One way to observe evidence of the Earth's spherical shape when looking at the horizon is through the phenomenon known as the "ship disappearing over the horizon" or the "curvature of the Earth." Here's how it works:
Observing Ships: When you watch a ship moving away from the shore, you'll notice that as it gets farther from you, it gradually disappears from view, starting with the hull, then the lower parts of the ship, and finally the mast and upper parts. This gradual disappearance happens because of the Earth's curvature.
Line of Sight: As you stand on the shore, your line of sight to the ship is a tangent to the Earth's curved surface. This means that as the ship moves farther away, it goes over the curvature, and eventually, only the top parts of the ship are visible above the curve.
Horizon's Distance: The distance to the horizon depends on the observer's height above the Earth's surface. The higher you are, the farther you can see, but eventually, the Earth's curvature will obscure objects beyond the horizon.
Sunrise and Sunset: The shape of the Earth is also evident during sunrise and sunset. As the Sun appears to rise on the horizon, it first illuminates the highest points of distant objects (like mountains), and as it sets, these same points are the last to be illuminated.
These observations collectively demonstrate that the Earth's surface is curved, and when combined with other evidence (such as the way the stars change as you move from one hemisphere to another or the way airplane flight paths are planned), they strongly support the conclusion that the Earth is indeed a sphere.
I hope this helped!
~~~Harsha~~~