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29

Depends on your eye. You can realise the curvature of the Earth by just going to the beach. Last summer I was on a scientific cruise in the Mediterranean. I took two pictures of a distant boat, within an interval of a few seconds: one from the lowest deck of the ship (left image), the other one from our highest observation platform (about 16 m higher; ...


17

the horizon is a circle centered at the viewer's position There are two things wrong with this. The first is the assumption that the Earth is entirely spherical - there are no hills, mountains or other bulges to block the view. But let's make that assumption, because there's a more fundemental misunderstanding in the geometry. The horizon is a circle that ...


15

A quick Google turned up a published article answering precisely this question (Lynch, 2008). The abstract states: Reports and photographs claiming that visual observers can detect the curvature of the Earth from high mountains or high-flying commercial aircraft are investigated. Visual daytime observations show that the minimum altitude at which ...


11

It's hard to see the curvature of the earth from an altitude of 7 miles or 37,000 ft (typical cruising altitude of a jetliner) but easy to see from 250 miles (typical altitude of the ISS). The line of sight from an aircraft at 37,000 feet = 235 miles. That's only about 3.4 degrees of the earth's surface. From the ISS at 250 miles, the line of sight is 1,...


6

Further to DrGC's excellent answer, a subjective assessment of visibility of the Earth's curvature can be gleaned from pilot's experioence over many decades. These can be summarized as: Commercial aircraft normal maximum ceiling of 13.7 kilometres : The curvature isn't apparent. Concorde's ceiling was 18.3 kilometres, and reports are inconsistent. Some ...


5

What is the Moon's distance from viewer at horizon? As noted by others, the moon follows an elliptical orbit, which will lead to the greatest change in distance regardless of the observation angle. However, we can place some upper and lower bounds on what the distance at the horizon would be by using the maximum and minimum orbital radii (the apogee and ...


5

the horizon is a circle centered at the viewer's position, the whole horizon is at the same level, hence why it's flat. But it only looks flat as long as you are seeing that circle from within the same plane where the circle is. If you are in the plane of the circle, it becomes indistinguishable from a flat rectangle or any other shape. However, if you are ...


4

The horizon is a circle centered below the viewer's position. (Ignore for this question that the Earth is bumpy and not exactly spherical.) Imagine the lines of sight from your eye or camera to the points on the circle forming a cone. When viewing the horizon from near the surface the cone is very flat and the circle is edge-on and it is difficult to see ...


4

The Moon's orbit is elliptical, not circular, and the maximum and minimum distance from the Moon to the center of the Earth (apogee and perigee, 405,385 and 363,630 km respectively) are much larger than the radius of the Earth (6370 km). Therefore, the distance you are asking for is very variable and it does not depend so much on the position of the Moon ...


1

An unobstructed horizon such as an ocean horizon dips below the horizontal due to Earth's curvature. The dip of the ocean horizon is noticeable from a height of 10 meters. So it is not necessary to be at high altitudes to notice Earth's curvature.


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