This is different from the theme of the last few posts, but I believe it's still interesting.
Clearly, stethoscopes work. A doctor puts a thingy somewhere on you, and the sounds bounce around a tube until they reach a doctor's ears.
The propagation of whalesong works the same way - a whale make a really, ridiculously loud sound (by far the loudest sound in the animal kingdom), and those sounds bounce around the ocean for a very long distance.
But what is it exactly that they bounce off of?
Total internal reflection, which is the concept on which things like stethoscopes and lasers and optical fibres work, is based on the difference in refractive indices between the two materials at the interface point. It's a little complex, but sometimes physics phenomena are just hard to understand. One of the coolest examples of total internal reflection is how, when you grip a glass full of water, you can clearly see where your fingerprints grip the glass if you look into the water. While the refractive index difference between water and glass isn't too much, the difference between those two things and air is. Where your fingerprints don't contact the glass, the light reflects off the glass-air interface back into the water. Where your fingerprints do contact the glass, however, light is absorbed by the fingerprints and that is why they are clearly visible.
Now, the ocean has a few different thermoclines in it, or layers which have different temperatures, and these thermoclines very gently change the refractive index of the water. We're talking very gently - the Earth curves only about 0.3mm for every kilometer of travel. This is about the width of the smallest possible mechanical pencil lead you can currently buy. It also means they only bend 0.03% for every kilometer. I can post the math for that conclusion if anyone asks, but it's not very hard to come up with yourself.
In everyday life, you can see how different temperatures change the refractive index of a material without changing the chemistry of the material itself - such as watching heat waves rise off of a hot road or a flame. If you look through those heat waves, the light gets all wavy and miragey. This is because hot air bends light slightly differently - but the waves are caused by that hot air moving. Now imagine air layers of different temperatures floating (mostly) stable on top of each other instead of rising up in waves - this sort of stratification phenomenon occurs in the ocean (and also on a large scale in the atmosphere too, as I'll discuss in a bit).
Knowing that total internal reflection is caused by an interface of two things with a different refractive interface and knowing that two layers in an ocean can contain an extremely slight refractive index difference, it's easy to see how sound emitted from whales bends around a spherical ocean.
This isn't my main point though. It is very important to note that the same thermal stratification occurs in the atmosphere. The lower layers are much warmer than the upper layers, which is something that's easily verifiable if you've ever been to some place with high elevation. Near where I live, there is a mountain that ascends 1,500m and at the top it is almost always 15c colder than at the base. 15c is a lot - you can tan at the base, but you'll need a heavy jacket at the summit.
With the total internal reflection of the ocean caused by thermoclines in mind, it is important to compare this knowledge to thermoclines which exist in the atmosphere. The same refractive index differences exist in the atmosphere, and the same sort of thermoclines also exist.
What can you expect from this sort of thing?
You can expect that, when looking out in a straight line away from you, the light from distant objects gets curved around the thermoclines much like a whalesong. It's not always perfect, so faraway objects always look a little wavy and distorted. But you can see objects that are just a little bit further beyond the horizon than you could see without the atmosphere. It makes the world look just a little bit - a tiny little bit - more flat.
So why am I bothering to put this explanation up, anyway?
Specifically because FE theory claims the exact opposite of this, with absolutely no mechanics to back it up. This model claims that instead of being able to see a little further, you actually can only see a lot less, and the only explanation given is the simple word "refraction" or the made-up term "aetheric edification".
The method proposed for why the horizon appears so close in a flat earth model has absolutely no bearing on reality, and though the model claims refractive phenomena for this sort of thing it is anything but.
While we should expect to see further beyond the horizon as the principle of total internal reflection shows, FE theory in fact states the exact opposite with no sort of evidence to back it up.