Taking a break from magnetic fields, I wanted to talk about a very rare event that started taking place on Tuesday, April 15, 2014. The first of four lunar eclipses took place that night. This is a rare event as this tetrad of eclipses will occur six months apart from each other; the first one on April 15, 2014, the next on October 8, 2014, the third on April 4, 2015, and the last one on September 28, 2015. All of the eclipses will be visible from North America.
All these eclipses will be total eclipses. That is when the entire moon is completely engulfed in the Earth’s shadow. This is the most spectacular eclipse as the whole moon turns a bright red, reminiscent of a sunset. This is also called the blood moon. The next kind of eclipse is a partial eclipse. This is when the Moon crosses into the Earth’s umbra, but is not completely consumed by it. The last and least noticeable is a prenumbral eclipse. The Moon enters the Earth’s prenumbra, but doesn’t cross into the umbra. This is a very subtle eclipse. The most one will notice is a drop in brightness. Luckily for us, all the eclipses during this tetrad of eclipses will make the moon glow red. But why red?
That is because, when the sun obstructs the Earth, most of the light is being blocked, but the light hitting the atmosphere is bending towards the Moon. While that occurs, the atmosphere is also scattering the shorter wavelengths of the spectrum into the atmosphere, leaving behind the red wavelength, which is the longest and the least likely to scatter. This is why the moon looks red during a lunar eclipse, and this is why sunsets are red.
Unlike a solar eclipse, this eclipse is safe to view without any eye protection, and it is visible across a whole continent, whereas solar eclipses are visible in a thin, 250 km region during its path. That will be another post…
Thank You for reading.