You don't have to be an astrophysicist to appreciate the incredible beauty of the night sky... and tomorrow there will be a cosmological event that everyone can enjoy, just by looking up.
Amateur astronomers and casual skywatchers on four continents will have the opportunity to watch the last total lunar eclipse for three years as the next one isn't until March 14, 2025, according to NASA. The Moon, our planet's only natural satellite, will turn a blood-colored red as it slips into Earth's shadow, creating a celestial spectacle visible to viewers in North and Central America, Asia, Australia, the Pacific Islands and parts of South America.
So, what is a 'Blood Moon' eclipse exactly?
A lunar eclipse occurs when the Sun, Earth and Moon align so that the moon passes into Earth’s shadow. In a total lunar eclipse, the entire Moon falls within the darkest part of Earth’s shadow, called the umbra. When the Moon is within the umbra, it will turn a reddish hue because of the little remaining sunlight being refracted through the atmosphere before it hits the lunar surface.
If no light was able to reach the Moon, as often happens, it simply isn't visible from Earth (that's called a New Moon). This doesn't happen every time the Moon makes its monthly trip around our planet because the Moon’s orbit around Earth is inclined to Earth’s orbit around the Sun by approximately 5 degrees. Space is three-dimensional after all. Twice a month the Moon intersects the ecliptic (Earth’s orbital plane) at points called nodes. If the Moon is going from south to north in its orbit, it’s an ascending node. If the Moon is going from north to south, it’s a descending node. If the full Moon or New Moon sweeps close to one of these nodes, then an eclipse is inevitable.
OK, but why is it called a 'Blood Moon' eclipse?
Good question. The same phenomenon that makes our sky blue and our sunsets red causes the Moon to turn red during a lunar eclipse. It’s called Rayleigh scattering. While most of the sunlight is blocked, some rays bent around the edge of Earth and reach the Moon’s surface. Light travels in waves and different colors of light have different physical properties. Blue and green light have shorter wavelengths and are scattered more easily by particles in Earth’s atmosphere than red or orange light, which have longer wavelengths.
I understand the physics now, but how can I watch it?
Tuesday's 'Blood Moon' eclipse will officially begin at 3:02am EST when the moon begins to enter the outermost region of Earth's shadow. The UK is back on Greenwich Mean Time (GMT), so you don't have to worry having to include daylight savings in your calculations. Eastern Standard Time (EST) is five hours behind GMT and Pacific Standard Time (PST) is three hours behind EST and eight hours behind GMT.
To put all that nonsense into context, if you're on the west coast, the spectacle begins at a much more palatable time of 12:02am. Sadly, folk in the UK and Europe will struggle to see it.
However, NASA is live-streaming the event here.
This won't affect any other aspect of nocturnal night sky observations, since shooting stars and such like are a result of meteorites burning up in our planet's atmosphere. Let's hope Starlink's cubesats don't spoil the event for anybody.
Will the world as we know it come to an end?
Well, that always seems to be on the cards these days and it's entirely possible...but it probably won't have anything to do with this.
However, the Bible references a 'Blood Moon' in Acts 2:20 and, most notably, Revelation 6:12. In the latter, the verse reads, 'And I beheld when he had opened the sixth seal, and, lo, there was a great earthquake; and the sun became black as sackcloth of hair, and the moon became as blood.'
So you know, anything could happen between now and then.