This is a long time scale creature - it experiences a thousand years in the fashion that we experience one.

It grows by pulling one neutron from a $C^{12}$ molecule and building it onto other carbon molecules to make $C^{14}$. Time frame for that isn't too important as the $C^{13}$ is stable. The $C^{11}$ decays with a fast half life of 20 min to $B^{11}$ and the $C^{14}$ decays to nitrogen with a half life near 6k years.

Energy changes:

  • removing neutron from $C^{12}$
  • adding neutron to make $C^{13}$ and $C^{14}$
  • decay of $C^{11}$ to $B^{11}$
  • decay of $C^{14}$ to N

Is it gaining or losing energy here?

  • 1
    $\begingroup$ this seems more like a physics question than a biology one $\endgroup$
    – zackit
    Mar 29, 2021 at 16:44
  • $\begingroup$ Yea probably, but it is for a xeno creature that works on those scales with that being one if its primary energy interactions. added physics tag $\endgroup$
    – Allan
    Mar 29, 2021 at 16:47
  • $\begingroup$ @Allan the issue being that while /for/ a xeno creature the question asks nothing about the creature. This is nothing but physics with a couple very loose relations. $\endgroup$
    – IT Alex
    Mar 29, 2021 at 16:51
  • $\begingroup$ should it be migrated from worldbuilding? $\endgroup$
    – Allan
    Mar 29, 2021 at 16:53
  • 2
    $\begingroup$ I do enjoy the handwavium of "pulling one neutron". This is so wildly unlikely for anything biological to do that it's breathtaking. $\endgroup$
    – jdunlop
    Mar 29, 2021 at 17:36

1 Answer 1


Take a look at the masses of all those isotopes, for Carbon, Boron, Nitrogen and neutron:

  • $C^{11}$ = 11.01143260
  • $C^{12}$ = 12
  • $C^{13}$ = 13.00335483521
  • $C^{14}$ = 14.003241988
  • $B^{11}$ = 11.009305167
  • $N^{14}$ = 14.00307400446
  • $n^0$ = 1.00866491588

The process you describe is (neglecting the electrons emitted in the beta decays) $3 C^{12} \rightarrow 2 C^{11} + C^{14} \rightarrow 2 B^{11} + N^{14} $.

The initial mass is $3\cdot 12 = 36$, while the final mass is $2\cdot 11.009305167 + 14.00307400446 = 36.02168433846$.

Since we know that $E=mc^2$, the fact that the final mass is higher means that the whole process doesn't produce net energy, but rather absorbs it.

If you instead go for the path $3 C^{13} \rightarrow C^{11} + 2 C^{14} \rightarrow B^{11} + 2 N^{14}$ you start with a mass of $3\cdot 13.00335483521=39.01006450563$ and finish with a mass of $11.009305167 + 2\cdot 14.00307400446 = 39.01545317592$, which is also slightly higher, thus also this chain doesn't produce net energy.

  • $\begingroup$ Thus this can only be its building blocks not its energy source. $\endgroup$
    – Allan
    Mar 29, 2021 at 17:28
  • $\begingroup$ The "process" absorbs a lot of energy, about 50.4 TJ / kg for the first "reaction". That's about the equivalent of 10,000 tons of TNT, or about the amount of electric power produced by a typical 600 MW reactor group of a nuclear power plant in a day. $\endgroup$
    – AlexP
    Mar 29, 2021 at 19:12

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