Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

Big crater

World annihilation

Everyone is dead

[Lord Shonus]

According to a calculator used by a physicist I know, 250 pounds of antimatter is equal to a 4.88 gigaton. The total yield of all known atomic weapons is roughly 10.0 gigatons. The K-T asteriod was roughly 10 teratons. The described bomb would be massively powerful, but hardly on the scale that is implied.

[Criptfeind]

But there's my point. You have to remember that air is going to be considerably less dense than uranium and therefore have less atoms.

It is less dense, but it will have wayyyy more atoms. I would expect most of it would go fairly quickly, and anything that did not would be pushed out in a expanding wall of explosions.

[RedWarrior0]

See, as someone else pointed out earlier, none of the energy is wasted on that useless little "kinetic energy" stuff. You'd get a shitload of light, a shitload of heat, and a shitload of gamma rays. Several shitloads, probably. Unless you're using metric.

Depending on the proportions, we could have a molten crust or just a new volcano.

[Bauglir]

To be fair, I suspect that a lot of that is going to get translated into kinetic energy in the immediate aftermath. Hot things have a tendency to expand, and then you'll have a big low-pressure area where there use to be a landmass (if a smallish one, if Shonus is correct about the size).

[RedWarrior0]

Ah, true, I forgot about Hot Shit Expands. Again, if I had a solid number on what portion of antimatter becomes heat, it would be easier to tell.

Also, use anti-iridium instead of anti-uranium. It's one of the densest (competing with osmium) macroscopic materials on earth. Antineutronium would be even more efficient.

[ChairmanPoo]

But there's my point. You have to remember that air is going to be considerably less dense than uranium and therefore have less atoms.

Fail
Actually, nevermind. MSH has the right of it, I think.

[Bouchart]

Go with crater.  For bonus points tie it in with the Tunguska incident.

[Glowcat]

As long as we're voting on the physical laws of your universe, I vote for antimatter bombs that cause puppies to rain from the sky.

Reality shall bow to democracy!

[ChairmanPoo]

http://www.youtube.com/watch?v=zn7-fVtT16k

[Ultimuh]

Reality shall bow to democracy rule of awesome/funny!

Much better.

[Darvi]

Depending on the proportions, we could have a molten crust or just a new volcano.

Drop it on Yellowstone.

[Firnagzen]

I would personally go with antihydrogen, compressed to a metallic state. (Hey, if you have the ability to come up with that much antihydrogen, I would expect that compressing and containing it wouldn't be very much of a problem.)

Here's my projections.
1. Release
2. Annihilation begins, producing 2 gamma rays and 2 high energy pions, remaining heat energy per atom annihilated. (Another reason I'm going with antihydrogen. Known annihilation products.)
3. Now, initially, only the surface layers annihilate, but that's the good part of using antihydrogen; it will expand into a gas with much enthusiasm, thus mixing better.
4. A gamma ray pulse is released, flashing the atmosphere surrounding the initiation* into plasma. It also flash-heats the now-plasma and all other gamma ray absorbtive objects nearby. (basically, everything conductive.) It's true that this energy transfer is not very efficient, but keep in mind, we are dealing with a LOT of energy (2x10^16J) in total here...
5. Now, pions don't really interact with macroscale matter very much (their interactions are of the strong nuclear force, so they have to pass within femtometers of an atomic nucleus to have any effect), but there'll be so damn many of them (13.6x10^28 of them), that they'll inevitably leave a good chunk of energy in the plasma, heating it further and giving it that all-important shockwave. The shockwave travels out at hypersonic speeds.

So, end effects:
-Gamma ray pulse. Will probably roast everything within a couple hundred kilometers, fatal irradiation in line of sight and probably a few degrees past the horizon. Damage radius: Approximately 7km at ground level, radiating out into space. Will likely damage satellites.
-Plasma cloud, largely incidental, but will consume anything left by the gamma ray pulse, partically organic items (if there's anything left by the gamma rays, anyway.) Damage Radius: Approximately 5km. Contributes directly to shockwave.
-Shockwave at probable speeds of several of hundreds of kilometers per second, if not low thousands. Will flatten buildings, trees etc. Damage radius: Worldwide. May** deform atmosphere sufficiently to deorbit low earth orbit satellites and debris directly above initiation.


*Not an explosion, strictly speaking. An explosion can be summed up as 'combustion, confinement, explosion'. No combustion involved, no explosion. Same is true of nuclear 'bombs' (devices), they don't explode, and they're not bombs in the standard definition. But eh.
**Guess. A shockwave does not move the medium it is travelling through in any significant manner, but the heating and production of plasma in the immediate area may cause sufficient displacement of air to result in that.

Disclaimer: I'm sure of the interactions, (as in, mechanism of gamma rays producing a plasma cloud and how a shockwave would result) however, the energy transfer issues are rather iffy. I'm using a rough guide of 1% energy transfer for the rest of the calculations.

[RF]

But there's my point. You have to remember that air is going to be considerably less dense than uranium and therefore have less atoms.

It is less dense, but it will have wayyyy more atoms. I would expect most of it would go fairly quickly, and anything that did not would be pushed out in a expanding wall of explosions.

Derp, you're right.

I should've said quark density. :p How does annihiliation work between two non-equal materials, anyway?

[Another]

It will just be a nuclear explosion. You have the numbers about energy released and that energy determines most of the features of the explosion. There is no magic in antimatter and burns from being directly exposed to a nuclear blast are mostly from normal visible spectrum (+near ultraviolet and infrared) light emitted by a giant hot fireball relatively [as opposed to the Sun] close.

1) One point of reference is about 200x Tunguska event. 2000 sq km of forest fallen, atmospheric shock wave vaguely heard in England.

2) About 50x Tsar Bomba (detonaded in the atmosphere above an arctic island, some windows broken a few hundred kilometers away, Earth ionosphere disturbed for some time preventing some global radio communications).

3) About 10x Krakotoa volcano explosive eruption of 1883 AD. Suffice to say that we are alive and not many people remember it.

4) About 3x Tambora volcano 1815 AD. One year of "volcanic winter" the following summer.

It is also worth noting that the power of a thermonuclear bomb is not much theoretically or technically bound and any country that possess technologies to produce any kind of a thermonuclear bomb may relatively cheap scale it up by adding more D+T to the core and making the bomb slightly bigger. Only 2 countries have tested their thermonuclear capabilities so far but it could not be prohibitively difficult for e.g. Pakistan to semi-secretly assemble an underground installation with a 10-20 gigaton "screw everyone" thing.

P.S. Gamma rays and fast neutrons don't have much chance to travel even a km in low altitude Earth atmosphere. Not much to speak about would be left after 5 km of atmosphere. Incidentally expected hot plasma fireball radius will be a few km. Secondary ultraviolet radiation however may result in some damage. Satellites are already built with rather high background of cosmic gamma rays in mind. And pions interact with normal matter quite fine - "strong" force here is of the same order of magnitude as what determines interaction of neutrons with matter and they are reflected/slowed/absorbed by a few cm of water in reactors, it's the muons that will likely escape farthest not counting neutrinos.

P.P.S.,Fake Edit: Precise description of everything involved in non-trivial annihilation is long and hard but one can be sure that eventually total energy released will be 2mc^2.

[Rysith]

Although it's intended for calculating the yields from antimatter space weaponry, I suspect that this site would be useful in terms of calculating what kind of effect you'd have, and why. Given the weight of antimatter that you're looking at, it looks like it's going to fall into the 'big crater' category.