If Earth stopped rotating, what would happen?

How would the atmosphere be affected...
20 September 2022


The Earth see from space, with the Sun just beginning to emerge from behind it



What would happen to our atmosphere if the Earth suddenly stopped rotating?


Peter Haynes answered this question...

Peter - Well, yeah, there are mass equations for almost anything interesting. I mean, actually, this is interesting. So there are many ways to answer this question. If the earth suddenly stopped rotating, a whole bunch of things would probably sort of fly off. In some ways, it's almost more interesting to think about if it slowly stopped rotating, but I may be misinterpreting the question because there are planets that don't rotate. If I go to this topic of exo-planets, which I don't know very much about, but is very interesting. That many of the exo-planets that have been detected are what's called "locked". They're tidally locked. So the same side of the planet is facing the star. There's obviously very extreme difference between the sunny side, so to speak, and the not so sunny side —and one effect of the earth stopping rotating would be that the days would become much longer.

Chris - Well that is sort of happening, isn't it? Because Earth's rotation is slowing down indeed, because we are losing some energy to the moon. Cause there was that story earlier this year saying it's been slowing down and we have to keep adding the odd second here and there to keep track of time. But then suddenly it's speeded up again. And we actually covered the fact that the earth was about a millisecond per day, less long than it should have been in July.

Peter - There's a whole bunch of interesting things there. Which, actually another thing that effects on short time scales - another thing that affects the rotation rate of the Earth is actually the weather patterns because there's this thing called angular momentum: the amount of spin. And you can exchange angular momentum between the atmosphere and the Earth. So fluctuations on short time scales can be a result of that. If in an atmosphere that wasn't rotating, another answer would be that actually somehow, is the tropics would sort of expand, right? Which isn't to say that everything would become warmer, but we'd sort of have tropical weather over a much broader proportion of the Earth's surface. Because the rotation of the Earth is very important in determining how weather systems work. And if you go to the tropics, then actually it turns out the rotation isn't so important. So, the tropics would expand if the Earth stopped rotating.

Kathryn Harkup - So can I ask in true Bond villain fashion... Will global warming, if I could speed it up, will that also speed up the rotation of the earth as we get more violent weather systems going on?

Peter - I think these are more fluctuations than systematic effects.

Kathryn Harkup - Damn, I almost had plot the of the next film.

Peter - Yeah. You could imagine dangerous variability in the rotation of the Earth. Is it slowing down? Is it speeding up? But I mean, that's stretching things a bit far, but hey, if the people writing this Bond movie wants some new science.

Kathryn Harkup - If the Broccolis are listening, I thought of it first!

Chris - Your name will go on the credits, Kathryn.


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