Tuesday, October 10, 2006

Eggcentric Universe

The universe might be egg-shaped, according to stories in USA Today, the LA Times, and the People's Daily in China, among other publications.

It's a cute story, though a tad overblown in a couple of ways.

First of all, although it's based on research published in Physical Review Letters, the authors themselves are more cautious about their conclusions than you might guess from the coverage.

It's true that if they are right it will be the simplest way to explain one mysterious feature in the measurement of the cosmic microwave background. On the other hand -- interpreting the data with the simple explanation that the universe is not perfectly spherical will lead to a question that might be much harder to answer - specifically "Why the heck would it be anything other than spherical?" I'm guessing that most cosmologists are going to look into the other alternatives before they turn to the egg-shaped universe possibility.

The news stories are also eggzagerating the egg-shape, or eccentricity, a little bit. One percent eccentricity is hardly egg-shaped. I doubt you could tell if your bowling ball were out of round if it was only 1% eccentric.

Here's an applet that lets you fiddle with the eccentricity of an ellipse to help you get a feel for the affect on shape - the more eccentric it is the more egg shaped it is. It doesn't look very egg-like to me until the eccentricity reaches about 60% (0.60) at least. At 1% (0.01), which is the eccentricity that the researchers proposed for the universe, it looks essentially round.


  1. makes me hungry for a chocolate bunny...

  2. Even at higher eccentricity the shape looks oval to me and not egg shaped. To me egg-shaped is a oval with one end having a smaller radius. Am I wrong?

  3. There are many shaped eggs, including some that are completely spherical. So this author should do his biology homework before concluding that 1% eccentricity is not consistent with the egg theory. He is obviously thinking about a CHICKEN egg.

  4. Scott, you are correct, I am thinking of chicken eggs. The same is true of the authors of all the egg-shaped universe articles I was writing about. Other than on TV, I can't recall ever seeing an egg from an animal other than a chicken or duck. I assume the same is true of most people. Try typing "egg" into a Google image search and tell me how far down you have to go before you find a spherical egg.

    Egg-shaped in common parlance means chicken egg-shaped.

  5. Before concluding that the Universe is egg-shaped, we should first consider whether it is an Ellipsoid which is the shape of practically everything else in the Universe.