Credit: The Telegraph (UK)
Human junk has been accumulating around the Earth, almost from the time of the first space launch. At the moment, the oldest known object is the, now derelict, Vanguard 1, launched in 1958. Approximately 19,000 objects larger than 5 cm are being tracked.
Large infrographic, courtesy of World Science Festival at: http://www.worldsciencefestival.com/2014/06/space-junk-infographic/
Is this a problem? Yes. Humanity has a large & growing investment in satellites for purposes including astronomy, geology, weather forcasting, environmental studies & communication. Orbital objects move at tens of thousands of kilometeres per hour. I.e. many times the velocity of a bullet. A collision between two pieces of space junk at such velocities can be very expensive.
A further risk is multiple pieces of orbiting debris from such a collision. A chain reaction leading to a growing mass of space junk may occur.
Not all the news is bad: all artificial satellites finally either leave Earth's orbit (many falling into the Sun) or re-enter the Earth's atmosphere. Almost all re-entering satellites burn up without reaching the surface. For some, this will not occur for thousands of years.
Modern, responsible launchers plan for controlled re-entry, both to reduce space junk & for the safety of us below.
Various schemes have been proposed to remove junk from space. Many are impractical. All are expensive & so far, unproven. Some examples: http://www.space.com/24895-space-junk-wild-clean-up-concepts.html
More about space junk:
http://en.wikipedia.org/wiki/Space_debris
http://www.telegraph.co.uk/science/space/8135495/Space-junk-a-risky-game-of-space-invaders.html / humans space program programme garbage buildup rubbish junk trash Earth accumulation junk poses problem future generations orbital debris space junk threats satellite spacecraft International Space Station sidestep dangerous pieces trash satellite launches factor debris timetables spacefaring nations clean up mess ever growing clutter makes launches launch garbage orbit orbiting /
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