KSJ Tracker November 16, 2012

BOSS III Dark Energy Survey: Call Wittgenstein! News for which plain English (so far) fails.

I've been puzzling for hours today, well into a Friday afternoon, over a technically arcane but important bit of progress in dark energy observational cosmology. Several news outlets wrote it up. All agree that the remarkable Sloan Digital Sky Survey, which is now in its SDSS III stage, has provided to its large team of users a terrific new tool piecing together the history of how the universe has expanded. It was about 15 years ago that news broke that the cosmos, rather than yielding to its gravity and slowing as it expands, is instead speeding up. Recent Nobel Prizes recognized how important that was. The project in news this week  aims to move the ball forward by charting the history of that reversal of cosmic acceleration's vector.

     It is called the BOSS project, for Baryonic Oscillation Spectroscopic Survey and that relies largely on the Sloan Survey's pretty little telescope at New Mexico's Apache Point Observatory. It released some early results of its spectroscopic analysis of the light of thousands of very distant quasars. The light carries the fingerprint of all the hydrogen gas it encountered in the billions of years it has spent reaching us. And somehow, the news reports tell us, from this the astronomers are starting to see how dark energy 11 billion years ago was already resisting gravity, keeping the universe expanding a little faster than one might expect. About all that had been known from earlier surveys, mostly of supernovae behavior as seen at various distances, is that around seven billion years ago the deceleration of the Big Bang's expansion's turned to acceleration - throwing glactic clusters farther apart at an ever increasing pace and into a far future of cold, infinite void. Now, it appears, something of the earlier push me - pull you contest is being inferred.

   But man oh man, nothing I've read - not press release, not news stories derived from it and the raw paper (see Grist) and not additional reporting gives a sense, in layman's terms, what these astronomers and theoretical astrophysicists have done to get their answer. Oh, they have jargon. They include of course baryonic oscillations because that's in the name of the project, and Lyman-Alpha forest because that's the spectroscopic fingerprint of intergalactic hydrogen which indicates how much hydrogen was going how fast, and where and when.

    But that's about it. This isn't like quantum mechanics or relativity or string theory where one has to do the math to really appreciate it. Separately the phenomena - early vibrations kind of like sound waves, absorption lines, etc - are describable. It's the whole package that eludes comprehensible description. Hence the allusion in this post's hed to Wittgenstein, the Austro-British logician who puzzled out examples of ideas that could not be expressed without logical contradiction or ambiguity in some systems of language while others might do the job. Science writers pride themselves on jugglng allusions, metaphors, analogies, and deft quotes at least to provide lend a sense of what a complicated science story is about and some of the scientific method employed to put it together.

   Maybe it's just me. This post points no fingers. It simply shares my struggle to internalize this news and the science behind it. But take a look at a few examples from among news stories and at the press releases and the paper and stuff like that. If you're a little fuzzy on your data deconvolution algorithms and acoustic baryonic oscillation, do YOU get it? What feature in these schmeared-together Lyman-Alpha spectroscopic features combined with baryonic oscillation hints and all coming from the same pixels simulateneously told them not only how fast gas at varying distances was going, but when? I think my brain has multivariate paralysis.


  • Symmetry Magazine - Kelen Tuttle: BOSS collaboration meausres expansion of the universe 11 billion years ago ; Symmetry is not quite general media, but is more of outreach by Fermilab and Stanfords Linear Accelerator Ctr and aimed at a very techie crowd. The piece says what they did, but not how they did it. One gets the sense that these baryonic accoustic oscillations mediated the large scale distribution of matter, but how does one know the exact distance to given pieces of it?
  • Astronomy Now/ Spaceflight Now - Stephen Clark: New technique brings ancient dark energy into focus ;
  • KSL.com - John Hollenhorst: Utah dark energy study hints at the end of the universe ; I love this story, not becuase it is so good but because this TV newsman in Salt Lake didn't even try to relay what the basic importance of the news is, but charged in anyway. He interviewed the Univ. of Utah man features in that school's press release, didn't say anything at all about what the larger project is by name or other institutions, and writes it as though it's chiefly a Utah-based effort and as though debate between eternal expansion or big crunch is still running hot in the halls of science. But the story does get the gist of the issues involved and the general spookiness of contemporary cosmology.
  • BBC - Jonathan Amos: Quasars illustrate dark energy's roller coaster ride ; Amos does make a stab at how the baryonic oscillations left behind indications of distance - a "preferred scale" of galactic and supercluster distribution. Still don't get it.
  • Space.com : Distant Black Holes Map Universe's Dark Energy History ; The lede refers to "Extremely bright black holes," which is pretty much what a quasar is even though it's not the supermassive black hole itself that's bright, it's its sloppy eating habit and the blowing, glowing leftovers.
  • Guardian (UK) Stuart Clark: Dark energy map puts the squeeze on dark matter ;

Grist for the Mill: SDSS-III Press Release ; Lawrence Berkeley National Laboratory Press Release ; University of Utah Press Release ; arXiv paper preprint.

- Charlie Petit


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