Quote:
Originally Posted by Augi
You seeing the curvature of the Earth is an optical illusion. To demonstrate, get a toothpick, a sharpee marker with its cap, and a basketball. Fix the marker so that the marking end is against the ball and the other end is fixed to the top of the toothpick. The toothpick should be sticking as straight as possible out of the ball, don't pop it.
The basketball is the Earth, the toothpick is you standing straight up and the marker is the line of sight to your eyes. Turn the marker around and you get a circle that is the edge of your vision of the world. This circle does not curve down at all, it curves around you! Your brain thinks it is curving down only because it perceives the horizon to be against a perfectly flat plane perpendicular to your line of sight.
So you get higher and higher, the line of sight can trace further towards the equator of the Earth.
|
The point is, if we follow your prescription, there is a point at which we are hight enought to see the full circle of the world.
At zero altitude, the horizon looks like a perfect plane.
At infinite altitude (say, for example, from the Moon) the horizon is clearly circular, as one can view the entire hemisphere.
There must be some transition zone. I have seen the curvature of the earth from airliners (very high), light aircraft (moderately high) Mount St Hellens (pretty high), and the French alps (fairly high).
I have not seen it from the hills near my house, or the beach.
This would make me think that the transition zone lies between 1,000 and 6,000 feet altitude.