From the April 2010 issue

If Earth had more than one moon, how would it have affected life’s evolution on the planet?

Samuel Heinitz, Edmond, Oklahoma
By | Published: April 26, 2010 | Last updated on May 18, 2023
Far Side of the Moon
Earth’s Moon.

If we had such a moon, its lower mass likely would not affect our planet much other than to annoy astronomers yearning for moonless nights. Only a massive extra moon would affect Earth’s tides and therefore influence the long-term stability of the planet’s spin axis. There are a number of reasons not to expect earthlike planets to have more than one large moon.