Interesting Links for 10-07-2025

[andrewducker]

1. Let Kids Be Loud

(tags:children noise )

2. Fascinating essay on photography lighting techniques that predate AI and why they are confused for it (amongst other things)

(tags:lighting photography )

3. What if you Threw a Paper Airplane from the Space Station?

(tags:space paper airplanes viaPatrickHadfield )

4. Cellos totally belong in rock bands

(tags:music video awesome )

5. Time keeps on slipping - literally. Why today might have been the shortest day you'll ever experience

(tags:time earth )

Comments

[simont]

#3: hmm, my first thought was to wonder if a paper plane thrown from the ISS would even reach Earth's atmosphere in the first place.

My knowledge orbital mechanics is not very profound, but I thought that if you took an object in a circular Earth orbit and adjusted its velocity by a small vector (as when the astronaut on EVA hurls the paper plane), the effect would be to give the object a slightly different orbit, probably a bit elliptical. So its closest approach to Earth might be closer than that of the ISS itself, but the closer it got to Earth, the faster it would be moving (gaining kinetic energy to match the loss of gravitational potential energy), and after perigee it would rise back up away from Earth and start slowing down towards its apogee. You'd need a big change to the orbit to make its perigee close enough to graze the atmosphere and start on a re-entry path.

But this analysis seems to skip lightly over that part, and focus entirely on what happens after atmospheric contact, without explaining how we get as far as the atmosphere in the first place!

[andrewducker]

I'm pretty sure that no orbit is stable perpetually. So at some point in the next billion or so years that thing is coming down!

I *am* curious about the assumption that it would burn up. It seems to me that it's light enough that even a tiny amount of air would be enough to accelerate it to match the speed of the atmosphere. So there might never be a Mach 7 wind speed difference.

[jack]

I'm not sure if you're talking about general orbits or earth orbits specifically?

I think a lot of earth orbits still experience some drag from atmosphere. And orbits can experience drag for other reasons like tides, although that can lead to orbiting further in or further out.

But I think (??) "unstable" usually means things like a three body problem. I think if something is just going round and round vaguely newtonianly with no atmosphere etc then it will just keep going. Maybe an asteroid will bump into it. But the things that can go wrong are likely to be longer than a billion years (like EVENTUALLY losing energy from gravitational waves...)

[andrewducker]

Something in orbit around the Earth is definitely having an n-body problem. There's a constant variable pull from the moon, and even other planets will exert small gravitational effects. Not by a huge amount, but enough that over the next billion years it's likely to come down.

[jack]

I felt uneasy about that without quite realising why

But the internet thinks that the ISS is low enough that it does constantly experience a low level of air resistance. So the plane would presumably fall for the same reason, but not because of the throw.

4.

[emperor]

Have you encountered Apocalyptica?

Re: 4.

[andrewducker]

I've seen them live! They were awesome.

[wildeabandon]

I have slightly mixed feelings about "Let Kids Be Loud" - it seems to me that there's some competing access needs going on. I agree that play is important and often inherently loud and there need to be (easily accessible) spaces for children to play. But I also find noise pretty unpleasant (although contra what the article says, I find adult generated noise at least as bad, often worse, because it comes with a side of feeling that they ought to know better).

I don't think that wanting there to be (easily accessible) spaces where quiet is the norm is unreasonably, even though such spaces will exclude some people. There are obviously discussions to be had about what the norms should be in different spaces, and in particular how that plays out in residential spaces where people are living in close proximity, where there will inevitably need to be compromise. But it makes it harder to have those discussions when the tone (more, admittedly from the comments than the original post, but a bit there too) seems to be that even a desire for space which is mostly silent makes me a joyless, out-of-touch, old grouch. (Though I acknowledge that at least some of that tone is probably in response to people who have expressed that desire in joyless, out of touch, grouchy ways).

[andrewducker]

I agree.

I think that there's a big difference between "Children talking excitedly on the bus" and "People playig music loudly on the bus". And a big difference between "Children talking excitedly in a restaurant" and "Children having screaming competitions in a restaurant, while running in circles."