(WHTM) — Six planets in our solar system are moving “in retrograde” right now, and that’s getting a lot of people excited.

Astrology sites are full of explanations on how retrograde motions are affecting horoscopes, including talk of “stagnation in the cosmos,” “retrograde energy swaying” and “challenges to relationships” as well as advice to “avoid new ventures,” “stick to routine jobs” and “evaluate how we are transforming our lives.”

There’s also a lot of bad science suggesting how the “planet slows down,” which certainly causes a lot of fuss over what is essentially an optical illusion.

So what’s really going on when a planet travels in retrograde?

To begin, the following planets (in order from the sun) will be moving in retrograde for a while:

  • Mercury from Sept. 10 to Oct. 2
  • Jupiter from July 28 to Nov. 23
  • Saturn June 4 to Oct. 23
  • Uranus Aug. 24 to Jan. 23
  • Neptune June 28 to Dec. 4
  • Pluto April 29 to Oct. 8 (Yeah, we know Pluto is a “dwarf planet,” but it’s still in an orbit, and it still displays retrograde motion.)

According to NASA, retrograde motion is an “apparent” change in a planet’s movement through the sky when seen from Earth — when a planet appears to go backward in orbit. In other words, it’s the optical illusion that was just mentioned.

Planets, including Earth, orbit the sun. This idea is called heliocentrism. (Helios was the god of the sun in Greek mythology.)

Because the planets orbit the sun at different distances, planets have years of different lengths:

Mercury88 days
Venus225 days
Mars687 days 1.88 years
Jupiter4,333 days11.86 years
Saturn10,759 days 29.46 years
Uranus30,687 days84.01 years
Neptune60,190 days164.79 years
Pluto(248.59 years) 90,520 days248.59 years
Orbits of Planets in days and years

Planets with shorter years will “overtake” slower-moving planets.

Planets with different orbit speeds (NASA)

As a faster orbiting planet overtakes a slower one, it will appear (from the vantage point of the faster-moving planet) as though the slower-moving planet stops moving forward and then drifts backward even though it is still moving at its original speed.

“It is not REAL in that the planet does not physically start moving backwards in its orbit,” NASA states. “It just appears to do so because of the relative positions of the planet and Earth and how they are moving around the Sun.”

Graphic showing the retrograde motion of Mars. Notice how Mars seems from Earth to travel in a loop. (NASA)

We can actually see this effect on Earth. Imagine two cars traveling in the same direction in two different lanes. One travels slightly faster than the other. As the faster car overtakes the slower, it will appear (from the vantage point of the faster car) as though the slower car stops, then moves backward, even though its actual speed has not changed. (This thought experiment works with different modes of transportation, from walking to cycling to flying in airplanes.)

It’s worth noting that one of the reasons heliocentrism replaced geocentrism (the notion that the Earth is in the center of the Solar System) is that geocentrism couldn’t explain the retrograde motion of planets. With heliocentrism, explaining retrograde motion was simple.

So why does the idea of retrograde bring with it a sense of doom and gloom?

Well, according to the Farmers’ Almanac, the planets each rule a different aspect of life, and when they appear to move backward, their positive influence on those aspects is believed to be disrupted.

Mercury’s retrograde is the most common to be associated with chaos. That’s because it is the closest to the sun, and therefore the fastest to orbit around it, causing it to become retrograde three or four times a year, according to the Farmers’ Almanac.

“Believers in the malevolent power of Mercury retrograde blame the phenomenon for everything from arguments to lost mail or luggage to automobile accidents and technology issues, and warn people to hold back on conducting important business during this time,” the Farmers’ Almanac says.

According to Astrology.com, retrograde motion is a “side-effect of proximity,” and it suggests that perceived problems as a result may be due to “being too close to someone or something to see it objectively.”

“Taking our time, getting a little distance, and changing perspectives may be very helpful,” it advises.