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Comment by b112 | Hacker News Reader

With global warming, trillions upon trillions of acres of immensely fertile bogland, in Northern Canada is thawing. The problem is, global warming doesn't affect daylight. 4 hours of "the sun barely makes it over the horizon" means no crops, no matter if the temp is above 0C in September.

Obviously this satellite isn't viable, but all things start small. Large tracts of land could be illuminated.

But of course, I question the logic of redirecting more sunlight, especially such large amounts, onto a world already warming uncontrollably.

Still, it could be useful for the polar caps on Mars?

These seem like unlikely things though.

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Though I have to ask the value of illuminating large tracts of mostly uninhabited land. Lighting areas where no humans are around to want the light seems like a proposition that’s mostly useful for further disturbing nocturnal wildlife.

What might be more useful is to illuminate just the areas where a human currently needs to see well. It would hypothetically be both more useful - you can concentrate more light in just the areas you need it - and less expensive.

What would be particularly cool about this hypothetical technology is that it could work equally well under foliage and indoors.

Though I have to ask the value of illuminating large tracts of mostly uninhabited land.

Crops means farmland. Farmland means food. Food prevents people from starving to death.

With global warming, existing croplands will become unusable. We'll need new farmland.

That was the whole point of my post, which also discusses other concerns.

Mars… needs something rather bigger. I don't know what the most cost-effective solution would be, but Mars gets about half the per-area sunlight as Earth so it would need a reflector about the size of Mars to get the same overall insolation.

My guess is it's probably easier to make a bunch of greenhouses on the surface? But the scale is so huge that which is best will be affected by technology invented after you start.

If sattelites can reflect enough light to make an impact on e.g. global warming, they can also reflect enough to circumvent it. Point them back at the sun or into space and in theory it redirects the same amount of energy away from the earth as it would pointing towards it.

That said, I'm (armchair) confident it'll be good for moonlight-level illumination on a local area at best. They'll need to scale up to thousands / tens of thousands to make any measurable impact - which is their objective by the looks of it, but it'll take a while yet. If this one creates enough backlash, a fleet won't make it. Assuming they get the money and customers to justify a fleet in the first place.

For those purposes, why would it need to be mirrors? We don't care to coherently reflect the light; we just want to block it.

(For reference, I think all of these are likely to be somewhere between moderately and incredibly bad ideas...)

> We don't care to coherently reflect the light; we just want to block it.

The energy has to go somewhere. If you're not reflecting it you're absorbing it and you eventually have to do something else with it.

In fairness, a white sheet and a mirrored sheet will have much the same impact in this regard.

This is where people who think space access is only for satellites and LEO space stations have no imagination. We’re at a place now where if global warming did suddenly start to run away, within a year, we could realistically launch enough solar shades to meaningfully impact the situation. It’s far fetched, but this is why innovation in general is important. Not for what we know now, but for all the unknown ways it could be used in the future.

Right now we're still not close to that kind of capacity.

I suspect just painting all the rooftops and tarmac white will be about as effective as 2000 Starship launches filled with mylar sheets, plus an L1 delivery system because one thing you really don't want for a global warming mitigation is for them to fall out of LEO and burn up almost immediately from the huge drag-to-inertia ratio.

> The problem is, global warming doesn't affect daylight.

In my book, that would have been a "Fortunately," entry.

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