what is a blue moon?

Answer 1

A blue moon is when there are two full moons in one month.
It is a rare occasion, therefore comes the saying "once in a blue moon" when soemthing happens once in a long time.
And this sprouts songs.

Answer 2

The term blue moon has at least four related meanings. One is a common metaphorical phrase for a rare event. Full moons are given names in folklore, and two definitions of blue moon are a name for a rare full moon that does not have a folk name. One modern blue moon definition is a result of a misinterpretation of the Maine Farmer's Almanac, where a second full moon occurs in a calendar month. The older definition of blue moon is for an extra full moon that occurs in a quarter of the year, which would normally have three full moons, but sometimes has four. Oddly, it is the third full moon in a season that has four which is counted as the "extra" full moon and named blue moon. According to certain folklore, it is said that when there is a blue moon, the moon has a face and talks to the items in its moonlight.

Answer 3

A blue moon does not exit. the Earth's Moon is certainly not blue as far as we can see.
We have only twelve months in our calendar,but in realitiy there are 13 months in a side real year .
A month represents one moon cycle around the Sun and the Earth. So Each month shows one full moon. But there are 13 months in a year and we only count 12.
Therefore, there is an extra full moon missing.
That missing moon is called Blue moon.

Answer 4

The blue moon is the second full moon of the month

Answer 5

... every 2 1/2 to 3 years), the second has been christened a "Blue Moon. ... containing four full Moons, then the third of that season is called a Blue Moon! ...

Answer 6

In recent times, people have taken to calling a full moon a blue moon based on the Gregorian calendar. By this use of the term, a blue moon is the second of two full moons to occur in the same calendar month. This definition of blue moon originated from a mistake in an article in the March 1946 Sky & Telescope magazine, which failed in an attempt to infer the earlier definition used in the original Farmer's Almanac (see above). It was helped to popularity when Deborah Byrd of Earth & Sky walked into the Peridier astronomy library at the University of Texas at Austin one day, leafed through some old magazines, and found the 1946 blue moon article in Sky & Telescope. She used the definition – the second full moon in a single month – in the radio series Star Date for some years. As a result, the game Trivial Pursuit used a question and answer about blue moon. Sky & Telescope discovered the error nearly sixty years later and the magazine printed a retraction and correction.[2] By the time the correction came the calendar definition had already come into common use. As it is easier to understand, the mistaken calendar-based meaning has stuck.

Calendar blue moons occur infrequently, and the saying once in a blue moon is used to describe a rare event. However, they are inevitable because of the mis-match between the solar and lunar cycles. Each calendar year contains twelve full lunar cycles, plus about eleven days to spare. The extra days accumulate, so that while most years contain twelve full moons to match the twelve months, every two or three years there is a year with thirteen full moons. On average, this happens once every 2.72 years. Additionally, in some years there is no full moon in February at all, since February is slightly shorter than the time from one full moon to the next. This condition, known as black moon, gives additional 'blue' moons in the preceding and following months.

When there are thirteen moons in a year, twelve of them are given the twelve traditional names associated with that time of year (the names vary from culture to culture), and the extra one is termed a blue moon. Which of the thirteen moons is termed 'blue' depends on whether it is calculated by the old or the new method.

The months of the Gregorian calendar are all very close to the 29.5306-day period of the moon's phases: the synodic month, or lunation. Most of the months are longer than this by one or two days, except February, which is the only month which cannot contain a calendar blue moon. Since February is one or two days shorter than the moon's cycle, very occasionally it has no full moon – there is a full moon at the end of January, and the next one is at the beginning of March. What this means is that both January and March will have blue moons. This happens, on average, once every thirty-five years.

The previous calendar blue moon (based on UTC) was on June 30, 2007 (but May 31, 2007 in the Western Hemisphere; see below); and the next calendar blue moon will be December 31, 2009. Because February, according to UTC, will have no full moon in 2018, January and March will each have a calendar blue moon that year.

