The Earth spins about her axis with a surface velocity of close to a thousand miles an hour at the equator, which translates to about sixteen miles per minute or a quarter mile per second. The Earth also revolves around the sun at a velocity of approximately eighteen and a half miles per second.
But our sun, too, is moving, for our Milky Way Galaxy is rotating, and so the sun is carried around that galactic axis at the rate of about a hundred and fifty miles per second. Just as Earth’s motion about the sun is about seventy-five times as rapid as the motion of a spot on Earth’s surface about Earth’s own axis, the velocity of galactic rotation is about eight times as great as that. Yet even this is relatively insignificant. The known universe is expanding, so all matter is in motion with respect to Galactic Rest. In that sense, we are traveling at approximately half the speed of light, or ninety thousand miles per second.
Piers Anthony, Bearing an Hourglass