is this what it sounds like!?
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Imagine lying in bed trying to sleep and suddenly it's daylight because your neighbour ordered sunlight on Uber.
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Nah, don't get too worked out over it.
It can't be economically viable either, so as soon as that company stops gifting investors out of their money, it will just disappear and the mirror will fall back into Earth.
Given the ridiculous financial gymnastics propping up the AI industry, I'm not sure that "not economically viable" is always a failure state for a business any longer.
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Haha, perfect fit
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To get daylight illumination on even a small area from a 600km orbit you'd need about 20 km² of reflectors. Which is obviously absurd.
What is the physics or math behind that? Light from the sun is essentially aligned by the time it reaches earth. If the mirror is perfectly reflective, a 10 m^2 mirror should light up a patch of Earth roughly 10 m^2 times the cosine of the angle of the mirror. So unless the angle is close to 90°, most of the losses would be from poor reflectivity.
I totally agree it's a stupid idea. But maybe it's even worse than I am thinking of?
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What is the physics or math behind that? Light from the sun is essentially aligned by the time it reaches earth. If the mirror is perfectly reflective, a 10 m^2 mirror should light up a patch of Earth roughly 10 m^2 times the cosine of the angle of the mirror. So unless the angle is close to 90°, most of the losses would be from poor reflectivity.
I totally agree it's a stupid idea. But maybe it's even worse than I am thinking of?
The Sun has an angular diameter of about half a degree viewed from Earth. To light up a location as brightly as the Sun would, you need to cover a half-degree circle in the sky (viewed from that location) with mirrors that reflect the Sun directly at the location. You can't get away with less because a mirror can't appear brighter than what it's reflecting; this is a fundamental property of optical systems.
A mirror 600km away and 5km in diameter has an angular diameter of arctan(5/600) = 0.48°, close enough to half a degree. It has an area of π(5km/2)² = 19.6km² which is pretty much 20km².
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The Sun has an angular diameter of about half a degree viewed from Earth. To light up a location as brightly as the Sun would, you need to cover a half-degree circle in the sky (viewed from that location) with mirrors that reflect the Sun directly at the location. You can't get away with less because a mirror can't appear brighter than what it's reflecting; this is a fundamental property of optical systems.
A mirror 600km away and 5km in diameter has an angular diameter of arctan(5/600) = 0.48°, close enough to half a degree. It has an area of π(5km/2)² = 19.6km² which is pretty much 20km².
wrote last edited by [email protected]To light up a location as brightly as the Sun would, you need to cover a half-degree circle in the sky (viewed from that location) with mirrors that reflect the Sun directly at the location.
That's the best, simplest example I've seen for why this doesn't work. But...I wanted to look at it from the perspective of irradiance losses from the beam spreading. It's been a long time since I did any optics, so I could be way off-base with my approach. Feel free to correct anything I screw up.
Here are my assumptions:
- Near space irradiance from the sun is 1,367 W/m^2 [0]. Let's round up and assume the mirror gets 1400 W/m^2 from the sun.
- We want 1000 W/m^2 on the ground to qualify as daylight [1]
- Collimated light
- No attenuation or scatter from the atmosphere, but we will assume the beam diameter spreads 0.5 degrees [2]
- Perfectly reflective mirror
- Mirror 600 km away from the earth
Beam spreading loss is a function of distance. So however large the beam width (mirror diameter) starts, it'll be this much bigger when it reaches the ground:
600km * tan (0.5 degree) = 5.24km
That means if we have a 1m diameter mirror, we get a beam 5.24km + 1m on the ground. If we have a 5km diameter mirror, we get a 10.24km beam on the ground.
To get our target of 1000 W/m^2, we need at least
1000/1400 = 0.71of what hits the mirror to hit our target.mirror/(mirror+spread) >= 0.71
mirror >= 12.83km[0] https://en.wikipedia.org/wiki/Sunlight#Measurement [1] Wikipedia says that we actually get more like 1100 W/m^2 when the sun is at its zenith. [2] https://en.wikipedia.org/wiki/Collimated_beam#Distant_sources -
This is literally the plot of one of the James bond movies.
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Given the ridiculous financial gymnastics propping up the AI industry, I'm not sure that "not economically viable" is always a failure state for a business any longer.
It hasn't been since at least "too big to fail."
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i wouldn't worry about it. The whole business is built on an extremely huge miscalculation.
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Came here to make sure this one was in the comments.
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https://jamesbond.fandom.com/wiki/Icarus
Satellite to direct sunlight for agriculture
I think there was something similar in a Batman film too, the bad one with Arnold Schwarzenegger in it iirc
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You can't get away with less because a mirror can't appear brighter than what it's reflecting; this is a fundamental property of optical systems.
I can understand that a single flat mirror cannot ever appear brighter than whatever is being reflected. But why can't multiple mirrors pointed at one spot have a total intensity greater than that of any one of the mirrors (or a curved dish that focuses the light)?
