autumnal equinox

These periods begin and end at the vernal and autumnal equinoxes, the days that are the same length all over the earth.

On the vernal and autumnal equinoxes, the wind turbine's shadow also aligns with the walkways by length.

At the vernal and autumnal equinoxes, the morning and afternoon sun produce the illusion of a serpent along the side of the staircase.

Incised in the bench and paving are arced lines representing shadows on the vernal and autumnal equinoxes.

"At noon on the vernal and autumnal equinoxes, the sun lines up perfectly with the opening," Mr. Tulipane said.

It's Ohigan in Japan right now, the biannual Buddhist holiday that falls on the vernal and autumnal equinoxes.

An amazing thing happens there every year on the vernal and autumnal equinoxes: On the rising and setting of the sun, the corner of the structure casts a shadow shaped like a serpent.

Three arcs inscribed in the semicircular area in front of the bench coincide with its shadow lines at 10 A.M., noon and 2 P.M. at the vernal and autumnal equinoxes.

At noon each year on the days of the vernal and autumnal equinoxes, around March 21 and Sept. 22, the sun on the Equator is directly overhead, so that neither the monument nor visitors cast a shadow.