Is this an error?

[losfomot]

While reading Isaac Asimov's book "ATOM" I came across this paragraph and it seems difficult to believe, I am wondering if it is a mistake?

Here is the paragraph exactly as it is in the book:

 

The positron behaves exactly as Dirac's theory suggested. It quickly undergoes mutual annihilation when it encounters one of the numerous electrons in its immediate environment, producing gamma rays of energy exactly equal to that of the combined mass of the electron and proton.

 

Well, that is actually half the paragraph, but the other half is unrelated to the error. My problem is with the word proton. Was it supposed to say positron? Because it seems like your getting an awful lot of extra energy from nothing if it is really supposed to say proton.

 

Thanks

[Klaynos]

My understanding of this is that it is meant to say positron, and I would read it as such, else there is not conservation of mass-energy.

[timo]

Yes, positron. Easily made typo. Also note that "mass" refers to the relativistic mass and not the more commonly used rest-mass (or to rest-mass only as an approximation).

[[Tycho?]]

Yeah, i didn't even notice that until I read it through a second time. It should be positron.