> Correct me if I'm wrong, but aren't LEO satellites only going to reflect light from the sun when they're at low angles near sunrise and sunset? For night time stargazing, they're going to be in Earth's shadow, too.

Iridium's LEO satellites were sometimes (impressively) visible after midnight.

With the difference that cars can steer and stop to avoid collisions and aren't necessarily in your field of view every time you look at the night sky ;)

I have no idea if the number is actually a lot shrug but it's surely different than cars on a planet's surface

It is already impossible - all the remaining Space Shuttles are in a museum, not to mention all Space Shuttle missions were (and were always intended to be) to Earth orbit. No Space Shuttle ever went past 600 km hight Earth orbit.

These satellites are low Earth orbit (LEO)

They're extremely sparse. Imagine putting 12,000 satellites randomly over the surface of the Earth. You're just not going to bump into one, statistically. Now expand that into 3D space in an orbital zone above us.

It's not a collision risk.

> wonder if there's a limit to space junk beyond which leaving the Earth in a space shuttle becomes impossible

There is. We don't have the industrial capacity, as a species, to do it.

> How many causes Kessler syndrome?

Space is huge. Try this trick: the number of satellites in orbit is about the same as the number of planes in the air at any time. (~12,000 [1].)

The volume of space from the ground to 50,000 feet is about 200x smaller than the volume from the Karman line to the top of LEO alone (~2,000 km).

Put another way, we approach the density of planes in the sky in LEO when there are milliions of satellites in that space alone. Picture what happens if every plane in the sky fell to the ground. Now understand that the same thing happening in LEO, while it occurs at higher energy, also occurs in less-occupied space and will eventually (mostly) burn up in the atmosphere.

Put another way, you could poof every Starlink simultaneously and while it would be tremendously annoying, most satellites orbiting lower would be able to get out of the way, those that couldn't wouldn't cause much more damage, the whole mess would be avoidable for most and entirely gone within a few years.

There are serious problems with space pollution. Catastrophic Kessler cascades that block humans from space, or knock out all of our satellites, aren't one of them.

[1] https://www.travelandleisure.com/airlines-airports/number-of...

At the altitudes these mega-constellations operate at, kessler syndrome is not a real threat. Even if left unpowered, everything there will naturally re-enter the atmosphere in ~5 years.