Starship Asterisk*

Rauf wrote: ↑Fri Sep 22, 2023 4:18 am There's been a mistake I guess. Today's APOD incorrectly shows the date as September 21, and the link to Asterisk Discussion page also directs you to September 21.

johnnydeep wrote: ↑Fri Sep 22, 2023 1:56 pm I don't get why the reflected sky shows so much wavy distortion of the star trails. Are the mirrors of the array not almost perfectly flat? The "surreal mirrored reflection" video link does seem to show clear undistorted images of the sky, which would seem in indicate very flat mirrors.

Chris Peterson wrote: ↑Fri Sep 22, 2023 2:05 pm

johnnydeep wrote: ↑Fri Sep 22, 2023 1:56 pm I don't get why the reflected sky shows so much wavy distortion of the star trails. Are the mirrors of the array not almost perfectly flat? The "surreal mirrored reflection" video link does seem to show clear undistorted images of the sky, which would seem in indicate very flat mirrors.

Hmm. What I see in the video looks like a highly distorted view of the sky. There is no reason for the mirrors to be very flat. Between their intrinsic nature and whatever frame is holding them, I'd expect quite a bit of "waviness".

johnnydeep wrote: ↑Fri Sep 22, 2023 2:19 pm One other dumb question: since the mirrors aren't being used to capture solar energy at night, I don't suppose there would be any practical and cost effective way to design a dual purpose configuration of specially made mirrors what would focus sunlight for power during the day, but then switch to focusing incident radiation onto a detector for astrophotography at night?

Chris Peterson wrote: ↑Fri Sep 22, 2023 2:25 pm

johnnydeep wrote: ↑Fri Sep 22, 2023 2:19 pm One other dumb question: since the mirrors aren't being used to capture solar energy at night, I don't suppose there would be any practical and cost effective way to design a dual purpose configuration of specially made mirrors what would focus sunlight for power during the day, but then switch to focusing incident radiation onto a detector for astrophotography at night?

Well, then you would need optically flat mirrors, which would be astronomically (ha, ha!) more expensive. There might be astronomical applications that are fundamentally about energy collection (as opposed to imaging), like the cosmic ray detectors that detect Cherenkov radiation flashes, that could ride piggyback on a system like this.

Jim Leff wrote: ↑Fri Sep 22, 2023 4:13 pm Don’t miss the photographer’s two minute making -of video (linked in the APOD text) which gives great context plus a witty reference to the “Three Body Problem” sci-fi trilogy: https://www.youtube.com/watch?v=3Pbr2wIgCHE

A late sequence in The Three-Body Problem—whose translation, by Ken Liu, is now out in paperback—depicts a massive project to unfold a single proton into two dimensions, etch microprocessor circuitry on to its surface, and turn it into a supercomputer. The idea is ambitious, fantastic geek porn. Subatomic particles, under superstring or M-theory, exist in as many as eleven space-time dimensions, of which we only perceive the standard three (plus time); and just as one can unfold a cube into a flat, larger cross, or a 4-D hypercube into a ‘larger’ three-dimensional shape, the scientists in Three-Body unfold the proton’s compact eleven-dimensional shape into lower-dimension shapes, each more expansive than the last—with the 2-D proton so large, it has to be manipulated in orbit because it wraps around the planet.

Avalon wrote: ↑Sat Sep 23, 2023 2:12 am This sounds like a perfectly benign energy source, but the price is often high as the beam of concentrated 900 degree solar energy kills birds that unfortunately fly through it. https://www.youtube.com/watch?v=emBY6phmn9E