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[-] deegeese@sopuli.xyz 29 points 10 months ago

The suns angular diameter is about 0.01 radian, so at a distance of 100km, the suns reflection will spread out to a disc about 1km across.

392MW over a disc that size is 500w/m2, which is weaker than direct sunlight.

[-] Ilovethebomb@lemm.ee 5 points 10 months ago

They can aim each mirror individually though.

[-] deegeese@sopuli.xyz 1 points 10 months ago

And each one makes a 1km2 spot.

It’s not the aiming, it’s that the sun is not a point source.

[-] mozz@mbin.grits.dev 1 points 10 months ago

Yes; it is well known that if you look at yourself in a flat mirror, and then back up, your reflection will spread out bigger and bigger and get dimmer and dimmer, the further away you get.

Wait

[-] deegeese@sopuli.xyz 1 points 10 months ago

“You” are the sun in this scenario.

As you back up, you fill a smaller and smaller fraction of the mirror. The reflection becomes less sun and more space.

[-] mozz@mbin.grits.dev 2 points 10 months ago

I have a little reflective disc. I will bet you $100 that a reflection of a sunbeam off of it will be exactly the same size (i.e. the same intensity, since it's not getting any bigger) several meters away as it is a few inches away.

[-] deegeese@sopuli.xyz 1 points 10 months ago

Try that in your backyard with a small mirror. You’ll find the sun’s reflection expands by about 1% of the distance.

[-] mozz@mbin.grits.dev 1 points 10 months ago

Ooooh

Yes you're 100% right - it's not a point-source, so it will expand out slightly. I don't know the math well enough, but I believe if you if you say you do + it works out to about 1% of distance.

this post was submitted on 15 Feb 2024
457 points (95.4% liked)

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