10 Rollback to Revision 8
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A picture gives a sense of proportion. To the Earth, a rock diameter 13000km, clings a wisp of atmosphere. The Internationaltroposphere, where everyone has ever breathed, is thinner than 20km. Above, space. The Internal Space Station orbits at about 400 km.

enter image description here

THE THIN BLUE LINE: Earth’s thin atmosphere is all that stands between life on Earth and the cold, dark void of space. Our planet's atmosphere has no clearly defined upper boundary but gradually thins out into space. The layers of the atmosphere have different characteristics, such as protective ozone in the stratosphere, and weather in the lowermost layer. The setting Sun is also featured in this image, which was photographed by the crew of the International Space Station in 2008.

Source: NASA

The International Space Station orbits at about 400 km.

A picture gives a sense of proportion. To the Earth, a rock diameter 13000km, clings a wisp of atmosphere. The troposphere, where everyone has ever breathed, is thinner than 20km. Above, space. The Internal Space Station orbits at about 400 km.

enter image description here

THE THIN BLUE LINE: Earth’s thin atmosphere is all that stands between life on Earth and the cold, dark void of space. Our planet's atmosphere has no clearly defined upper boundary but gradually thins out into space. The layers of the atmosphere have different characteristics, such as protective ozone in the stratosphere, and weather in the lowermost layer. The setting Sun is also featured in this image, which was photographed by the crew of the International Space Station in 2008.

Source: NASA

    Post Undeleted by Oddthinking
9 Removed all the parts that weren't relevant.
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A picture gives a sense of proportion. To the Earth, a rock diameter 13000km, clings a wisp of atmosphere. The troposphere, where everyone has ever breathed, is thinner than 20km. Above, space. The InternalInternational Space Station orbits at about 400 km.

enter image description here

THE THIN BLUE LINE: Earth’s thin atmosphere is all that stands between life on Earth and the cold, dark void of space. Our planet's atmosphere has no clearly defined upper boundary but gradually thins out into space. The layers of the atmosphere have different characteristics, such as protective ozone in the stratosphere, and weather in the lowermost layer. The setting Sun is also featured in this image, which was photographed by the crew of the International Space Station in 2008.

Source: NASA

A picture gives a sense of proportion. To the Earth, a rock diameter 13000km, clings a wisp of atmosphere. The troposphere, where everyone has ever breathed, is thinner than 20km. Above, space. The Internal Space Station orbits at about 400 km.

enter image description here

THE THIN BLUE LINE: Earth’s thin atmosphere is all that stands between life on Earth and the cold, dark void of space. Our planet's atmosphere has no clearly defined upper boundary but gradually thins out into space. The layers of the atmosphere have different characteristics, such as protective ozone in the stratosphere, and weather in the lowermost layer. The setting Sun is also featured in this image, which was photographed by the crew of the International Space Station in 2008.

Source: NASA

The International Space Station orbits at about 400 km.

8 edited answer to be acceptable to site
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How high does the International Space Station orbit? We can calculate from observations. If you've seen the space station after dark, it takes about 90 minutes to come back around. However the space station takes only a few minutes to cross the sky—not 45 minutes. It takes longest if it passes directly overhead, when it takes 10 minutes (this is the longest any ground station can be in radio contact.) We can now relate the altitude h of the space station to the radius r of the Earth.

Let θ be the angle at the centre of the Earth between us and the space station rising over the horizon. Restating our observations, 2θ / 2π = 10 minutes / 90 minutes. Drawing the triangle, trigonometry tells us cosθ = r/(r+h).

Taking the radius of the Earth r to be 6500 km (thanks @Erasthones), calculating h = r*(1/cos(pi*10/90)-1) gives 400 km, an estimate accurate to 1 significant figure.


A picture gives a sense of proportion. To the Earth, a rock diameter 13000km, clings a thin wisp of atmosphere. The troposphere, where everyone has ever breathed, is lessthinner than 20km thick. Above, space. The Internal Space Station orbits at about 400 km.

enter image description here

THE THIN BLUE LINE: Earth’s thin atmosphere is all that stands between life on Earth and the cold, dark void of space. Our planet's atmosphere has no clearly defined upper boundary but gradually thins out into space. The layers of the atmosphere have different characteristics, such as protective ozone in the stratosphere, and weather in the lowermost layer. The setting Sun is also featured in this image, which was photographed by the crew of the International Space Station in 2008.

Source: NASA

How high does the International Space Station orbit? We can calculate from observations. If you've seen the space station after dark, it takes about 90 minutes to come back around. However the space station takes only a few minutes to cross the sky—not 45 minutes. It takes longest if it passes directly overhead, when it takes 10 minutes (this is the longest any ground station can be in radio contact.) We can now relate the altitude h of the space station to the radius r of the Earth.

Let θ be the angle at the centre of the Earth between us and the space station rising over the horizon. Restating our observations, 2θ / 2π = 10 minutes / 90 minutes. Drawing the triangle, trigonometry tells us cosθ = r/(r+h).

Taking the radius of the Earth r to be 6500 km (thanks @Erasthones), calculating h = r*(1/cos(pi*10/90)-1) gives 400 km, an estimate accurate to 1 significant figure.


A picture gives a sense of proportion. To the Earth, a rock diameter 13000km, clings a thin wisp of atmosphere. The troposphere, where everyone has ever breathed, is less than 20km thick. Above, space.

enter image description here

THE THIN BLUE LINE: Earth’s thin atmosphere is all that stands between life on Earth and the cold, dark void of space. Our planet's atmosphere has no clearly defined upper boundary but gradually thins out into space. The layers of the atmosphere have different characteristics, such as protective ozone in the stratosphere, and weather in the lowermost layer. The setting Sun is also featured in this image, which was photographed by the crew of the International Space Station in 2008.

Source: NASA

A picture gives a sense of proportion. To the Earth, a rock diameter 13000km, clings a wisp of atmosphere. The troposphere, where everyone has ever breathed, is thinner than 20km. Above, space. The Internal Space Station orbits at about 400 km.

enter image description here

THE THIN BLUE LINE: Earth’s thin atmosphere is all that stands between life on Earth and the cold, dark void of space. Our planet's atmosphere has no clearly defined upper boundary but gradually thins out into space. The layers of the atmosphere have different characteristics, such as protective ozone in the stratosphere, and weather in the lowermost layer. The setting Sun is also featured in this image, which was photographed by the crew of the International Space Station in 2008.

Source: NASA

    Post Deleted by Oddthinking
7 Improved fomatting.
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6 Improved fomatting.
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