Explanation:
1. Watch a ship sail off to sea
Without being in the sky, it is impossible to see the curvature of the Earth. However, you can always see a demonstration of this if you visit a harbor or any place with a wide-open view of the water.
2. Watch a lunar eclipse
Solar eclipses get all the attention, but if you are able to catch a glimpse of a lunar eclipse, you can see evidence that the Earth is, indeed, round. Here's how it works: Earth passes between the moon and sun, so that the sun projects Earth’s shadow onto the Moon in the night sky
3. Climb a tree
Imagine a vast plane with but one tree smack in the middle. If the earth were flat, your vision would extend exactly as far while standing at the base of the tree as it would when at the top of the tree
4.Measure shadows across the country
Pick two locations that are some distance apart (at least a couple hundred miles from each other and on the same meridian). Grab two sticks or dowels (or other objects) of equal length, two tape measures, and a friend. Each of you will take one stick/dowel/object and one tape measure to your location, stick the object into the ground, and measure the shadow. (For accuracy, you should both take your measurements at the same time of day.)
5. Watch a sunset
Pick a nice spot from which you can watch a sunset (we'll call this point A). Ideally, you'd have a clear horizon in front of you, and behind you would be some sort of elevated point that you can quickly access (a hill, a building with at least two floors, or perhaps the aforementioned tree; we'll call this point B).
