[Merry-go-round.](https://www.youtube.com/watch?v=_36MiCUS1ro) Spins at like 5 mph. Ball curves.
Earth. Spins at like 1000 mph. Ball goes straight.
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Because the Earth is so much bigger, meaning that the constant change in velocity caused by moving in a circle is next to completely unnoticeable.
You still can observe it with a pendulum that has a particularly heavy weight on the end, but not with something as simple as a ball lying on the surface of the planet.
The Earth is about 13,000km across. A merry go round a few metres. This means that the ball would have to travel a really long distance for you to notice it on the Earth’s surface.
The merry go round is also rotating once every second or so but the Earth is taking almost 24 hours.
It’s not the speed of travel that matters, it’s the rate that your angle is changing. The Merry-go-round goes all the way around 360 degrees in five seconds or so. The Earth takes 24 hours to do the same. But it’s the difference between the path of the moving object and its angle to the rotating object that causes the effect.
If you increased the size of the merry-go-round but kept the speed the same, the effect would appear diminished because the rate of angular change would have decreased.
Good question. The reason is that Coriolis force depends upon the _angular_ velocity.
Think of this way: In the above video, merry-go round completes 1 revolution in around 5-6 seconds. That’s 360°/6 = 60° per second of angular velocity.
Compare that to the Earth: Even though it’s rotating at 460 m/s, it takes ~24 hours to complete one revolution. That’s 360°/(24x60x60)= 0.0041° per second, _much_ slower than a merry-go round.
Earth spins at ~~1,000 mph~~ 0.000694 rpm.
The coriolis effect happens because the ‘ground’ rotates a lot by the time the projectile reaches the other end.
If you rolled a ball all the way from the north pole towards the south pole, it would be different, but the Earth is actually rotating quite slowly. The effects of this rotation are, as such, pretty small.
Its about proportions. A ball can traverse the merry go round in seconds while the merry go round does 1/4 of a turn in that second. That’s a lot of variation of angles.
On earth you experience coriolis effect all the time but it’s too small to be noticeable. But if you move on the planet fast enough to matter, like 1000kmh, then it starts to be a noticeable factor. For example in ww1 and ww2 naval combat they were shooting projectiles at 3000 km/h at distances of 20 km, and they had to plot the compass angle in the firing computer, cause firing north or south or west or was would give massive deviations, at 20km of distance.
Same for inertial navigation on planes, the plane records its own movements, and it should know where it is, but the actual inertial calculation gives you a wrong result because of coriolis and the earth rotation. The computers on board will run a calculation to compensate for those effects and give the pilot a correct answer.
(Inertial mia ovation is like if you are blindfold and walk in your room, you know where you are because your ear records your acceleration, then you brain guesses where you may have ended up, the plane just does it a million times more accurately)
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