As Fall is upon us, here in the Pacific Northwest, we are treated with warm and vibrant sunsets. This one occurred on the September Equinox, when the plane of Earth's Equator passes the center of the Sun. At that instant, the tilt of Earth's axis neither inclines away from nor towards the Sun.
The two annual equinoxes are the only times when the subsolar point—the place on Earth's surface where the center of the Sun is exactly overhead—is on the Equator and, conversely, the Sun is at Zenith over the Equator. The subsolar point crosses the equator, moving northward at the March equinox and southward at the September equinox.