Cut-And-Paste Campaign?

Got a question for folks. There has been a spate of nearly identical letters sent to magazines and newspapers all over the US. The writer claims something like "I've been a hunter for 60 years" and goes on to say that he can't seen any reason for having a "machine gun/assault rifle/Saturday night special/large capacity magazine." The letters are well written and the author knows enough about guns to avoid major mistakes, but sometimes uses anti-gun terminology instead of actual firearms terminology.

There's a lot of speculation among gun owners that this is part of a campaign by anti-gunners, since no-one in the pro-firearms community seems to actually know the writers. I just wondered if any of you have seen such a letter and perhaps know anything about its true status.

Astounding Ignorance

During a History Channel program on the Moon, the twice-daily tides of the Earth's oceans were given an astonishingly wrong explanation.

A man (didn't catch his name) held up a tennis ball (the Moon) and a football (the Earth) with one of the football's points toward the tennis ball. He explained that the tide on the side facing the Moon were due to its gravitational attraction. And that the tide on the side away from the Moon was due to the centrifugal force of the Earth's motion.

Unbelievable.

For the record, the Earth's rotation has nothing to do with the tides beyond affecting their timing. There are two tides because the Earth and Moon orbit each other. Now, all pairs of orbiting bodies orbit each other, around a mutual center of gravitation. It's just that for most such pairs one partner is so large with respect to the other that the displacement of this point away from the center of the larger mass is trivial. However, the Moon is very large for a satellite of a body the size of the Earth, and the common center is noticeably displaced away from the Earth's center towards the Moon. But that's not why there are two tides, it's simply another feature of our unique system.

What does cause the tides is orbital speed. Because the orbital speed of the Earth around the Moon is the average for the whole Earth, the side facing the Moon (or Sun, for solar tides) is moving a bit too slow for the orbital distance. Likewise, the side away from the Moon is moving a bit too fast for its orbital distance.

If the Earth were solid this wouldn't be noticeable (though in situations where matters are more extreme, at or beyond the Roche Limit, solid bodies can actually be broken in to pieces by tidal forces). The Earth is a big ball of molten rock with a thin solid skin. On top of this skin are the oceans and the atmosphere. Not only are there ocean tides, there are air and ground tides, but the latter two are really only noticeable with sensitive equipment.

Because the water (and air and molten rock) on the part of the Earth currently closest to the Moon is moving a bit too slow, it tends to fall towards the Moon. Because the water on the side away from the Moon is moving a bit too fast, it is flung outwards. (Here's where the narrator made the mistake. The tidal bulge away from the Moon could be described as being due to the centrifugal motion of the Earth's orbit around the Moon. However, he mistakenly attributed it to the Earth's rotation around its axis. Maybe he knew it right and just said it wrong. In which case he should have asked for another take.)

In both cases, the Earth's gravity is so much stronger than these inward and outward tidal forces that the oceans (and atmosphere and molten rock) only move a tiny bit with respect to the size of the Earth. It just happens that the oceans are big enough and fluid enough and noticeable enough for their tides to be obvious to us.