Why can small masses do damage in space?

09 December 2007

Question

I saw an astronaut on the shuttle lifting a piece of very heavy equipment with one hand, but they said he had to put it down very slowly, as it could still do a lot of damage. I don’t understand how that could be!

Answer

There are two concepts involved here, which are very often confused. One of them is weight, which is how heavy things feel, and the other is mass. Mass can be considered as being how hard it is to accelerate or stop things. It just happens that the bigger the mass, the heavier the weight, i.e. the amount they are attracted to the Earth; this is because weight is a product of the mass and the strength of gravity.In orbit, you take away the weight but the mass is still there. This means that if you try to start it moving, or stop it moving, it's very difficult. So if you were to throw a hammer at someone on the shuttle, although it's weightless it will still have mass and inertia, and so it will still hurt when it hits!

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