August 26, 2009 | David F. Coppedge

Cosmic Accounting Is Wildly Inaccurate

Counting faint celestial objects is admittedly hard, but the task should be within the capabilities of expert astronomers.  It is, after all, as simple as counting.  So much theoretical work relies on accurate counts of what’s out there, they need to get at least in the ballpark.  Recent indications hint that their counts have been way off.

  1. Galaxies:  Pavel Kroupa (U of Bonn) has told his colleagues that counts of mini-galaxies don’t match expectations.  In New Scientist, he said, “It is the cleanest case in which we can see there is something badly wrong with our standard picture of the origin of galaxies.”  In theory, there should be thousands of mini-galaxies orbiting the Milky Way; in actuality, only 25 have been found.  What’s more, they orbit in unexpected ways, casting doubt on standard theories of gravity.  Kroupa believes that Newtonian gravitational theory has to be modified to account for the observed motions.  The accounting of mini-galaxies, the article said, “has the latest battleground between the proponents of dark matter and theories of modified gravity.”  Can something as basic as gravity be questioned?  Yes.
  2. Stars:  400% off?  “Galaxies Demand a Stellar Recount,” announced a Jet Propulsion Lab feature story this month based on a paper in Astrophysical Journal last April 10.1  The upshot is that there appear to be far more small stars than thought – four times as many.  Astronomers have been using a ratio of 500 small stars to every giant, but results from the Galaxy Evolution Explorer indicate the actual count might be more like 2,000 to one.  Gerhardt Meurer used a fruity analogy: “the melons grab your eyes, even though the total weight of the blueberries may be more.”  The recount affects an important parameter called the Initial Mass Function.  The IMF is the basis for a great deal of theoretical work.  Astronomers think they understand galaxies by looking at the light they can see, but “this common assumption has been leading astronomers astray,” Meurer said.  The article said, “This belief, based on years of research, has been tipped on its side with new data from NASA’s Galaxy Evolution Explorer.” 

Theories, like vending machines, may not work when tipped on their sides.  Many ideas about stellar and galactic evolution have depended on estimates that now appear to be highly oblique.


1.  Meurer et al, “Evidence for a Nonuniform Initial Mass Function in the Local Universe,” The Astrophysical Journal 695 (2009) 765, April 10, 2009, doi:10.1088/0004-637X/695/1/765.

Here are more reasons to be wary of the confident statements of scientists.  We can police them when their work produces a cell phone or printer that works or doesn’t work, but how is a layperson to judge a cosmologists’ assertion that dark matter constitutes 95% of reality, or galaxies evolved from mergers of mini-galaxies?  Most of us can’t, so we tend to give them the benefit of the doubt and trust their superior knowledge.  The training they’ve gone through and the knowledge they’ve acquired do command respect, but it’s dangerous to trust scientists overmuch.  There are some things they just cannot know very well.  In most respects they are just like normal people: mortal, fallible, and given to overconfidence.
    Scientific television shows are among the worst for transforming theoretical work into brazen propaganda.  Visualization techniques like animation can make dubious hypotheses seem certain.  Dust grains can grow into planets right before your eyes (cf 08/21/2009); comets can deliver oceans to the earth, and mineral grains washed into the oceans can morph like magic into living cells (these miracles were all seen on a recent TV show about earth history).  Don’t be fooled.  Those are tricks by graphic artists, not findings by the Knowers of the Deep Knowledge of All.
    Here are three warning signs that can help laymen to keep a healthy skepticism when evaluating scientific claims: (1) a new finding undermines long-held assumptions (like those above); (2) a deep, long-lasting controversy is taking place between competing theories; and (3) a scientist says, “We now know….”

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Categories: Astronomy, Cosmology, Physics

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