Week of April 22-28, 2018
The moon shines beautifully in our evening sky this week, just as it does every month.
We astronomers know the moon's patterns quite well, and we often schedule our observing programs around its obscuring light. Whenever I'm invited to an event and I must decline because of the moon's phase, well, the looks I receive are priceless.
With improving springtime weather, it might be fun to gaze up at the moon with some interesting new knowledge about our nearest cosmic neighbor. So here goes.
Our moon lies 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 closest (perigee), it can lie about 225,623 miles away, and at its farthest (apogee), about 252,088.
How long would it take to travel this distance? That, of course, depends on the speed at which we travel. 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 the vacuum of space — it would take us half a year, while the Apollo astronauts of the 1960s and 1970s needed only three days to reach 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 a second to make the journey.
Suppose we could stand on the moon. Since the moon is much less massive than the world on which we live, its gravitational pull is significantly less as well — one-sixth of what we normally feel. That means that a person who weighs 120 pounds on Earth would weigh only 20 pounds on the moon.
The weaker lunar gravity would affect most of what we've grown accustomed to here. Just imagine watching a lunar baseball game, for example, where a towering home run ball would sail for miles before finally landing!
Temperatures on our natural satellite are also quite different than those 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 Fahrenheit, while one in the darkness would show a blistering minus 244 degrees F.
The visible features of the moon are also quite interesting. The large dark regions are ancient planes of solidified magma known as maria, and they 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 the bucket around you. The open part of the bucket always faces you, even though other people would see all parts of the bucket as it sails around you.
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 with our nearest celestial neighbor.
Visit Dennis Mammana at www.dennismammana.com. To read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate website at www.creators.com.