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I was thinking of an organism that has evolved to get its energy through nuclear fusion. It has its own fusion rector inside its body that is capable of fusing hydrogen to helium to derive energy. It is not only capable of deriving energy from fusion but if there is not enough of the elements that it needs to survive such as too little carbon and oxygen it can produce those elements in its fusion reactor.

What types of conditions would cause an organism to evolve a biological fusion reactor? What would be the minimum size for an organism that derives its energy from a biological fusion reactor? What would an organism that gets energy from nuclear fusion look like?

Anders Gustafson
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Unless there is a viable cold fusion process that we don't know about, the energy, pressure and temperatures required for nuclear fusion are not attainable in any "evolved" way. We can barely manage to "intelligently design" a viable fusion reactor with all our technology. The odds that all the intermediate steps would prove beneficial enough to be selected for are unimaginably low.

Spending a week's worth of energy to raise internal temperature to 100 degrees might have some remote benefit. But a creature that burns off a year in feeding to attain 10,000 degrees for a few minutes, without any actual benefit, is going to get outcompeted by creatures spending that energy on growth, claws, brains or other useful traits.

If it did exist, it would probably be a Dyson Jellyfish. This creature grows in space, orbiting a young star where planets have not formed yet. It lives on solar power and absorbs all the dust and gas in the accretion disc, until it can surround the star entirely. At that point it grows inward to manipulate the star with extremely strong magnetic fields, allowing it to trigger solar flares at will.

It will reproduce by budding, slingshotting the buds past the sun and out through holes it creates in its shell. In a million years or so, they reach their target gas cloud, by now a star, and the process repeats. This couldn't have evolved naturally in the life time of our universe, I'm afraid.

Cyrus
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    Dyson Jellyfish. Possibly one of the more terrifying and amazing concepts I've seen come out of this site. – Joe Bloggs Dec 03 '15 at 11:34
  • Maybe you don't need to enclose a star - https://www.iaea.org/newscenter/news/meet-oklo-the-earths-two-billion-year-old-only-known-natural-nuclear-reactor – ShrekOverflow Oct 16 '18 at 17:03
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I reasoned this out in this Answer back in July.

To summarize, (fictional) cold fusion can evolve from the mechanism of photosynthesis.

To deal with the high energy, single-use fusion units are placed in a droplet of water in a mist. The superheated steam can then warm a larger quantity of water or otherwise be spread out over an area so the energy density can be handled, or "cook" a chemical reaction in the same droplet with the products harvested after they collect in a cooler run-off.

For the specific questions mentioned here, the nano-scale single-use reactor is the size of a bacteria, and a chamber to contain them might be the size of a pumpkin.

Community
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JDługosz
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  • but again "Fusion would be impossible unless you presume cold fusion is possible" – sdrawkcabdear Dec 04 '15 at 00:47
  • The Farnsworth fuser does acheive fusion and you can hold it in your hands. It doesn't produce net gain, but it makes you wonder how little energy you can use to cause a reaction. It doesn't need to be "cold" to be small scale. – JDługosz Dec 04 '15 at 01:57
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Fusion would be impossible unless you presume cold fusion is possible (in which case JDlugosz's answer is good).

However, it is worth noting that there exists at least one species that uses a fission reaction as a power source. Candidatus Desulforudis audaxviator is a fascinating species of bacteria. Not only does it appear to be a single species ecosystem (no other organisms have been detected in the deep cracks it inhabits), but it has genetic coding to gather energy from the nuclear decomposition of uranium around it.

Cort Ammon
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  • The abstract you linked to does not mention anything about Uranium or fission. You think they would have lead with that. – JDługosz Dec 04 '15 at 02:48
  • From Wikipedia, however, "The source of hydrogen needed for their respiration comes from the decomposition of water by radioactive decay of uranium, thorium, and potassium." So that's why there is (still) hydrogen there, but it's not using uranium as a "power source" in a realistic meaning. – JDługosz Dec 04 '15 at 02:53
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    @JDługosz It is actually using uranium just as much as a nuclear reactor does. After all, the source of energy in a nuclear reactor comes from heating water. How might "using nuclear decomposition of water" be any less nuclear than "using nuclear heating of water?" – Cort Ammon Dec 04 '15 at 03:57
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    It's incidental, and the organism doesn't have any adaptations for Uranium or radioactivity. It needs hydrogen in the environment, and is agnostic as to its ultimate source. The use of uranium is interesting in the establishment of an ecological niche, but not for any adaptive trait or metobolic process of this organism. – JDługosz Dec 04 '15 at 04:03