What causes global winds to appear to turn instead of blow straight across the earths surface?

The truth is ... and I hope you can handle this ... they not only appear to turn.

They actually do turn !

-- The circumference of the Earth all the way around the equator is almost 25,000 miles.

-- The circumference of the Earth all the way around the north pole is zero.

-- The circumference of the Earth half way in between the equator and the north pole,

at 45 degrees north latitude, is about 17,600 miles.

-- The farther north you go from the equator, the smaller a circle around the Earth is.

-- But the Earth is a solid rock. The whole thing rotates once a day, all in one piece.

-- So the closer you are to the equator, the faster the ground is moving, because

it has farther to go to finish a whole rotation once a day.

I assume that you're sitting in the US, or the UK, or Europe, or India right now.

-- The ground under you, the air around you, and your feet, your head, and the

ball in your hand, are all traveling at the same speed. Whatever it is, it's the

speed necessary to finish a whole rotation once a day at your latitude.

Now, if you will, kindly throw the ball for me.

Thank you.

-- If you throw it north, to a place where the Earth is slightly smaller, then the

ball is moving faster than it needs to in order to finish a rotation once a day. It's

moving faster than the things around it up there, and it gets slightly ahead of

them.

-- If you throw it south, to a place where the Earth is slightly larger, then the

ball is moving slower than it needs to in order to finish a rotation once a day.

It's moving slower than the things around it down there, and it lags slightly

behind them.

-- If somebody is watching the ball and draws its path on a map, the path of the ball

is curved on the map.

-- When a patch of air warms and rises, air from all around must flow into the

empty space. Any air that tries to flow north or south into the hole follows a

curved path on the map.

-- When a patch of air cools and sinks, some of it must get out of the way,

flowing out of the center to places all around. Any air that tries to get out of the

way by flowing north or south follows a curved path on the map.

-- Similarly, a gunshot aimed accurately at a target north or south of it

strikes to the left or right of the target.

-- For the same reason ... see if you can follow through this one on your own ...

a rock dropped down the center of a deep, deep well, must hit the side of the

well after falling for a while !