Did you know that the moon isn’t always at the same distance from the Earth?
Did you know that the moon isn’t always at the same distance from the Earth? Credit: Creators.com illustration

We astronomers know the moon’s motions quite well, and we often schedule our observing programs around its obscuring light.

Whenever I’m invited to an event and must decline because of the moon’s phase — well, the looks I receive are priceless.

With improving springtime weather, it might be fun to forget about the starry sky for one week and consider our nearest cosmic neighbor instead.

And armed with some interesting facts, who knows, the moon might just become your favorite celestial object.

Our moon lies at an average distance of 238,855 miles from Earth, but its distance changes throughout the month.

That’s because the moon orbits our planet not in a circular path but in an ellipse. When it’s at its nearest (perigee), it can lie about 225,623 miles away, and at its farthest (apogee), about 252,088.

How long would it take for us to travel this distance? That depends on our speed, of course.

For example, driving at an average speed of 60 mph — assuming there was a road heading in that direction and that our cars could operate in space — we would need half a year, while the Apollo astronauts of the 1960s and ’70s spent only three days journeying to the moon in a spacecraft.

Light, on the other hand, travels at about 610 million mph (186,282 miles per second) and takes little more than one second to make the journey from the moon to the Earth.

Suppose we could stand on the moon. Since the moon is much less massive than the Earth, its gravitational pull is significantly less as well — one-sixth of what we normally feel here.

That means that a person who weighs 120 pounds on the Earth would weigh only 20 pounds on the lunar surface.

This weaker lunar gravity would affect nearly everything we’ve grown accustomed to on our planet. Just imagine watching a lunar baseball game, for example, where a towering home run ball would sail for miles before finally coming to rest!

Temperatures on our natural satellite are also quite different than here on Earth.

Since the moon has no significant atmosphere to absorb the sun’s heat and distribute it around the lunar globe, temperature extremes are common.

A thermometer in direct sunlight would register about 273 degrees, while one in the darkness would show a bone-chilling minus 244.

The visible features of the moon are also quite interesting. The large dark regions are ancient plains of solidified magma known as maria and always appear to face us here on Earth. Does that mean that the moon doesn’t rotate?

Not at all. The moon rotates, but the Earth’s relatively strong gravitation has locked one face in our direction.

It’s much like tying a rope to a bucket handle and swinging it around you. The open part of the bucket always faces you, even though other people would see all parts of the bucket as sails around your head.

If the weather is nice this week, I hope you’ll get outdoors to do a little moongazing. It’s always fun to think about some of these amazing facts while spending time enjoying our nearest cosmic neighbor.

Dennis Mammana

Dennis Mammana

Dennis Mammana is an astronomy writer, author, lecturer and photographer working from under the clear dark skies of the Anza-Borrego Desert in the San Diego County backcountry. Contact him at dennis@mammana.com and connect with him on Facebook: @dennismammana. The opinions expressed are his own.