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Is Mercury in retrograde? A few times a year, it is - though it's not likely to have any effect on your day-to-day life.
- Mercury retrograde - or more scientifically, Mercury apparent retrograde motion - is a real phenomenon.
- It's an optical illusion that astronomers can observe as Mercury speeds past the Earth a few times every year.
- But it doesn't have any effect on your personal life.
As our world continues to orbit the star at the center of our solar system, we can gaze at the night sky - like people have for thousands of years - and watch the stars and the planets that rise and set around us.
One of those planets - tiny, sun-scorched Mercury - frequently causes some consternation for followers of astrology, the belief that the position of Earth in relation to other planets and stars has an effect on human lives and futures.
On Thursday evening, Mercury entered what's known as apparent retrograde motion, a phrase often shortened to "Mercury in retrograde" or simply "Mercury retrograde."
This phenomenon occurs when the super-speedy planet appears to be moving across the sky in a different direction than it normally does.
It's an optical illusion created when Mercury catches up to and then passes Earth in its orbit around the sun.
As one NASA website explains it:
"You can experience this effect for yourself. Start out standing side by side with a friend. Have a friend walk forward slowly. Now you walk forward at a faster speed. Watch your friend and think about how they are moving relative to you. At first, they move away, then as you pass them, they appear to be moving backward relative to you - even though they are still walking forward."
It's all about perspective.
Since Mercury moves so quickly, a "year" on that planet (the time it takes to complete its orbit around the sun) takes approximately 88 Earth-days. So Mercury's apparent retrograde motion relative to Earth happens three or four times a year, and tends to last approximately three weeks each time.
As NASA and countless astronomers have pointed out, there's absolutely no scientific evidence that astrology can tell you anything about the future, how you should behave, or what your personality is based on the position of Earth relative to the stars when you were born.
In fact, we should be grateful that we don't observe any effects from the motion of Mercury or other planets.
As theoretical cosmologist Katie Mack, as assistant professor at North Carolina State University, told The Guardian, life on Earth would be pretty wild if we were truly affected by surrounding celestial objects.
"It would be fascinating but rather dystopian if the planets COULD affect our lives. Like, the 'Mercury in retrograde' thing," she said. "Like if the apparent motion across the sky, from Earth, of a planet we can almost never actually see, somehow meant that it, the planet, would suddenly start to meddle in our lives and screw things up for a time."
Those who actually want to observe Mercury retrograde in the sky for themselves face a bit of a challenge, since you need to look toward the sun to do so. It's much easier to see Mars retrograde, which happens about every two years, when Earth passes Mars in its orbit.