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Old 13th February 2020, 04:25 PM   #1
Hercules56
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Clouds don't bend towards horizon?

Ok, so how come clouds off in the far distance and by the horizon don't appear to bend downwards? Contrails from airplanes do this, we've all seen it. But I don't recall seeing a cloud to this.

Any answers? Thanks.


....And no, I am not Flat Earther. The Earth is clearly an oblate spheroid.
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Old 13th February 2020, 04:26 PM   #2
theprestige
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They do?
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Old 13th February 2020, 04:28 PM   #3
Hercules56
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Originally Posted by theprestige View Post
They do?
Yes. Airplane contrails appear to be going up or down, when they are in fact flying at the same altitude, by the horizon.
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Old 13th February 2020, 04:45 PM   #4
curious cat
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Originally Posted by Hercules56 View Post
Ok, so how come clouds off in the far distance and by the horizon don't appear to bend downwards? Contrails from airplanes do this, we've all seen it. But I don't recall seeing a cloud to this.

Any answers? Thanks.


....And no, I am not Flat Earther. The Earth is clearly an oblate spheroid.
I am not really sure what you mean. Maybe a photo would help?
Whatever it is, I have a sneaking suspicion altitude has something to do with it. Contrails normally appear at some 30,000 ft. Most of your everyday cumulus etc clouds hang around a third of that altitude or less.
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Old 13th February 2020, 04:57 PM   #5
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Originally Posted by curious cat View Post
I am not really sure what you mean. Maybe a photo would help?
Whatever it is, I have a sneaking suspicion altitude has something to do with it. Contrails normally appear at some 30,000 ft. Most of your everyday cumulus etc clouds hang around a third of that altitude or less.
Nope. Contrails may or may not form at any altitude right down to 0, although far more likely/common at 25k+. That doesn't seem to be the question he is asking. Truthfully, I have no idea what he is asking really. On an overcast day, the cloud base quite clearly still meets the horizon. It is merely a sheet instead of a line as a contrail would be. Absent some elaboration from the OP, nobody can even start to interpret the question, let alone hazard an answer.
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Old 13th February 2020, 04:59 PM   #6
theprestige
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Clouds appear to be parallel to a flat earth, even in the distance. Why?

I assume the answer is that the human eye isn't calibrated to detect curvature at that scale. Nor even estimate distance.
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Old 13th February 2020, 05:13 PM   #7
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Because the Earth is flat, nothing bends.
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Old 13th February 2020, 05:16 PM   #8
abaddon
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Originally Posted by theprestige View Post
Clouds appear to be parallel to a flat earth, even in the distance. Why?

I assume the answer is that the human eye isn't calibrated to detect curvature at that scale. Nor even estimate distance.
I have no idea what nonsense the flatties invent to explain clouds meeting the horizon. probably "perspective" or "refraction" or some such garbage.
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Old 13th February 2020, 05:52 PM   #9
Hercules56
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Originally Posted by curious cat View Post
I am not really sure what you mean. Maybe a photo would help?
Whatever it is, I have a sneaking suspicion altitude has something to do with it. Contrails normally appear at some 30,000 ft. Most of your everyday cumulus etc clouds hang around a third of that altitude or less.
That, is something I did not know.

Might explain it. Thanks.
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Old 13th February 2020, 06:07 PM   #10
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Originally Posted by theprestige View Post
Clouds appear to be parallel to a flat earth, even in the distance. Why?

I assume the answer is that the human eye isn't calibrated to detect curvature at that scale. Nor even estimate distance.

It's worse than that. The human eye is curved, so everything projected onto the nerves gets curved. The brain can sort some of this out, based on how important it was to our survival as a species.

So, if you are standing on train tracks, looking straight down the track, the rails will appear to grow closer and meet in the far distance. We may insist that they're parallel to each other but only because: a) we know they are; and b) our experience has conferred on us the general understanding that lines like that are really parallel.

The ocean doesn't appear to fall away, nor do the clouds. They just eventually meet because that's how we perceive them, even though this is not reality.

This gives rise to all sorts of crazy optical illusions like that window thing that spins around and makes you question everything you think you know to the entryway in Willy Wonka that appears to be a long hallway and is just a little box with a tiny door.
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Old 14th February 2020, 03:19 AM   #11
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Clouds would curve, but they are too small to see it. A contrail is a long trail that goes from overhead to the horizon. Clouds get smaller and closer to the horizon. It's pretty much the same mechanic, perspective making them smaller and then Earth Curve getting in the way. If you were able to stretch a cloud from the horizon to above you, you'd see the same effect as that of the Contrail.
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Old 14th February 2020, 02:32 PM   #12
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A relatively low flat cloud base at 2000 feet off the ground would intercept the horizon at a distance of about 20 miles beyond the distance of the visible horizon itself. That's not taking into account atmospheric refraction, which extends that distance farther.

With foreshortening, atmospheric scattering, and with clouds typically being low contrast in the first place, I don't think it's possible to clearly see the cloud base at that distance.

For a typical contrail at 25000 feet altitude, the distance of the contrail's horizon beyond the ground horizon is about 72 miles. A contrail is clearer than a cloud layer, but with that distance, you won't be able to see it "meet" the horizon clearly under most conditions.

As for curvature, a 72-mile stretch of contrail only curves about half a degree. That's enough to be clearly visible if the contrail is highly foreshortened (i.e. if it's on a course passing close to directly overhead). It's going to be harder to see the smaller amount of curvature in e.g. a 20 mile stretch of cloud layer.
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Old 16th February 2020, 03:01 PM   #13
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Back in 2003, at 39,000' over New Mexico, I was struck by two things.

1) I could actually discern the curvature of the Earth's limb.

2) I could see the *underside* of cirrus clouds (which were all at a lower altitude than me) as they curved downward over the curving earth at great distance.
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Old 16th February 2020, 03:06 PM   #14
Lurch
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Myriad,
The Earth's surface curves pretty much exactly 1 degree over a 60 nautical mile traverse, and so for a 72 statute mile long contrail, it will curve just a tad over a degree.
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Old 16th February 2020, 06:45 PM   #15
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Me: "Contrails NORMALLY appear at SOME 30,000 ft...."

Originally Posted by abaddon View Post
Nope. Contrails may or may not form at any altitude right down to 0, although far more likely/common at 25k+.......
????????????
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