What makes the Earth spin on its axis?
Short answer: the stuff from which Earth was made was spinning when the Earth formed, and thus the Earth continues to spin because of the law of conservation of angular momentum. Trivia: The moon-earth tidal friction effects are reciprocal, and because of this effect the Earth’s spin is slowing down. One day the earth may be slowed such that it is locked in synchronous rotation with the moon. The moon is already locked in synchronous rotation with the earth. The earth is “donating” its angular momentum to the moon, and the moon is using this energy to slowly move away from the earth. If the solar system lasts long enough, might the earth stop spinning and the moon float off on its own? Longer answer: You can take a look at the site linked below, because the short answer I gave raises other questions: why was the stuff the earth’s made of spinning? Does everything spin in the same direction? If your 4-year-old is like most, these and other questions should be forthcoming. Sources:
