Detonating an antimatter bomb high above a city?

[Fanghur]

Can anyone who has seen/read "Angels and Demons" tell me whether flying the antimatter high above Vatican City in a helicopter should have made any difference whatsoever, assuming the helicopter could even get that high that fast? I mean, wouldn't the shock wave from an antimatter explosion shatter everything for miles around, including buildings? Not to mention the fact that anyone anywhere near the 'blast' would most likely get fried by a massive flux of high-energy gamma rays rivaling a solar flare in intensity.

 

Did Dan Brown just hugely drop the ball on this one? Or am I missing something?

[Janus]

The size/destructive ability of the explosion would depend on how much antimatter there was. (one of the inaccuracies of the story is the fact that there isn't enough antimatter on Earth to produce more than a modest bang.)

[insane_alien]

well, the point of aerial explosions (which are extensively used to maximise the blast of nuclear bombs) is that the shockwave refelects off the ground, so where the shock front meets the ground you get a double shock (one direct from the bomb and the other reflected off the ground a few milliseconds later)

 

but really, the radiation would already be enough to permanently disable everyone in the city.

[csmyth3025]

well, the point of aerial explosions (which are extensively used to maximise the blast of nuclear bombs) is that the shockwave refelects off the ground, so where the shock front meets the ground you get a double shock (one direct from the bomb and the other reflected off the ground a few milliseconds later)

 

but really, the radiation would already be enough to permanently disable everyone in the city.

The Little Boy bomb was detonated about 1900 ft above Hiroshima with a yield af about 13 kilotons of TNT.

(ref. http://en.wikipedia....aki#The_bombing )

 

In that explosion

 

...Approximately 600 to 860 milligrams of matter in the bomb was converted into the active energy of heat and radiation (see mass-energy equivalence for detail). It exploded with an energy between 13 and 18 kilotons of TNT (54 and 75 TJ) (estimates vary)...

(ref. http://en.wikipedia....wiki/Little_Boy )

 

It's important to note that the above quote refers to "...heat and radiation..."

 

An explanation of how this might relate to an anti-matter bomb (producing a burst of pure gamma radiation) is also found in another Wikipedia article:

 

...When a uranium nucleus fissions into two daughter nuclei fragments, about one-tenth of 1 percent of the mass of the uranium nucleus^[4] is converted to energy of ~200 MeV. For uranium-235 (total mean fission energy 202.5 MeV), typically ~169 MeV appears as the kinetic energy of the daughter nuclei, which fly apart at about 3% of the speed of light, due to Coulomb repulsion. Also, an average of 2.5 neutrons are emitted with a kinetic energy of ~2 MeV each (total of 4.8 MeV). The fission reaction also releases ~7 MeV in prompt gamma ray photons. The latter figure means that a nuclear fission explosion or criticality accident emits about 3.5% of its energy as gamma rays, less than 2.5% of its energy as fast neutrons (total ~ 6%), and the rest as kinetic energy of fission fragments ("heat")...

(ref. http://en.wikipedia...._fission#Output ) (Bold added by me)

 

Suppose you had a mass equivalent of one half of a paper clip piece of antimatter in the container shown in the movie (about 0.5 gram). This is a quantity that we have so far not been able to even come close to isolating - a point that Janus makes. This would react with 1/2 gram of matter (1 gram total) to produce a Hiroshima size bomb. If it was detonated 1900 ft above Vatican City I believe everyone outside in the coutyard would definitely be fried unless they were standing under a stone arch or some other substantial covering.

 

I don't know what the blast effects would be of the sudden heating of the air by this intense burst of gamma rays, but I'm thinking that it would be considerable.

 

Chris

 

Edited to change reactants from 1 gram to 1/2 gram.

Edited June 7, 2011 by csmyth3025

[John Cuthber]

The yield you quote is from uranium fission. Antimatter annihilation will probably be different. In principle I think all the energy is initially released as high energy photons. Those will hit the air and heat it providing some sort of shock wave and EMP.

 

In any event, a bomb that you just have to get a few hundred feet away from would be pretty trivial by the standards of WWI never mind some sort of sci-fi super-weapon.

[csmyth3025]

The yield you quote is from uranium fission. Antimatter annihilation will probably be different. In principle I think all the energy is initially released as high energy photons. Those will hit the air and heat it providing some sort of shock wave and EMP.

 

In any event, a bomb that you just have to get a few hundred feet away from would be pretty trivial by the standards of WWI never mind some sort of sci-fi super-weapon.

I think you would have to get a bit more than "...a few hundred feet away from..." 1 gram of matter/antimatter annihilating if you expect to survive.

 

Chris

[John Cuthber]

I think you would have to get a bit more than "...a few hundred feet away from..." 1 gram of matter/antimatter annihilating if you expect to survive.

 

Chris

So would I which implies that Dan Brown did indeed screw up on this (at least in the film; I don't remember the book doing that, but it's a while since I read it.)