[bearnard1212 (OP)]

A chance for profits, recycling satellites. Lot's and lot's of rare earth in them I guess. But mostly they burn up. You could make it a International law that once they've done 'their thing', they still should be able to push themselves to earth to burn. But with the new types of micro satellite's miniaturized to a extreme degree we might not even notice them.  Well, maybe? The problem relates to the scale of them, doesn't it?

That is a good point. They should be able to push themselves to earth to burn. And that is a good idea that can be used for futher usage of sats and microsats that don`t have large term of longevity. But space junk it`s not just used sats, There are a lot of fragments and parts from rockets and space shuttles.

[charles1948]

If you go out on a dark, clear, night, and look up at the sky, sooner or later you'll see a "meteor".  In the form of a thin streak of white light, briefly passing downwards through the sky.

These meteors have been observed since ancient times. The explanation for them, in ancient times, was that they were a purely terrestrial atmospheric phenomenon.  Like a kind of weak form of lightning.

The true explanation didn't emerge until the 19th century.  When they were recognised as particles of extra-terrestrial matter, plunging into the Earth's atmosphere.  Getting heated up by atmospheric friction, which made the particles become incandescent.  And so become visible as meteors. The particles were usually very small. Like grains of sand.

All this is well-known and obvious.

 The question I'd like to ask is this:  Why don't we see our modern skies streaked with showers of meteors caused by thousands of tiny particles from our decaying satellites and rockets?

[Bored chemist]

The question I'd like to ask is this:  Why don't we see our modern skies streaked with showers of meteors caused by thousands of tiny particles from our decaying satellites and rockets?

Partly because they are

tiny

But also because there aren't many of them.

[charles1948]

I admire BC's sophistry in not answering the question

[alancalverd]

And also because most of the space junk is in orbit around the earth, unlike the classic meteor showers which orbit the sun.

[Bored chemist]

I admire BC's sophistry in not answering the question

Is there something wrong with your computer or whatever?

Here's the answer I gave

The question I'd like to ask is this:  Why don't we see our modern skies streaked with showers of meteors caused by thousands of tiny particles from our decaying satellites and rockets?

Partly because they are

tiny

But also because there aren't many of them.

Can you see it?

[charles1948]

And also because most of the space junk is in orbit around the earth, unlike the classic meteor showers which orbit the sun.

And that I think is the answer, alan.  Most of our space junk comes from stuff in low Earth orbit.  So when this  weak LEO stuff decays from orbit, it isn't travelling fast enough to get really incandescent..  Not like classic solar-orbiting meteors, which hit our atmosphere at huge velocities, and burn up in a spectacular light-show..

How come you knew the answer, and BC didn't?

[Bored chemist]

it isn't travelling fast enough to get really incandescent.. 

Orbital speed for low Earth orbit is about 8 km/s
So, for example a 1 Kg lump of aluminium would carry 32 MJ of energy
The specific heat capacity of aluminium is about 0.9 J/g/K
So 1Kg heats up by about 1.1 K for each KJ of energy you add to it.
And with 32000 KJ of energy, (if nothing else happened) it would reach about 29000K

Roughly 5 times hotter than the surface of the Sun.

How come you knew the answer, and BC didn't?

Because it's the wrong answer.

[alancalverd]

It's the right answer. Meteors are not in earth orbit. space junk mostly is. Now and again a bit falls to earth but, far from "nothing else",  stuff happens en route, like low-temperature ablation because the orbit decays gradually whereas meteors plunge into the atmosphere in travel in pretty much a straight line and convert their kinetic energy to heat very quickly.

[Bored chemist]

The idea that 8 km/s isn't fast enough to induce incandescence is wrong.
The issue is that it's in the wrong direction.

The other big problem is that there aren't many of them.
Sure, there's a catalogue with 128 million entries, but most of them have been there for a while and will be there for decades or centuries, so the number that fall in a given year is small.


And, of course, small things are more affected by the thin "atmosphere" up there but, as you say, they are gradually brought to a halt, so the effect isn't spectacular.

Only the big bits could hope to give us a firework display, and those are rare.
But we do see them sometimes
https://futurism.com/the-byte/footage-nasa-satellite-burning-up-reentry#:~:text=A%20NASA%20satellite%20that%20launched,spotters%2C%20as%20reported%20by%20CNET.
So the the answer to this question

The question I'd like to ask is this:  Why don't we see our modern skies streaked with showers of meteors caused by thousands of tiny particles from our decaying satellites and rockets?

Is that we do see them.

[alancalverd]

The idea that 8 km/s isn't fast enough to induce incandescence is wrong.

Which is why nobody suggested it.

small things are more affected by the thin "atmosphere" up there

Depends on the density of the thing. A steel bolt has loads of kinetic energy and very little drag, whereas a spent first rocket stage is huge (lots of aerodynamic drag) and relatively light, so quickly slowed down and deorbited by the wispy fringe of the atmosphere.

[bearnard1212 (OP)]

The idea that 8 km/s isn't fast enough to induce incandescence is wrong.

Which is why nobody suggested it.

small things are more affected by the thin "atmosphere" up there

Depends on the density of the thing. A steel bolt has loads of kinetic energy and very little drag, whereas a spent first rocket stage is huge (lots of aerodynamic drag) and relatively light, so quickly slowed down and deorbited by the wispy fringe of the atmosphere.

The density of the space junk is very high, so that is why space companies are afraid of their space crafts can be damaged by these space junk on the Earth's orbit

[alancalverd]

I think the main problem is tracking the small, high density bits. Rocket casings and suchlike will have a big radar profile and one of Buzz Aldrin's gloves (if it hasn't burned up yet) won't do a lot of damage, but a 2 x 1/4 (note the US dimensions) nut and bolt travelling at 8 km/s has 5 times the kinetic energy of a rifle bullet.

[Bored chemist]

Which is why nobody suggested it.

It seems a little harsh to call Charles a nobody.

So when this  weak LEO stuff decays from orbit, it isn't travelling fast enough to get really incandescent

Quote
small things are more affected by the thin "atmosphere" up there
Depends on the density of the thing. A steel bolt has loads of kinetic energy and very little drag,

Would a small bolt be affected more than a big bolt... you know... like I said?

[alancalverd]

As with most aerodynamics, it's all about form factors. A small bolt will have a larger surface to mass ratio than a large bolt of the same general design, so will ablate more rapidly in the upper atmosphere, and a deorbiting cargo door (a friend had one fly open on his 757 freighter recently, and the DC10 was wont to shed the shed from time to time) may either burn up or float relatively gently to earth depending on its initial angle of attack, whereas most of a large bolt may survive the trip and impact at very high speed, like a  metallic meteorite.