I just asked Donald Yeomans of JPL about the, um, “U.S. Government sensors” that, for a while, released occasional information about meteoric fireballs that were picked up from time to time.

As I understand it, there are satellites staring at the Earth, looking for a sudden flare of light with the characteristics of a large rocket launch. Naturally, the details of their operation, and the data they gather, are sensitive defense information. However, they are good at picking up meteoric impacts, and in the 1990s persuasive DoD insiders succeeded in arranging the release of fireball reports, recognizing that they would be very useful in characterizing the number, spatial distribution, and energy release of incoming near-Earth objects.

It’s classic example of data gathered for military purposes that, when declassified, can be useful to scientists in the wider world.

The program of releasing declassified reports seems to have stopped after 2008. Scientists were not happy.

Imagine my surprise when Dr. Yeomans told me that releases of fireball data have begun again. Today. On his Web site.

The only item on the list is the Chelyabinsk event, at the moment. Nevertheless it is good to see data flowing again.

Yes, you are right of course — but that is the point: the only reason the blast effects were less from the meteor is that it was higher up. I have no disagreement with that view — obviously.

I made this point above:
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K. Yes, I agree w/ you there — it is not exactly like X times Hiroshima mainly because of the different altitude.

If it was the same altitude as Hiroshima it would be X times Hiroshima. (minus fallout, radioactivity)

We got lucky with the altitude. That’s all.

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Also see the post from JB below.

It beggars logic to say that it is OK to express nuclear weapons yield in terms of chemical TNT, but not meteors for some reason. I made this point above several days ago:

“TNT is a chemical explosion. Similarly kt and Mt are also.”

If two explosions are of equivalent chemical TNT yield (at the SAME altitude, of course) their blast effects will be very similar: similar enough so as to make no difference to people dying on the ground.

Yes with a pressure transducer very close to the center of the explosion and an oscilloscope you could maybe tell one apart from the other (before you die) — but then with a pressure transducer and an oscilloscope very close to the center of nuclear blast vs. an equivalent TNT blast you could also perhaps tell the difference.

The fact that people routinely use chemical TNT to explain nuclear blast effects is in itself an obvious reason this blog post is internally inconsistent.

It beggars logic to say that it is OK to express nuclear weapons yield in terms of chemical TNT, but not meteors for some reason. I made this point above several days ago:

“TNT is a chemical explosion. Similarly kt and Mt are also.”

The Cubed root law is your friend.

Perhaps if we compare it to the non-radiation portion of the atomic bombs.

It was due to the extreme altitude that mitigated the damage on the ground due to the blast effect.

People understand the damage that a Hiroshima type device can do, and an equivalent kilton of TNT rapid released as the aerodynamic pressure retards a meteor, will have extremely similar effects and Hiroshima is a *excellent* way to describe what would happen to a city below a meteor explosion if the nuke blast and the meteor blast occur at the same altitude.

People saw what Hiroshima looked like — this is a good way to explain what the effects of an equiv. kt in meteor would do.

You say: “reasonable people can disagree whether the differences in the nuclear release of energy or the meteor release of energy are similar enough to be more or less equatable or whether different blast radii, different heat properties, different mechanisms of energy release, or the fact that meteors lack a whole host of effects characteristics of nuclear explosions, and so on. Any analogy requires throwing out some dissimilarities, I’m happy to concede that.”

Maybe reasonable people but not any scientists. If they both have the same kt of TNT exploded, the bulk effects are the same — aside from radiation and fallout, the blast effects are v. similar.

cf. Tunguska

If you want to learn more about the subject read eg.:

http://www.nature.com/nature/journal/v361/n6407/abs/361040a0.html

Or ReVelle, D. O. J. geophys. Res. 81, 1217−1230 (1976).

It is not wise to start pontificating on this, thinking you know what is best for the common people without getting things straight yourself first.

After you’ve read the ref’s we can talk further.

Let me know if you have reason to believe that there is a difference in the blast from a 470kt nuclear weapon vs. a 10,000 T rock moving at 18,000 m/sec rapidly retarded, if they explode at the same altitude?

Again, read the post more carefully if you think I’m saying that meteors should be pooh-poohed. I’m not. I’m saying that explaining their effects in terms of nuclear weapons 1. misrepresents a lot of the differences in how that energy is deposited, 2. doesn’t really mean a lot to most people anyway since they don’t know the difference between 10 kilotons or 100 kilotons 1000 kilotons.

On point #1, reasonable people can disagree whether the differences in the nuclear release of energy or the meteor release of energy are similar enough to be more or less equatable or whether different blast radii, different heat properties, different mechanisms of energy release, or the fact that meteors lack a whole host of effects characteristics of nuclear explosions, and so on. Any analogy requires throwing out some dissimilarities, I’m happy to concede that.

On #2, though, I think there can be no real disagreement. Even trying to explain what a 10 kiloton blast means in human terms is hard and requires appeals to things other than the kilotonnage — it requires appeals to effects. My entire point, if you wanted to boil it down, is rather than assume nukes can be understood by the general public as a proxy way of explaining effects, just explain the effects.