"How does water stay perfectly leveled on the Earth if it is round?"
Standing on the shore, the horizon is about 13km away.
The apparent ‘drop’ in the curvature of the earth from one horizon side to the other is about 24cm from the central point.
So here's a genuine question to answer your question:
Do you REALLY think you can see 24cm difference from 13km away?
You couldn’t see a 24cm plant growing on a dead flat desert surface from 1km, let alone 13.
But let's get scientific about it anyway...
Thornton Bank windfarm near the Belgian coast.
The inability to see the Earth's curvature on the ocean's horizon is primarily due to two reasons: the vast size of the Earth and the limitations of human perception.
Earth's Size: The Earth is an enormous sphere with a circumference of approximately 40,075 kilometers. When standing on the surface, the curvature of the Earth is subtle over short distances. The curvature becomes more apparent over larger distances, but the human eye has its limits.
Human Perception: Our eyes have a limited field of view and can only perceive a certain level of detail. The curvature of the Earth is gradual, and the angle at which it curves away from us is very gentle. As a result, when we look out at the vast expanse of the ocean, the curvature is not immediately noticeable to the naked eye. Our visual perception tends to perceive the horizon as a straight line, even though it is actually following the Earth's curved surface.
However, there are ways to observe and demonstrate the curvature of the Earth:
Higher vantage points: As you ascend to higher altitudes, such as in an airplane or at the top of a tall building or mountain, the curvature becomes more evident. The increased distance allows for a wider field of view, making the curvature more apparent.
Photographs from space: Astronauts aboard space missions and satellites capture stunning images of the Earth from space that clearly show its curvature. These images provide a perspective that is not easily visible from the surface.
Ships disappearing over the horizon: Observing ships or other objects gradually disappearing from view as they move away from the shore is another evidence of the Earth's curvature. As they travel farther, the curvature of the Earth obstructs our view, making them appear to sink below the horizon.
In summary, while the curvature of the Earth is not immediately apparent from the surface, it can be observed through different means, such as viewing the Earth from higher altitudes or through images taken from space.
The section where we explain the above to 5-year-olds (and Flat Earthers).
Imagine you're standing on a very big beach, and you're looking out at the sea. The Earth is like a giant ball, and we're standing on top of it. But when we look at the sea, it seems like the surface is flat and straight, like a straight line where the sky meets the water.
The reason we can't see the curve of the Earth from the beach is because the Earth is so big and we are so small. It's like when you look at a very big ball up close, it may look flat because you can't see the whole round shape. You need to step back or look from a high place to see the roundness.
To see the curve of the Earth, we can go up really high, like in an airplane or on top of a tall building or mountain. When we are higher up, we can see farther and more of the Earth's round shape. It's like when you're on a slide and you can see the whole slide when you're at the top.
We can also see pictures taken from space by astronauts and satellites. They can take pictures of the Earth from way above, and we can see its round shape clearly in those pictures.
So even though we can't see the curve of the Earth from the beach, there are ways to see and understand its round shape. It's just that we need to look from higher places or see pictures taken from space to get a better idea of what the Earth really looks like.
You’ve come this far…
Why not venture a little further into A.S.S. - our exclusive Australian Space Society.
And keep thrusting Australia into the deep unknown…