## Earth

At this scale the Moon is about 30 centimeters away. (The Earth is 13 000 km in diameter and the Moon is 390 000 km away, or about 30 times the diameter of the Earth. Since the Earth at this scale is about 1 cm in diameter, the Moon is about 30 centimeters away.) Since the Sun is about 400 times farther away from Earth than is the Moon, the Sun would be about 120 meters away and about one meter in diameter. The Earth moves across this square in one hour while it rotates counterclockwise on its axis just 15 degrees. The Earth travels around the Sun at a zippy 30 km/s and that is the motion I am referring to when I say that it takes the Earth an hour to cross this square.

But the Sun is moving also. Recall that the Sun is orbiting the center of the galaxy in a clockwise direction about 30 000 light years from the center and completing an orbit in about 250 million years. To accomplish this, the Sun and most of our neighboring stars are moving in the direction of the bright star Deneb in the constellation Cygnus, the Swan, at an estimated 250 km/s, more than 8 times faster than Earth orbits about the Sun.