1: Go to the beach.

2: Look at the sunset while laying down.

3: The moment the sun disappears behind the horizon, stand up quickly.

4: You will see the sun again, and a second sunset.

The only way this is possible is if the earth is curved. Or if someone turned off the sun, and turned it back on the moment you stood up.

Alternatively, if a westbound beach is too far to reach, watch this video (just two minutes):

If you want a little more, check this clip: Two experiments done here prove that Earth is curved. The second experiment, impressed even me - so watch it to the end. Just eight minutes long.

A similar 1-minute clip for the curious:

Photos via Google