Atmosphere
Atmosphere is both a gas and a unit of pressure.
Contents
Gas
An atmosphere is layers of gas surrounding a planet or moon, held in place by gravity. In spacecraft, the atmosphere is created and maintained by a ship's life support systems.
A planet is able to retain its atmosphere when the gravity is great and the temperature of the atmosphere is low.
On starships, it is relatively easy to adjust the atmosphere, and can be done for a myriad of reasons. Different species may have different atmospheric requirements,
certain medical procedures may call for a different atmospheric pressure, and in emergency situations, the systems maintaining the atmosphere in choice areas may have their power re-routed for the safety of the ship.
Examples
- The atmosphere of Earth is primarily composed of nitrogen and oxygen, with notable amounts of water vapor, carbon dioxide, and noble gases.
- In 1986, as the HMS Bounty was approaching Earth, Captain Kirk asked Spock to find out which time period they had arrived at.
Upon scanning the planet, Spock informed the captain that based off the pollution content in the atmosphere, that they had arrived at the late 20th century.
- Following an asteroid impact on the planet Terra Nova, the toxic debris in the atmosphere was too dense to let a transmission pass.
Measurement
As a unit of measurement for pressure, it is defined by the force exerted by the weight of air molecules in an atmosphere (as defined by above).
In the classic atmospheric model, the atmospheric pressure decreases at high altitude because of the diminishing mass of the gas above the point of barometric measurement.
The height at which the atmospheric pressure declines is called the scale height.
A pressure of 1 atm can also be stated as:
- 101325 pascals (Pa)
- 14.6959 pounds-force per square inch (lbf/in2)
- 2116.22 pounds-force per square foot (lbf/ft2)
- 1 ata (atmosphere absolute)
Examples
- The Federation typically measures the atmospheric pressure of planets they encountered by relating to "Earth normal."
