By Pecier Decierdo
EARTH, the planet we all live on, is round. A little more accurately, we could say that the Earth is spherical in shape, like a ball or globe. If you want to get really accurate, you would say that the Earth is an oblate spheroid. That is just a fancy way of saying that the Earth is a sphere that is a little bit squished to the side.
Unfortunately, an increasing number of people are denying that the Earth is round. Instead, they claim the Earth is flat! Those people are wrong. Let us go through some of the evidence that shows the Earth is definitely round.
Before we go through them, a note on the language. As I mentioned above, the Earth is an oblate spheroid or a squished sphere.
However, it is not squished by a lot. Around the equator, the Earth is 40,070 km in circumference. However, if you go around through the poles, it would be around 39,931 km.
The difference between the two circumferences is only 139 km, or like the distance from Manila to Tarlac City. That is less than half of one percent of the circumference of the Earth.
Since the Earth is not squished by a lot, we can approximate it as a sphere.
Now, back to the question: How do we know the Earth is a sphere?
The simplest answer is: pictures. We know the Earth is a sphere because we have pictures of it from outer space that show it to be spherical in shape!
Some people claim that the hundred of thousands of pictures of Earth taken by satellites and astronauts are all fake. But which is more likely—that all those pictures are genuine or that all the thousands of satellites and hundreds of astronauts from all over the world are in on a conspiracy to trick us? Obviously, those pictures are telling the truth.
But we do not even need to leave the Earth to see the signs that it is a sphere.
One of these days, when you find yourself on a beach, look far out into sea. Sometimes you will see ships coming to or going from a nearby harbor. Notice that as the ships are moving away, the last part of the ship that will disappear from sight is the top part, such as the mast or chimney. That is because the ship is moving around the curve of a spherical Earth.
Another sign that the Earth is round is the way planes fly. Notice the path of planes on a map. Often, you will see that their paths curve. Sometimes, the curve follows a coastline or some other geographical feature. However, even in the middle of the ocean, their paths seem to curve.
Why is this? Imagine a beach ball. Next, imagine drawing a straight line on the ball using a marker. Get a knife and rip the ball open. Finally, flatten the ball on the ground. You will observe that the “straight line” you draw is now a curve!
Scientists call the shortest path between two points a geodesic.
The shortest path from Manila to Davao around the Earth is the geodesic between those two places. If the Earth were flat, this geodesic would be an actual straight line. However, since the Earth is round, the geodesic between Manila and Davao looks like a curve on the map.
Speaking of flying from one place to another, we can also see signs of the Earth’s spherical shape by looking up into the night sky from different parts of the world.
If you were in Manila, the North Star is around 15 degrees above the northern horizon. If you hold your fist at arm’s length toward the horizon, that measures 10 degrees of the sky.
Now, if you were in Zamboanga City, the North Star would be hard to find, because it would only be around 7 degrees above the horizon.
Meanwhile, if you were in Iloilo City, the North Star would be close to 10 degrees above the horizon.
This change in the position of the North Star in the sky is a result of you seeing it from different parts of a spherical Earth.
Another piece of evidence from astronomy is the shadow cast by the Earth on the moon during a lunar eclipse. A lunar eclipse is when the moon enters the Earth’s shadow. In every lunar eclipse documented, the shape of the shadow is circular. This can only happen if the Earth were a circle when viewed from all angles. In other words, the Earth has to be a sphere.
There are so many other clues that tell us that the Earth is definitely round. What other simple pieces of evidence can you think of?
Pecier Decierdo is the resident physicist and astronomer of The Mind Museum.