How to prove to anyone that the earth is round

We live in an amazing time. Most of the celestial bodies in the solar system have been explored by NASA probes, GPS satellites are circling the Earth, ISS crews are flying steadily into orbit, and returning rockets are landing on barges in the Atlantic Ocean.

Nevertheless, there is still a whole community of people who are sure that the Earth is flat. Reading their statements and comments, you sincerely hope that they are all just trolls.

Here are some simple proofs that our planet is round.

Ships and horizon

If you visit any port, look at the horizon and watch the ships. As a ship moves away, it doesn’t just get smaller and smaller. It gradually disappears behind the horizon: first the hull disappears, then the mast. Conversely, approaching ships do not appear on the horizon (as they should if the world were flat), but rather come out of the sea.

But ships don’t come up out of the waves (with the exception of the Flying Dutchman from Pirates of the Caribbean ). The reason why approaching ships look like they’re slowly rising from the horizon is because the Earth isn’t flat, it’s round.

Varying constellations

Different constellations can be seen from different latitudes. This was noticed by the Greek philosopher Aristotle as early as 350 BC. e. Returning from a trip to Egypt, Aristotle wrote that “in Egypt and <…> in Cyprus there are stars that are not visible in the northern regions.”

The most striking examples are the constellations Ursa Major and the Southern Cross. Ursa Major, a bucket-like constellation of seven stars, is always visible at latitudes above 41° north latitude. Below 25° south latitude you will not see it.

Meanwhile, the Southern Cross, a small constellation of five stars, you will find only when you get to 20 ° north latitude. And the further south you move, the higher the Southern Cross will be above the horizon.

If the world were flat, we could observe the same constellations from anywhere on the planet. But it’s not.

You can repeat Aristotle’s experiment when you travel. Find constellations in the sky with these apps for Android and iOS.

Lunar eclipses

Another proof of the sphericity of the Earth, found by Aristotle, is the shape of the earth’s shadow on the moon during an eclipse. During an eclipse, the Earth is between the Moon and the Sun, blocking the Moon from sunlight.

The shape of the Earth’s shadow that falls on the Moon during an eclipse is perfectly round. That is why the moon becomes a crescent.

Shadow length

The first to calculate the circumference of the earth was a Greek mathematician named Eratosthenes, who was born in 276 BC. e. He compared the length of the shadows on the day of the summer solstice in Syene (this Egyptian city is today called Aswan) and Alexandria located north.

At noon, when the sun was directly over Siena, there were no shadows. In Alexandria, a stick placed on the ground cast a shadow. Eratosthenes realized that if he knew the angle of the shadow and the distance between cities, he could calculate the circumference of the globe.

On a flat earth, there would be no difference between the length of the shadows. The position of the Sun would be the same everywhere. Only the sphericity of the planet explains why the position of the Sun is different in two cities at a distance of several hundred kilometers from each other.

Observations from above

Another obvious proof of the sphericity of the Earth: the higher you go, the farther you can see. If the earth were flat, you would have the same view regardless of your elevation. The curvature of the Earth limits the range of our view to about five kilometers.

World travel

The first circumnavigation of the world was made by the Spaniard Ferdinand Magellan. The voyage lasted three years, from 1519 to 1522. It took Magellan five vessels (of which two returned) and 260 crew members (of which 18 returned) to circumnavigate the globe. Fortunately, in our time, in order to make sure that the Earth is round, it is enough just to buy a plane ticket.

If you’ve ever traveled by plane, you may have noticed the curvature of the Earth’s horizon. It is best seen in flight over the oceans.

According to an article published in the journal Applied Optics, the curve of the Earth becomes visible at an altitude of about 10 kilometers, provided that the observer has a view of at least 60 °. From the window of a passenger airliner, the view is still less.

More clearly, the curvature of the horizon is visible if you fly above 15 kilometers. It is best seen in photographs from the Concorde, but, unfortunately, this supersonic aircraft has not flown for a long time. However, high-altitude aviation is reviving in the Virgin Galactic passenger rocket plane – Space Ship Two. So in the near future we will see new photos of the Earth taken in suborbital flight.

An airplane can easily circle the globe without stopping. Round-the-world travel by plane was carried out repeatedly . At the same time, the planes did not detect any “edges” of the Earth.

Weather balloon observations

Ordinary passenger airliners fly not so high: at an altitude of 8-10 kilometers. Weather balloons rise much higher.

In January 2017, students at the University of Leicester tied some cameras to a hot air balloon and launched it into the sky. It rose to a height of 23.6 kilometers above the surface, significantly higher than passenger airliners fly. In the pictures taken by the cameras, the curve of the horizon is clearly visible.

Shape of other planets

Our planet is pretty ordinary. Of course, there is life on it, but otherwise it is no different from many other planets.

All our observations show that the planets are spherical. Since we have no good reason to think otherwise, our planet is also spherical.

A flat planet (ours or any other) would be an incredible discovery that would contradict everything we know about planet formation and orbital mechanics.

Time Zones

When it’s seven in the evening in Moscow, it’s noon in New York, and it’s midnight in Beijing. In Australia at the same time, 1:30 am. You can see what time it is anywhere in the world and make sure that the time of day is different everywhere.

There is only one explanation for this: the Earth is round and rotates around its axis. On the side of the planet where the Sun shines, it is currently day. The opposite side of the Earth is dark, and there is night. This forces us to use time zones.

Even if we imagine that the Sun is a directional searchlight that cruises over a flat Earth, then we would not have a clear day and night. We would still observe the Sun, even if we were in the shade, as we can see the spotlights shining on the stage in the theater, while being in a dark hall. The only explanation for the change in time of day is the sphericity of the Earth.

Center of gravity

It is known that gravity always pulls everything towards the center of mass.

Our Earth is spherical. The center of mass of the sphere is located, which is logical, in its center. Gravity pulls all objects on the surface in the direction of the Earth’s core (that is, straight down) regardless of their location, which is what we always observe.

If we imagine that the Earth is flat, then gravity will have to attract everything on the surface to the center of the plane. That is, if you find yourself at the edge of a flat Earth, gravity will not pull you down, but to the center of the disk. It is hardly possible to find a place on the planet where things fall not down, but sideways.

Images from space

The first photograph of the Earth from space was taken in 1946. Since then, we have launched many satellites, probes and astronauts (or astronauts or taikonauts – depending on the country) there. Some satellites and probes have returned, some remain in Earth orbit or fly through the solar system. And in all the photographs and videos transmitted by spacecraft, the Earth is round.

The curvature of the Earth is clearly visible in photographs from the ISS. In addition, you can see photographs of the Earth taken every 10 minutes by the Himawari-8 satellite of the Japan Meteorological Agency. It is constantly in geostationary orbit. Or here are real-time photos from the DSCOVR satellite, NASA.

Now, if you suddenly find yourself in a flat earth society, you will have several arguments in arguing with them.