The reason the horizon is approximately 3 miles away has to do with the curvature of the Earth. Our planet is, of course, roughly spherical in shape, which means that if you're standing on its surface, you can only see so far before the earth curves away from your line of sight. It's kind of like trying to see around a huge ball - at some point, the ball is going to curve away from you, and you won't be able to see what's on the other side.
To put it in perspective, imagine you're holding a big beach ball - if you're standing right next to it, you can see the entire surface, but as you move away, more and more of the ball will be hidden from view by its own curvature. It's the same principle with the Earth, just on a much, much bigger scale. So, the horizon is essentially the point at which the earth curves away from our line of sight, creating the illusion of a sharp line where the sea meets the sky.
Now, you might be wondering - what if I'm not at sea level? What if I'm standing on a mountain or a hill? Well, it turns out that the distance to the horizon changes depending on your height above sea level. The higher you are, the farther away the horizon will be - it's like being able to see over the top of the beach ball, if you will.
For example, if you're standing on a mountain that's 1 mile above sea level, the horizon will be around 40 miles away - that's a big difference from the 3 miles we mentioned earlier. It's all about the angle of view - the higher you are, the more of the earth's surface you can see, and the farther away the horizon will be. It's a pretty cool effect, and it's something you can experience for yourself if you ever find yourself on a high mountain or hill.
How Far Away Is The Horizon At Sea Level | Detroit Chinatown
