One Hundred Years of the Cosmological Constant: from ‘Superfluous Stunt’ to Dark Energy

Some months ago I did a little post on the occasion of the 100th anniversary of the introduction of the cosmological constant which included a link to the original paper on this subject by Albert Einstein. A nice thread of well-informed comments followed that post and one of the contributors to that thread, Cormac O’Raifeartaigh, is lead author of a paper that has just appeared on the arXiv. It’s quite a lengthy paper (62 pages) that gives an account of the cosmological constant in the context of modern observational cosmology. You can get a PDF of the paper here. It’s well worth reading!

The abstract reads:

We present a centennial review of the history of the term known as the cosmological constant. First introduced to the general theory of relativity by Einstein in 1917 in order to describe a universe that was assumed to be static, the term fell from favour in the wake of the discovery of cosmic the expanding universe, only to make a dramatic return in recent times. We consider historical and philosophical aspects of the cosmological constant over four main epochs: (i) the use of the term in static cosmologies (both Newtonian and relativistic; (ii) the marginalization of the term following the discovery of cosmic expansion; (iii) the use of the term to address specific cosmic puzzles such as the timespan of expansion, the formation of galaxies and the redshifts of the quasars; (iv) the re-emergence of the term in today’s Lamda-CDM cosmology. We find that the cosmological constant was never truly banished from theoretical models of the universe, but was sidelined by astronomers for reasons of convenience. We also find that the return of the term to the forefront of modern cosmology did not occur as an abrupt paradigm shift due to one particular set of observations, but as the result of a number of empirical advances such as the measurement of present cosmic expansion using the Hubble Space Telescope, the measurement of past expansion using type SN 1a supernovae as standard candles, and the measurement of perturbations in the cosmic microwave background by balloon and satellite. We give a brief overview of contemporary interpretations of the physics underlying the cosmic constant and conclude with a synopsis of the famous cosmological constant problem.

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14 Responses to “One Hundred Years of the Cosmological Constant: from ‘Superfluous Stunt’ to Dark Energy”

  1. Thanks for the plug Peter! I can’t believe I didn’t spot the typo in the second line of the abstract, ah well. More importantly, the paper is actually only 40 pages long. I must have been possessed when I posted it

  2. I will swear that word ‘cosmic’ survived 60 drafts, incredible!

  3. “Submitted to the European Physical Journal (H)”

    What do readers here think of the EPJ in general and EPJH in particular?

  4. Good question Phillip! If I remember rightly, the European Physical Journal was the name given to the amalgamation of several major European journals such as Zetischrift fir Physik, Journal de Physique and Il Nuovo Cimento. I gather it hasn’t really had the big impact one might expect from such big names, I suspect a lot of people don’t know it’s pedigree.
    As for EPJ(H), it’s only about 10 years old, but I think it has established itself as a good journal for the history of physics by physicists and for physicists (as opposed to sociological history of science). My own experience with EPJH has been very positive – good rigorous comment from referees, fast turnaround, lovely journal in hardcopy. The downside is that it has a very small readership in the US, but I guess that’s true of all the history of science journals

    • Yes, it was an amalgamation (Like Astronomy and Astrophysics and, as you say, doesn’t seem to have the impact one would expect from the pedigree. As for readership, surely arXiv has levelled the playing field?

      A while back I had occasion to read an article in EPJC which is probably the worst article I have ever read in a “serious” journal. Despite big names on the editorial board, the pedigree, etc; the article was really bad: at least a dozen major errors any one of which (if not corrected) should have prevented publication.

      But this is a sample size of 1, so there is a large error bar on any conclusions derived from this.

      I also don’t know how independent the various EPJs are of one another.

  5. Finally found the time to read it. Excellent paper!

    What is the current status?

  6. Thanks Phillip!
    Re status, right now I’m working in some good suggestions from the referees, should be done by Monday. Just to give you an idea, of the sort of points raised:
    (i) The paper is a bit thin on the pre-Zeldovich history of zero-point energy and the quantum vacuum given the importance of such considerations in modern explanations for the cc. So I’m adding a short section on work on this by Nernst, Lenz, Jordan, Pauli etc
    (ii) I mentioned the old argument for a cc from the standpoint of mathematical generality, but I didn’t say anything about the use of the term in unified field theories, from Eddington onwards…so I’m adding a few sentences on that too!
    This is why I like this EPJH, good suggestions from the referees within less than a month of submission

    • (i) Presumably the book by Kragh and Overduin will come in handy here (I think you already cite it).

      (II) I think it might be nice to mention that Schrödinger also worked on this stuff in his later years. (Some of the early quantum-mechanics people fizzled out (de Broglie, say), some continued to do mainstream physics (Pauli, Fermi), some worked outside the mainstream (Einstein, Schrödinger).

      I recently read elsewhere that EJPH is open-access. Which colour? 😐

      One of my complaints (but it might be house style or whatever): references should either refer to the people doing the work as people, with the year in parentheses for informational purposes, or at least, if it can’t be avoided, parsed such that “Jones et al.” is shorthand for “the paper by Jones et al.” Thus, “Jones et al. show” and “it was shown by Jones et al.”, not “it was shown in Jones et al.”. In general (not just in relation to references), stuff in parentheses should be able to be left out without making the sentence sound strange. Thus “in (…” with respect to references is for me like scraping one’s nails on a chalkboard or, worse, the top of an old car.

    • Another point (though perhaps one could write a whole paper on it): you mention the idea of the cosmological constant “causing” the expansion. I’ve seen this in several popular books (written by professional astrophysicists) and, as you point out, it can also be found in journal papers. But the Friedmann-Lemaitre equation is time-symmetric. The universe is expanding because of initial conditions. Their cause is a different matter, but has nothing to do with the presence or absence of a cosmological constant, since the same equation describes a collapsing (or, indeed, static) universe.

      If I have time, I’ll read through it again and see if I find anything else (typos, etc) worth fixing by Monday. 🙂

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