What Really is the Shape of Earth

What Really is the Shape of the Earth?

 

For long, the controversy between flat-earthers and round-Earthers has been raging. Though that the Earth is balanced on a large tortoise belongs to the realm of mythology, even in the present century many people still believe the Earth to be a disk-shaped planet. So, the question arises what really is the shape of the Earth?

The Greeks were the first to doubt if the Earth was flat. Among the Greeks, the most eminent philosopher was Aristotle. Born in 384 BC, he was one of those eminent scientists who proposed that the Earth is round instead of flat; he had figured out that during an eclipse (i.e., when Sun, Moon, and Earth align in a straight line), the shadow of the Earth on Moon was always round, and not elliptical as would have been had the Earth been flat. He also pointed out that the Southern constellations rose higher above the horizon as one travelled South; it was possible only if the Earth was round.

 

                                                     Aristotle (reference: Wikimedia Commons) 

 

Aristotle though believed that the Earth was stationary and at the centre of the universe and other planets and stars, including the Sun, orbited the Earth in a circular path.

The Greeks had another argument against the flat earth theory: the sail appears before the hull of the ship on the horizon, and this is possible only if the Earth is round.

Eratosthenes

Eratosthenes, another great Greek mathematician and the head of the Library of Alexandria, was also against the belief in a flat earth. He is best known for calculating the circumference of Earth by just putting a stick in the ground.

Eratosthenes had heard that in the city of Syene, which is 800 km south of Alexandria, no shadows were cast that noon because of the summer solstice. Eratosthenes wanted to know if this happens in Alexandria too, so on the same date, he put a stick vertically in the ground and check if it cast a shadow. And it did.

Eratosthenes (reference: Wikimedia Commons)

 He realized that on the same date in Syene there were no shadows as the Sun was directly overhead, but this did not happen in Alexandria on the same date which could only be possible if Earth were round.

Eratosthenes then measured the angle of shadow which was 7.2 degrees. He knew that Syene was 800 km South of Alexandria and a circle measures 360 degrees, so using his geometrical skills, he calculated the circumference of Earth by using the formula:

Step 1:

  `\frac{7.2^\circ}{360^\circ}=\frac{800}x`

Step 2:

   `\frac1{50}=\frac{800}x`

Step 3:

 `800\times50` = 40,000 Kilometres

 this was how Eratosthenes calculated the circumference of Earth long ago which is remarkably close to the exact figure.

Ptolemy

Born in 85 A.D., Ptolemy was a Greek mathematician, astronomer, and geographer who lived in Alexandria in Egypt. Just like Aristotle, he believed the earth was spherical and had a geocentric view of the universe and later he began studying planets and calculating their motion. He later came up with his model of the universe, called the Ptolemaic system. This model showed that earth was at the center of the universe and other celestial bodies revolved around it in this manner: moon, Mercury, Venus, Sun, Mars, Jupiter, and Saturn. And after Saturn, other stars revolved around the earth. Uranus and Neptune were not discovered at that time which is why this system did not include them.

His model was accepted because it predicts the positions of planets accurately enough for naked-eye observations due to which it seemed accurate at that time. Ptolemy held the dominant position till the 16^th century when Nicolaus Copernicus disproved his ideas.

Nicolaus Copernicus

Nicolaus Copernicus born in 1473 was an astronomer, physician, priest, and mathematician. With these many jobs, he treated astronomy as a hobby. He had always been interested in space and science. He is famously known for his heliocentric view of the solar system, that is, the sun and not the earth at the center of the solar system. He thought that the Sun would be more suitable if it were at the center of the solar system and being revolved by 6 other planets (at that time Uranus and Neptune were not discovered). He spread the belief of a heliocentric system which later came to be known as Copernicanism.

Nicolaus Copernicus (reference: Wikimedia Commons)

At that time the geocentric system was a more accepted theory which turned the Catholic Church and ancient philosophers in the opposition of Copernicus. They started questioning Copernicus to which he did not know the answer because at that time they lacked modern science laws and instruments.

His heliocentric model was rejected by Catholic Church and ancient philosophers for many reasons, few of them are:

1.      The heliocentric model states that Earth is in motion, revolving around the Sun and rotating on its axis. If Earth is in motion, we cannot “feel” the motion. So, the earth must be stationary.

 

2.      If the Earth is orbiting the Sun, then there should be a slight difference in the positions of stars. This effect is called parallax. Since no stellar parallax has been observed (with the naked eye) then the Earth must be stationary.

 

Copernicus’ heliocentric model (reference: Wikimedia Commons)

As we are living in a modern era of science, we know the answers to the above questions regarding which ancient philosophers and Catholic Church rejected Copernicus’ heliocentric model.

Copernicus knew he was right, so even after getting criticized by many people, he kept on spreading Copernicanism. In 1543 he published his work and in the same year, he died. His formula of the heliocentric system is one of the most important scientific hypotheses in history, which led to the beginning of modern astronomy.

If you are probably wondering that why did the Catholic Church believe in Ptolemy’s geocentric model, the answer is because the geocentric model did not contradict the biblical texts.

Even after getting rejected by Catholic Church and ancient philosophers, he was still strongly followed by Galileo.

Galileo Galilei

The famous astronomer and mathematician Galileo Galilei was born in 1564 in Pisa, Italy. He contributed greatly to the mathematics of motion and mechanics. That the objects released from the same height hit the ground at the same time is one of his most famous experiments. In 1609, telescope, invented in Holland, allowed people to see far away objects and fascinated him. He improved on the idea and studied the planets in great detail. In 1610, while observing Jupiter, he noticed that four small celestial bodies revolve around it; these were the moons of Jupiter.

Galileo Galilei (reference: Wikimedia Commons)

 This dealt a dead blow to the Aristotelian theory which stated that every celestial body directly orbited the Earth.

After his discovery, he started spreading Copernicanism throughout his country. In 1616, Catholics banned Copernicanism. In 1632, he published a book called Dialogue Concerning the Two Chief World Systems where he described why he thought that the Earth orbits the Sun and the Sun is at the center of the solar system. This book drove many people and Catholic Church in his opposition because he challenged the geocentric model with the heliocentric model. At first, Church sentenced him to life in prison, but later they put him under house arrest.

Even under house arrest, he did not stop studying science. After 9 years under house arrest, Galileo died in 1642. There is still a long list of contributors after Galileo, but they were not such tall figures as Copernicus and the others, they are not mentioned here but will always be remembered by scientists and the folks interested in the subject.

Now, we have convincing evidence about the shape of the earth from the pictures taken from various satellites revolving around it. Still, many people with strong belief in their religious scriptures may not accept in these facts. The long journey on the path of science has imperilled many of scientists, with some of them even killed in their pursuit of truth, but it also tells us that one should be a rationalist rather than a blind believer.