There may be trouble ahead... Soon we'll be without the Moon. Humming a different tune, and then...
Last week, I was listening to an old vinyl record with Fred Astaire singing the Irving Berlin song, "There May Be Trouble Ahead". A few of the lyrics-repeated above-got me thinking about what the Earth would be like without the Moon.
This intriguing question isn't just a fanciful "what if" exercise, but an inquiry into what makes our planet such a unique place in our solar system. Raytheon astronomer Stan Odenwald-founder of the Internet's popular Astronomycafe.net-tackled the problem of a Moonless Earth; he came up with some intriguing possibilities.
First, let's look at tides. Without Luna, Earth would still have high and low tides thanks to the Sun, but these tides would be half as high as lunar high and low tides. Spring tides (or Neap tides) would disappear since both the Sun and the Moon-on opposite sides of the Earth or on the same side-create these effects. However, large coastal breakers, familiar to residents of California and Oregon, would still occur thanks to the effects of Earth's rotation and maritime storms.
When it comes to time-keeping, there'd be no need to keep a 12-month calendar without the Moon, said Odenwald. Also, take away the influence of Luna's gravity upon Earth and fewer volcanoes might have been created during our planet's long geological history. This problem, with reduced out gassing from volcanoes, might have reduced the density, and perhaps the complex composition, of the terrestrial atmosphere. Such an effect might have reduced or even eliminated the chance of life arising early in the Earth's history.
Would the lack of a moon near Earth also have prevented continental drift? Odenwald asked. Probably not, he concluded, since convection of molten materials deep within the Earth's mantle is the result of internal forces not lunar forces.
One intriguing effect of a Moonless planet Earth, Odenwald surmised, would be a world without seasons-or at least seasons very alien to those we're used to. Many astronomers think the proto Moon was an "interloper", a planetary wanderer, which came from elsewhere in space and impacted the Earth to form the Moon we know today. If true, then the Earth's rotation axis-in pre-lunar epochs-could have been tilted perpendicular to the "ecliptic" or plane of the solar system (rather than titled at nearly 24 degrees as it is now).
Without the Moon, sunlight would reach the Earth's surface at the same angle throughout the year. At Vermont's latitude, for example, the Sun's rays would strike the ground at 45 degrees daily. At both poles, the Sun would never rise above the horizon. Thus, at the equator summer would continue year round; at mid-latitudes spring would reign; and at higher latitudes, winter would continue throughout the year.
Such a hodgepodge of seasons would create wild, unpredictable planetwide weather. So, when the Moon recedes far from Earth in the distant future, as many astronomers believe, there may indeed be trouble ahead.
Louis Varricchio, M.Sc. lives in Vermont. He was a science writer at the NASA Ames Research Center in California. Currently, he is is a member of the NASA-JPL Solar System Ambassador program.