Put all your bad omens aside— This is what it really means when a planet is in retrogradeYou usually hear about a planet being “in retrograde” from astrologers, which might give you the impression that the term is mystical jargon. In fact, it does have an astronomical meaning. That meaning just happens to come from a rather outdated concept, when the Earth was still the center of the solar system. Today, it explains why planets seem to go backwards in the sky.A long time ago, some astronomer looked at the sky, noticed that one of these moving stars had started moving backwards, and thought, “This can’t be good.” That set the precedent for the astrological concept of retrograde astronomical motion as an omen of bad times for people on Earth.When people finally understood that Earth and the traveling stars were actually all planets moving around a central sun, things became a bit more clear. The reason they change direction is because our orbits are different. In the case with Earth and Mars, Mars has a longer orbit and so when we overtake the planet we view it on the starry background as if it is moving backwards.Retrograde Mars (APOD)Via io9

Put all your bad omens aside
— This is what it really means when a planet is in retrograde


You usually hear about a planet being “in retrograde” from astrologers, which might give you the impression that the term is mystical jargon. In fact, it does have an astronomical meaning. That meaning just happens to come from a rather outdated concept, when the Earth was still the center of the solar system. Today, it explains why planets seem to go backwards in the sky.

A long time ago, some astronomer looked at the sky, noticed that one of these moving stars had started moving backwards, and thought, “This can’t be good.” That set the precedent for the astrological concept of retrograde astronomical motion as an omen of bad times for people on Earth.

When people finally understood that Earth and the traveling stars were actually all planets moving around a central sun, things became a bit more clear. The reason they change direction is because our orbits are different. In the case with Earth and Mars, Mars has a longer orbit and so when we overtake the planet we view it on the starry background as if it is moving backwards.

Retrograde Mars (APOD)

Via io9

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