What would happen if an aspiring villain, a scientist who’s a little too old and deaf, and a group of clumsy and spiteful assistants ventured into the construction of rockets and anti-gravitational weapons? You can find out in Despicable Me, Universal Pictures’ 3D animated feature coming out in cinemas on 15 October. In the film, our odd heroes struggle with the Moon, its mass, and the force of gravity.
So let’s just have a little talk about these key concepts in order to understand better what happens in the film. Have you ever seen a fruit or object falling from a tree? And have you ever tried to throw a stone and watch it fall? This force that ‘brings down’ things is called the force of gravity.
We are constantly attracted to the Earth by its gravitational force , That is the reason why we always keep our feet on the ground. We don’t need to be in direct contact with Earth to be attracted by it however; not being too far away is just enough for the same forces to act. This is why our own planet orbits around the Sun, and the Moon orbits around the Earth.
A força gravitacional é determinada pela massa de um objeto. A força gravitacional entre dois objetos é proporcional à massa desses objetos e diminui muito rapidamente no momento em que os separamos. Na verdade, também atraímos objetos com a ‘nossa’ força gravitacional, mas somos demasiado leves para perceber os efeitos! O Sol, no entanto, é tão grande que consegue manter-nos próximos mesmo estando tão longe. A Lua também exerce a sua força gravitacional; como é mais pequena e mais leve do que a Terra, se pudéssemos pesar-nos nela, descobriríamos que pesamos cerca de um sexto do nosso peso na Terra.
Poder-se-ia perguntar por que razão a Lua não cai na Terra como uma maçã da árvore. A razão é que a Lua nunca fica parada. Está constantemente a mover-se à nossa volta. Sem a força da gravidade da Terra, ela simplesmente flutuaria para o espaço. Esta combinação de velocidade e distância da Terra permite que a Lua se mantenha sempre em equilíbrio entre a queda e a fuga. Se fosse mais rápida, escaparia; se fosse mais lenta, cairia!
We said the force of gravity depends on distance too. If we were to distance ourselves enough, we could escape its hold. That’s what we try to do with spacecraft. We need to reach and exceed the so-called ‘escape velocity’, that is about 11.2 km/s (at such velocity, we would be able to move from London to New York in just ten minutes!). Once a shuttle reaches this velocity, it is free to travel in the Solar System.
Inside an orbiting shuttle we do not feel the gravitational force of the Earth. Objects don’t fall, they float; if you jump up, you don’t come back down. A similar thing also happens to astronauts when they are in space stations orbiting the Earth.
In Despicable Me you will see rockets flying and the effects of gravity on the Moon. Gru has a group of assistants called Minions who will help him in his quest to steal the Moon and become the most famous villain in the world. We hope you enjoy the film!
