About 76km (~47 miles).
How big are golf ball dimples?
In order to determine how deep earth size golf ball dimples would be, we have to first look at the actual average diameter and dimple depth of a golf ball which are roughly 42.67 mm and 0.254mm respectively.
How big is the earth?
The earth is not a perfect sphere, so we’ll use the average diameter of 12,742 km.
So, how big would those dimples be?
The depth of a dimple is 0.59% of the ball’s diameter (0.254/42.67). Apply that percentage to the diameter of the earth, we get just under 76km (12742 x 0.59%).
The deepest part of the ocean – the Mariana Trench – is only 11.03 km deep. This means that a golf dimple would be 7 times as deep as the deepest point in the ocean.