• mozz@mbin.grits.dev
    3·
    1 year ago

    I will bet $1,000 (or $100) that this is wrong:

    Lets assume each of the mirrors reflects 850 watts. The distance to the ISS is 408,000 meters.

    The energy reflected by one mirror as received by the ISS is subject to the inverse square law (because it is incoherent).

    E = (850 watts) / (4pi408000m)2,, or about 4.06x10 −10 watts/m2

    A 5 milliwatt, off the shelf laser pointer with a beam divergence of 1.5 millirads would deliver approximately 4.25x10-9 watts/m2, or about 10x as much energy as the 850 watt mirror.

    You can not melt a spy satellite with mirrors. You might be able to with lasers. A laser will be approximately 8.9x106 times as power effecient at getting light from earth to the ISS as a mirror would be.

    And this is right:

    E = 850 watts / 149,597,971 km^2 * 149,597,871 km^2 = 849.998864 watts

    I will also bet on the behavior of an idealized flat mirror. I won’t bet on whether you can actually shoot down satellites with the Ivanpah solar plant, because there are real-engineering issues that interfere with it aside from the physics of how mirrors and sunlight work.

    If you want to try to chart a middle ground, I think it’d be better to talk about something actually testable than trying to argue about the real-world behavior of the Ivanpah mirrors. I’d be happy to bet $100 that:

    Take a mirror and find the sun. Send a reflection to the wall nearest you. Then send the reflection to a wall further away. The reflection on the wall further away is larger and therefore, the energy more spread out.

    … is wrong, as long as the mirror is flat. This one is easy to test so this might be a better bet.

      • mozz@mbin.grits.dev
        4·
        1 year ago

        I care so much that I was outside earlier today, messing with my little reflective discs. It’s actually really hard to get the angles right and I couldn’t find a wall that was at the right type of angle to be able to test it without the reflection skewing from where the sun was, and a couple of people came near me, and clearly looked at me sort of wondering “what the hell is this guy doing.”

        I made no attempt to explain. Y’all can think I’m insane or whatever. I’m doing science. Get the fuck away.

    • TropicalDingdong@lemmy.worldEnglish
      1·
      1 year ago

      … is wrong, as long as the mirror is flat. This one is easy to test so this might be a better bet.

      But that was never the bet. The bet was about transmitting light through the atmosphere. This is just some weird little aside you got yourself tangled in. More than happy to take on a bet about the transmission power of mirrors versus lasers from space, which is what were actually discussing.

      (Dug this one out of the grave because I’m trying to find another bet I just won, so was searching for “bet”)