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Naked speed
The article “Running barefoot cushions impact of forces on foot” (SN: 02/27/10, p. 14) says a lot about whether running barefoot is or isn’t healthier than running shod. Has anyone looked into which is faster?
Henry Jones, Baton Rouge, La.

“No,” responds Daniel Lieberman, a professor of evolutionary biology at Harvard University. But he does note that Abebe Bikila set a world record for the marathon at the 1960 Rome Olympics running barefoot. And Zola Budd set quite a few records running middle distances barefoot. “There is no theoretical reason why barefoot runners are necessarily slower,” he says. “Further, slight differences in speed are probably irrelevant from an evolutionary perspective. Humans evolved to make animals gallop in the heat, not to win races.” — Laura Sanders

Cosmic question
Reading the article “Relic radiation refines age of cosmos” (SN: 02/27/10, p. 7), I was struck by a question: How could any of the radiation from the Big Bang be reaching our planet just now? How are physicists able to analyze “snapshots of the earliest light in the universe”?
Christopher Kendall, via e-mail

The ultrahot radiation produced in the Big Bang was emitted throughout the entire visible universe. So everything in the universe, including Earth, is bathed in the remnants of that radiation. Astronomers observing that radiation today see it after it has been stretched out by the expansion of the universe and cooled (putting it in the microwave range of the electromagnetic spectrum). Slight temperature differences from point to point on the sky in this cosmic microwave background radiation reflect its last interactions with matter. Most of the microwave background photons last interacted strongly with matter 13.7 billion years ago, roughly 380,000 years after the Big Bang, says cosmologist David Spergel of Princeton University, a member of the WMAP team analyzing the microwave data. So when we observe these photons today, we see the effects of interactions that occurred 13.7 billion years ago. Be­cause of the travel time of light, we are in effect viewing the surface of a sphere 13.7 billion light-years in radius, Spergel notes. On this sphere we see conditions that are similar, but not identical, to conditions of the early universe in the location now occupied by Earth. “While we like to claim that our CMB observations are taking ‘our baby picture,’ we are actually taking the ‘baby pictures’ of stars that will form in a galaxy far, far away from us!” Spergel comments. — Ron Cowen

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