Mad about Science: Our moon is weird

By Brenden Bobby
Reader Columnis

A total solar eclipse occurred April 8 over parts of Mexico, the eastern United States and eastern Canada. Some people gave away their life savings in anticipation of the end of days. Some people drove halfway across the country and fought other people for water. Some of us just had really bad luck that was totally unrelated to the eclipse.

In the grand scheme of things, eclipses aren’t all that rare. Two to five solar eclipses happen every year with a total eclipse happening about every five years. These eclipses are seldom in the same spot for a variety of reasons, so you’ll have to burn up your travel miles if you want to view them consistently.

One of the reasons why these eclipses seem to move around has to deal with the wobble of the Earth and the elliptical nature of the moon’s orbit. The moon does not orbit the earth in a perfect circle. The Earth also wobbles up and down as it orbits the sun, giving us seasons as more sunlight reaches either the northern or southern hemisphere. This confluence of interactions leads to seemingly erratic patterns of eclipses, which contrary to popular belief isn’t some supernatural occurrence or signal of the end times, but is just a big rock passing in front of our primary light source. Every time someone with a big hat goes to a crowded movie theater they create the same effect for the folks sitting behind them.

Our moon is weird for a lot of reasons, even if “weird” is a relative term. Weird for Earth is completely regular on the moon, but I don’t live on the moon so I have no plans of checking my Earthly privileges — I’m going to call it like I see it.

One weird behavior is that the moon is perpetually moving away from Earth. Despite being tidally locked, meaning the moon always has the same side facing the Earth, it’s perpetually drifting farther and farther from us at a rate of about 3.8 centimeters per year. This is common in orbital physics, and in most cases it’s nothing to worry about. We’ll have far bigger problems as a species and a planet before we have to worry about tidal disruptions.

It’s difficult to tell from Earth, but the moon doesn’t consistently travel at the same speed. As is true of any orbit, the moon travels faster as it reaches its nearest point to Earth, called the perigee (roughly 226,000 miles from Earth). As the moon reaches its apogee, its furthest point from Earth at about 252,000 miles, it approaches its slowest travel speed. If you want to exercise this at home, you can try this simple trick: jump. Your apsis is the highest point of your jump (when your speed reaches zero), while your periapsis is the moment you impact the ground.

In orbital physics, these points are extremely important. If you’re trying to elongate the orbit of your craft, effectively expanding your reach, you’ll point in the direction you’re traveling and initiate a burn, called a prograde burn. This increase in speed will have an exponential effect as you travel, elongating your orbit and making your furthest point — your apsis — much farther than it was previously. This is tremendously useful when interacting with other physical bodies and may allow the potential for slinging your ship even farther away. NASA has done this regularly and it’s exactly how Voyager has managed to break free of the solar system, by slinging off much larger celestial bodies and vastly increasing the craft speed without unrealistic expenditures of fuel.

I know what you’re thinking, this physics lecture isn’t weird, it’s just the moon! Well, what if I told you the moon smelled funny?

In order to smell, one needs air for particulate matter to be carried — something in alarmingly low quantities on the moon. However, astronauts who  traveled to the moon reported that upon re-entering an environment with oxygen, their gear had a strange scent to it. It supposedly smelled like spent gunpowder or fireworks. However, this smell did not occur from samples collected from the moon that have since been studied at Earth. Scientists haven’t pinpointed the cause of this, but they believe it may be a brief chemical reaction between particulate matter on the lunar surface and oxygen that dissipates over time.

Another weird trait of the moon is “Earthshine.” While you may be thinking about a tinfoil-clad bootlegger wearing a fishbowl for a helmet, it’s actually light that bounced off Earth first, then bounced off the moon and bounced back to Earth to create a faint glow effect that almost appears as a shadow on the moon.

Speaking of light on the moon, another really weird trait of our satellite is the sunrise and sunset. On Earth, light from the sun is diffused by the atmosphere to create gradual hours of twilight in which the sky may turn shades of red and purple. On the moon, there is no atmospheric diffusion, so the sunrise is actually quite sudden. One moment there is darkness, the next there is light and long shadows.

There are craters on the moon that are perpetually shadowed. These areas remain consistently cold — very cold! Some places on the moon have been recorded at -410 degrees Fahrenheit. Many of these craters are also home to perpetual ice. This is frozen water that likely became trapped during the moon’s formation, when various gasses were still present on its surface. It froze before it could evaporate and has been stuck there as ice ever since.

Stay curious, 7B.