If you rarely look at the moon, tonight you should do so.
It’s a lunar trifecta of sorts, and it’s all the rage. This month’s full moon is being called a “super blue moon.”
Don’t know what this is? Read on.
What is a supermoon?
The Moon orbits the Earth once every 27.3 days, and lunar phases occur once every 29.5 days. However, the orbit is not circular, but elliptical, resembling an elongated circle. This means that the Moon’s distance from the Earth changes. When it is closest, it is called perigee, and when it is farthest, it is called apogee.
Because the moon is closer, brighter, and slightly larger in the sky, it is colloquially called a “supermoon.”
WATCH | What Makes a Supermoon Super?
Supermoons occur about three to four times a year. The last one occurred on the day of a total solar eclipse on April 8.
The term “supermoon” is not a scientific term. It does not come from astronomy, but from astrology. It was coined in 1979 by astrologer Richard Nolle, who claimed that supermoons cause earthquakes and an increase in extreme weather events. However, no connection has been found. In fact, a 2018 study found that there is no connection between supermoons and earthquakes.
What is a blue moon?
There are several definitions of a blue moon.
The first is when there are two full moons in a month; the second is when there are four full moons in a season instead of the usual three. And it is not the fourth moon that is considered blue; it is the third, as is the case with the full moon in that month.
Since the beginning of summer on June 20, there have been full moons on June 21, July 21, and today. The next full moon will be on September 17, and yes, it will be great too.
Why do we call it a blue moon? According to Britannica, the term comes from something rare that dates back to the 16th century.
A supermoon and a blue moon rarely occur together. This is because about 25 percent of all full moons are supermoons, while only three percent of all full moons are blue moons. On average, a super blue moon occurs about every 10 years.
Will it look different?
Yes… and no.
When the full moon is at perigee (closest), it can appear as much as 14 percent larger and 30 percent brighter. But unless you compare it to any other full moon, it’s hard to tell the difference. And no: it won’t look blue.
“If you look up at the moon tonight, you won’t notice that it’s about 10 percent larger than usual. You just don’t have a point of reference,” said Paul Delaney, an astronomer and professor emeritus in the department of physics and astronomy at York University in Toronto.
“Because of this apparent increase in angular size, it also means it’s brighter — in this case, about 20 percent brighter. But again, you won’t be able to see that because it’s going to be bright, like all full moons.”
If you want to compare, you can take a photo of the full Moon at perigee in a month when it is not at its closest, then take a photo when it is at its closest and compare.
But if you really want to visually see a big moon, there is a way. When the moon rises or sets on the horizon, it appears much larger, especially when there are other objects around as a frame of reference.
It’s called the moon illusion, and it’s not entirely clear why it happens. But generally speaking, it has to do with several factors, including how our brains perceive the size of things nearer or farther away.
There are several ways you can convince yourself that the moon on the horizon is not actually larger than when it is in the sky.
You can try holding a round Aspirin when the moon is on the horizon and when it is higher in the sky and compare. You can also put your fingernail on it and do the same. You will find that the moon is always the same size.
Even if you can’t tell the difference yourself, the moon is always a beautiful sight. Use binoculars and the flatness of the moon disappears. Instead, you may see craters and other beautiful features.
“The full moon is a really big attraction. People usually stop and look and say, ‘Wow, that’s beautiful!’ Mainly because it’s so close to the horizon,” Delaney said.
“And you know, perspective really creates good photographic opportunities.”
