Preposterous Universe

Thursday, May 13, 2004

Some reactions to my list of misconceptions about cosmology. Chad Orzel at Uncertain Principles has misconceptions about quantum mechanics and thermodynamics. It's a very good list, even if he does say that vacuum energy is useless. It's useless in the sense that it cannot be made to do thermodynamic work (because the vacuum energy is spread absolutely uniformly), but in another sense it's quite useful: it makes the universe accelerate, thereby giving cosmologists something deep to think about. (And occasionally get them a job.)

Chris C Mooney notes that a planetarium show at the Smithsonian doesn't even mention the Big Bang, although it's supposed to be a tour of the universe. So perhaps one of the sources of misconceptions is that we aren't clear enough about what we actually do think people need to know? Right off the top of my head, here are some facts about cosmology I think every educated person should know:
  • The universe is big. The Sun is a star, located in a galaxy with about a trillion other stars. There are a lot of other galaxies in the observable universe (about 100 billion), distributed evenly on large scales.
  • It's getting bigger. Very distant galaxies are moving away from each other.
  • It's old. If we trace the expansion backwards in time, everything crunches together about 14 billion years ago, at what we call the "Big Bang."
  • We don't know how it started. The Big Bang itself lies outside our current understanding, although we do understand things very well at a time only about 1 second after the Bang. During or before that first second, we have good ideas but no direct empirical constraints.
  • It's dark and mysterious. Only five percent of our universe is "ordinary" matter; about 25% is some dark matter particle we haven't yet discovered in the lab, and about 70% is a smoothly-distributed and nearly-unchanging dark energy.
  • We don't know how it will end. To predict the future would require a better understanding of what the dark energy is and how it will behave in the future. This is one of the things we're trying to understand.
That's not so many, for such a big universe. How do we get these into high school curricula?

Ideas on culture, science, politics.
Sean Carroll

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