On which altitude does the heaven turns in black?

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Discussion Overview

The discussion revolves around the altitude at which the sky appears to turn black, prompted by a question from a participant's nephew after a flight. The conversation explores various altitudes and perceptions of sky color, touching on both subjective experiences and atmospheric conditions.

Discussion Character

  • Exploratory
  • Debate/contested

Main Points Raised

  • One participant notes that the transition from blue to black is gradual rather than sudden as altitude increases.
  • Another participant cites test pilots claiming the sky appears black at 100,000 feet, while Concorde passengers reportedly observed it at 60,000 feet.
  • A participant mentions specific atmospheric pressures at various altitudes, indicating that the sky is definitively black at 250,000 feet due to the absence of atmospheric pressure.
  • One response suggests that there is no specific altitude where the sky turns black, comparing it to the gradual onset of darkness at night, with a rough estimate of it being very dark around 70,000 feet and more or less black by 100,000 feet.
  • A later reply questions the interpretation of Concorde passengers' experiences, suggesting that they might have perceived blackness when looking up rather than in the ambient environment.

Areas of Agreement / Disagreement

Participants express differing views on the specific altitude at which the sky appears black, with no consensus reached on a definitive answer. The discussion includes both subjective experiences and varying interpretations of atmospheric conditions.

Contextual Notes

The discussion lacks specific empirical data to support the claims made, and participants rely on anecdotal evidence and personal experiences. The definitions of "black" and the conditions under which it is perceived are not clearly established.

nickek
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Hi!
Just got a question from my 6 years old nephew who just traveled in an aeroplane for the first time. He wonders where (which altitude) the heaven turns in black? Someone who knows?
 
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I don't have any specific numbers, but the transition is gradual (not sudden) as you go higher.
 
Test pilots unanimously assert the sky appears black at 100,000 feet. Concorde passengers have claimed the sky appears black at 60,000 feet. The air pressure at 60,000 feet is about 1 lb/in^2, at 100,000 feet it is 0.162 lbs/in^2, at 250,000 feet it is 0.000 lbs/in^2. Obviously, the sky is indisputably black when atmospheric pressure reaches 0.000.
 
Thanks for your answers!
 
While there's no point at which the sky turns black, you could ask when has it turned black by (in the same sense that you can't say exactly when it gets dark at night, but you could say that it will happen sometime before, e.g., 9pm. At around 70,000ft it will be very dark, and it will be more or less black by 100,000ft.

Edit: Oops, looks like Chronos snuck in while I was typing. Though, Chronos, maybe I'm misremembering but I thought the Concorde passengers said it looked black if they looked up out of their windows. So, not necessarily ambient blackness.
 
Nickek: That's a very bright question. You're nephew's one smart guy. :-)
 

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