15 things you can check yourself
Is the Earth flat?
Lots of people sincerely wonder. So instead of asking you to trust anyone, this page puts the flat-Earth map and the globe side by side in 3D, shows what each one predicts, and tells you how to check it with your own eyes.
Every scene below has a Flat map and a Globe switch. The flat map is the one most flat-Earth groups use: the North Pole in the middle and Antarctica stretched into a ring of ice around the edge. Each check gives the flat-Earth explanation in its own words, what each model predicts, what people actually see, and a way to test it yourself.
01 / 15
The Southern Cross is due south for everyone
What flat Earthers say
Stars sit on a dome not far above a flat Earth, and the southern stars, like the Southern Cross, circle somewhere above the outer edge of the disc.
The flat map predicts
On the flat map, south means away from the centre. From those four cities south points four very different ways, more than 150° apart, so no single group of stars could be due south of all of them at once.
The globe predicts
Every observer in the southern hemisphere looks the same way to find the south celestial pole: parallel to the Earth's axis. Sydney, Cape Town, Santiago and Auckland all see the Southern Cross due south, turning around the same point in the sky.
What we actually see
On the same night, people in all four cities see the same Southern Cross due south, at about the same height, wheeling around the same point. Sailors have steered by it for centuries.
Try it yourself
On a clear southern night, find the Southern Cross and its two bright pointer stars. Follow the long arm of the cross about four and a half lengths: that spot is due south anywhere in the southern hemisphere. Ask a friend in another southern country to do it tonight and compare.
02 / 15
Polaris sits at your latitude, then disappears
What flat Earthers say
Polaris is fixed above the North Pole in the middle of the disc, and it looks lower the further away you are because of perspective.
The flat map predicts
A star 5,000 km above the middle of a flat Earth would be visible from everywhere on it: about 27° high from the equator and still about 20° high from Sydney.
The globe predicts
Polaris lies almost exactly above the North Pole and so far away that its light arrives parallel everywhere. Its height above the horizon equals your latitude, and south of the equator the Earth itself hides it.
What we actually see
From the equator Polaris sits on the horizon, and from Sydney nobody ever sees it. Navigators found their latitude by measuring Polaris for centuries, and it works to within a degree.
Try it yourself
Your fist at arm's length covers about 10° of sky. Measure how high Polaris stands and compare it with your latitude on your phone's map.
03 / 15
The sky turns two ways at once
What flat Earthers say
The dome of stars turns above the disc around Polaris, once a day.
The flat map predicts
One dome turning above the middle can circle only one point. Looking south from Sydney means looking away from the middle, so the stars would slide sideways in long arcs and nothing would circle a southern point.
The globe predicts
The Earth spins once a day, so the northern sky circles Polaris anticlockwise while the southern sky circles a point in the south clockwise, at the same moment.
What we actually see
Long exposures from Australia, South Africa and Chile show the stars making perfect circles around a point in the southern sky, clockwise, on the same nights that northern photographers record circles around Polaris.
Try it yourself
Put a phone on a tripod in its night or star-trail mode, point it south if you are in the southern hemisphere (north in the northern), and leave it for an hour.
04 / 15
Ships sink hull first
What flat Earthers say
Ships vanish only because they get too far away to see, and a good zoom lens brings them back.
The flat map predicts
On a flat sea nothing can hide any part of the ship. It only gets smaller, and zooming in would show the whole hull.
The globe predicts
The sea curves away, so a ship beyond your horizon has its lower part hidden behind the water. From 2 m above the sea the horizon is about 5 km away.
What we actually see
Through binoculars or a telescope, distant ships and islands disappear from the bottom up, and zooming in does not bring the hidden part back. The air bends light slightly (refraction), which usually lets us see about 7% further. On rare days, warm air over cold water makes a mirage that lifts distant shores into view: that is why the Chicago skyline is sometimes seen from about 90 km across Lake Michigan, and why on most days it is hidden.
Try it yourself
On a beach with a clear view, follow a departing ship with binoculars. Or photograph a distant headland from water level, then again from higher up the beach, and see more of its base appear.
05 / 15
The Sun keeps its size and sets
What flat Earthers say
The Sun is small and close, circling about 5,000 km above the disc, and it seems to set because of perspective, like a streetlight at the end of a long road.
The flat map predicts
A Sun 5,000 km up and about 50 km wide would shrink to around a third of its noon size by evening and, seen from the equator, never sink lower than about 14° above the horizon. Perspective makes distant things smaller and lower, but never below the horizon.
The globe predicts
The Sun is 150 million km away, so its size in the sky does not change during the day, and as the Earth turns your horizon rises in front of it.
What we actually see
Photographed through a solar filter, the Sun is the same 0.53° wide at noon and at sunset, and it goes below the horizon bottom first. After sunset, clouds high overhead are still lit from below.
Try it yourself
With a proper solar filter (never look at the Sun without one), photograph the Sun at the same zoom at midday and just before sunset, and compare the two discs.
