Moon Question of the Day

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.

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I've heard that if you cut your hair on a full Moon, your hair grows healthier and faster. Is this true?

According to folklore, if hair is cut during the Moon's waxing phase (between new and full), growth is encouraged. The opposite will occur if hair is cut during the waning phase (the day after the Moon is full to the day before it's new).

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.

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.

I was told about a documented case in which onlookers saw a blood-red Moon and stars falling from the sky. Where might I find this piece of documentation?

Astronomically speaking, it is possible to observe a "bloody" Moon during a lunar eclipse, when Earth's shadow casts a dark reddish color on the Moon. And, indeed, stars often appear to "fall" from the sky. But we think that what you have in mind is not an astronomically documented case but a quote from the Bible, specifically from Revelation (6:12-13): "And the sun became black as sackcloth of hair, and the moon became as blood; And the stars of heaven fell unto the earth, even as a fig tree casteth her untimely figs, when she is shaken of a mighty wind."

What causes the distance from Earth to the Moon to vary?

The celestial mechanics of the Moon's motion are very complex. When the distance to the Moon is measured at different times of the month, it is found to vary by more than 10 percent because the Moon's orbit is basically an ellipse, with Earth at one focus. The Moon may come as close as 356,334 kilometers (220,927 miles) to Earth's center and then move as far away from it as 406,610 kilometers (252,098 miles). The dates when the Moon is at apogee (the point in its orbit farthest from Earth) and perigee (the point in its orbit closest to Earth) can be found on each month's calendar page in The Old Farmer's Almanac. However, to understand the "mechanics," as mentioned above, we recommend consulting a basic astronomy textbook.

How old is the Moon?

The Moon is approximately 4.6 billion years old.

How did the special names that we give some of the Moons, such as the Hunter's Moon, begin?

Historically, the Native Americans of the northern and eastern United States kept track of the seasons by giving a distinctive name to each full Moon. With some variation, the same names were used throughout the Algonquin tribes from New England to Lake Superior. These remain the full Moon names we use today.

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