion with respect to us, because it's bound to us. We realized that we could look in the catalogue of red stars for one that had this motion that you expect and that we could use the same telescope we were using for the robotic supernova project. So I developed the astrometric techniques to make this precise measurement of the parallax motion.

Have you done any work on Nemesis since?
No, it was one of the things I was doing, but my main project was working on the robotic nearby-supernova search. I had developed some new software. We were running the search and finding  supernovae, cataloging and keeping track of everything so you could compare it to everything we found.

Are you more of a theory guy, or are you more of a gearhead?
I'm really an experimental type. I really enjoy trying to catch the universe in the act of doing something very surprising and perhaps figuring out what it's doing by making measurements.

You were the team leader of the Supernova Cosmology Project in the 1990s, which consisted of a dozen members or so. How did you delegate responsibilities to your team members?
You're trying to figure out what are the critical paths to get to the result you want. And sometimes you think it's faster doing it yourself, and other things come along and you'd like to do them, but I'm trying to get this one done and somebody else comes along in your group and they start doing it. So it's much more organic in the sense that you find that you can't do everything. The best world would be one in which everyone you find to work with is better than you, because then you're doing better work than you could ever do.

What were the downsides to working on the project?
The worst thing about my research life was that I was always worried about something that had to happen in the next 24 hours, or sometimes, the next two hours. It was a terrible way to lead an ordinary life.

10 Comments

1. 1. srchuck 04:19 PM 4/21/08

   Congratulations! Science without politics.

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2. 2. rcglinsk 05:29 PM 4/21/08

   Since there is no proof of the hubble relationship (red shift v. distance), this research means nothing.

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3. 3. Wayfarer 05:25 AM 4/22/08

   What causes redshift?

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4. 4. sardar 12:52 PM 4/22/08

   I have alot of rispect for this man.

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5. 5. Dario Aris 10:04 AM 4/23/08

   There is large part of universe beyond the part that sends us radiation and is observable. The remaining of the universe is unobservable by radiation but hits gravitation field fills our part of the universe. Angelo Mula via Plinio,87 Taranto Italy +39 3486047680

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6. 6. gmusser 06:35 PM 4/23/08

   rcglinsk writes that there is no proof of the Hubble relation. There is actually ample proof, such as the Key Project on the Extragalactic Distance Scale.
   George

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7. 7. gmusser 06:36 PM 4/23/08

   In the big bang model, redshift is caused by the stretching of light waves by cosmic expansion. See http://www.sciam.com/article.cfm?id=misconceptions-about-the-2005-03

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8. 8. shebatd 02:05 PM 8/8/09

   This is really a question. How can light or anything else travel from point A to point B, without consuming energy. Doesn't light traveling through space violate the conservation of energy?
   I was thinking that the cosmological constant (the dark energy) is a requirement to prevent light from violating the conservation of energy law. I thought only an expanding universe would keep light from violating this law by reducing its frequency and hence energy. Think of light as being embedded in space and stretched with it's expansion.

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9. 9. poeteye 08:26 PM 8/30/11

   SUPERLUMINELLE
   -- James Ph. Kotsybar
   
   The Universe is expanding,
   Faster than the limit of light,
   Beyond common understanding.
   
   Cosmology is demanding.
   Its study is by no means slight.
   The Universe is expanding.
   
   Physics’ heroes, quite outstanding,
   Have applied their full mental might
   Beyond common understanding.
   
   There’s no point in reprimanding,
   As we gaze out into the night,
   The Universe is expanding.
   
   The truth of fact is commanding.
   Whatever is has to be right,
   Beyond common understanding.
   
   Einstein’s physics notwithstanding,
   Much quicker than what we call bright,
   The Universe is expanding
   Beyond common understanding.

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10. 10. Gribov 10:39 PM 4/9/12

    Dear Dr. Perlmutter, congratulation with the Nobel Prize 2011 and the tremendous Dark Energy (DE) discovery - the Problem Nr. 1 in the XXI century! Could you look in the “Gribov Periodical Multiverse” (GPM) concept, solving interrelated DE&DM&SUSY&Higgs problems. See: Gribov 2012. Dark Matter as Pico-Windows to physically equal Multiverse Worlds with Myriads Civilizations Around Us (in extra dimension). http://www2.hu-berlin.de/leibniz-sozietaet/journal/archive/13_12/01_gribov.pdf. Once we spooked about it by phone.
    The GPM provides unifying physical alternative to the global Minkowski 4D-spacetime, it consists of elastic 3D-waveguides, periodically embedded into a global isotropic Euclidean 4D-hyperspace, filled by Diracian-like superfluid ghost medium - nongravitating, chargeless supersymmetric vacuum, which is built from Cooper-like (e-/e+) bosonic composites with elementary particles - holes-defects in it. Waveguided - orthogonal harmonics realize quantized rest mass, electrostatic and gravity charges creation mechanisms of elementary particles, being confined in the waveguides as the Einsteinian-like C4-quanta E4=hv4 via polygonal /\/\/\/\/\ C4-dynamics, kipping C4-gauge symmetry. This creates all the emergent SR & quantized Equivalence Principle - GR & QM & Kaluza’s cyclical condition, resulting of the same 3D-waveguided wave-interference. The GPM-period has waveguides thickness Lo~10(-10)cm = Compton length of electrons. There are physically equal coupled, periodical matter/antimatter (gravity/antigravity) Universes with enormous density ~10000000000 Universes/cm4.
    The GPM design creates:
    (1) the interconnected nature of DE&DM & flatness & accelerated bubble large-scale Universe structure expansion, (with estimated theoretical ratio DE/(DM + Ordinary Matter) ~74%/26% - very near to the latest observational data;
    (2) string-like fermions / antifermions and black holes, all free of singularities;
    (3) predicts antigravity in the antihydrogen - CERN / positronium - Mills lab gravity tests;
    (4) the Cooper-like (e-/e+) composite - ghost SUSY, with zero vacuum energy density;
    (5) absence of elementary Sparticles & Higgs bosons;
    (6) explains the spin-nature of the Planck constant h and masslessness of bosonic Einsteinian C-photons - quasiparticles as spin waves in the cellular (e-/e+) vacuum medium;
    (7) predicts physically equal periodical dark Universes, with enormous density of hyper-civilizations (placed proximally near 10 -100 light minutes in a R4-distance around us)!
    

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