The Science Behind Mercury Retrograde


    Mercury retrograde is a term that has recently come under the spotlight, becoming a scapegoat for nearly all minor inconveniences during its occurrence. Are you in a bad mood? Blame mercury retrograde. Spilled coffee on your shirt? It’s not your fault, Mercury is just in retrograde. Even popular television shows have joined the bandwagon, with the reality competition series “RuPaul’s Drag Race” tweeting a succinct “Eek!” to the most recent retrograde last month.

    But what exactly is mercury retrograde? Turns out that there is a lot of physics and astronomy behind the phenomenon.


    According to “Star Child,” a site run by NASA, retrograde motion is only an illusion: Mercury is not actually moving backwards. It only appears to be doing so because of its position in the solar system relative to our planet and its movement around the Sun.

    Planets typically move through the sky from west to east, which astronomers call prograde motion. Sometimes though, especially when it came to Mercury, these planets would move the opposite direction— from east to west—typically for a few weeks.

(Wikimedia Commons)

    This is due to the fact that Mercury travels much faster than our planet Earth. Not only is Mercury fast, but its orbit is also very elliptical, meaning that its path around the Sun is more stretched out in an oval than circular. When Mercury is furthest from the Sun, that’s when it travels slower than its speed when it is closer to the Sun. This phenomenon is due to a concept in physics called conservation of angular momentum. Think of an ice skater when they’re spinning—when they extend their arms outward, they travel much slower than if they were to draw their arms in. A similar idea applies to Mercury’s movement.

    There is an added layer of weirdness to Mercury though, because astronomers found that every time it would orbit the Sun, the planet would be slightly ahead of where it was predicted to be from their calculations. Albert Einstein’s theory of general relativity actually explained Mercury’s irregularities. Since Mercury is so close to the Sun, it is also traveling through a piece of space, time bent by the enormous mass of the Sun, influencing its movement.


    In the end though, sometimes blaming everyday problems on mercury retrograde is just pure fun, and maybe even adds a bit of mystique. It is clear that mercury retrograde has captured the interest of social media, with countless tweets, articles, and Facebook posts on the subject. Behind the astrology and seemingly-terrifying term though is science. So instead of seeing mercury retrograde as something bad, see it as a scientific phenomenon that reveals a deeper layer of complexity to the universe beyond us.