What Would be Different if the Earth Didn't Spin?

I looked at what’d happen if the Earth suddenly stopped spinning in yesterday’s post. Today I’m looking at a more sedentary option… (see the rest at the spin me right round tag)

What if the Earth Didn’t Spin?

With this question I’m thinking about what differences we might notice if the Earth had never spun in the first place. The first thing that springs to mind is the length of our day, which comes directly from how fast the Earth spins*. If the Earth didn’t spin at all our day would last the same length of time as our year does: this might seem counter-intuitive at first so I’ll suggest that for us to have no real day (i.e. it’s always daytime or night time depending on where you are) the Earth would have to spin very slowly to keep the same part of the Earth’s surface facing the Sun at all times.

The weather would be affected too, and not just because the slow turning of the Earth would mean much longer periods of sunshine and darkness. A really important part of our weather systems are Hadley cells, which are a direct result of something called the Coriolis effect. This is atmospheric effect caused by the rotation of a body with an atmosphere, and is affected by its speed of rotation. The detail would be better suited to a post of its own**, but here’s a synopsis: air tends to be heated at the equator, which rises higher and moves towards the poles, where it cools, sinks and moves back towards the equator where the cycle starts again. The whole moving body of air is known as a Hadley cell. The Earth’s rotation produces a shearing force which splits the cell into smaller cells- three in the Northern hemisphere and three in the Southern. The bits where two Hadley cells meet are at the same latitudes that we find the tropics. Indeed, the tropics are there because of  the Hadley cells. If the Earth didn’t rotate we wouldn’t have these weather cells, and our global weather systems would be markedly different.

Another difference would be in the shape of the Earth. Our planet is not perfectly spherical, but an ‘oblate spheroid’. This is the kind of shape you get if you rest your foot on a football: kind of spherical, but flattened at the top and bottom, and bulging out a bit around the middle. This shape is, again, caused by the Earth’s rotation: in the same way that if you spin around your arms are pulled outwards, so the spinning overcomes some of the Earth’s gravitational pull and the Earth bulges a bit. Without spinning, Earth would be more spherical.

For similar reasons, we’d have a different distribution of water around the globe: the Earth’s oceans also bulge out around the middle due to centrifugal ‘force’. Without our spin, we’d also be without the bulge and we’d have shallower seas around the equator, and deeper seas towards the poles. This would also be affected by the differing global geography caused by the redistribution of mass discussed in the previous paragraph.

There’s probably some stuff I haven’t thought of too… feel free to wax about it in the comments!

* It spins at a speed of one revolution per day…
** Ask me if you’re interested!

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