The Carnival of Cosmology: Bloggers on Dark Energy

Supernova SN1994d, the type of supernova first used to measure the acceleration of the Universe. (Credit: NASA/ESA/Hubble Key Project/High-Z Supernova Search)

Welcome to the first Carnival of Cosmology! (Well, it’s the first I know of, so we’ll say it’s true.) In the spirit of blog carnivals, several of us—cosmologists, physicists, astronomers, and writers who just love all these subjects—decided to write about one of the abiding mysteries of modern cosmology. That mystery is dark energy, the name we give to the accelerated expansion of the Universe. The submissions to the carnival cover some of the basics and some of the hard questions; I’ll list the posts in a kind of logical order, in hopes of constructing a coherent narrative. (The links to the posts themselves are in bold, while links to other materials are in normal format.)

Dark Energy is Real…

  • Ethan Siegel (of the blog Starts With a Bang) contributed two posts, though admittedly his first was an update of a old post. However, that post serves as a great introduction to the Carnival, complete with a Boromir meme: he tells the story of how he started as a dark energy skeptic, but was brought around by the overwhelming evidence. (I’m sure many of us could tell similar tales—I know I could!)
  • Kelly Oakes (of Basic Space) interviewed Nobel Laureate Brian Schmidt, one of the astronomers who discovered dark energy in 1998. His story is a fascinating one, again highlighting how the observational evidence forced him to accept cosmic acceleration. However, the interview also brings up an important point: dark energy solved some of the outstanding problems in cosmology, including the huge amount of missing energy required to make other observations consistent.
  • Astronomy writer Desiree Abbott (AKA Ms. Disarray) explains why white dwarf supernovas are an excellent way to measure the rate of cosmic expansion, including acceleration. Her post is an excellent introduction to the concept of “standard candles”, astronomical objects whose intrinsic brightness is either known or can be determined in a straightforward way.
  • Sacha Vongehr (of the blog Alpha Meme) examines some of the reasons why people might reject dark energy, including psychological factors, then argues for the reasonableness of including dark energy through analogy with a simple (and possibly familiar) physical system. (In my opinion, he understates the case for dark matter, but since that’s a kind of a brief mention in his post, I won’t pick a fight with him now!)

…But What Is it?

  • Katie Mack (the only one of this crowd to be featured in PhD Comics, as far as I know) delves into what we know about dark energy and how it constrains some of our kookier theoretical ideas. Specifically, she provides some reassurance against one of the scarier scenarios (known as the “Big Rip”) that’s been promoted around the internet recently.
  • On a similar note, Ethan Siegel’s main contribution to the carnival answers many of his readers’ questions about dark energy: what it could be, and why some of the language used to describe it sometimes works against our understanding.
  • My own contribution (’cause I’m long-winded) covers a lot of the same ground as the other writers: what we know and don’t know about dark energy, but also some ideas about how to distinguish between the various explanations.

Thanks to everyone who participated in the Carnival! I hope you all enjoyed reading the contributions as much as I did, and let’s keep this going.

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11 Responses to “The Carnival of Cosmology: Bloggers on Dark Energy”


  1. 1 D July 30, 2012 at 17:37

    The background makes this page unreadable :-(

    • 2 Matthew R. Francis July 30, 2012 at 20:25

      The background shouldn’t be behind the text, based on my design. What browser and operating are you using? We’ll get it figured out. :)

      • 3 D July 31, 2012 at 13:37

        Sorry, I posted too soon without investigating fully. It was due to a Firefox add-on blocking third party requests from galileospendulum.org to wp.com (presumably where the CSS is hosted). Entirely my fault. Sorry.

  2. 4 Torbjörn Larsson, OM August 1, 2012 at 12:18

    I have been meaning to ask, has anyone else problems with commenting on Vongehr’s site of Science 2.0? It happened at the same time I lost commenting on Discovery News, so I didn’t make much of it at the time.

    Turns out it isn’t the choice of browser or accounts. (Or at least the old accounts; since I’m commenting under my name I don’t want to fuzz much with that.) On the other hand, if they lost a lot of commenters and hence some viewers, you would think they would notice and fix anything broken.

    So I’m at a loss.

    PS Many of Vongehr’s accounts wouldn’t pass peer review, so to speak.

    • 5 Sascha Vongehr August 7, 2012 at 10:21

      Sad to hear you cannot comment. Perhaps you can tell the administrator there about the problem?
      About peer-review: Lots of my stuff is peer-reviewed, and the stuff that does not pass – so much the worse for peer-review ;-) [everybody by now agrees there is a bit of a crisis with peer-review.]

  3. 6 Sascha Vongehr August 7, 2012 at 10:26

    “he understates the case for dark matter”
    I don’t mean to kick the bullet cluster into the dirt. I just tried to ensure that the difference between dark energy (as basically true no matter what) and dark matter as a hypothesis that might be wrong is well understood. If you ask me about MOND or dark matter, I would bet on dark matter.

    • 7 Matthew R. Francis August 8, 2012 at 08:16

      The Bullet Cluster is only one example, though perhaps it’s the most clear direct evidence for the presence of dark matter. However, other galaxy clusters, the large-scale structure of the Universe, and the cosmic microwave background all require some sort of dark matter, even with MOND. Since MOND was proposed to eliminate the need for dark matter in spiral galaxies, adding dark matter back in for clusters kills any power the “theory” supposedly has.

      When I talk about “modified gravity” for dark *energy*, I’m not talking about MOND. There are a variety of theories which modify Einstein’s equations in general relativity, whereas MOND is a modification to Newton’s law of gravitation. Most of these schemes don’t have much merit, or are so complicated they run against Occam’s razor. However, some of them do have some promise.


  1. 1 Carnival of Cosmology: Dark Energy « Galileo's Pendulum Trackback on July 30, 2012 at 11:16
  2. 2 White Dwarf Supernovae: Standard Lamposts on Dark Energy Road « Ms. Disarray Trackback on July 30, 2012 at 19:18
  3. 3 Calling for Cosmology Posts! « Galileo's Pendulum Trackback on August 20, 2012 at 15:27
  4. 4 Carnival of Cosmology 2: Observational Challenges « Galileo's Pendulum Trackback on August 31, 2012 at 15:49
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