Upside Down is the frustration of a film that comes with a science-fiction premise that is absurd two planets live in conjunction almost touching where people on either world are oriented either up or down depending on the influence of their native gravity that also ends up being a surprisingly well made and imaginative film. It is worth examining what gravity is and how this relates to its depiction in Upside Down. Gravity is something that is created by an astral body (like a planet or a moon, even a sun) that causes objects to be drawn down towards it the greater the mass a body has, the more gravity there is hence why people appear much lighter when walking on The Moon, which has smaller mass than the Earth. There is no absolute up or down in gravity whether you stand at the North or the South Pole of the Earth, for instance, down is always the ground you are standing on and up is always the sky, facing away from the gravity source.
There are vast problems with the application of this in Upside Down. The film seems to assume that every person and even molecule on each world has some magic property of gravity that orients them in a particular direction. In scientific reality, there is a very limited sense in which this would be the case. If The Moon and Earth were brought closer together then two people standing on either world in the directions closest to the other would each be facing in the opposite direction. HOWEVER, if one person travelled from one world to the other, then all that would happen is that they would rotate to face down in the direction of the body of gravity, you wouldnt get them floating around upside down on the ceiling or having to weigh themselves down as you do here. The other big issue in the film is that the two worlds are so close together they are almost touching people being able to pass things to another person on the other world; or buildings, rooms and elevators that have been built between worlds. The problem with this is that planets rotate rather than exist in a single stationary spot. Thats how we have tides that come and go, weather patterns and changing seasons. Moreover, the amount of gravity and pull exerted by a world is massive. If two worlds existed in such close proximity, the combined gravity would have torn either planet apart into a vast asteroid belt well before either had even evolved life. You kind of wish that rather than spending what looks like a good deal of money designing its world, the film had spent a few dollars on hiring someone who could have pointed out matters of scientific realism.
You brain hurts trying to make logical sense of the world and you have to regard Upside Down less as a science-fiction film and more as a fantasy film. On the other hand, you are constantly being amazed at Juan Solanass visuals. Extraordinary images like vistas of city streets where other entire cities hang upside down in the sky in the parallel world; cocktails where the glass is turned upside down and filled with reverse liquid that tries to escape upwards; ballrooms where parties are seen dancing on both the floor and the ceiling; an office building where there are rows and rows of cubicles filled with people on both the floor and ceiling and where objects are passed back and forth between floors; an interview where Jim Sturgess must sit in an elevator chair that rises up from the floor so that he can sit upside down at near-ceiling height to be questioned by boss James Kidnie at his desk; the extraordinary image of Jim Sturgess diving into the water Up Top and kicking off his weights to explode out of the water and into the sky, flying through it to land into the waters of Down Below.
It is a superbly designed world and with some fantastic effects. Like all good science-fiction, even if it is bad science, the film takes a premise and has fun exploring the logical parameters of the world, how people there live and the contortions and logical complications that might ensue. The story itself is a fairly standard one of forbidden romance, which fails to particularly set anything alight, while the film goes out on a frustratingly abrupt and out-of-the-blue last minute happy ending. Not to mention that the film arbitrarily throws in amnesia as a romantic plot device and then equally arbitrarily writes it out again.
Not long after, the same premise of a topsy-turvy world with two different cultures living with reversed gravity and the forbidden romance that occurs between a boy and a girl of either world was conducted, albeit with slightly more scientific rationale, in the anime Patema Inverted (2013).