Are we safe from a rain of satellites or as they permanently fixed forever in Earth’s orbit. Will their velocities not slow with time due to minute particles of dust?
At some point they will crash to Earth if not whisked away by a passing large mass.
Since the OP did not specify artificial satellites, it is worth noting that the moon is actually receding from the earth.
You might be interested in the NASA Orbital Debris Program FAQ:
Nothing is permanent. Do you mean “Will they stay in orbit until the sun goes nova?”
Short answer: Lower earth orbit satellites do fall down after some time and burn up in the atmosphere. Satellites above a certain altitude (including geostationary ones) will stay there pretty much permanently.
Were you around in 1979? Read the “Abandonment and reentry” section.
Our sun cannot go nova, it’s too small. It will expand and consume the earth, but that isn’t the same as a nova.
Great Story!
I was shingling a garage roof that day. Everyone was looking up because we knew Skylab was coming down but noone was sure where. My brother and I heard that debris was falling in Windsor, Ontario which is near our home. We were blown away. What are the chances?
Later we found out the debris was from two planes colliding.
Even those will eventually decay. The key word there is eventually, since it will take a very long time for a geostationary satellite to decay. Figure thousands of years or more, though.
OT: What is the oldest satellite (man-made) that is still in use today? And, umm, what is it used for?
Vanguard 1 is the oldest (51 years) piece still up there. It has an estimated orbital lifetime of 240 years. While it’s long dead, it can still be tracked by radar and is useful for long term data on orbital decay and the outer atmosphere.
IIRC NASA purposely put up a satellite that was nothing more than a small, dense retro reflector.
Small, dense, in a high orbit, its gonna be up there a LONG time, though I forget how long.
Think more like trillions. The Sun will engulf the Earth long before it happens.
Those wanting to know why the moon’s orbit gets slightly larger each year can go here:
http://www.astronomy.ohio-state.edu/~pogge/Ast161/Unit4/tides.html
Interesting stuff.