Reports of the Russian meteor event (2013) say that it released more energy than 20 atomic bombs of the size dropped on Hiroshima, Japan:

Scientists estimated the meteor unleashed a force 20 times more powerful than the Hiroshima bomb, although the space rock exploded at a much higher altitude. Amy Mainzer, a scientist at NASA's Jet Propulsion Laboratory, said the atmosphere acted as a shield.
The shock wave may have shattered windows, but "the atmosphere absorbed the vast majority of that energy," she said.


Really? Wouldn't that have done more damage than was seen? How does the damage depend on how quickly the energy is released?

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    $\begingroup$ Can you add some links to the reports you mention? $\endgroup$ – Bernhard Feb 16 '13 at 13:16
  • $\begingroup$ Just a thought, but aren't atomic weapons detonated above the ground to maximise the effects of the explosive yield? When set off at ground level, a lot of the energy from a bomb goes into excavating the area underneath the device, rather than out to the sides, where it would cause more damage. $\endgroup$ – Peter J Morgan Feb 16 '13 at 20:06
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    $\begingroup$ Above ground, yes, but not nearly so far above the ground as the meteorite exploded, which was 12-15 miles. $\endgroup$ – LarsH Feb 16 '13 at 21:56
  • $\begingroup$ What really matters is $\text{Intensity}=I=\frac{P}{A}=\frac{\text{Energy}}{4\pi r^{2}t}$ $\endgroup$ – raindrop Feb 17 '13 at 3:58
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    $\begingroup$ Meteor did not hit Russia, Russia hit meteor. $\endgroup$ – TROLLHUNTER Apr 10 '13 at 23:42

Hiroshima exploded 67 terajoules of energy i.e. $6.7\times 10^{13}$ joules. We may calculate the mass of the Russian meteor assuming that the speed is $v=20,000$ m/s: $$ \frac{1}{2} mv^2 = 6.7 \times 10^{13} $$ We obtain 335 tons. The numbers aren't precise but they're in the ballpark and reasonable. The Russian academy of sciences actually estimates 10,000 tons which would be something like 700 Hiroshimas.

The Hiroshima bomb was harmful because its energy was focused on a small place, several kilometers around the explosion were destroyed. The energy of the Russian meteor was distributed to a much larger area of radius closer to dozens if not 100 km and much of the energy was deposited to the atmosphere, so the local impact was significantly smaller than it was in Hiroshima. If we exaggerate a bit, the energy was spread to 20 times longer distances than in Hiroshima and the dilution scales as something in between the second and third power, so one gets about 500 times smaller "local impact" at the relevant places than in Hiroshima even if we add the factor of 30 (30 Hiroshimas).

Some individual collisions detected on the ground were estimated to have just 1 TJ or so, 67 times weaker than the Hiroshima. The bulk of the energy was deposited to the atmosphere.

But I guess that the main reason why you find the numbers counterintuitive is the widespread antiwar propaganda that prefers to present a nuclear blast as a nearly supernatural event of nearly infinite proportions. This ain't the case. The bomb in Hiroshima was just another bomb, a bit stronger one (plus some annoying radioactive stuff that had other consequences, something that wasn't caused by the meteorite). Five kilometers from the ground zero, they experienced similar symptoms as they did in Chelyabinsk – broken windows and a reasonable but not infinite sound of the explosion. Hundreds of meters from the explosion, things vaporized and the Russian meteor had no place with this much concentrated energy.

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    $\begingroup$ Similarly a tropical storm/hurricane release about 10^18 Joules/day. Roughly = a Hydrogen bomb/minute! $\endgroup$ – Martin Beckett Feb 16 '13 at 15:02
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    $\begingroup$ + I'm not sure you made it clear that, neglecting radioactive fallout, the initial damage is caused by 1) radiative heat and 2) acoustic blast wave/sonic boom. In this case, since the event was about 19km above the ground, the heat was not too bad at the surface, especially considering slant range. The acoustic wave was also at a distance, but it still pulverized a lot of windows (2 minutes later), which injured a lot of people who were looking out those windows. Many people injured in Hiroshima/Nagasaki were hurt the same way. $\endgroup$ – Mike Dunlavey Feb 16 '13 at 15:06
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    $\begingroup$ It seems to me that using the Hiroshima bomb as a scale to measure the energy output of things that aren't bombs is potentially misleading and politically-charged. $\endgroup$ – Garrett Albright Feb 17 '13 at 2:23
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    $\begingroup$ Dear Mike, right, 80% of the energy from a nuclear blast is emitted in the form of photons. The fuel just gets heat up to 60-100 million Celsius degrees which means that the typically emitted thermal photons - it's glowing like crazy - are X-rays with energy 10-200 keV. It's sort of important to emphasize that they're X-rays because when we say "thermal", we tend to think about infrared (thermal for room temperatures or close ones). But at those high temperatures of the fuel, thermal means X-ray. $\endgroup$ – Luboš Motl Feb 17 '13 at 6:04
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    $\begingroup$ @GarrettAlbright Disagree for practical reasons. An explosion of that size is outside the span of normal human experience; and there's a lack of well known natural events that created explosions in the 10-100kt range that could be used instead. $\endgroup$ – Dan Neely Feb 17 '13 at 18:05

The duration of the energy release has a huge effect on the destructive potential. A single stick of TNT has roughly 1 MJoule of energy which is released in a fraction of a second. [1] Spread the same 1 MJ over an hour and you get 277 W or roughly the same power consumption as an ATI Radeon HD 7970. [2]


[1] http://en.wikipedia.org/wiki/Dynamite

[2] http://forums.atomicmpc.com.au/index.php?showtopic=264

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    $\begingroup$ This begs an important question that belongs tacked onto any energy estimate: do you mean for the one biggest explosion, or for the entire dissipation of kinetic energy of the meteor? The latter "release" of energy was neither instant nor continuous, not like either a stick of TNT nor a smoking game card. I recall a news report of 5 or 6 explosions, and of course there was the impact. Each were relatively instantaneous. Then there was a buildup of heat as the meteor slowed, that energy heated air and debris. Comparisons to a bomb should be made about the explosions only. $\endgroup$ – Bob Stein Feb 16 '13 at 21:26
  • $\begingroup$ @BobStein: The impact? I thought the rock shattered in mid-air, so there would have been several impacts. "Some meteorite fragments fell in a reservoir outside the town of Chebarkul, the regional Interior Ministry office said. The crash left an eight-meter (26-foot) crater in the ice." ... $\endgroup$ – LarsH Feb 16 '13 at 21:56
  • $\begingroup$ @LarsH you're right there must have been several. I only saw the one picture of the hole in the lake ice. Multiple impacts further complicates comparing the energy to a bomb. $\endgroup$ – Bob Stein Feb 17 '13 at 0:11
  • $\begingroup$ @BobStein It is a fairly complex problem and depends a lot on how you choose to measure the energy release. It is much easier to use the total dissipation, all you need then is the mass and the velocity. I assumed that the energy estimate was using this measure so the period would be very long. $\endgroup$ – Tyler Waugh Feb 17 '13 at 3:17
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    $\begingroup$ That same MJ of energy is also less than the energy you extract from a single slice of cake, or a decently sized salad. $\endgroup$ – user10851 Feb 17 '13 at 3:48

protected by Qmechanic Feb 17 '13 at 18:46

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