Add Yahoo as a preferred source to see more of our stories on Google. Here's what it means and what to know. Three to four times a year, the planet Mercury appears to travel backward across the sky — ...

Retrograde mean motion resonances occur when orbiting bodies, moving in directions opposite to the dominant sense of motion, experience periodic gravitational interactions that can stabilise their ...

Forbes contributors publish independent expert analyses and insights. An award-winning reporter writing about stargazing and the night sky. From July 17 to Aug. 10, Mercury will appear to move ...

Astronomers have recently been taken aback by the discovery of an object in space that seems to be defying the common laws of celestial movement by orbiting backwards. This surprising discovery, which ...