Atmospheric pressure decreases as altitude increases.
Here's a more detailed explanation:
As you move higher in the atmosphere, there is less air above you pressing down. This is because air is compressible and gravity pulls it downwards, resulting in the highest density (and therefore pressure) at sea level. The higher you go, the less air there is above you, and the weaker the downward force.
- Air Density: The density of air is greatest at sea level due to the weight of the atmosphere above compressing the air. As altitude increases, the air becomes less dense.
- Gravitational Force: Gravity plays a crucial role in atmospheric pressure. It pulls air molecules towards the Earth's surface, creating a pressure gradient with higher pressure at lower altitudes.
- Weight of Air Column: Atmospheric pressure at any given point is essentially the weight of the column of air above that point. Naturally, a taller (higher altitude) column of air weighs less.
To further illustrate this:
- Imagine a stack of books. The book at the bottom bears the weight of all the books above it. Similarly, the air at sea level bears the weight of all the air above it.
- Now, remove some books from the top of the stack. The pressure on the book at the bottom decreases. Analogously, as you increase altitude, there's less air "above" you, leading to lower pressure.
| Altitude | Approximate Atmospheric Pressure |
|---|---|
| Sea Level | 1013.25 hPa (hectopascals) |
| 5,500 m | ~500 hPa |
| 8,848 m | ~317 hPa |
(These are approximate values as atmospheric pressure can fluctuate due to weather patterns)
The effect of altitude on atmospheric pressure is why airplane cabins are pressurized. At typical cruising altitudes, the atmospheric pressure is so low that humans would experience hypoxia (oxygen deprivation). Pressurization maintains a more comfortable and safe pressure inside the aircraft.
In summary, the higher the altitude, the lower the atmospheric pressure due to the reduced weight and density of the air above.
