Does the Earth’s Rotation On its Axis Slow Down Because of Friction With the Atmosphere?

Yes, sometimes, but it is not a simple slowing because of friction with a stationary air mass.

The effect of the atmosphere on the rotation came about because of the way the sun’s heat and the absence of it alternate to stir up the atmosphere.

The resulting wind patterns sometimes speed up the earth and sometimes retard it.

However, many other factors influence the earth’s speed of rotation far more than the negligible effects of air friction.

For example, there is some wobble related to the shifting of internal masses.

A very big influence, geologically speaking, comes from the fact that the pull of the moon in its orbit and that of the sloshing tides on earth affect each other in turn.

The net outcome of the alternate braking and acceleration is that the moon is gradually retreating from the earth, climbing to a higher and higher orbit and moving faster.

As a result, you lose a bit of the angular momentum from the earth, which is transferred to the moon, so the earth goes slower.

It would take a long time to notice even this big effect, as it amounts to days in a hundred million years.

However, it has left its mark.

Corals from the Devonian period show daily and monthly growth rings.

They precipitated calcium carbonate as they formed their skeletons. And we can see that at that period, a month had fewer days.