Moon Question of the Day

Why do stars twinkle, while the visible planets (and our Moon) shine constantly when viewed?

First, the stars themselves do not twinkle. We are seeing the effect of Earth's atmosphere on the light they produce. The starlight is bent by moving volumes of air in our atmosphere. The bending effect makes the stars appear to be larger than points, to dance around slightly, and to change in intensity, which is what is commonly called twinkling. Planets don't usually appear to twinkle because they are close enough to Earth that they appear as tiny disks of light. The total intensity doesn't seem to change -- hence no twinkling is apparent to the naked eye.

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Last 7 Days

How old is the Moon?

The Moon is approximately 4.6 billion years old.

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.

What would happen if Earth's rotation started to slow down?

Earth is already slowing down and has been doing so for billions of years. At the present time, our planet is slowing down by about .002 second per century. The slowing occurs mainly because of friction between solid earth and ocean tides. Earth's loss of rotational energy is transferred to the Moon, which goes into a wider orbit, thus lengthening the time between successive full Moons.

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 temperature colder during a full Moon?

Air temperature is not affected by Moon phase. It is affected by the season and whether there is a cloud cover, among other things. On a clear night, heat rises from Earth if there is no cloud cover holding it in. This might make you think it's colder because there is a full Moon, but it's really colder just because the sky is clear.

Is there such a thing as "Moon weather"?

Country wisdom says that the full Moon brings frosts in spring and fall and periods of extreme cold in winter. Researchers have found a striking correlation between the full Moon and cloudiness, rainfall and thunderstorms.

Why is there a crescent Moon cutout in outhouse doors?

We don't know whether the crescent Moon was the standard cutout in every outhouse door in the country, but it's certainly the embellishment of choice for artists and illustrators. Such an opening may have been chosen because (1) it provided some ventilation and illumination and (2) it afforded a modicum of privacy for the occupant.

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