Comment on "Moon landing" photo where the angles of the shadows are all off.
GreenShimada@lemmy.world 4 days agoJust tell him small-minded people can’t comprehend big things and see if he even gets it. Which is true, but also a dick thing to say like that if he is smart enough to understand the slight.
Sadly, apparently bouncing a laser off the moon via the reflectors left up there by Apollo missions isn’t hard exactly, just expensive to get the right equipment to do it right.
Buddahriffic@lemmy.world 3 days ago
Which is pretty crazy when you think about it, hitting a target about 1.3 lightseconds away. As in, if you could sight it, you’d be looking at where it was 1.3 seconds ago. Because it is moving at about 1km/s relative to us. And don’t read that as km/h, that’s one kilometer every second, so by the time you see it, it’s already about 1.3km from where you see it, so you need to lead it by about 2.6km to hit it but aim your sensor at the apparent image.
Though it’s so far away that it doesn’t look that hard and the angle of difference between where you aim the laser and where you pick up the return signal is less than 0.00001 degree (thus you can solve that problem by ignoring it but still, just hitting that tiny distant moving target at all is impressive).
GreenShimada@lemmy.world 3 days ago
When looking at the process, it’s actually bonkers in a totally differet direction.
Any laser shot from Earth ends up spread out an area of about 26km diameter on the lunar surface. So you need a high-power laser pulse to get any sort of concentration of photons to hit the lunar surface that are detectable there. Then the reflection gets spread out over a similar large area on reflection to Earth, so you’re trying to detect a few photons from the original laser pulse of 10^17^ photons (or whatever the actual number is).
So to your question about sighting - actually not necessary. But you’ve turned the laser pulse into a photon shotgun, which is equally bonkers. You’re shooting a pinpoint laser that still spreads out to the size of a large city just to hit a meter or two-sized target. Then the same thing again just to get the reflection.