Globe vs Flat Earth: what this page does
Two models of the Earth, side by side: the Globe Earth (GE) and the Flat Earth (FE) on the Gleason map. Pick any place and time and each model draws the sky it predicts: the Sun, the Moon, the stars and the horizon. The table under the views lists each prediction next to the real sky, so you can see which model matches. Better still, step outside and compare with what you observe.
How each model is built
- Real sky: Astronomy Engine, an ephemeris that matches telescope observations to well under 1 arc-minute, including the bending of light by the air.
- Globe: plain sphere geometry, directly computed in this page. The Sun is the only light, so day, night, Moon phases and eclipses come out by themselves.
- Flat: given its strongest version. It uses the real point on Earth under the Sun and Moon, and places both 4,828 km (3,000 miles) above the Gleason map, each 51 km wide. Night assumes the Flat-Earth Sun is a "spotlight": it is dark more than about 10,000 km from the point under the Sun (adjustable). Stars sit on a dome (the "firmament") 10,000 km high over the North Pole that comes down at the "Ice Wall" in Antarctica. You can change these figures in Flat model settings.
Short names in the views: GE means Globe Earth and FE means Flat Earth. FE Sun and FE Moon are the flat model's own Sun and Moon. On the flat view, the red and blue circles labelled GE Sun and GE Moon show where the real Sun and Moon are, as the globe model predicts.
Horizon: the air bends light slightly round the curve, so the real horizon is about 7% farther than plain geometry gives. On a flat disc there would be no horizon at all, only haze.
This page is free, with no ads and no tracking. If you would like to help future work, such as a phone app, you can support it on Ko-fi.
Stars: the 520 brightest (magnitude 4 and above) from the Hipparcos catalogue, with lines for 18 constellations, via d3-celestial by Olaf Frohn (BSD). Earth images: NASA Blue Marble and Black Marble. Moon map: NASA Lunar Reconnaissance Orbiter.
Options
Top bar
- Model
- Both models side by side, or one alone, full width.
- View
- Observer: what you would see standing there. Space: the whole planet from outside.
- Scale
- Enlarged makes the Sun and Moon visible in Space view. True shows real sizes and distances.
- Stars
- Off, on, with names, or Trails: the paths stars draw across the sky during playback.
- Planets
- Shows Mercury to Neptune at their real positions among the stars. On the flat model they sit on the firmament with the stars. Paths shows where each one goes among the stars over two months either side of the date, solid where it has been and dotted where it is going, with a dot on the 1st of each month: you can watch planets turn back.
- Solar filter
- Removes the Sun's glare so you can see its disc, for example during an eclipse.
- Labels
- Shows or hides the names on the views.
- km | mi (top right)
- Shows distances, altitudes and speeds in kilometres or in miles (feet for low altitudes, mph for speeds).
- EN | FR (top right)
- Switches the whole page between English and French.
Left panel
- Observer
- Choose a place, type coordinates, or set the altitude from the ground up to space. Face buttons turn the view toward the Sun, Moon, Polaris or the Southern Cross; Follow keeps it there, and can also track the FE Sun and Moon, Venus, Mars, Jupiter and Saturn.
- Saved places
- Keep your own locations in this browser.
- Date and time
- Any date, in the time zone you choose (yours by default), with playback at several speeds. Real events jumps to famous eclipses and observations.
- Distance
- The distance between two cities on each model, drawn as each model's shortest route. Tick the box to see both routes on both models; Erase removes the lines.
- Real flight routes
- Real flights with their actual flight times, and the speed each model would need.
- Flat model settings
- Try other heights and sizes for the FE Sun, Moon and firmament, and other sizes for the Sun's spotlight.
Mouse: drag to look around (or to orbit in Space view), scroll to zoom. In Space view, or from 2,000 km up, click any point on the planet to go there. Each section of the left panel folds when you click its title.