As the earth moves around the sun, different constellations are visible because the sun will be blocking a different portion of the night sky throughout the year. similarly, as the earth moves around the sun, the different hemispheres will have more direct or indirect sunlight due to the earth's tilt. this interactive lets you select dates to get a general idea of the position of the sun in the sky and the differing constellations that are visible. the dates listed are either identical to or very close to the true dates of the summer or winter solstice and the spring or fall equinox. using the position of the sun in the sky on the given dates (june 21, december 21, march 21, and september 21). define the terms equinox and solstice.