Moon Phases and Tides, the Dummies Version

Ocean tides and moon position

If you haven't been to our index of Dumbasses by Day lately, you may not have realized that we keep track of our older posts and regularly check the links to the original material. Either Leaf Group has noticed that some of their eHow.com posts are, shall we say, "deficient," or they've been watching us to see what we identify as crap. Either way, they're replacing at least some of the dross (we mark the deleted ones with red in our index). Unfortunately, the replacements are sometimes fodder for a DotD award themselves – like Susan King and her Sciencing.com post "Relationship Between Moon Phases & Tides."

King opens with an introduction that more or less describes how lunar tides work:

"The moon's gravitational field is so strong that it affects the Earth, most notably the water in the oceans. The side of the Earth that is closest to the moon will have a distinct bulge. The rise and fall of the ocean level results from the moon's gravitational field pulling as it moves in orbit around the Earth."

We find that scientifically inaccurate: there is no "distinct bulge" on the side of the Earth, just in the water column -- the bulge in the solid earth is anything but "distinct." That, however, is the sort of imprecise language we've come to expect from scientific illiterates trying to write science-y stuff. Moving on, Susan goes into details of how the different tides come to be, telling us (for instance) that,

"The phases of the moon also affect tides. When the moon is at its full or new moon phase, high tides are at their highest, while low tides are lower than usual. Called spring tides, these tides occur when the sun, moon and the Earth all line up. The added gravity of the sun can make the oceans bulge more than at other times..." ...which is basically correct. However, King merely regurgitated factoids from another source (probably Wikipedia), while failing to explain the relationship between moon phase and the positions of the sun and moon relative to the earth. We find her explanation weak at its core.

Finally, King wanders all the way into cloud-cuckoo land with this claim:

"The side of the Earth facing the moon will have a tidal bulge called the direct tide. Similarly, on the opposite side of the planet, the ocean will also be bulging. This is called the opposite tide, and it happens because the inertial force of the Earth exceeds the gravitational force of the moon at this location. Therefore, high tides occur simultaneously on the the opposite sides of the Earth."

Say what, Susan? The "inertial force of the Earth"? WTF is that crap supposed to mean? Well, King endeavored mightily to copy-reword-paste an article from NOAA, but got confused by technical jargon like "inertia" and "force." The reality? NOAA was talking about the inertia of the water. Sheesh – and this is a "teacher with 27 years [sic] experience"... not to mention, our Dumbass of the Day. Small wonder kids are failing STEM classes.

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SI - OCEANOGRAPHY