3 ms·

They seem to be talking about each satellite managing the luminosity of the full moon over a few square kilometres, and getting a few tens of thousands of them.

by ben_w 4mo ago

They seem to be talking about each satellite managing the luminosity of the full moon over a few square kilometres, and getting a few tens of thousands of them. Even if you ignoring how much drag these must have, and hence how much electrical power you'd need for an ion drive just to keep them up, each spot being a few km across (and only getting light while the satellite is over your horizon) is just not compelling. Given most people don't have any reason to illuminate several square kilometres at once, for realistic scenarios it will take a lot of satellites before you beat the cheap battery-powered floodlights in my local Aldi or Kaufland, and the batteries in those lasts a lot longer than the 10-15 or so minutes each of the satellites will be over the horizon, and reflectors like these can only supply sunlight close to sunset otherwise the earth blocks the sun from them. In the list of things which, if you could make them at all useful, would also be relatively easy to redesign as weapons.

b112 4mo ago
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.
- deleted 4mo ago
  [deleted]
- ben_w 4mo ago
  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.
- bunderbunder 4mo ago
  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.
  - b112 4mo ago
    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.
- Cthulhu_ 4mo ago
  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.
  - danaris 4mo ago
    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...)
    - wolrah 4mo ago
      > 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.
      - ben_w 4mo ago
        In fairness, a white sheet and a mirrored sheet will have much the same impact in this regard.
  - eagerpace 4mo ago
    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.
- pyrale 4mo ago
  > The problem is, global warming doesn't affect daylight. In my book, that would have been a "Fortunately," entry.
buckle8017 4mo ago
This has pretty obvious military applications in addition to the "solar all day" application.
8cvor6j844qw_d6 4mo ago
> relatively easy to redesign as weapons There is a fiction I've read years ago that mentioned satellites becoming makeshift weapons by overheating exposed objects (think reactors, gas trucks, oil refineries) by acting as a solar furnace [1] via mirrors. Not sure/don't recall how it deals with practical issues such as clouds and distance/intensity, but good enough for a story I guess. [1]: https://en.wikipedia.org/wiki/Solar_furnace https://en.wikipedia.org/wiki/Solar_furnace
- giantg2 4mo ago
  Probably easier to use a MASER
  - adrian_b 4mo ago
    Unlike for light, in the microwave frequency domain it is easy to make very powerful microwave sources by other means than by using masers, i.e. with various kinds of vacuum tubes. Masers are not useful as powerful transmitters, but only as amplifiers with a very low noise or as generators with a very stable frequency.
- kristjank 4mo ago
  007: Die Another Day has it as a main plot point.
- appplication 4mo ago
  > The temperature at the focal point may reach 3,500 °C I thought this was interesting because it doesn’t really seem like an applicable top level claim, surely this is referring to a specific furnace, not all solar furnaces? Then this got me thinking if there is some universal upper bound constraint to these temperatures. E.g. if I recall a telescope can’t make a source object brighter than it actually is, and this just seems like a thermal telescope, so I wonder if that principle applies here or not.
  - ben_w 4mo ago
    > I wonder if that principle applies here or not It applies, but also in practice the maximum temperature is lower than the theoretical upper bound. https://what-if.xkcd.com/145/ https://what-if.xkcd.com/145/
digdugdirk 4mo ago
In regards to people with reasons to illuminate several sq km at once - I'd bet that major metro areas would see a massive savings in electricity/maintenance if these were deployed over a metro region. Whether that is more than the cost of a satellite? Who knows, it's still fiction until these people try it out. But it's at least an interesting use case.

by ben_w 4mo ago

b112 4mo ago

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.

deleted 4mo ago
[deleted]
ben_w 4mo ago
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.
bunderbunder 4mo ago
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.
- b112 4mo ago
  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.
Cthulhu_ 4mo ago
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.
- danaris 4mo ago
  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...)
  - wolrah 4mo ago
    > 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.
    - ben_w 4mo ago
      In fairness, a white sheet and a mirrored sheet will have much the same impact in this regard.
- eagerpace 4mo ago
  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.
pyrale 4mo ago
> The problem is, global warming doesn't affect daylight. In my book, that would have been a "Fortunately," entry.

buckle8017 4mo ago

This has pretty obvious military applications in addition to the "solar all day" application.

8cvor6j844qw_d6 4mo ago

> relatively easy to redesign as weapons There is a fiction I've read years ago that mentioned satellites becoming makeshift weapons by overheating exposed objects (think reactors, gas trucks, oil refineries) by acting as a solar furnace [1] via mirrors. Not sure/don't recall how it deals with practical issues such as clouds and distance/intensity, but good enough for a story I guess. [1]: https://en.wikipedia.org/wiki/Solar_furnace https://en.wikipedia.org/wiki/Solar_furnace

giantg2 4mo ago
Probably easier to use a MASER
- adrian_b 4mo ago
  Unlike for light, in the microwave frequency domain it is easy to make very powerful microwave sources by other means than by using masers, i.e. with various kinds of vacuum tubes. Masers are not useful as powerful transmitters, but only as amplifiers with a very low noise or as generators with a very stable frequency.
kristjank 4mo ago
007: Die Another Day has it as a main plot point.
appplication 4mo ago
> The temperature at the focal point may reach 3,500 °C I thought this was interesting because it doesn’t really seem like an applicable top level claim, surely this is referring to a specific furnace, not all solar furnaces? Then this got me thinking if there is some universal upper bound constraint to these temperatures. E.g. if I recall a telescope can’t make a source object brighter than it actually is, and this just seems like a thermal telescope, so I wonder if that principle applies here or not.
- ben_w 4mo ago
  > I wonder if that principle applies here or not It applies, but also in practice the maximum temperature is lower than the theoretical upper bound. https://what-if.xkcd.com/145/ https://what-if.xkcd.com/145/

digdugdirk 4mo ago

In regards to people with reasons to illuminate several sq km at once - I'd bet that major metro areas would see a massive savings in electricity/maintenance if these were deployed over a metro region. Whether that is more than the cost of a satellite? Who knows, it's still fiction until these people try it out. But it's at least an interesting use case.