Mercury is in Retrograde… whatever that means #astronomy #planet #science

Mercury is in retrograde! It started December 28th and will continue through January 18, 2023. Then again April 21 to May 14, August 23 to September 14, and December 13 through the end of the year.

What does that mean, physically? Mercury is an inner planet of the solar system and orbits closer to the sun than Earth does, so…

Mercury, from a 1550 AD illustration. No, the planet doesn’t look like that.

Sometimes, it can appear (from our perspective) that a planet has abruptly switched directions and has started to move in reverse across the sky. This is, of course, an illusion caused by the position of Earth in relation to that of the planet, since a planet in orbit always travels in one set direction and can’t suddenly reverse course. This is why we call the phenomenon apparent retrograde motion, as it only looks like the planet is moving backward. Old Farmer’s Almanac

Say you were driving on a multi-lane highway and you pass another car going in the same direction but a little slower than you. That car appears to move backwards. It retrogrades.

Why should we care? Well, optical illusions can be fun to observe, but they don’t change anything about the reality of orbital mechanics or our love lives. But the night sky has fascinated people for centuries – for as long as we looked up and wondered, I suppose.

During the spiritualism craze of the Victorian era, interest in astrology boomed, with many believing that the stars affected the Earth in a variety of (often inconvenient) ways. Late 19th-century publications like The Astrologer’s Magazine and The Science of the Stars connected Mercury retrograde with heavy rainfall… séances and crystal gazing gradually faded, [but] astrology grew even more popular.

By the 1970s, horoscopes were a newspaper mainstay and Mercury retrograde was a recurring player. Because the Roman god Mercury was said to govern travel, commerce, financial wealth, and communication, in astrological circles, Mercury the planet became linked to those matters as well. Mental Floss

That’s what Mercury looks like

Observations of the planet we call Mercury have been found from the 14th century BC. It’s name then has been translated as “the jumping planet,” which is a nice description of how it shifts from the morning to evening sky and back as it passes on the other side of the sun from Earth’s perspective. Other ancient cultures also documented the planet. The Romans came to the sky party late with their name “Mercury.”

For the next few days, while Mercury is in retrograde, you have a chance to observe (and perhaps to experience) confirmational bias. That’s the all-too-human characteristic we share to interpret new evidence as confirmation of one’s existing beliefs or theories. For those who follow astrology, any disruption can be blamed on that super-heated rock and our earthly view of its orbit.

Clouds permitting, for now you can enjoy catching views of Mercury and Venus (another planet closer to the sun than Earth) in the evening sky shortly after sunset. All five of the classically-observed planets are visible over the night. Click here for more on observing them.