Daily Archives: June 16, 2010
Leon's Getting Larger
Fact or Fiction: The Days (and Nights) Are Getting Longer
Forces from afar conspire to put the brakes on our spinning world—ocean tides generated by both the moon and sun’s gravity add 1.7 milliseconds to the length of a day each century, although that figure changes on geologic timescales. The moon is slowly spiraling away from Earth as it drives day-stretching tides, a phenomenon recorded in rocks and fossils that provides clues to the satellite’s origin and ultimate fate. “You’re putting energy into the moon’s orbit and taking it out of the Earth’s spin,” says James Williams, a senior research scientist at NASA’s Jet Propulsion Laboratory in Pasadena, Calif.
The Banana Equivalent Dose
I’ve used bananas as examples of radiation sources before, in terms of equivalent dose and the knee-jerk reaction to the mention of “radiation” in news stories.
Well, it turns out that the banana equivalent dose is a more common unit for dose comparisons than I had suspected — it even has its own wikipedia page
The average radiologic profile of bananas is 3520 picocuries per kg, or roughly 520 picocuries per 150g banana.[3] The equivalent dose for 365 bananas (one per day for a year) is 3.6 millirems.
I had given the radiation level for a banana as about 300 picocuries, so obviously I was estimating the banana as being 80 – 100 g, rather than the 150 g used here.