Ants(or immortals?)

[Alej]

Why is it if you drop an ant from a high hight it doesnt even hurt it? Could an ant dropped from a mile up in the sky survive the fall? Why!!!

[New Forester]

It's all to do with surface area. Ants are so small that they have a large surface area compared with their volume (and therefore mass). When they fall, like anything else they churn through the air -- but with such a tiny weight behind them, the air is able to slow them right down. Any object falling through a viscous fluid (in this case air) accelerates against resistance. As it goes faster, the resistance increases -- but the weight pushing it down remains the same. Eventually the resistance balances the weight, and the object reaches a stable speed, the "terminal velocity". What the terminal velocity is, depends upon the shape, air viscosity, the density and many other things -- but most of all, the overall surface area, compared with its weight. You can easily calculate how this changes with size: A 1 cm cube with the density of water weighs 1 gramme. It has a surface area of 6 square centimetres. A 1 metre cube of the same material weighs one tonne, and has a surface area of 6 square metres. 6 square cm is 10,000 times less than 6 square metres -- but 1 gramme is a million times less than a tonne. This means that the smaller cube has 100 times as much surface for its mass, and so 100 times more air resistance when falling. A very small mote of dust (even of something dense such as lead) has such a high relative surface area that it will float about almost for ever, falling slower than the tiniest draught can push it up again. A large thing like a human will accelerate to over a hundred miles an hour, and so hit the ground rather hard. A mouse would fall slow enough so it would stagger a bit, but be uninjured. An ant would probably hardly notice hitting the ground, any more than you notice the impact when you sit on a chair.

[Alej]

Thanks for contributing, you gave a fantastic answer new forester, clear and detailed

[New Forester]

Thank you Alej. Ansteyg: "One small drop onto a hard surface for an ant...?" In fact you could show falling without air perfectly well on Earth, by pumping the air out of a vertical pipe. Feathers, ants, elephants, lead piping (-in-the-library-by-Colonel-Mustard...?), all would hit the ground at the same speed. There is another effect though, which I glossed over before. Smaller animals are built much tougher in proportion, so you'd have to fire an ant much faster at a wall to hurt it.

[TommyC]

...but please don't try that at home....!! :o)