If the earth (NOT including buildings, people etc, just the crust/magma/core) stopped spinning for one second, what would be the immediately noticeable effects? (Assume that it started and stopped very quickly, within ~0.1 seconds.)

Assume this was done by an incredibly powerful magician, ignorant of the effects of such magic, who wanted to test his powers. (It's part of a story I'm working on.)

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    $\begingroup$ globalized earthquake $\endgroup$ – ratchet freak Apr 4 '16 at 11:22
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    $\begingroup$ "I felt a great disturbance in the Force, as if millions of voices suddenly cried out in terror, and were suddenly silenced. I fear something terrible has happened." $\endgroup$ – Cyrus Apr 4 '16 at 11:52
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    $\begingroup$ The same thing that would happen to you if your car — but not you — stopped instantly for 0.1 seconds... while you are riding at about 1000 mph, or more than the speed of sound. In other words you would continue forward... rip out the safety belt... be crushed against the wheel, the firewall and the windshield... and then disintegrate in a very messy manner. Your magician would essentially destroy everything on the surface of the planet. $\endgroup$ – MichaelK Apr 4 '16 at 13:09
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    $\begingroup$ I'm voting as too broad because we would easily give you a list of all loose (and not so loose) parts that would fly off, but Michael Karnerfors describes it quite good. Imagine yourself standing 400 meters away from a mountain. Next second you are on the side of the mountain, as the equatorial rotation speed is ~465 m/s. Apply to everything mentioned as exception (also what happens with manmade structures buried? Kind of meteorhits below surface at 465 m/s? Not good! $\endgroup$ – J_F_B_M Apr 4 '16 at 13:24
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    $\begingroup$ @AnonymousShadow I would strongly suggest to choose something else for your magician to test his powers on, or else, your story will be a post-apocalyptic one on an uninhabited desert wasteland. $\endgroup$ – mg30rg Apr 4 '16 at 13:24

The most conspicuous effect would be the instant and very painful death of all the inhabitants of the planet.

You see, the rotational speed of the planet is 465.11 m/s (1674.396 km/h or 1040.421 mph) if it is stopped within the time span of 0.1s the negative acceleration would be 4651.1 m/s² which is somewhere around 465g. Fighter pilots specially trained to bear massive g-forces are capable to handle around 9-12g for a short period of time. Oh, and don't forget, your magician also restarts the rotation, which means a second acceleration with 4651.1 m/s² which is somewhere around 465g, on the opposite direction. So I guess all people (and animals, plants etc.) on the planet would become little spots on the nearest walls.

  • $\begingroup$ only birds in flight would remain untouched but would suddenly find themselves moved 46.5 meters. $\endgroup$ – ratchet freak Apr 4 '16 at 13:24
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    $\begingroup$ @ratchetfreak Since every object - including all oceans suffer the effects of the acceleration - I guess the air would be quite full of debris, mist and such. The coriolis forces would also create massive (supersonic) windstreams, so I guess there would be no luck for the birds too. $\endgroup$ – mg30rg Apr 4 '16 at 13:28
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    $\begingroup$ DM: "I'm going to need everybody to roll a dex save." $\endgroup$ – Liesmith Apr 5 '16 at 7:11
  • $\begingroup$ I don't think you'd experience 465g acceleration. You continue to move at the same speed, together with everything but the crust and core. I read it as if air isn't stopped as well, so if you happen to stand on an open field (500m clearance) the only thing you would notice is that you moved ~465 m on that field (which, due to friction, might prove fatal for your legs). Also people inside a city would survive the first second, but then die because all buildings collapse due to their foundations being 465m westwards. $\endgroup$ – J_F_B_M Apr 5 '16 at 18:38
  • $\begingroup$ I object to the "painful" part. Due to nerve conduction velocity maxing out at 120 m/s, the 465 m/s shockwave from the event would've liquefied all living organisms before they even realized it, starting with our brains smashing into our skulls, from inside. Source: en.wikipedia.org/wiki/Nerve_conduction_velocity $\endgroup$ – Oskuro Jan 3 '17 at 17:33

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