Do they need to re-enter? Could they not be directed out into the void?

That would require lots of energy to escape the planets pull vs just waiting until gravity does its thing.

Thanks for the explanation!

what sort of components are the Sat's made up of? Are we all happy with the idea of "burning up" wont have long term issues with not completely "burnt up" parts floating around the sky and eventually being breathed/drank/eaten in the biosphere?

Try to ask this in a non-hyperbolic way, I dont want to sound alarmist and I'm no "chem trail" loon. but "Burning up" doesn't just make it magically go away.

Any parts that didn't completely burn up (of which, again, there shouldn't be be any) would not float, they would fall. But it's a good question if the burned up mass would have any bad effects. My intuition is that the amount of mass is so miniscule in comparison to the whole atmosphere that it really doesn't make a difference what the satellites are made of as long as it's not radioactive. But I haven't done any math about it.

in a short term view yes i agree, but its more than just starlink (we have all sorts of sat's made of highly refined materials falling from the sky), and its over years... decades even.

I haven't seen articles on this, so either its being ignored or it's not an issue. :-/

I hope its the later.

I strongly suspect it's the latter - since "Every day, Earth is bombarded with more than 100 tons of dust and sand-sized particles." [1] and the satellites burning up aren't going to approach that mass simply due to launch costs.

[1] https://www.nasa.gov/mission_pages/asteroids/overview/fastfa...

the difference for me is that the stuff that we put up there is highly refined materials. not just a load of unrefined rock dust.

I wonder what the stats of Uranium/Plutonium we let "burn up" in the biosphere is compared to stuff we get while cruising through space is...

There is no uranium or plutonium in these satellites, nor anything else radioactive. On the other hand, according to [1] the abundances on this page multiplied by [2] 40000 tons per year, the stuff naturally hitting the atmosphere each year includes 0.3 kg uranium, 1.6 kg thorium, 3 kg radioactive isotopes of potassium, 10 kg mercury, 18 kg cadmium, 50 kg lead, 72 kg arsenic, and 120 tons of chromium, among other things. This stuff burns up in the atmosphere all day long, and has for billions of years.

[1] https://periodictable.com/Properties/A/MeteoriteAbundance.v.... [2]https://link.springer.com/chapter/10.1007%2F978-1-4419-8694-...

Well Starlink will be the majority of all satellites pretty soon, so it really only matters for Starlink for the foreseeable future, if it matters at all.