Subsolar point

At this point, the Sun's rays will fall exactly vertical relative to an object on the ground and thus cast no observable shadow.

[2] To an observer on a planet with an orientation and rotation similar to those of Earth, the subsolar point will appear to move westward with a speed of 1600 km/h, completing one circuit around the globe each day, approximately moving along the equator.

However, it will also move north and south between the tropics over the course of a year, so will appear to spiral like a helix.

The subsolar point crosses the Equator on the March and September equinoxes.

The subsolar point moves constantly on the surface of the Earth, but for any given time, its coordinates, or latitude and longitude, can be calculated as follows:[3]

The subsolar point at Honolulu during Lahaina Noon with the range of possible subsolar points shaded in pink – the angle between the Sun and the local horizontal level is exactly 90° at the subsolar point
On this azimuthal equidistant projection centred on Mecca, when the subsolar point is on the Ka'bah, shadows of vertical poles on the sunlit hemisphere point away from it