Lunar Tetrad: 4 Blood Moons


If you are like the rest of us – asleep like a baby when the Blood Moon was taking its center stage up in the night sky, from midnight to around 2 AM, you’ll have to catch another total lunar eclipse in May of 2021.

“Blood Moon” or Lunar Tetrad is a term that describes an occurrence of 4 total eclipses lining up, spaced 6 lunar months apart, with no partial eclipses in between. There will be 8 tetrads in the 21st century. The next 4 total eclipses will happen in 2032 and 2033. Nowadays, the term is used for any total lunar eclipse, and not necessary 4 in row.

What makes the moon look bloody red? During a lunar eclipse, Earth’s shadow appears dark and gradually covers the moon completely, and at that totality moment, our atmosphere renders a ring around the Earth. As the sun’s ray passes through this ring, green and violet get filtered out while red doesn’t. This red light is bent when it enters the Earth’s surface and is bent again when it leaves through the other side. This double bending emits the reddish glow onto the moon. The shade of red (from copper to crimson) will be determined by various conditions that might affect the atmosphere such as dust, humidity, temperature… at the time of the lunar eclipse.

Back in the old days, every full moon had a name. January full moon was also called Wolf Moon (hence the name Super Blood Wolf Moon for the January 20, 2019 total lunar eclipse); February was Snow Moon; March was Crow Moon; April was Grass Moon; May was Flower Moon or Milk Moon…November was Hunter’s Moon…December was named Strawberry Moon by people living in the Southern Hemisphere. Approximately every 19 years, there will be no full moon in February.

In many Asian cultures, particularly in regions that depend on fishing for a living, people worship the moon due to its powerful effects upon the tides. In the past, pregnant women were forbidden from going outside during a total lunar eclipse for fear of miscarriage. Some ancient cultures advise against eating during the hours of total lunar eclipse because they believe it causes harmful effects upon the body, which could bring permanent poor health and bad luck. To modern artistic souls, total lunar eclipse is a much celebrated opportunity for new creations.

Just in case you’ve missed yesterday’s Blood Moon, see it comes to life again through the lens of photographer Kim Bao Tran (who braced the -20 °C weather for 2 hours, all for art’s sake).