In mid-February, the Moon returns to the evening sky. This brings up an ancient puzzle: How does the Moon affect us? This issue often confuses people.
We all know the Moon DOES control the tides which, in turn, controls much else.
Certainly, the Moon can certainly can affect our emotions—from a sense of awe and wonder to perhaps a self-contemplative and spiritual feeling. But I’m speaking of the Moon’s effect on our bodies, not whether the Moon drives us crazy which a whole other story!
Physically, the bright light from a full Moon has been shown to affect sleep—which could make us feel out of sorts.
However, does it affect our fluids—our blood flow, mucus, and brain chemicals? You might think, “If I’m made mostly of water, and the Moon pulls untold tons of seawater as it controls the tides, why shouldn’t the Moon personally affect me?”
Nope. The Moon cannot budge even a gram of your bodily fluids. That’s for two reasons:
- First, the lunar tides arise mostly because there’s a 7% difference in lunar gravity between its pull on the side of Earth nearest it, and the side farthest away. This difference is the tidal effect.
- But since there is no difference between the Moon’s gravity-strength acting on your head and acting on your feet, your body is bathed in equality so far as the Moon is concerned. Nothing budges. So you see, the Moon has no attraction for water! Rather, its effect depends on any distance-variations.
But on the immediate small scale, something else happens, which I think is quite interesting …
How the Moon Affects the Oceans
Want to be the only one on your block who understands how the Moon affects the seas?
Credit: Alan McKnight
The above illustration really makes it clear how the Moon creates its three-foot tidal bulge on Earth’s oceans, even if the lunar gravity is far too weak to lift anything—even single atoms—upward in any way.
Look at the two spots in Earth’s oceans marked A and B. The Moon’s gravity is pulling upward on each drop of ocean water. The pull is NOT straight up, but toward the Moon, which almost always is in some direction at an angle. This lunar torque thus has a vertical and a horizontal component, each of which is depicted by a thin line.
The vertical component has no affect on the water, because it’s more than counter-balanced by Earth’s much stronger gravity in the opposite, downward direction.
But the horizontal vector is not opposed by anything. Thus, each drop of sea water is nudged SIDEWAYS, toward the Earthly spot that’s right beneath the Moon. Each bit of nudging is tiny, but it adds up until, at that region beneath the Moon, the ocean piles up to a height of three feet above normal.
(When the rotating Earth brings this tidal bulge toward land, the shallowing seabed accentuates it, so that the average coastal tide is five feet.)
So now you know why tides happen. Nothing is pulled up toward the Moon. However, all the seawater is moving SIDEWAYS.
Is this cool, or what?