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Comment by timthelion | Hacker News Reader

The idea expressed at the end of the article "orbiting mirrors could be used to extend the length of daylight hours for harvests" actually sounds like it could be very reasonable. Vertical farming and aquaponics is currently restricted by light to a large extent. If this solves the lighting problem for vertical farming, we could end up with a 10000 layer farm built into an old mine quary that could feed a large country. And then all of that farm land could be left to nature :) Deforestation could be reversed, and the reversal of deforestation could play a key roll in reducing the roll of carbon emissions...

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I think you're vastly overestimating how much area would be available in a farm built into an old quarry.

A 4km by 1km parcel of land is not large for farming. But put vertically, it represents the biggest open cut mines ever made.

So, working with 4Km2... There are 13 million square kilometers of arible land on earth: https://en.wikipedia.org/wiki/Agricultural_land . If the virtical farm is strung up with 400 meters of 10cm layers, that makes 4000 layers. That would be 16 000 square kilometers of farming area, or a bit over 0.1% of all arible land. I think that with modern vertical farming, using a 24 hour year around light source, the farming surface can produce several times the avarage arible land production. Lets say 4 times... That would make almost 0.5% of the world farm production in just one tiny area. So it would take just 200 such constructions to replace tradtional farming entirely...

You need arable soil for all 4000 layers. You will be taking valuable topsoil from just as much land.

That is not how aquaponics and vertical farming work. They use solulable nutrients which are either gained through a nutrient cycle (the water flows down to a pool which has fish in it), or via mining of otherwise hard to get nutrients. Soil is not used. While the source of all these nutrients is a problem, it is comparible to the huge quantities of petrolium based fertilizers that we use today. It is bad, but what we have now is bad too...

... so you are proposing a bad idea that seems pretty wrong from multiple aspects. generally hydroponics is a sht cheap substitute for real growing for those who cannot afford quality vegetables (sadly, I sometimes fall down that hole too and then regret this decision while eating this tasteless cr*p full of unhealthy chemistry).

no, thank you for many reasons

If you have 4000 layers, you need 4000 times as much light, so you need a 16000km^2 orbital mirror focusing on your farm's elaborate set of light-pipes. The highly focused light, like a CSP plant, would ignite birds that flew into the beam. At that scale it would probably alter the local climate, given the amount of heat transferred to the air.

Few questions:

- How does a mirror make the foliage transparent?

- How does transparent foliage absorb energy for photosynthesis?

- How do you boost the energy from the light 16000 times (4000 layers * "lets say 4 times") without destroying the plants (and probably a lot more)?

- What are these <10cm crops we can replace the current unwieldy crops with?

A satellite doesn't help you with vertical farming at all, as the light is still coming down from above.

You can move light. Light flies really fast [citation needed] and is easilly and efficiently reflected.

How are you going to reflect it into 10000 layers? Your mirror surface area needs to be as big as the area of light you want to capture, and it all needs to be in clear view of the satellite.

You may as well just remove the mirrors and put the farms where the mirrors are.

If you do farming in space, you have many problems. You have to get the food down, and water up, you have to bring up all sorts of materials and store them in space... It is much easier to get light down than to get seeds and water and nutrients up, and then food back down again.

If you get light into a clear material which has a reflective surface( almost any clear material does ;) ) then the light will reflect internally and flow down the material, while seeping out the sides. That is how fiber optics works, but it doesn't have to be fiber, almost any clear material would do...

A lot of plants measure seasonal change by the length of the day. This might work for some crops but your broccoli would probably bolt or never grow flowers in that environment.

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