It is common knowledge that 500 years ago, people believed the Earth was spherical. However, it is also entirely false.
Using methods that can be replicated, astronomers have been able to demonstrate our planet’s sphericity for over 2,000 years.
The earliest known mention of a spherical Earth is found in ancient Indian religious scriptures.
The Rigveda, composed between 1500 and 1000 BCE, contains the verse, “The spherical Earth remains in the center of the universe.”
Despite abundant evidence of ancient India’s exceedingly advanced astronomical knowledge, few records of their techniques have survived.
We must consult the Greek ‘natural philosophers’ for this information.
Observe the shadow of the Earth during a lunar eclipse
Around 430 BCE, Empedocles and Anaxagoras observed that the Earth’s shadow appeared spherical during a lunar eclipse, providing the first written evidence that the Earth is a sphere.
During the next eclipse, you can observe its curve for yourself.
Observe the vessels at the horizon
Aristotle added more evidence in 350 BCE.
He observed that when a ship sailed beyond the horizon, the masts remained visible after the hull had vanished, as would be expected if the ship had sailed around a curved edge.
If you are near a port, you can do the same with modern ships, but you will need to search for their upper decks instead of sails.
Observe the shifting location of the North Star
It was common knowledge at the time that distinct constellations appeared in various locations; for instance, the North Star is closer to the horizon in Cairo than in Athens.
However, Aristotle was the first to propose that because Egypt is located further south, it would view the star from a shallower angle if the world were a globe.
During your next vacation in the Northern Hemisphere, keep an eye out for the North Star and compare its position to that of your home location.
Determine the duration of shadows
The Greeks also observed that the same effect caused the lengths of shadows to vary depending on your latitude.
Several scientists measured the circumference of the Earth using this method, but the earliest account dates back to approximately 240 BCE.
Eratosthenes, a native of Cyrene (modern-day Aswan, Libya), was aware of a well where, at noon on a certain day of the year, the Sun would illuminate the water but not the well walls, indicating that the Sun was directly overhead.
Hundreds of kilometers to the north, he later labored at the Library of Alexandria in Egypt.
On the same day of the year, he erected a pole and used the length of the shadow to calculate the Sun’s angle as 7.2°, or approximately 1/50th of a full circle.
This meant that the distance between the two cities was one-fiftieth of the circumference of the Earth.
Thankfully, the distance had already been accurately measured, so he knew they were separated by 5,000 stadia.
In the ancient world, the precise length of a stadia varied, but this places Erastothenes’ measurement between 38,000 and 46,000 km – not far from the current circumference measurement around the poles of 40,008 km.
Complete a circumnavigation of the globe
Throughout the succeeding centuries, astronomers in Europe, India, and the Arab world gained knowledge of the globe-shaped Earth.
In 1519, however, the Magellan–Elanco expedition circumnavigated the globe for the first time, providing the first direct evidence that the Earth was spherical.
Unless you are exceedingly affluent and an expert sailor, it may be difficult to replicate this one at home.