[edby]

Here’s an experiment I did on holiday by the sea, requiring no equipment.

1. Choose a day with little wind (although this doesn’t actually matter).

2. Look for a boat sailing out to sea, i.e. in direction of horizon, and wait until the bottom of the hull at the water line is just sitting on the horizon line.

3. Move your head down as close as possible to the surface of the water so you can still see the horizon line.

4. At that point you will see the hull disappear. Note, This is not because of any ripples or small waves at the foreshore. You should be able to see the whole surface of the water right up to the horizon line, but with only the mast visible.

5. If you move head up and down, you can actually see the bulge in the water, a few miles away by my estimate.

Hence, the water looks curved. Ergo, if it looks curved, it is curved.

[Mysfit]

Hence, the water looks curved. Ergo, if it looks curved, it is curved.

This is the best approximation of zetetic reasoning I have seen.
And I have been looking and asking for it.

[RonJ]

You wouldn't ever expect to see the curvature of the earth under these circumstances.  The earth is so large compared to a man.  At sea, in any direction you care to look, the visible horizon is always at the same distance away.  This is why the horizon will always look like a flat line at sea.  Sure, you can climb a mast and look from there, but you will still see the same thing.  Trust me, I've had to do it countless times.  There are other ways to verify that the earth is a sphere, but looking at the horizon won't get you very far.  Even looking at a another ship coming towards you, or going away from you can be difficult.  The atmosphere can cause the light to bend and deceive your eye.  This is especially evident at sea because off all the moisture in the air for obvious reasons.  A radar is a little better tool for observing the effect of another ship coming up over the horizon of a spherical earth, but even then the microwave energy can also bend a little because it just like light, but of a lower electromagnetic frequency.  You can see some of the effect, for sure, if you carefully observe the target echo on the radar, but it is still difficult to see even if you know exactly what you are looking for.  Even the radar on an aircraft at 42000 feet looking down on the earth would only see a difference in distance between a flat earth target and a spherical earth target of about 0.1%.  There are other ways to verify the spherical earth paradigm.  Experiments have been done for 1000's of years but the results still aren't believed by some.  Let the struggle continue.

[edby]

You wouldn't ever expect to see the curvature of the earth under these circumstances.  The earth is so large compared to a man. 

But this was exactly what I saw. With the eye close to water level, the hull disappears. A few feet further up, it reappears.

[edit] In fact the curve calculator confirms this.

Boat 6 miles away, when eye is close to water, 25 feet is hidden. Just by moving 1 foot higher, only 15 feet hidden, so 10 feet is revealed by small movement up. Standing, a further 10 feet is revealed, 20 feet in all.

The curvature is visible. Theory aligns with Zetetic observation. Trust the senses.

[RonJ]

My comment was meant to mean that you wouldn't expect to see a curved horizon no matter which way you looked when nothing else is visible.  The fact that you saw a boat partly hidden by the curvature of the earth is one of the reasons why sailors for many hundreds of years came to the conclusion that the earth is a sphere.  A good marine radar will also confirm what your eyes see.  You have to be very careful about completely trusting your senses.  Don't believe that?  Well, just visit a good magician and he will school you.  All the moisture at the surface of the sea and swell can cause much of the hidden view of a vessel to disappear then reappear over a short period of time.  The fact that you could see more of what was hidden by the earth's curvature the higher you got was the reason for a crow's nest on a mast of the old sailing ships.  A sailor with a telescope on that mast was usually the first one who shouted 'land ho' while approaching the coast.  Additionally some of the 'ole time' sailors would even keep numerous land birds with them.  They would be released if shore was believed to be nearby.  A 'birds eye view' would be even higher than a sailor in the crow's nest.  If a bird suddenly took off in a straight line away from the ship you would have some certainty that the bird is making a 'bee line' towards land.  Sometimes the bird would be mistaken and come back and land on the mast somewhere.  In that case it meant you had to keep sailing in your intended direction some more and keep a close watch on that bird.  Now we have GPS and radar. The radar can usually start to see echos from the coast line long before your eye can.  Those echos will start to appear right out of what used to be empty ocean.  Again another indication of the curved earth.  On the flat earth paradigm it wouldn't matter how high you were.  Sure, you would be able to see farther inland at height but all you really need is to see is the initial vestiges of land.