Even though the moon moves around the Earth, this Sun-moon distance doesn't significantly change. If I use this gravity model, I can calculate the force per unit mass for an object in the location ...

Learn the differences between our Earth, the Sun and the Moon. Then explore how together they create day and night and our different seasons with their orbits.

Let's say we want to build a model of the sun and Earth alone. Earth has a radius of about 6,371 kilometers (3,959 miles), but let's represent this with a marble 1 centimeter in diameter.

The sun, moon and Earth will line up in a rare celestial event Monday that, from coast to coast, will turn day to night. The total solar eclipse will be the first in the United States in nearly a ...