What does it really mean when we say last week's meteor delivered a force 30 times the size of the Hiroshima bomb?
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Perhaps you saw the reports last week, as the world tried to wrap its collective mind around the piece of outer space that had arrived at our small piece of inner space, that the Russian meteor exploded "with the force of 30 Hiroshima bombs."
And, wow, that sure seems big. And it's true: The Russian meteor was a monster -- the biggest in a century, rocking the city of Chelyabinsk and injuring more than a thousand of its residents.
But even so, even considering the destructive potential of meteors and the punch they can deliver, comparing a meteor's force to a nuclear bomb is a pretty sloppy equation, argues atomic historian Alex Wellerstein, and in its sloppiness, the comparison runs into all sorts of troubles.
"Every time we have a natural disaster, somebody translates the energy output into kilotons and then tells you, using a simple division equation, how many times more that is than Hiroshima," Wellerstein told me. "This is something I find really problematic."
"In general," he added, "What I don't like is ... the idea that kiloton or a megaton is just an energy unit, that it's equivalent to so many joules or something. Because you could do that. You could claim that your house runs so many tons of TNT worth of electricity per year, but it sort of trivializes the notion."