1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Angels & Demons - The anti-matter bomb

  1. May 20, 2009 #1
    Hey,

    First off note, I did not see the movie yet (so please don't spoil any of it for me :p ), I am merely talking about the book.

    In the book Angels & Demons, a 'blob' of anti-matter is stolen and used as a bomb. The blob is very small (but still visible to the naked eye) and in the book it finally produces a HUGE explosion (I can't remember the exact figure, but it was very large). It's not a normal explosion, but it also annihilated all the air in a sphere of the same size (I think it was kilometers across??).

    My question really is, how could a tiny blob of anti-matter annihilate a HUGE volume of air?

    On CERN's http://public.web.cern.ch/Public/en/Spotlight/SpotlightAandD-en.html [Broken], they answer a few of the obvious questions, such as this:
    Ok, obviously we can't produce enough anti-matter to make a bomb.


    But let's assume for a moment that we COULD do this. Let's go along with the book and imagine that a blob of anti-matter has been created, let's say a few grams.

    What would really happen if we would 'release' this blob into open air?

    I have always told friends (who also read the book and are convinced that anti-matter bombs might be created in the future) that we would not get a big explosion for the following reason:

    Even if we assume that all the anti-matter is annihilated by matter instantly, then surely only an 'explosion' of the same size as the blob of anti-matter would result?! The matter and anti-matter annihilate and produce pairs of photons. Why would these photons cause an explosion? Isn't it just a flash of EM-radiation, possibly light? Sure, it might be lethal to be exposed to that much radiation, but I am pretty sure it wouldn't cause an explosion, would it?! And I am even more sure that 1 gram of anti-matter would be able to annihilate a sphere of air of a few kilometers in diameter...

    What I imagine here is that we let a blob of anti-matter loose in ordinary air, and a very bright spot of 'light' is created, of the same size as that blob of anti-matter. Big deal?


    Am I wrong about this?
    I am asking because I was kind of expecting the CERN website to explain that there would not be an explosion, instead of saying that it is impossible to create enough anti-matter. So CERN (implicitly) seems to say that, provided we have enough anti-matter, we could make a huge explosion like in the book?
     
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. May 20, 2009 #2
    It would annihilate "a few grams" of it's sister particles, and release some radiation.

    An amount of Anti-"something" will annihilate an equal amount of "something".


    In order to eliminate a lot of air, you have to have a lot of "anti-air".

    As for how much radiation is released, I'm not sure, but if I had to guess, I would say that since matter was "annihilated", the radiation would have an amount of energy determined by E=MC^2

    As in, if 1 Kg of hydrogen interacted with 1 Kg of anti-hydrogen, 2 Kg of matter would be converted into the equivalent amount of energy, which would be 2*C^2. A.K.A. A lot.




    Can someone verify this?
    (not through experiment, please)
     
  4. May 20, 2009 #3
    Yes, my thoughts were exactly that. If you have 1g of anti-matter 'air' it would annihilate with 1g of air. Since 1g of air (actually 2g if you can't the anti-matter) is not very large (in volume), how could this ever cause a spherical volume of air (multiple kilometers in diameter iirc) to be annihilated into pure energy?


    Here is another quote from the CERN website:
    So, apart from the limitation of not being able to produce enough anti-matter of course, CERN seems to say that half a gram would be a very destructive quantity.


    So in my mind, the amount of energy release versus the size of the anti-matter 'blob' don't really correspond... Of course the amount of energy released is right, but I can't see how that energy is used in any destructive way... It's just photons, right?



    So I guess what I'm saying is... I know the book is fiction, and that I mustn't take it seriously. But I looked it up on CERN's website because I wanted to know what would really happen if we had a gram of antimatter. I was expecting the website to verify my thoughts that it wouldn't be very destructive at all (even though a huge amount of energy is released), but instead, all they do is say that we simply cannot make enough of it. So if we could make enough of it, we could potentially have a bomb similar to the one in the book...

    It's like someone asking "Would it hurt if a bullet from a gun hit you at only 1 m/s?" and someone else answering "No, because bullets don't travel at 1 m/s."... It doesn't answer the question you see?
     
  5. May 20, 2009 #4
    Had some fun with my friends the other day working out the radius of the explosion if the table we were sitting at was suddenly anti-matter (don't ask me why or how), needless to say, run!
     
  6. May 20, 2009 #5
    So, how did you do that? And why would there be an explosion? Do you mean an explosion in the generic sense, eg a fire ball or something? If so, where the heck does that come from? As far as I know annihilation can only produce photons, so all that would be released is intense radiation...?
     
  7. May 20, 2009 #6

    HallsofIvy

    User Avatar
    Staff Emeritus
    Science Advisor

    Only photons? Those photons will contain a LOT of energy- and that energy, absorbed into wood or other flammable material, will cause fires, etc.
     
  8. May 20, 2009 #7
    I see. But still, there would be no huge volume of air 'missing' after the 'explosion', kilometers in diameter, would there?

    I can remember the book describing a blinding sphere of light (like the sun but very large), which left a vacuum in its wake into which the surrounding air poured... Or something like that...

