Al Stahler: Moon to suffer eclipse |

Al Stahler: Moon to suffer eclipse

We landed a six-wheeled rover on Mars last winter, and nearly every day since, scientists and engineers have sent radio messages, California to Mars, giving the vehicle instructions: Where to go, what to do, what to look at.

Those instructions were radioed to the rover, every day … until last October, when the messages stopped. The rover was told to just hang out, for a couple of weeks.

The sun, last October, was in the constellation Virgo. Mars, too, had recently moved into Virgo. For a couple of weeks, last October, sun and Mars were in the same part of Virgo.

With both sun and Mars very close in Virgo … NASA had to shut down operations.

Constellations are a quick-and-easy way to map the sky. With both Mars and sun in the same part of Virgo, Mars and the sun were almost directly in line: Mars was almost directly behind the sun.

Radio signals, California-to-rover, would thus have to pass very close to the sun. And close to the sun, space is electrically … magnetically … contorted. Radio signals traveling through that electromagnetically-mangled space could easily be corrupted. Twisted radio messages could tell the rover to do something stupid, even dangerous. So, for two weeks, the rover was instructed to just … hang … out.

* * *

Everything in the universe is falling. Falling objects usually smash into things.

But if the falling object is also moving sideways … rather than smash into something … it might fall around. That’s what it means, to be in orbit: An object in orbit is falling around something else.

The moon orbits Earth – the moon falls around the Earth – once a moonth … pardon me, once a month. And twice a month – at full moon and new – sun, moon and Earth are aligned in a straight line, as they are in the photo … much as sun, Earth and Mars were aligned last fall.

Such a straight-line alignment of sun, Earth and moon is coming up during this Thursday’s full moon. And so nearly perfect is Thursday’s alignment, the moon will fall into something it rarely falls into: the moon will fall into Earth’s shadow – the moon is going to suffer eclipse.

The lunar eclipse begins when the moon touches Earth’s shadow, 11:19 p.m., Thursday night. The moon then falls deeper into our shadow, until it maxes out, a few minutes after 1 a.m.

Not quite total, a sliver of the full moon will still shine brightly at maximum eclipse.

Please – do not expect fireworks. Watching the sky, naked eye, will never be like watching a sci-fi action movie … though it does have its own attractions. Let me explain, here, something about gravity.

Picking up a rock, we feel the Earth, pulling on that rock. Getting out of bed, we feel Earth pulling on us.

But that’s only half the story.

Gravity works both ways. The rock we lift is pulling on the Earth. Standing up, our bodies pull Earth toward us … exactly as hard as Earth pulls us downward. Of course, Earth, being a lot larger, doesn’t much notice our pull. But we certainly feel ourselves pulling on the Earth.

As we watch the eclipse, Earth tugs on the moon … the moon tugs on Earth … the moon tugs on us … and we … tug back … on the moon.

The one thing nature-watching has going for it is that it’s real. If we think about what’s happening … how moon and we tug on each other … we can feel it in our bones.

Al Stahler enjoys sharing science and nature with friends and neighbors in The Union and on KVMR-FM. He teaches classes for both kids and grown-ups, and can be reached at

Earth and moon, seen by a spacecraft between Earth and sun.
Photo courtesy NASA, NOAA/DISCOVR

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