At an altitude of about 100km above the Earth's surface, the density and temperature of the atmosphere are about 10^-14 kg/m^3 and 2000K, respectively. At this altitude, the major constituent of the atmosphere is atomic oxygen. Use this information to estimate the pressure of the atmosphere at an altitude of 1000km. On average, how far apart are the oxygen atoms? What is their root mean square speed? Discuss whether the temperature of a gas at this pressure can be interpreted in the same way as the temperature of a gas at normal atmospheric pressure. Attempt: The first thing that crossed my mind is whether the pressure of the atmosphere oxygen changes linearly with the height of the atmosphere. But how do I know whether it's a linear variation or not? What other factors should I consider when attempting the question? P=ρhg doesn't really help, I think. Thank you!