Why is it colder at the top of a mountain despite being closer to the sun ?
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I’m actually super interested in this. I’ve lived at 5000ft. It was significantly colder at a lower elevation in the winter but significantly hotter at a lower elevation in the summer. Never really understood how that works.
The difference in distance to the sun it irrelevant. The sun is around 150 million km from you so any mountain is a legible
Earth radius is 6,371 km so on the equator on the equinox you get 6371 km closer to the sun from sunrise to noon, which takes 6 hours, then the same distance faster away until sunset.
Mount Everest is just under 9 km tall so even if it was on the equator it will be close to the sun for a short part of the. A ravine calculation of how long part of the day the peek is close to the sun compared to where it is noon is 9/6371 * 6 * 60*2 =1 minute The speed you move towards and away from the sun is not constant, I remember doing it in the past and the answer was around 8 minutes. You do not feel an enormous change in the heat from the sun in an 8 minutes period around noon so the distance effect is not relevant.
Mountains are cooler because the pressure is lower. A gas that expands cools down in temperature so when air is raised up the temperature gets lower. The sunlight will heat up the ground at the same rate at high altitudes but it will be surrounded by cooler air so the net effect is that it is cooler.
If you use a spray bottle you will feel that it and the nozzle get cool when you use it. That is because the high-pressure gas in it expands and cools down
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I’m fairly sure that the greenhouse effect is the real answer to this question. At lower altitude there is more air above your head trapping heat.
Distance to the Sun is irrelevant. In fact the earth’s distance to the sun varies by over 3 millions miles, between the closest and furthest point.
It is colder up higher because of low pressure. The atmosphere which hood all the heat in the air spreads out the further away from the surface you get. It gets colder the further is spreads.
As other people said, distance to the sun is irrelevant, but there are a bunch of different factors that determine the temperature. If you Google graphs of average temperature vs height you will see it’s not always colder the higher you go, so it’s colder the higher you go up to a point, then it gets hotter, then colder…
The sun is on average at
149,597,870 km at sea level
149,597,861 at Everest
That’s 0,000006% negligible difference. Other factors come in place. Like air density.
It’s to do with the pressure of the air up there. The molecules are further apart so they do absorb as much heat from the sun. From there they do not conduct that heat around them as well because there is less stuff to bump into to pass it.
A visualization that may help is imagine opening a 400 degree oven. You will feel hot air pass you but you will not get burned because the air molecules are so far apart that few bump into to you to pass that heat. Compared to a pot of boiling water on top of that stove at 212 degrees. Put your finger in there and you will immediately feel a burn. The water molecules are densely packed so much more touch your skin and pass that energy.
Another fact that may bake your noodle is the Earth is closer to the sun at 91 million miles (called the perihelion) during the northern hemisphere’s winter than in the summer at 95 million miles (aphelion).
First let’s talk about pressure. Pressure is force divided by area, which is why your cat laying on your lap is much more comfortable than them standing on it, same force (weight), concentrated into a much smaller area. You can kind of think of pressure as “force density.” When it comes to air pressure, you get air pushing against itself, and most of that cancels itself out, except for the force pushing down from gravity. Wherever you are, the air pressure you feel is that of the weight of how much air is above you (divided by the surface area of the top of your head).
Now let’s talk about thermodynamics. There’s a relationship between pressure, density, and temperature. The temperature of air (or whatever) is essentially the average speed of the molecules in it. When pressure goes down, temperature goes down, since pressure is just how hard air molecules are hitting things, and things hit less hard when they’re moving slower.
Putting these together, when you go higher, there’s less air over you because more of it is below you. Less air means less weight, less weight means less pressure, less pressure means lower temperature. This difference is much, much bigger than any other change you’ll get when you climb a mountain.
In simple terms:
The amount of warmth you feel as you get 1 mile closer to the sun is VERY small in comparison to the amount of warmth lost in the air at that altitude.
e.g. Being on top of a mile-tall mountain, you might feel 0.0001 degree warmer for being closer to the sun, but feel 40 degrees colder due to the air. Therefore, in total, you feel 39.9999 degrees colder on top of the mountain.
The reason the air is colder is because the density is lower. Less air = less heat (in simplistic terms).
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