Answer 7

The second full moon to occur in one month. It happens in august this year. Full moon around the 1st and again at the end of the month.

Answer 8

"Once in a Blue Moon…" you know what they mean: Rare. Seldom. Maybe even absurd. After all, when was the last time you saw the moon turn blue?

On July 31st, you should look, because there's going to be a Blue Moon.

According to modern folklore, a Blue Moon is the second full moon in a calendar month. Usually months have only one full moon, but occasionally a second one sneaks in. Full moons are separated by 29 days, while most months are 30 or 31 days long; so it is possible to fit two full moons in a single month. This happens every two and a half years, on average.

Right: One way to make a blue moon: use a blue filter. That's what Kostian Iftica did on July 2nd when he photographed this full moon rising over Brighton, Mass.

July has already had one full moon on July 2nd. The next, on July 31st, is by definition a Blue Moon.

But will it really be blue? Probably not. The date of a full moon, all by itself, doesn't affect the moon's color. The moon on July 31st will be pearly-gray, as usual. Unless....

There was a time, not long ago, when people saw blue moons almost every night. Full moons, half moons, crescent moons--they were all blue, except some nights when they were green.

The time was 1883, the year an Indonesian volcano named Krakatoa exploded. Scientists liken the blast to a 100-megaton nuclear bomb. Fully 600 km away, people heard the noise as loud as a cannon shot. Plumes of ash rose to the very top of Earth's atmosphere. And the moon turned blue.

Krakatoa's ash is the reason. Some of the ash-clouds were filled with particles about 1 micron (one millionth of a meter) wide--the right size to strongly scatter red light, while allowing other colors to pass. White moonbeams shining through the clouds emerged blue, and sometimes green.

Blue moons persisted for years after the eruption. People also saw lavender suns and, for the first time, noctilucent clouds. The ash caused "such vivid red sunsets that fire engines were called out in New York, Poughkeepsie, and New Haven to quench the apparent conflagration," according to volcanologist Scott Rowland at the University of Hawaii.

Still smoldering after all these years: a recent picture of Krakatoa. Credit: Robert W. Decker of Volcano World.

Other less potent volcanos have turned the moon blue, too. People saw blue moons in 1983, for instance, after the eruption of the El Chichon volcano in Mexico. And there are reports of blue moons caused by Mt. St. Helens in 1980 and Mount Pinatubo in 1991.

The key to a blue moon is having in the air lots of particles slightly wider than the wavelength of red light (0.7 micron)--and no other sizes present. This is rare, but volcanoes sometimes spit out such clouds, as do forest fires:

"On September 23, 1950, several muskeg fires that had been quietly smoldering for several years in Alberta suddenly blew up into major--and very smoky--fires," writes physics professor Sue Ann Bowling of the University of Alaska. "Winds carried the smoke eastward and southward with unusual speed, and the conditions of the fire produced large quantities of oily droplets of just the right size to scatter red and yellow light. Wherever the smoke cleared enough so that the sun was visible, it was lavender or blue. Ontario and much of the east coast of the U.S. were affected by the following day, but the smoke kept going. Two days later, observers in England reported an indigo sun in smoke-dimmed skies, followed by an equally blue moon that evening."

Right: Smoke from forest fires can cause blue moons, too. Photo credit: John McColgan of the Bureau of Land Management, Alaska Fire Service.

In the western U.S., there will be wildfires burning on July 31st. If any of those fires produce ash or oily-smoke containing lots of 1-micron particles, the Blue Moon there could be blue.

More likely, it'll be red. Ash and dust clouds thrown into the atmosphere by fires and storms usually contain a mixture of particles with a wide range of sizes. Most are smaller than 1 micron, and they tend to scatter blue light. This kind of cloud makes the Moon turn red; indeed, red Blue Moons are far more common than blue Blue Moons.

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Answer 9

it only happends once in a blue moon

Answer 10

I read about that before ... it's when the moon appears full twice in one month .. the second time it appears blueish