    Also, the explosion occured in the air. Nothing was destroyed, and nobody was hurt, even though there was a large crowd directly beneath the explosion.

    (Of course, the main character also survives a fall from a helicopter by using a metal sheet as a parachute, so ... :p )
     
  9. May 20, 2009 #8
    Most of the matter/antimatter annihilation would produce energetic pions (perhaps 200 MeV each). 2/3 of these (charged pions) will decay in about 26 nanosecnds to muons plus neutrinos. The muons will either decay into electrons in about 2 microseconds, or be captured in nuclei, releasing neutrons, neutrinos, and sometimes gammas. 1/3 of the pions (pi zeros) will immediately decay to two gammas, roughly 67 MeV each (plus kinetic energy of pi zero).

    1 gram of antimatter (mainly antiprotons) will annihilate with roughly 2 grams of air (half protons), which is about 1.5 liters of air. Neutrons in air are very unlikely to be annihilated.

    [Edit] The positrons (about 0.05% of antimatter) would produce two 511 KeV photons each.
     
    Last edited: May 20, 2009
  10. May 20, 2009 #9
    And 1.5 liters of air is a spherical volume of kilometers in diameter? I thought not :p

    I still don't see how 1g of matter/antimatter annihilation could cause such a large volume of air to be annihilated. It simply doesn't make sense to me.
    Of course, the book is probably wrong. But then, I am wondering why the CERN website doesn't simply tell me that the book is wrong, instead of 'avoiding' the question and answering that we cannot produce that amount of antimatter in the first place.
     
  11. May 20, 2009 #10
    It doesn't cause such a large volume of air to be annihilated, 1g of antimatter would annihilate 1g of matter, but the problem is the energy that's given off when they annihilate, consider 1g of antimatter reacting with 1g of matter, that's 2g.

    E = m * c^2

    M = 0.002, huge amount of energy, absolutely huge.

    We then looked at a source for an atomic bomb used at hiroshima in terms of Joules and the radius and scaled up.
     
  12. May 20, 2009 #11

    russ_watters

    User Avatar

    Staff: Mentor

    ...or absorbed by the case of the bomb and turned into heat (vaporizing the bomb case) and nearby objects, then a regular explosion blast (a strong pressure wave).

    In a nuclear explosion, Nick, first you get a blast of radiation, which vaporizes things near the bomb, then, you get a regular shock wave, which disintegrates objects over a much larger area.
     
  13. May 21, 2009 #12
    Ok, that makes sense. So it would indeed create a large explosion, but it would not annihilate a huge volume of air like described in the book in a ball of 'pure light'.
     
  14. May 21, 2009 #13

    russ_watters

    User Avatar

    Staff: Mentor

    Fireball yes, removal of air, no.
     
  15. May 21, 2009 #14
    I'm going to see the movie today, let's see what they made of it :p
     
  16. May 21, 2009 #15
    wouldn't that much energy cause fusion in the atmosphere?
    I mean there are molecules in the air. These photons being produced would give them sufficient energy to break up the strong nuclear force and break them into atoms of smaller atomic mass. Some may even get broken to protons. These can then cause fusion.

    Also if an anti-Hydrogen and a Hydrogen at rest anihiliates then the photon released have energy equivalent to 1.67*10^-27*9*10^16=1.53*10^-10 Joules now the wavelength of the EM radiation produced would be 1.29*10^-15 Meters.
    A Gamma ray has a wavelength of 10^-11m. So this amount of radiation would kill life around the explosion site and will have catastrophic side effects. Quite contrary to the book.
     
  17. May 21, 2009 #16
    Indeed... There's a large crowd of people right underneath the (mid-air) explosion and nobody even got hurt... Hehe...
     
  18. May 21, 2009 #17

    russ_watters

    User Avatar

    Staff: Mentor

    I'm not sure if that was ever seriously considered a real possibility or if it was just an anti-nuke crackpot idea from the '60s that took hold, but no, that isn't a possibility.
     
  19. May 21, 2009 #18
    Well I just saw the movie. (Slight spoiler alert maybe?)




    Did you know anti-matter looks like a ball of blue fire? And did you know they can generate three of these balls (roughly the size of a ping pong ball) in 3 seconds?
    Also, I now know that matter/antimatter annihilation produces a large, multi-coloured cloud of... something.

    /sarcasm.
     
  20. May 21, 2009 #19

    diazona

    User Avatar
    Homework Helper

    lol ;-) Was it a good movie though? (worth the price of a ticket?)
     
  21. May 21, 2009 #20
    It was enjoyable, but you really have to go without having the story of the book in the back of your mind. My friend didn't enjoy the movie because he was expecting it to be as good as the book. Of course, being a movie, it wasn't. They left out half the plot, probably to save time, but the movie could have been longer in my opinion so there really wasn't any need.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Angels & Demons - The anti-matter bomb
  1. Anti matter ? (Replies: 4)

  2. Anti matter vs matter? (Replies: 2)

  3. Anti matter (Replies: 6)

Loading...