Once you’ve crossed that boundary, you can't see it at all - it's blocked by the curve of Earth in that direction. So, you can see Polaris, the star nearly directly above Earth's north geographic pole, quite easily in northern latitudes.īut as you travel south, approaching the equator, Polaris sinks lower and lower toward the horizon. First, there is the division between the northern and southern hemispheres.

This phenomenon, a side effect of Earth's curvature, isn't a sure-fire guarantee of our planet's curve, but it’s a start.īut even if you can't look to the horizon for evidence, you can look up.ĭifferent stars are visible from different parts of Earth, in two very peculiar ways.

'The photograph showed the troposphere-stratosphere boundary and the actual curvature of the Earth and demonstrated the potential for long-range reconnaissance from high-altitude balloons,' NASA officials wrote.Įarth's atmosphere is capable of playing funny tricks on our eyes, with different layers of air bending light into interesting directions. Orvil Anderson took a photo from a balloon that lifted off from Rapid City, South Dakota and soared to a maximum altitude of 72,395 feet (22,066 m). The Earth's curvature is also visible laterally in the photograph, although the effect is subtle as the image encompasses only 1/360 of the Earth's circumference.'Īnd in November 1935, Stevens and Capt. 'The Earth's curvature explains this phenomenon, as described in the diagram accompanying the photograph.

'The Andes Mountains, 287 miles away, and although taller than the plane's altitude, lay below the sensible horizon, marked by the white horizontal line in the photograph,' NASA officials wrote in a description of the flight. In December 1930, for example, Stevens snapped a photo looking westward while flying at an altitude of 21,000 feet (6,400 meters) above Villa Mercedes, Argentina. Similarly, from a great distance, the tops of tall objects like mountains are visible well before their bases.Īnd Earth's curvature is clearly apparent from high altitudes, as Capt. If you've ever watched a ship on the horizon, you've seen this for yourself. There are so many experiments, observations and demonstrations that have, time and time again, revealed the curve of the Earth.Īs objects recede from you, they begin to look smaller and slowly disappear in a very unique way: first their bottoms become hidden, and then their tops. To put it bluntly, we know more about the curvature of Earth than almost any other topic in the realm of physical science.

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