Moon Question of the Day

What does neaped mean in reference to a ship?

A boat that is neaped has gone aground on a mild tide and needs a spring tide or stormy waters to float it off. The boat is only barely aground, as opposed to being hard aground, where even a very high tide or rough waters might not be enough to set it free. The expression comes from the term "neap tide," which is a moderate tide. Neap tides occur when Earth, Moon, and Sun are in quadrature. In other words, instead of being lined up in a straight line, as at syzygy, they are more nearly at right angles. True quadrature happens at regular intervals, about twice a month, at the first quarter and last quarter Moons, but neap tides occur for several days around those dates. Take a look at the tides on the right-hand calendar pages of The Old Farmer's Almanac, and you'll notice that high tides are considerably higher around the full Moon and new Moon than around the first and last quarters.

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Last 7 Days

What have our astronauts left behind on the surface of the Moon?

Well, there's quite an inventory. Of course, there's the American flag, left by the first visitor, Neil Armstrong. The first Apollo landing crew also left a commemorative plaque. The remains of seven unmanned lunar probes, Surveyors 1 through 7, are there, plus three lunar rovers. There are six long-term scientific stations on the Moon, which include seismometers to measure tremors in the Moon's crust and some reflectors to bounce back light beams that we send up there. The Russians left several unmanned probes and assorted lunar rovers on the Moon as well.

Does the Moon rise and set in any particular time pattern?

The rising and setting of the Moon is retarded from day to day, but the delay is not consistent. At moonrise, the Moon occupies a particular place in the celestial sphere. Approximately 24 hours later, the Moon has moved to the east in the sphere, so moonrise and moonset occur a little later. In the northern United States, the daily delay can vary from a few minutes to well over an hour.

Why did the old almanacs always recommend planting potatoes on Good Friday?

We can't speak for other old almanacs, but certainly The Old Farmer's Almanac has never recommended planting potatoes on Good Friday; our only recommendation has been to plant by the dark of the Moon. Further, all our research has turned up contrary advice -- neither to plant nor to dig potatoes on Good Friday. It was thought the timing would produce poor crops. The Creoles of Louisiana believed that if the ground were cut open on this day, Christ's blood would run out into the rows. The only exception we found was an old belief that seeds planted on Good Friday will thrive.

Is the distance between Earth and the Moon increasing?

Yes. Because Earth spins slower every day (that's just what spinning objects do), the Moon moves not quite two inches away from it each year. The rate decreases by 1-1/2 thousandths of a second every 100 years -- not enough so that you'd notice, but enough for the Moon's gravitational pull to lessen. This allows its orbit to increase, which results in a greater distance from Earth. Got that?

Exactly how long is a lunar month?

The Moon's synodic period (the length of a lunar month) is 29.53059 days -- or 29 days, 12 hours, 44 minutes, and 2.8 seconds.

As we watch the Moon move across the sky, how much is it moving, versus the Earth's own movement?

When you watch the Moon move from east to west, it travels its own diameter in about 3 minutes. The speed at which we see it move is mostly due to the Earth's movement, not the Moon's. The Earth's movement accounts for 95 percent of the shifting position of the Moon. The other 5 percent is actually the Moon itself moving.

As we watch the Moon move across the sky, how much is it moving, versus the Earth's own movement?

When you watch the Moon move from east to west, it travels its own diameter in about 3 minutes. The speed at which we see it move is mostly due to the Earth's movement, not the Moon's. The Earth's movement accounts for 95 percent of the shifting position of the Moon. The other 5 percent is actually the Moon itself moving.

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