The antagonist of the film Gravity is a wave of shrapnel which circles the earth every 90 minutes. The result of a "controlled destruction" of a defunct Russian Satellite (what is this, the cold war?!) the crew of the Explorer shuttle and the ISS are threatened by this because it matches their altitude, and is traveling at a much greater velocity.
The Hubble telescope is listed as being at an standard altitude of approximately 559 km, way above the Kármán line (the boundary of the earth's 'atmosphere' and the altitude at which foreign objects experience atmospheric effects in the way of friction/heat).
Towards the end of Gravity, Mission Specialist Ryan Stone (Sandra Bullock) manages to navigate her way to Tiangong, the Chinese space-station which has been affected by the same shrapnel wave and knocked off it's orbit, back towards earth.
The debris storm has its own musical motif, which begins to play: and Stone realises that as another 90 minutes have passed, the storm has re-orbited and is on its way back...
As Stone struggles to get inside the escape capsule, now entering earths atmosphere Pieces of satellite debris begin to strike the vessel, punching dents into the side of it.
If the satellite debris was orbiting at 559km, and yet the Tiangong is crossing the Kármán line at 100km, why would the debris have descended over 400km down?
Stone had to utilise a launcher pod to bring herself down to this altitude, so there obviously isn't enough gravitational pull to de-orbit the wrecked ISS, let alone the tiny pieces of shrapnel travelling at a much greater velocity...
The film is very, very good and a lot of extensive research has obviously gone into it, so I'm reluctant to say this is a goof... more likely either its:
A: Accurate according to some laws of physics im totally unaware of,
B: I've missed some major plot point where this is explained.
As it stands it's incredibly confusing. I know NASA spoke of a 'chain reaction' of satellites crashing into each other, but surely not at a girth of 400KM?
I know it might not go down to well, but can we limit answers to people that have seen the film; although I've done my best to try and explain the problem, there will likely be answers that will start with "I've not seen the film, but..." and end with an explanation that would immediately be ruled out by those who have seen the very specific scenario the film depicts