Hacker News Reader

Comment by mangecoeur | Hacker News Reader

I find the physics of wavelength-dependent materials properties oddly satisfying. You can do clever things like this, extracting energy from different parts of the spectrum by combining materials and conversion processes. You can beam waste heat back to space through the atmosphere’s “infrared window”. You can explain global warming from first principles. Fascinating stuff!

View on HN

One thing I’m curious about this from the plant perspective - we’re pretty sure we’re passing everything relevant down to the plant, but nature doesn’t normally leave signal or energy lying around without leveraging it somewhere, so what don’t we know about how the broccoli use the parts we’ve been assuming they don’t?

Plants are green because they _reflect_ non-magenta light! This energy is wasted. If you saw artificial grow lights, they are now often magenta-colored exactly because the green part of the spectrum does nothing, and you might as well save some energy.

These panels absorb that light before it gets to the plant, so it's a win-win.

The history of everything in biology is us looking at a plant and going “oh wow, it’s green, that means it’s only absorbing magenta!” and then finding out years later that the plant is almost entirely green except that every hundredth cloroplast is actually magenta and that’s the signal the plant uses to tell when the sun is up which is how it times its seed releases, which is why our crops all died this year and won’t grow back.

Sorry, but that's not how it works. Energy is energy, and we can measure what's reflected. Chloroplasts _themselves_ are green, btw. That's where their name comes from.

Why plants are green is a mystery. There is no accepted explanation. A compelling theory is that during the first ocean oxidation event, dissolved iron started crashing out as iron oxide, which strongly absorbs the green light.

I sure hope you’re right.

As far as I know, plants are not usually limited by sunlight, but CO2. Grabbing more wavelengths is not going to improve their growth potential.

Industrial (or home) grow lights are often already red and blue spectrum focused since those are most efficient for photosynthesis. There’s plenty of research on those if you’re curious

I feel the same way about how fiber optics can create bandwidth by just slicing up the spectrum for different channels of data (my rudimentary understanding anyway). I like how even after all this time we find new and clever ways to work with light.

And then doing amplification on that light without converting it back to electrical signals.

Even more wild than spectrum slicing is polarisation encoding multiple data streams on the same wavelength.

Is that something in practice (and does it have a name?)? (The thought tickled my brain as QAM/PSK but for light...ish)

Radio is just low frequency light, so all of the same encoding methods apply as-is.

I meant it makes sense! I just never considered it and it's a nifty thought

QAM can absolutely be used in fiber optics communication. Encoding and decoding systems are complicated (I won’t pretend to understand it), but it exists.

Example of a research paper using it: https://www.researchgate.net/publication/290224766_Investiga...

Wavelength-division multiplexing[1]... it's what they use with fiber-to-the-home to get bidirectional signals with a single strand of fiber. Or the big-boy version is DWDM which ISPs use to stuff dozens of customers on a single strand.

You might also be interested in https://phys.org/news/2026-11-air-holes-silicon-wafers-flat....

[1] https://en.wikipedia.org/wiki/Wavelength-division_multiplexi...

fiber optics doesn't slice up anything. it's just a pathway for light to travel.

I'm current taking composite construction certification courses because modern manufacturing provides for customizing the material for very specific uses. Low volume production with very specific mechanical and physical properties.

Wait we could reflect back infrared heat into space and still collect solar energy as electricity - so doing two jobs at once in, say, a desert.

Re-greening at a profit?

Careful engineering can help here.

Reflect back shortwave IR sunlight below the bandgap of the solar panels.

Make the solar panels "black" at longer IR wavelengths corresponding to the temperature of the panels and to IR windows in the atmosphere, to maximize emission of heat back into space.

It would be challenging but theoretically possible. You need very clear skies for the infrared heat not to be trapped by clouds

Reply on news.ycombinator.com