The persistence of false ideas

This is been a running theme of this blog, but sometimes, readers might suspect that I have been biased in my accounts here: perhaps Gene notes the falsity of the typical view of the Middle Ages simply because he is sympathetic to religion, or contends that the typical understanding of Berkeley is false because he is sympathetic to idealism.

But tonight I offer a case in which I cannot see that the persistent falsehood has any religious, ideological, or social implications, and yet it just goes on and on: The idea that Einstein's formula E=mc2 explains the power of atomic and nuclear weapons. Here is a good version of the true story. The true story has been pointed out again and again, yet the falsehood just keeps circulating: tonight I read it in a recently published Italian history book. Once a falsehood becomes popular, it is seemingly almost impossible to eradicate it from the world of thought.



13 comments:

  1. I don't think this is quite right, since it is about fission. The H bomb is a fusion reaction. Bonds are not broken, as in fission, but created. So this explanation cannot be right for fusion reactions, where mc2 rules.

    ReplyDelete
    Replies
    1. No, in both cases, the energy comes from the fact that iron is that an energy trough in the periodic table. As you break atoms to move down towards iron or fuse them to move up towards iron, you gain energy.

      Delete
    2. "Only with the systematics of these forces and binding energies well understood were physicists able to uncover the laws behind nuclear fission and fusion: The strength of the nuclear bond depends on the number of neutrons and protons involved. It varies in such a way that binding energy is released both in splitting up a heavy nucleus into smaller parts and in fusing light nuclei into heavier ones. This, as well as the chain reaction phenomenon, explains the immense power of nuclear bombs."

      Delete
    3. I am gonna check. I think when H fuses to become He there are no bonds to break. But I will ask a phycist and report back.
      Not that that matters to the common explanation of the atom fission bomb.

      Delete
    4. Right: You gain energy by forming bonds all the way up to iron. You only gain energy by breaking them above iron. And these are the strong and weak nuclear forces we are dealing with, not chemical bonds.

      Delete
    5. This is why massive stars produce an iron-nickel core before they go supernova:
      http://en.m.wikipedia.org/wiki/Type_II_supernova

      Delete
    6. "Because the nuclear force is stronger than the Coulomb force for atomic nuclei smaller than iron and nickel, building up these nuclei from lighter nuclei by fusion releases the extra energy from the net attraction of these particles." -- Wikipedia on nuclear fusion

      Delete
  2. That makes sense.

    ReplyDelete
  3. And as these articles note, E=mc2 is involved in these reactions: but so it is in chemical reactions. The huge increase in energy released is explained by the forming or breaking of nuclear bonds instead of chemical bonds.

    ReplyDelete
  4. Wait a second. Before reading this post, I would have had no trouble saying to someone, "A fusion reaction works by taking two hydrogen atoms and turning them into one helium atom. Since an atom of helium has less mass than two atoms of hydrogen, the difference is released as energy according to E=mc^2."

    Is that wrong?

    ReplyDelete
    Replies
    1. It is not wrong, but the same thing applies to burning wood. So only if you want to say "E=mc2 explains the heat of a fire" would you want to say it is true of a nuclear explosion. The more relevant explanation is the great energy tied up in nuclear bonds.

      Delete
    2. So the mistake is thinking that E equals MC squared is somehow especially relevant to a nuclear bomb, where it is in fact exactly as relevant to a fire.

      Delete
  5. Bob, It would be kind of like someone asking me "what is Mises explanation for inflation?" and I answer "human action."

    My answer is not wrong, but... We can do a lot better, right?

    ReplyDelete