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Life Under the Moon

Week of August 18, 1997

Earth and Moon from Galileo Last week, our tour outwards made a stop at our own home planet. Permit me to hold our tour a bit longer, to linger and gaze upon the Moon.

Everyone who is capable has seen the Moon. Unlike Venus, or Mercury, or any other object in the sky besides the Sun (which is too bright to look at anyway), it is the only nearby object we can see on which our unaided eyes can actually pick out features (in astronomical terms, our eyes can resolve features on the Moon). The Moon is bright enough to be seen easily by day, and it dominates our night. What lover's evening would be complete without the full Moon illuminating the gaze of the other's face? It is the first target of any young amateur astronomer, who can gasp in awe as, for the first time, they see with their own eyes the enormous impact craters scarring the bleached surface of the Moon.

But what practical purpose is it? Is it simply a fantastic bauble hanging in our sky for us to observe and leave footprints on? I will forgo here the obvious refrain of how much there is to gain from exploring and settling our nearest neighbor. The web is filled with such discussions. Instead, let me posit a scenario for you:

Four billion years ago, the Earth was covered in oceans, with land just poking through the waves. Complex molecules floated in the water, but the concentration of these compounds wasn't high enough for them to get any further along than making amino acids and the like. But there was another influence than simple collisions: the Moon exerts a tidal force on the water, sometimes drawing it high upon the rocky beach, sometimes pulling it away. Any depression in the rock would retain water which would not ebb away with the tide. Such tidal pools would collect the complex molecules, and as the water evaporated the concentration of these molecules would increase, likewise increasing the odds of evermore complex molecules forming. Perhaps after countless cycles of lunar waxing and waning, the molecules were able to reproduce themselves, and take in energy in the form of sunlight or by absorbing other, less complicated molecules. When the tide returned, these living chains of atoms were swept into the ocean, where they could establish a foothold.

Did life form on our own planet this way? Do we owe our very existence to our oversized, nearby Moon? No one knows. This is one idea among literally hundreds of how life came to be on Earth. The only way to find out for sure is to either use a time machine to see what happened here eons ago (not likely) or travel to all the Earthlike planets in the Galaxy and hope we stumble on one at that pivotal moment in its history (unfortunately, also unlikely). While some people are frustrated at the lack of certainty on such a big issue, I find it comforting. I think that there should always be big questions to solve. I have every confidence as well that when we solve this one, another one will come along.

The next time you are outside, day or night, look for the Moon. Lifeless, scorched and barren it may be, but it also may very well be the reason we ourselves are not in the same condition.

On a personal note, even my 18 month old daughter cries out "Ooooom! Ooooom!" and points to the Moon when she sees it. Without any training, and without even the capacity to express herself vocally with more than a dozen words, she sees it and wonders about it. Last week, she stared for more than a minute out the window at the first quarter moon, while I wondered what her young brain was making of it. And I also wondered, how many people pass through their whole lives without making the simple effort of looking up? Someday, I'll show my daughter the Moon through my own telescope, and I will delight as it is her turn to gasp in awe, as I myself did almost twenty years before she was born.

Want to know more about the Moon? Everyone should spend some quality time examining Bill Arnett's wonderful web pages, The Nine Planets. Without the information he has already established, and the images he has collected, my own pages would suffer greatly.

©2008 Phil Plait. All Rights Reserved.

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