I understand that the earth is constantly spinning. But why can’t we feel it?
In: Physics
Because we are moving the same speed as the earth, and the atmosphere near the ground is also essentially moving the same speed as the earth. Relative to our body nothing is moving, and any centrifugal force is offset by a much larger gravitational force.
This is a very simple explanation but we only feel the forces from acceleration and deceleration. The earth is spinning but it’s not accelerating so we don’t feel it.
Sorry it’s been a long time since I took physics
Because it takes one whole day just to make one circle, which, when you think about it, is so damn slow you wouldn’t even notice expect for the sun and stars appearing to move in the sky.
I’m going to go with the fun explanation of… YOU CAN!!!!
It’s very very minor, and is essentially pulling you directly upwards against gravity if you’re at the equator. Or a bit more sideways if you’re at a northern or southern latitude. Imagine one of those fair rides that spins, and pins you against a wall. It tries to throw you straight outwards.
In everyday life you won’t really notice it because gravity is so much stronger than the centrifugal force of the earths spin. But in some sports like pole vaulting it can actually make a difference https://xkcd.com/852/ .
Earth spins only once a day. That’s extremely slow and therefor we can’t feel it. If you stood on a merry-go-round that spinned with one rotation per day you wouldn’t feel it either.
The rate at which the Earth rotates is *half* as fast as the hour hand on a clock. That is about 0.0007 rpm.
The Earth is also traveling through space at over 60,000 mph. We don’t feel that either.
Just like when you are on an airplane, you do not feel that you are traveling at 600 mph. That is because you, the airplane, all the air inside the airplane, the drink on your tray table – everything is also moving at 600 mph.
When you get out of your seat to walk to the bathroom at the front of the plane you are moving at about 602 mph. But it doesn’t feel like you are walking that fast, it feels like normal walking.
You do feel it you just don’t notice it
You are *slightly* lighter at the equator than you are at the poles, very very slightly (~0.35%). For a 180 pound person that means you weigh in at just 179.37 pounds but you’ll probably have drunk some water that pushes you back up to that 180 pound figure.
Rotation is absolute so its not that you’re moving at a constant speed which causes you not to notice it, its that gravity is sooo much stronger than all of the other forces and accelerations in play that you can’t separate the others from the gravity.
Mainly because we haven’t drunk enough. But, apart from that… we are stationary with respect to the Earth’s gravity, that’s why. When you spin round on, say a fairground ride, you feel the spinning because you are moving in the Earth’s gravitational field, but just standing on teh ground you are not.
Imaging you are standing on a disk that spins once every 24 hours. It would be pretty hard to notice without your eyes. Now the radius of earth is large, so most of that rotational motion feels translational at our scale. Think of standing in an airplane that flies in a straight line. It goes very fast, and follows the curve of the earth (so technically it’s also “spinning”) but you don’t really feel that motion.
The centripetal force from the rotation is on one location constant in size and direction. The centripetal force will act in combination with a gravity that is constant for a location. So the net effect is just a slight change in the strength and direction of gravity.
The force is zero on the pole and strongest on the equator. If you calculate it you will find that it is 0.3% of the gravity on the equator.
The centripetal force has an effect on eath. It is a bit if you press on the top and bottom of a ball. The result is a difference in radius of 20 km between the pole and equator.
The net result is that the centripetal force from rotation and the radius difference it creates result in a 0.5% difference in gravity between the poles and equator.
The difference is so low you do not notice it if you take a trip between the poles and equator, perhaps you could notice it if you were teleported but we can’t do that. It is like how you do not feel that you weigh more after you drink a glass of water.
You can measure the difference and cheap scales are enough to measure it.
The good instruments can measure the difference in very accurate ways. The even detect if there is dense ore in the ground below you and the change in gravity if you go up a mountain
So you could perhaps feel the centripetal force if there was no gravity but we have gravity so the result is just a small change in it.
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