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Sat Feb 23, 2013, 12:06 PM

On Nuclear Weapons as Units of Measurement


On Nuclear Weapons as Units of Measurement

By Rebecca J. Rosen
Feb 22 2013, 4:14 PM ET

What does it really mean when we say last week's meteor delivered a force 30 times the size of the Hiroshima bomb?

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.


He breaks his concern down into two separate but related points: First off, he writes on his blog, the character of a nuclear blast is not really comparable to a non-nuclear explosion, even when the amounts of force delivered are similar. "It's just sort of a raw energy output with no attention to exactly how that energy is being delivered. And without attention to that, it doesn't really tell you what would happen other than that, yes, if a meteor hit your town directly it would flatten most of your town, and, yes, a nuclear weapon would also flatten most of your town."

But nuclear weapons deliver more than just sheer force; there's also incredible heat, orders of magnitude hotter than a meteor's explosion, (most of the people who died at Hiroshima and Nagasaki, Wellerstein says, died of fire), and, of course, the radiation. The radiation brings sickness, makes land uninhabitable in the long term, and can have residual genetic effects that long outlast the bomb's immediate destruction. "It's sort of the sum of these effects that we think of when we think of what's the problem with nuclear weapons," he says. To only think of an atomic weapon in terms of the kilotons of energy released glosses over the totality of the terror these bombs bring.


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Reply On Nuclear Weapons as Units of Measurement (Original post)
bananas Feb 2013 OP
DreamGypsy Feb 2013 #1

Response to bananas (Original post)

Sat Feb 23, 2013, 01:04 PM

1. A very good reminder. If 16,000 tons of TNT had been dropped on Hiroshima...

...instead of a nuclear weopon, the deaths and long term effects would have been much less than those caused by Little Boy.

From Wikipedia:
Approximately 600 to 860 milligrams of matter in the bomb was converted into the active energy of heat and radiation.

Less than a gram. Makes one think.

Here's Wikipedia on TNT Equivalent:

TNT equivalent is a method of quantifying the energy released in explosions. The ton (or tonne, i.e. metric ton) of TNT is a unit of energy equal to 4.184 gigajoules, which is approximately the amount of energy released in the detonation of one ton of TNT. The megaton of TNT is a unit of energy equal to 4.184 petajoules.

The kiloton and megaton of TNT have traditionally been used to rate the energy output, and hence destructive power, of nuclear weapons (see nuclear weapon yield). This unit is written into various nuclear weapon control treaties, and gives a sense of destructiveness as compared with ordinary explosives, like TNT. More recently, it has been used to describe the energy released in other highly destructive events, such as asteroid impacts. However, TNT is not the most energetic of conventional explosives. Dynamite, for example, has about 60% more energy density (approximately 7.5 MJ/kg, compared to about 4.7 MJ/kg for TNT).

The same wikipedia page has an interesting diagram illustrating "the explosive yield vs mushroom cloud height, illustrating the difference between 22 kiloton Fat Man and 15 megaton Castle Bravo explosions

Thanks for the post, bananas.

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