Sunday, March 15, 2009

What’s Wrong with "Parallel Universes" on the History Channel

While the TV series The Universe has much valuable content and I applaud every effort to make science more accessible, occasionally this program is incomprehensibly wrong. The episode Parallel Universes is heavy with hyperbole, and a grossly incorrect claim. It states as a matter of fact that scientists have shot lasers beams across the universe to measure its global flatness. That is total nonsense.

Reflecting laser beams off the other end of the universe and back to Earth is ridiculous in itself – we can’t even do that to all the planets within our own solar system. And even if that were possible, it would take at least 27 billion years for the laser beam to return at the speed of light. While that would allow plenty of time for commercials, we would all have turned off the show long before.

This completely erroneous statement was part of a description of the measurement of the curvature of the universe by NASA’s WMAP satellite that is a spectacular scientific achievement deserving better reporting. Max Tegmark of MIT explained that the curvature of the universe can be measured by measuring the angles of a triangle that has a vertex at the Earth and the other two vertices at a very great distance. He said if the sum of the triangle’s angles were 180 degrees then the universe’s curvature would be zero and its geometry would be called “flat.” If the universe were curved (in a fourth spatial dimension) like a balloon, then the sum of the angles would be more than 180 degrees. This episode didn’t mention this but the sum of the angles could also be less than 180 degrees, in which case the geometry of the universe would be hyperbolic, like a four-dimensional potato chip. All that is fine. Where they went wrong was when the narrator said “to find out, they shot laser beams into space and made a giant light triangle.” They then cut back to Tegmark who said “Now we can tell and the measurement is in and it works beautifully. The angles add up to exactly 180 degrees.” Let me emphasize that Professor Tegmark was not the one who said lasers were shot into space to make a giant triangle.

The Universe claims to have a scientific adviser for each episode. I find it hard to believe that any such advisor reviewed the final cut of this and numerous other episodes.

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