can you tell when you have gone out of the earths athmosphere?

Question: can you tell when you have gone out of the earths athmosphere?
- Keywords:
  atmosphere,
  earth,
  space
Asked by emilyshearsmith to Alan, Deepak, Francesca, Lilly, Nick on 18 Mar 2014.
- Francesca Day answered on 18 Mar 2014:
  
  Great question! The Earth’s atmosphere doesn’t end at a specific point, it just gets thinner and thinner until it’s not there any more. For example, the atmosphere is thinner on the top of Mount Everest than at sea level. One way you can tell this is because there is less oxygen so it’s harder to breath! We also notice the drop in pressure because the atmosphere is thinner.
  
  If you were in an aeroplane or a space ship that had a controlled oxygen level and pressure inside, you probably wouldn’t notice directly, but you would have measuring equipment to tell you!
- Alan Fitzsimmons answered on 18 Mar 2014:
  
  Nice question. Astronauts say that it is a gradual thing. When you start off in a rocket everything looks pretty similar to being on the ground, except the clouds are below you. But that’s not that special, I’m above the clouds when I work on mountain tops or I am flying in a plane.
  
  But as you get higher and higher, the sky begins to get darker and darker. At about 60 miles up astronauts notice that the sky is now black even in the daytime, and you can also see the Earth curving away on all sides. At that point you’re in space!
- Nick Wright answered on 21 Mar 2014:
  
  Yes you could, but its a slow process because the atmosphere doesn’t abruptly end at one point but slowly gets thinner and thinner whilst also changing slightly in composition and temperature.

Question: can you tell when you have gone out of the earths athmosphere?

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