# Why don't the contrails show the curvature of the Earth?

When we see contrails in the sky, let's say traveling left/right in your vision, you are seeing across a sky that is easily a couple of hundred miles wide. I mean, we can see one side of space and then another, so we can see across a great distance in the sky depending on the height of an object. Am I wrong? I mean, we can see entire cities from a long distance away on the ground, so an unobstructed view of the sky would give us the ability to see something very long, right?

That being said, an airplane is following a curve, and when a plane makes a trail it is essentially tracing out the shape of the earth. Being that this trail is very high up, and following the curve, why don't the trails curve (left/right trail), and we see a giant arch across the sky? None of the lines in the sky look curved from any direction, they are straight lines, or at least appear to be.

Am I missing something? Maybe it's a dumb question, but I remain ignorant on the topic because I haven't been able to find the answer from anyone with a clue. This site seems legit, so I asked it here. Thanks, in advance.

1. Some contrails disperse and therefore end up being short to show any curvature.
1. Long ones don't stay put because of the wind. They wiggle.

2. It's for the same reason flying at 30,000 feet the Earth's curvature is not apparent. Earth is huge and it takes higher altitudes for the curvature to become noticeable to our eyes.

1. Flying higher at or above 60,000 feet or so (where the Concorde cruised) the Earth curvature starts to become more noticeable.

To notice it from the ground, you need a very clear day, not the slightest haze on the horizon, calm winds, and the plane to come from the right angle, as the illustration below shows:

(metabunk.org) 5-mile grid at 35,000 feet seen from the surface.

Note that the lines are squashed together the farther they are, so it'll take a very long contrail at a low angle above the horizon (called an altitude in astronomical terms) for that curvature to be easily seen.

• The horizontal lines aren't as curved:

That's a property of one-point perspective, you see more depth than breadth.

• The contrails are at least a few hundred miles long:

Not when viewed moving side-to-side. Jetliners cruise at around 550 MPH. The grid above shows what 5 miles are like. A 250-mile long contrail would take a plane 30 minutes to draw. You can time the next plane you see for proof on how long it takes to pass side-to-side in your field of vision. A lot less than 30 minutes. Example below is from a time lapse video:

Click image to open the GIF.

The GIF duration is 1.29 seconds and the video is shot at 5-second intervals at 24 fps. The contrail moved right to left in ~2.5 minutes, or roughly 25 miles (5 squares).

• The horizontal lines are not curved and that can easily be a span of a few hundred miles that we are looking at. No matter how big the earth may be, we should see this curve represented by the trails. If you can see that kind of curve on the lines heading out to sea (because that is what the picture depicts), then why doesn't that apply to the horizontal lines across the same distance? Again, if we can see a boat go over a curve, then we are seeing curvature with the naked eye. There is a big difference to what we can see straight ahead and across the sky horizontally. Thanks for the respons Apr 27, 2018 at 23:11
• @Chris - see update.
– user14897
Apr 27, 2018 at 23:18
• @Chris: First, if you look closely you can see that the horizontal (left-right) lines are slightly curved. Second, the vertical lines are drawn brighter than the horizontal ones, thus it's very difficult to make out the distant ones, which would encompass enough distance to make the curvature obvious. Apr 28, 2018 at 18:04