Letters from the May 20, 2006, issue of Science News

Forget dessert

In “Got Data? Consuming calcium, dairy doesn’t keep off weight” (SN: 3/11/06, p. 147), you report, “Every 4 years, each volunteer completed a questionnaire about his body weight and dietary habits.” Any dieter knows that it is next to impossible to remember what one has eaten 4 days ago. Any more details on how the data was acquired and validated?

Ivan Mann
Hoover, Ala.

Volunteers were asked to state the frequency of their consumption of various foods over the past year. They had nine choices for each answer, from “never” to “at least 6 times per day.”—B. Harder

Speed trap

“Cosmic Triumph: Satellite confirms birth theory of universe” (SN: 3/18/06, p. 163) states that the early universe expanded “from subatomic scales to the size of a grapefruit in less than a trillionth of a second” or one picosecond. This would correspond to a velocity many times the speed of light (light only travels about 0.012 inch in a picosecond). How can this statement be reconciled with Einstein’s general theory of relativity that limits matter to a speed less than the speed of light?

Eric Rosenfeld
Gloucester Point, Va.

Researcher David N. Spergel agrees that general relativity requires that no object move through space faster than light. He adds, however, “General relativity also predicts that space itself can expand. . . . We can actually point to distant galaxies, on opposite sides of the sky, that are moving apart from each other at faster than the speed of light.”—R. Cowen

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