A MATTER OF PERSPECTIVE
Mercury, in perspective.
A planet that never really goes backward.
An Earthbound view that sometimes does.
THE INNER SOLAR SYSTEM
A view from above it all.
Drag to orbit · Scroll or pinch to zoom Planet sizes enlarged for clarity
A LITTLE TIME TRAVEL
Watch the perspective change.
THE VIEW CHANGES. THE ORBIT DOESN’T.
A small planet.
A little optical illusion.
Mercury laps the Sun in about 88 days. Earth takes about 365. As we move at different speeds, our line of sight shifts—and Mercury can appear to drift backward against the stars.
That’s retrograde. When it resumes its usual eastward drift, we call it direct. Both planets keep moving forward around the Sun.
The explanation, from NASAWHAT EARTH SEES
Mercury’s path across the sky
Geocentric ecliptic coordinates · east increases to the right
How this little observatory works
Positions come from Astronomy Engine. Retrograde means Mercury’s apparent geocentric ecliptic longitude is decreasing. We calculate its rate over a short time interval, including light travel time and aberration, and estimate turning points from changes in that rate.
The 3D model uses calculated heliocentric positions and proportionate orbital distances. Planet sizes and surface details are illustrative; background stars are decorative. The dashed line shows the geometric direction from Earth to Mercury. The sky chart shows Mercury’s apparent position, with its axes scaled independently to reveal the path.
“Live now” uses your device’s clock and updates every minute. Exploring a date uses 12:00 UTC; playback changes simulated time. Dates from 2000–2099 are supported. Turning times are approximate, shown to the nearest hour. This is an educational model, not an observing or navigation instrument.
Reference positions were checked against NASA/JPL Horizons. Everything is calculated in your browser; no location, account, or external data feed is needed.