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Why is it Colder at Higher Altitudes?

If you look at the top of a mountain, you’d think it is colder at higher elevations than

it is at sea level.

So what’s going on here?

Earth evidently has an atmosphere, and that atmosphere is made up of stuff, including

greenhouse gasses.

Those gases trap heat after it hits the surface, keeping us warm.

However, the further up in the atmosphere, the less dense and more sparse matter is.

Air near the surface is under pressure from air above it, but the air higher up is less

dense because it has less matter pushing down on it.

Since it has less pressure, it is able to expand.

That air uses up some kinetic energy in its efforts to expand, converting it into potential

energy.

Since temperature is the average kinetic energy of molecules, the temperature decreases.

But, there are parts of the atmosphere where other effects create warmer temperatures with

higher elevations.

The troposphere is the first 10 kilometres from the surface.

Mount Everest is roughly 9 kilometres high for comparison.

In this area, almost all of our weather happens.

After this, there is a tropopause from the 10 to 20 kilometre mark where the atmosphere

is stable.

This is the area where commercial planes fly.

From 20 to 50 kilometres, we enter the stratosphere, where the atmosphere actually warms up.

This is because of a high concentration of ozone, which absorbs ultraviolet light from

the sun.

After this, there is another area of stability called the stratopause.

Next, there is the mesosphere from about 55 to 85 kilometres, which cools for the exact

same reason as the troposphere.

Molecules losing kinetic energy.

After another level of temperature stability at the mesopause, there is the thermosphere;

thermo referring to heat.

This is where the International Space Station is.

Since it is the last layer, ranging from 90 kilometres to hundreds of kilometres out,

it has nothing above it to shield it from solar radiation.

This causes it to be extremely hot, reaching temperatures of up to 2000 degrees celsius.

Since molecules are spread out thinly, temperatures change by roughly 200 degrees celsius from

day to night.

It is for the same reason that Mercury, the planet in our solar system with the thinnest

atmosphere, experiences drastic temperature differences from its 427 degree days to its

-180 degree nights.

The atmosphere is one of many wonders of the cosmos, and we haven’t even considered the

massive expanse beyond our own world.

And until next time, thanks for watching.