So if you rise above the earth... what will you expect to see.

The horizon as a ring? No. You wont, not unless you go up for a very long time. Because imagine: When you look in front of you, the horizon will appear at a certain height. When you move a bit to you left, the horizon should be on the same level, would it not? This is because you are either on the top of a ball, or above a flat plane.

But what you will be able to see is the horizon dropping, both in flat as in round world.

horizon drop

horizon drop flat

For the same height the drop on a curved plane would be far bigger than on a flat plane.

But still.. These pictures above are not scaled.
In a globe world where earth has a 6.378km radius. When you are 30km above sea level the drop would be like the width of your hand when you hold it at arms length before you.

And if you scale the picture above it would look like this:

man30kmglobe You can barely see the tiny dot and lines on top man30kmglobe 2
 This is a magnification of the top of the circle.

There are a number of experiments, where a camera is attached to a balloon

A very new one is from Dwayne Kellum:



Above is a still from the video.
The horizon is below the centre of the picture, so any distortion would be in favour of a curve.

On the left hand side is the above picture, but resized to 10% of the width.

This looks a lot like I can see a curve.

Here you see a balloon rising to over 96.000 feet (that is almost 30km)

When you look at it, you have the impression (well I have) that you see a curve, but you can't, that is the camera (a gopro)

However, can you see the drop?

This is tricky, because the camera moves a lot, up and down and left to right. So I cannot tell from the video.




 Below is a nice simulation of rising in a balloon (it is in Portuguese) or you could have fun in google earth. If you download the video and play it locally (in VLC mediaplayer for instance) you can actually pan the view and look around.


This would be the amount of drop you can see at 30km.

As you can see, the amount of drop nearly is the same as the height of the hazy white border of the earth.

And meanwhile the camera is moving, so I cannot tell anything of dropping of the horizon from this



This video shows the view from an even higher altitude.

Note that you cannot tell the curvature from this (because of the fisheye effect), but the essential thing (for me) in this video is how little you can see from up there.



Lastly A great youtube site is from vsauce and especially (on this subject) "How Much of the Earth Can You See at Once?"