Why is it colder the higher up you go?

It’s a fact that you’ve acknowledged before and pretty much always knew. You’ve probably never even considered why it is that way because you knew it was just how it is. It is just a fact and it’s just the way that it works.

However, I’m not satisfied with that answer. There is something deeply flawed with the fact that it gets colder as you go higher up on Earth. Surely the higher up you go the closer you are to the sun, the source of heat, light and energy on the planet. This means that as you get closer to the sun, you should be getting warmer and warmer. So why doesn’t it work that way? Why are there heavy blankets of snow draping the Himalayas and the Alps rather than the streets of the cities beneath?

To answer this question we need to understand more about how the sun affects the Earth.

Alps - HDR

It certainly is beautiful,but it doesn’t seem to make any sense. (Photo credit: CyberMacs)

Something I want to clarify before we go any further is that pretty much all of the warmth that the Earth receives is from the Sun. It’s pretty much essential to us because it not only provides light and warmth but also energy. These are absolute necessities and we simple can’t do without them.

Although, you may argue that the earth can still depend on it’s immensely hot core to maintain the planet and it may be true that volcanoes and suchlike do contribute to the warming of the planet. But on the face of it, it’s very little compared to the sun’s relentless glare. Furthermore, we wouldn’t be able to differentiate between night and day because the Earth’s core isn’t really a viable source of light for us. I’ll be talking about just how badly we need the sun in a future post but for now, let’s get to the matter at hand.

First of all, the sun’s heat hardly warms the atmosphere of the Earth as it passes through it. On the heat’s journey to the ground, it acts almost exactly the same way as the sun’s light does (Or any light for that matter). It passes through the Earth’s relatively thick and protective atmosphere as though it wasn’t even there.

English: Diagram of the layers of Earth's atmo...

Diagram of the layers of Earth’s atmosphere. (Photo credit: Wikipedia)

As you can see from the graphic, that’s a lot of layers of the Earth’s atmosphere to go through, with human beings inhabiting only a tiny proportion of it. So if the sun’s heat doesn’t warm up the atmosphere, how do we feel it? Is the heat that we experience on a hot day actually coming from something else? The short answer to that is no.

The fact is, we don’t experience the sun’s heat directly. By that I mean that the heat (or radiation) doesn’t strike us straight away. Nearly all of the sun’s radiation is used up in warming up the land or the oceans on Earth.

As the land/ocean gets warmer and warmer, it warms up the air around it. As the air gets warmer, it receives more energy so the particles that make up it’s composition move about a lot more. This shakes up the particles on top of them, as well as around them, so those particles too start to vibrate. This means that as you go higher, the heat or energy that vibrates the particles in the air diminishes. So the higher up you go, the less the particles vibrate. Meaning that it isn’t as warm as it is down below.

You if didn’t quite grasp that you think of it as falling dominoes.

The energy that is used to push the first domino causes the other ones to fall too.

If you didn’t already know, something to keep in mind is that heat is a form of energy. You can imagine the sun’s heat energy as the thing pushing the first domino. The dominoes in this scenario are the air particles. As the first domino gets pushed, it pushes the other dominoes behind it. Similarly, the first particle closest to the land receives energy and vibrates. This in turn causes the other particles next to it to vibrate too.

The main difference between the air particles and the dominoes is that over time, the energy that causes the air particles to vibrate decreases. This is why it’s colder as you go higher up, because the particles move less.

The way this works is similar to how sound waves travel through the air.

Another crucial reason for why it’s colder on top of mountains rather than at sea level is because temperature and pressure are directly proportional to each other. This means that as one quantity increases, the other quantity also increases by the same percentage. When you pressurise any gas, the temperature increases.

And you may already know that as you go up to higher altitudes, the air pressure decreases. Meaning that the temperature also decreases, due to the fact that pressure and temperature and directly proportional to each other.

Trekkers need special equipment to ensure that the air pressure is suitable enough at high altitudes.

The below graph shows the relationship between the altitude and the atmospheric pressure. The atmospheric pressure is measured in kPa (kilopascal), a unit for measuring pressure.

English: Graph of atmospheric pressure (in kPa...

Graph of atmospheric pressure (in kPa) vs. altitude above sea level (in meters).  (Photo credit: Wikipedia)

You can see from the curved line that as the altitude increases, the atmospheric pressure decreases. It is this lower pressure at higher altitudes that causes the temperature to be colder on top of a mountain than at sea level.

Thanks for reading and if you liked this post, be sure to follow 😀

P.S: I kind of got carried away while looking for a suitable domino image. It’s a pretty impressive achievement.

References and lots more information:

http://science.howstuffworks.com/nature/climate-weather/atmospheric/question186.htm

http://usatoday30.usatoday.com/weather/resources/askjack/2004-06-23-cold-upper-atmosphere_x.htm

http://usatoday30.usatoday.com/weather/wdenalt.htm

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