06 / 15
Day and night, right now
What flat Earthers say
The Sun works like a spotlight, lighting part of the disc as it circles.
The flat map predicts
Drawn on the flat map, the real day side becomes a stretched shape that changes through the year. A spotlight makes a circle, which cannot match it.
The globe predicts
The half of the globe facing the Sun has day, the other half night, and the line between them sweeps round once a day. This scene shows the real Sun, now.
What we actually see
When it is noon in London it is night in Sydney and early morning in New York, exactly as the globe shows, and live webcams around the world agree.
Try it yourself
Open a world clock and a few city webcams at the same moment, or simply call a friend on another continent.
07 / 15
Antarctica gets 24 hours of daylight
What flat Earthers say
Antarctica is an ice wall running all the way around the edge of the disc.
The flat map predicts
Antarctica would be a ring more than 100,000 km around. Lighting all of it at once, while the North Pole in the middle stays dark, is impossible for any Sun above the disc.
The globe predicts
In late December the southern half of the Earth tilts toward the Sun, so the Sun circles the sky without setting over Antarctica while the Arctic has 24-hour night.
What we actually see
Research stations such as McMurdo and the South Pole station film the Sun circling the sky without setting every December, and tourists on Antarctic cruises see it too.
Try it yourself
Watch a 24-hour timelapse filmed in Antarctica in December, or an Antarctic station's webcam during the southern summer.
08 / 15
Flights across the south
What flat Earthers say
The flat map shows the true distances, and flights across the southern hemisphere stop over or take other routes.
The flat map predicts
On the flat map Sydney and Santiago sit on opposite sides of the disc, more than 25,000 km apart, and Perth to Johannesburg is over 18,000 km.
The globe predicts
Sydney to Santiago is about 11,300 km on the globe, and Perth to Johannesburg about 8,300 km.
What we actually see
Both routes are flown nonstop in about 11 to 13 hours, at normal airliner speeds of around 900 km/h. You can watch them on flight trackers any day.
Try it yourself
Look up Sydney to Santiago or Perth to Johannesburg on a flight tracker and follow a plane all the way.
09 / 15
The Earth's shadow is always round
What flat Earthers say
Lunar eclipses have some other cause, such as a dark object passing in front of the Moon.
The flat map predicts
A disc casts a round shadow only when the light hits it face-on. Eclipses happen with the Moon high or low in the sky, so a flat Earth would sometimes cast an oval, or a straight bar.
The globe predicts
In a lunar eclipse the Moon moves through the Earth's shadow. A ball casts a round shadow from every direction.
What we actually see
Aristotle pointed it out 2,300 years ago: every lunar eclipse shows a curved shadow edge, the same curve whether the Moon is rising, overhead or setting.
Try it yourself
Watch the next lunar eclipse and look at the edge of the shadow as it crosses the Moon. The dates are in our sky events list.
10 / 15
Everyone sees the same Moon phase
What flat Earthers say
The Moon is small and close above the disc, and its phases come from how we see it.
The flat map predicts
A Moon a few thousand kilometres up would be seen from different sides by different cities, so they would see different phases at the same time.
The globe predicts
The Moon is lit by the distant Sun, so its phase depends only on where it is in its orbit. Everyone sees the same phase on the same night, upside down from the southern hemisphere.
What we actually see
Photos of the Moon taken on the same night in the UK and in Australia show the same phase, one rotated relative to the other.
Try it yourself
Photograph the Moon tonight and swap pictures with someone in the other hemisphere.
11 / 15
Eratosthenes measured the Earth with two sticks
What flat Earthers say
Different shadow lengths come from a small, close Sun, not from a curved Earth.
The flat map predicts
A Sun about 6,300 km above a flat Earth also fits two sticks. A third stick splits them: the globe and the close Sun predict different shadows, and the further away the stick, the bigger the gap.
The globe predicts
Around 240 BC, Eratosthenes noted that at noon on the summer solstice the Sun stood overhead at Syene, while in Alexandria, about 800 km north, a stick cast a shadow at 7.2°. On a globe that makes 800 km a fiftieth of the way round: about 40,000 km. It is.
What we actually see
Schools around the world repeat the measurement at the equinoxes and solstices, in both hemispheres, and their shadows fit the globe.
Try it yourself
At local noon on an equinox (around 20 March or 22 September) measure the shadow of a vertical stick: the shadow's angle from vertical equals your latitude.
12 / 15
Different skies from different latitudes
What flat Earthers say
Everyone sees the same dome of stars, only from different distances.
The flat map predicts
Under a dome a few thousand kilometres up, every star would be above everyone's horizon: everyone would see every constellation, just lower.
The globe predicts
The Earth blocks half the sky. From northern Europe the Southern Cross never rises, and from Australia Polaris is never seen.
What we actually see
Travellers have noticed it for thousands of years: sail south and new constellations rise ahead while the northern ones sink behind you.
Try it yourself
Compare tonight's sky from Oslo and from Sydney in a free planetarium app, then look at real photos taken in each place.
