Sky

[hevs]

At what height does the sky begin and end ?

Scenario......A space rocket takes off in daylight, when it 'reaches' the sky, does the astronaut see the colour blue around the rocket ?

Another question...where does the sky go to at night ?

[hevs]

You got there eventually !

Thanx for your answer....very helpful.

[bernardo]

The air pressure in the atmosphere goes down by a factor of a million for every 100 km you go up.  Thus the pressure at ground level is c. 1000 millibars, at 100 km it is 10 ^ -3 mb, and 900 km it is 10 ^ -53 mb.

[source: Philips' Certificate Atlas 4th ed. 1987 p. 8]

P.S. This is my 9000th answer.

[hevs]

Thanx Bernardo........well done on your  9000th answer !

[Flurfl]

there is an unofficial limit of 50 miles, above which you are considered to be an astronaut.

the xprize awarded $10m to the first spacecraft to attain 100km altitude and repeat it it within two weeks

[bernardo]

It is sometimes said that the limit is 20 miles.  In about 1960 (I think), someone went up to 102,000 feet in a balloon and is sometimes considered to be the first person "in space".

[CT]

The internationally agreed boundary for space is considered to be at 100km (or 62 mi)