In short, please provide me with a scientifically plausible biochemical scheme for how an organism can harness the energy of long-wavelength electromagnetic radiation to produce food for itself. Thank you.

Requirements of the answer:

  • The organism in question should synthesize energetic compounds using the energy of incident electromagnetic waves with wavelengths over 1 mm (i.e. microwave or radio waves). It should not utilize anything with a shorter wavelength, but it's okay if the organism can only utilize a narrow wave band within that range.
  • Such a "long-wavelength photosynthesis" process must be able to happen at room temperature and in the earth's atmosphere. But the chemical compounds involved in the process do not need to be compatible with the biochemistry of life on earth.
  • The organism in question should be able to handle 1000 W/m2 of incident radiation (equivalent to intense sunlight at noon). However, it doesn't need to be too efficient in terms of energy. I expect it to convert at least 6% of the total energy of incident photons that are within the wave band it can utilize. (That is lower than the corresponding efficiency of chlorophyll, which is about 9%.)

Given condition:

  • The organism in question is unable to form any delicate macroscopic shapes. (You can imagine it like sponges or lichens.) So it can not grow large parabolic antennas or parts of heat engines. But it can grow to a few centimetres thick.

Note: This question is not asking about how to form an environment that is abundant in microwave and radio waves, and it is not asking about how the organism in question could have evolved.

Link to the opposite question: Photosynthetic life using gamma radiation


1 Answer 1


A Snowflake, a symphony of phonons and a shower of photons.

The issue with longer wavelengths is twofold:

  • Each photon has less energy the longer the wavelength, making it unable to function alone the way higher-energy short-wavelength photons can.

  • Photons of longer wavelength are (probabilistically speaking) less likely to interact with a molecule of the same size as regular chlorophyll.

On Earth, we've chlorophyll that absorbs photons of a particular set of wavelengths converting the energy into excited electrons - the chlorophyll molecules do this by acting as little aerials, tuned to these wavelengths:

Ring molecule with tail.

Labproducts, 2022, fair usage.

It's the tail of the molecule acting in concert with the ring part with the magnesium in the middle provides the tuning.

Magnesium's great, it's got just the right availability in the cosmos, and a convenient requirement of energy-levels to shed and capture electrons.

So, to counter the first sticking-point above, you need bigger molecules to capture the photons. The second point is dealt with by capturing more than one at a time.

You can do this by taking a leaf out of NASA's book when they grew genetically engineered aerials (technically, genetic algorithms evolved them, then NASA made the "survivor" with metal):

Weird twisted wires.

JPS, CIT Lunar 1992-2022, fair usage.

The phonons come into it when you have several photons simultaneously (or nearly so) hitting the target molecule - each making a wave in the surface electrons of the substance like dropping several tiny pebbles around the edges of a puddle at the same time making ripples. These ripples all converge at the active centre where the chemistry takes-place reinforcing each-other's energy, the total energy being just right to make the magic happen.

The whole molecule would ring like a thousand tinkling bells all at once, the brighter the light, the higher and more intense the ringing.

To sum-up.

Keep the basic chemistry the same with magnesium, but make the surrounding structure more like a snowflake (or a version of NASA's aerial). Of course, the longer the wavelength, the bigger the molecule:


Komarechka via fstoppers, 2022, fair usage.

  • $\begingroup$ Can you elaborate more on the relationship between the wavelength and the size of the pigment molecule? Assuming the relationship is linear, I calculated that the molecule to absorb 1 mm radiation would be 2 microns in size (nearly as large as a real-life chloroplast). $\endgroup$ Jul 11, 2022 at 1:55
  • $\begingroup$ I'm not sure how to do that, but I agree that the relationship is linear, just as the wavelength to energy is linear and inversely proportional. What I foresee is that since the wavelengths are in the order of a few million times the size here, regular organelles are not likely to fit the bill. How these things evolved is quite another long answer and speculative. Not sure what more to say. @VegetableNewMan See what others come up with I guess. $\endgroup$ Jul 11, 2022 at 2:02
  • $\begingroup$ On reflection, if you're going to need millions of times the photons to achieve what chlorophyll does, then the molecule would need to be millions of times the volume that a single long-wavelength photon would require (if it had the energy). It looks like you're into the millimetre range for this. @VegetableNewMan I'm off to sleep now, but will edit the answer in the morning. $\endgroup$ Jul 11, 2022 at 2:22
  • $\begingroup$ "the chlorophyll molecules do this by acting as little aerials, tuned to these wavelengths" - is this the coolest thing in the universe? I think it might be. $\endgroup$
    – thosphor
    Jul 11, 2022 at 13:48

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