4 ms·

One can also watch a boat leaving shore descend "under" the horizon with a telescope

• sigmoid10 2y ago
  You don't even need a boat or a telescope. Just watch the sun set on the ocean while lying down at the beach just in front of the water. The moment it disappears completely, stand up. You'll see part of it again. If you measure the time it takes disappear completely again and know your own height, you can even get a rough estimate of earth's radius.
  • yen223 2y ago
    Unless I'm picturing it wrong, wouldn't this still happen even if the world were flat?