July 17, 2010 | David F. Coppedge

Dark Energy: Can a Theoretical Entity Be Measured?

The redshift of galaxies has been measured for some 90 years, but the existence of “dark energy” was postulated only recently – in the late 1990s.  It was needed to explain unexpected dimness of the most distant galaxies, as measured by Type Ia supernovae.  Some cosmologists claim they are measuring dark energy – others say it is an unnecessary quantity that may not even exist.
    PhysOrg triumphantly announced that dark energy has been measured with more precision than ever before by astronomers using the SLAC National Accelerator Laboratory.  This measurement “Sheds New Light on Universe’s Expansion,” the article states.  Yet it becomes clear reading the article that what they were measuring were X-ray emissions from galaxy clusters, then combining the measurements with theoretical models of dark energy.
    It should be apparent that only light can be measured, not darkness (the absence of light).  For instance, a record-breaking gamma ray burst was announced by Space.com: “A violent cosmic explosion has unleashed the brightest blast of X-rays ever detected from distant space, a signal so bright it temporary blinded the NASA space telescope assigned to spot it.”
    Speaking of the Type Ia supernovae used to measure cosmic expansion, Science Daily said that the origin of these key cosmic explosions is still a mystery.  A spokeswoman for the Harvard-Smithsonian Center for Astrophysics said, “The question of what causes a Type Ia supernova is one of the great unsolved mysteries in astronomy.”  Scientists have models for them – such as the accretion of matter onto a white dwarf from a binary companion, or the collision of two white dwarfs – but no model explains all the observations.  This would seem to cast doubt on whether there is a single mechanism – and how, if not, astronomers can have confidence in their distance measurements (cf. 03/28/2010, bullet 5).
    Science magazine hosted a written debate this week on the question, “Is dark energy really a mystery?”  Eugenio Bianchi and Carlo Rovelli in France answered “No.”  Dark energy is nothing more than lambda, the cosmological constant Einstein erroneously tossed out of his original field equations.  Since lambda is an integral part of his theory, and the current Cold Dark Matter (CDM) model employs it, there is no mystery.  Dark matter is not a substance, they said.  It is part of the explanatory apparatus.
    Taking the affirmative, Rocky Kolb of Chicago acknowledged that the CDM model is the leader, with no observations against it, but said its success comes at a price: “In the model, only about 5% of the total mass�energy of the Universe is observed and understood, and 95% of the Universe is dark.”  Kolb is not impressed by attempts at alleging that a “new constant of nature” (the cosmological constant) “explains” dark energy.  To him, it fits the description of a mystery in the “non-theological” sense of the word: “Something not understood or beyond understanding.”  Moreover, if lambda is the measure of dark energy, it is “absurdly large” for a constant – on the order of 1028 per square centimeter.  Such a constant “cannot at present be related to any other known or expected length scale in nature, and “Attempts to explain this new length scale fail by many, many orders of magnitude.”  His objections then became philosophical and historical:

We must demand more of cosmology than just piling on components or constants to a model to reproduce observations.  Otherwise, we would still happily be adding epicycles to the Ptolemaic model of planetary motion.  Cosmological models, along with their constants and components, must be grounded in laws of nature that we understand.  The magnitude of the cosmological constant cannot currently be explained by any physics we know.  Until it is, it is a mystery.

See also the 09/28/2009, 06/30/2008 and 05/11/2006 entries, or search for “dark energy” in the search bar.


1.  Bianchi, Rovelli, and Kolb, “Cosmology forum: Is dark energy really a mystery?”, Nature 466, pp 321�322, 15 July 2010, doi:10.1038/466321a.

What kind of science ascribes 95% of reality to mysterious, unknown stuff (MUST) that must exist to keep a theory going? (see 02/28/2008).  If a religion did that, it would be laughed out of the observatory.  Kolb recalled a personal communication he had with maverick astronomer Tommy Gold: “for every complicated physical phenomenon there is a simple, wrong explanation.”  Scientists only fool themselves by giving names like “cosmological constant” to things they do not understand.  It’s a trick the Murphy’s Law books use for entertainment: (e.g., Skinner’s Constant: that quantity which, when added to, subtracted from, multiplied or divided by the answer you got, gives you the answer you should have gotten).  Make one up and explain the universe.  How about Darwin’s Constant: the tendency to speak beyond experience, defined in units of hubris per square paragraph.  Have some fun and send in your entry to the Feedback line.

  • Dawkins’ Constant: The tendency for evolutionists to think they could have designed a better universe, planet, and life than God did.
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Categories: Cosmology, Physics

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