How come the world spins when we don’t spin?
Luci Murray from Stockton on Tees (Aged 5-14)
Why does the world spin around?
Megan Cannell from Buckinghamshire (Age: 5-14)
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Filed under: age 5-14, Answered Big Questions, Peter Naish's Big Answers, Physics Big Questions, Planetary Science Big Questions |
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Hi Luci and Megan,
I’m a psychologist, not a cosmologist, but you deserve an answer, so I’ll do my best.
The Earth was formed out of a cloud of dust and gas that gradually collected together into a bigger and bigger lump. Why did the bits join together? Because of the force of gravity – everything attracts everything else. How strong the attraction is depends on how big the objects are – the Earth is large so the gravity is enough to keep us stuck to it. It also makes rain fall to Earth and even the water run down out of the bath.
You must have seen that the water running from the bath always spins round, like a whirlpool. Which way it spins depends on any slight movement the water has before it starts to run out, but it’s impossible for it to flow away without spinning – the nearer it gets to the hole the faster it goes.
When the bits that made the Earth started to fall in towards the growing lump in the middle they behaved just like the water, gradually speeding up as they spiralled in to the centre. As each one landed it gave the new Earth another nudge in the same direction – just as a mat starts to slide under your feet if you take a running jump on to it. So, we have ended up with a spinning Earth, and everything else that has formed like that does the same – the Sun, Moon, the rest of the planets.
Hope that helps.
Peter