13 / 15
The horizon curves when you go high enough
What flat Earthers say
The horizon always looks flat and rises to eye level, so the Earth must be flat.
The flat map predicts
The horizon of an endless plane stays exactly at eye level and dead straight, at any height.
The globe predicts
On a ball the horizon drops below eye level as you climb, and from high enough it bends into an arc. To be honest about it: from an airliner at 11 km the drop is only about 3°, and the curve is subtle and easy to miss or to fake with a wide-angle lens.
What we actually see
Pilots and balloon cameras see the horizon fall below eye level. From 30 to 40 km up the curve is obvious, and from the International Space Station the Earth is a ball.
Try it yourself
On a flight, check the horizon against a spirit-level app. Or watch footage from amateur high-altitude balloons, preferring cameras without fisheye lenses.
14 / 15
Gravity pulls big things into balls
What flat Earthers say
Gravity is not real; things fall because they are denser than the air around them.
The flat map predicts
On a disc the pull would lean toward the middle, more and more toward the rim. Oceans would flow toward the North Pole, and walking south would feel like climbing a hill that gets steeper toward the edge.
The globe predicts
Every bit of matter pulls on every other. Anything more than a few hundred kilometres across pulls itself into a ball: the dwarf planet Ceres (940 km) is round, while the smaller asteroid Vesta (525 km) is lumpy.
What we actually see
Every planet and large moon we have ever looked at is round, and a plumb line hangs straight down wherever you are on Earth.
Try it yourself
Open the 3D viewer and visit every planet and large moon. Then hang a weight on a string anywhere in the world: it points straight down.
15 / 15
Satellites, the ISS and GPS
What flat Earthers say
Satellites are fake, and GPS really works with towers on the ground.
The flat map predicts
Nothing can keep circling above a disc. Drawn on the flat map, the space station's real ground track winds across the disc in loops no orbit could make.
The globe predicts
The International Space Station circles the Earth every 92 minutes, about 420 km up. GPS uses around 31 satellites 20,200 km up, and your phone works out where it is from the distances to at least four of them.
What we actually see
The space station is easy to see with your own eyes as a bright, steady light crossing the sky in a few minutes. GPS works in the middle of oceans and deserts, far from any tower, and GPS apps show each satellite's place in the sky.
Try it yourself
Look up the next space station pass over your town (NASA's Spot the Station) and watch it. A GPS test app shows which satellites your phone is using and where they are.
Not a matter of trust
Nothing on this page asks you to believe NASA, a teacher or us. Each check is something you, a friend in another country or a cheap telescope can test. Any one of them on its own might have a clever answer. The globe is simply the one shape that fits every one of them at the same time, the same way it fits the photos, the flights, the stars and the shadows.
If you have a check we should add, or think we have got one wrong, tell us. We would genuinely like to hear it.
Questions
Is the Earth flat?
No. Every section on this page is a separate, checkable observation, and the globe is the one shape that fits all of them at once: the Southern Cross being due south for everyone, Polaris matching your latitude, ships sinking hull first, the Sun keeping its size as it sets, flight times across the southern hemisphere, the round shadow in lunar eclipses and more.
How can I prove the Earth is round myself?
The easiest checks need no equipment: measure Polaris against your latitude, watch a ship leave through binoculars, photograph star trails in both hemispheres, compare Moon photos with a friend across the equator, or repeat Eratosthenes' shadow experiment at noon on an equinox.
Why does the horizon look flat?
Because the Earth is very large compared with us. From 2 m up you see only about 5 km of sea, and the curve across your view is far too small to notice. It only becomes clear from tens of kilometres up.
Can you see the curvature of the Earth from a plane?
Only just. From 11 km the horizon is about 3° below eye level and the curve is subtle; wide-angle lenses can add or hide curvature, so judge it with a straight edge. From 30 to 40 km it is easy to see.
Why can we sometimes see Chicago from across Lake Michigan?
On some days a layer of warm air over cold water bends light down along the surface and lifts distant objects into view (a superior mirage). On ordinary days the base of the skyline is hidden by the curve of the lake, as the globe predicts.
What is the flat Earth map?
It is the azimuthal equidistant projection: a real map projection with the North Pole in the middle and distances true only along lines out from the centre. Stretching the globe flat this way makes Antarctica a ring around the edge and distorts the southern hemisphere badly, which is why southern distances and sky directions stop working on it.
Sources and further reading
- Crux, the Southern Cross: positions and how to find south
- Polaris and finding latitude
- Atmospheric refraction near the horizon
- Superior mirages and looming
- Eratosthenes' measurement of the Earth
- Lunar eclipses
- The midnight sun
- Azimuthal equidistant projection
- Hydrostatic equilibrium: why large bodies are round
- 4 Vesta
- Ceres
- GPS: the space segment
- Spot the Station
- Red Bull Stratos, the 39 km balloon jump
Star positions are from the Hipparcos catalogue; day and night use the same Sun position as our 3D viewer and what is up tonight. Flight times are typical scheduled nonstop times and vary with season and wind.