Why it's OK not to be Sean

By Julianne Dalcanton | August 7, 2007 3:59 am

Sean cheekily comments in a recent post:

If you know that something exists, what’s the point in thinking about it?

My response to this is much the same as the post-I-meant-to-write-but-didn’t-get-around-to on Simon White’s smackdown warning against all astronomers turning into “dark energy experimentalists”.

Thus, here is sampling of astronomical facts that had to be learned before the high-z supernova teams could discover dark energy.

  • That supernovae exist.
  • That supernovae are exploding stars.
  • That not all supernovae are the same.
  • That variations in supernovae properties correlate with the properties of the progenitor star.
  • That a significant subset of supernovae come from detonating white dwarfs (Type Ia SN).
  • That Type Ia SN have a characteristic spectrum.
  • That Type Ia SN have a typical luminosity of 1043 ers/s, which we learned from figuring out how to measure distances to nearby galaxies that happened to host Type Ia Sn in the past, using a list of facts that is much longer than this one.
  • That, in the absence of dust, the peak luminosity of Type Ia SN correlates with the color of the supernova and the rate at which it fades.
  • That dust causes reddening and dimming of light, but in a usually predictable way which depends on wavelength.
  • That the unreddened, undimmed color and luminosity of a distant, redshifted supernova can be estimated from the data alone.
  • That the peak luminosities of Type Ia SN at different redshifts can be compared, even though observations measure different parts of the spectrum due to the cosmological redshift.

As long as this list is, it’s still highly incomplete, and takes for granted that we know even more basic things like “how do I calibrate how many ergs/s are coming from an astronomical object that I detect as a fuzzy blotch in my CCD detector?”. It represents decades of efforts by many hundreds of people (many of them theorists, but theorists working on Stuff That Exists), most of whom didn’t think twice about the existence of dark energy.

Given the above, one possible physics-biased reading of Simon’s article is that if you limit astronomers’ ability to go forth and characterize what the universe is actually like, no one will be laying the foundations for the next generation of crazy-physics-you-can-study-in-space. For astrophysics, the Universe is our LHC, and we’ve got to be free to characterize our widgets, even if they’re boring ole brown dwarfs rather than panels of supercooled silicon wafers.

Now, all of this diatribe is not meant to minimize the role of outside the box theory. You absolutely need that too. However, it’s not the only necessary thing, and it’s not for everyone. There’s an old chestnut that theorists are judged by their best paper and observers/experimentalists by their worst. In other words, once Alan Guth came up with inflation, he was rightly marked as a superstar, and he can safely spend the next three decades writing papers on Romulan cloaking devices if he chooses. However, if an experimentalist writes a paper saying they’ve detected Romulan cloaking devices, no one is going to believe them when they later say they’ve discovered the Higgs. Tempermentally, most people are probably more suited to one camp than the other. I know that I have a pragmatic streak a mile wide, and thus I’m better off in the “stuff that exists” camp. I can understand why that sounds terribly dull to Sean, but I’d bet he’s glad me and my ilk are doing so.


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