Sounds like a stupidly easy question to find out with a quick internet search, but it’s not.
I don’t want to know the average surface temperature, or the average ocean surface water temperature, or read another article about climate change.
But that’s all I found in the past hour.
I’d like to know the average temperature of all molecules that comprise earth, or a best guess scientific estimate.
I think the median average temperature is around 2,200°C.
The Earth has a radius of 6,371km, giving a volume of 1.08e13km^3.
A sphere of half this volume would have a radius of 5,057km. Within the Earth, this sphere would sit at a depth of 6,371 - 5,057 = 1,314km.
From this chart, the temperature at that depth is around 2,200°C, so half the volume of the Earth has a temperature above that, and half a temperature below it.
The problem with that is the temperature inside that sphere gets over 4000 degrees above that value and the temperature outside that sphere only gets to around 2000 degrees below it.
Edit: Just realized you said the median, you may be right.
Higher than you think. The inner core of earth is ~5K degrees C and the outer core is ~3K degrees C
That’s actually lower than I thought.
For the record, you should probably use a lower-case ‘k’ (as in kilo, the SI prefix) rather than an upper case K (the unit of temperature, Kelvin), both in general and especially when referring to temperatures!
The crust is minuscule compared to the core and mantle.
The mantle makes up about 84% of Earth’s total volume. The temperature varies from about 1 300 K (1 000°C, 1 832°F) near its boundary with the crust, to 4 000 K (3 700°C, 6 692°F) near its boundary with the core. https://education.nationalgeographic.org/resource/mantle/
The temperature in the Earth’s core is uncertain: estimates at the inner core boundary range from 4 000 K to 8 000 K and at the core–mantle boundary from 3 000 to 4 500 K. https://www.homepages.ucl.ac.uk/~ucfbdxa/pubblicazioni/nat.pdf
By mass or by volume?
Genuine question, how would mass vs volume change the answer?
Volume would mean get the temperature of every m3 of earth and average them out, mass would mean the same, except before averaging you would weight(ahem) them, so a cube of air counts less than a cube of lava.
Counting by volume would get tricky with the atmosphere. Where do you draw the line of where the atmosphere ends? Even thousands of miles from Earth there is very thin atmosphere.
Karman line?
That’s reasonable, but it means that whether you count by volume or mass the atmosphere is a negligible contribution to the average.
The core is small by volume but very dense (massive) and very hot. An average temperature by mass would be much higher than an average by volume.
Let me get out my thermometer, brb
I have my apartment set to 72. My temperature is 98.7 and my wife’s temperature is “Leave me alone, I’m sleeping.”
Hope this helps.
When you say “all molecules that comprise earth,” are you including every molecule in the atmosphere out to the Karman line? Are you looking for an average of every molecule, or an average by volume? There are more molecules in solid matter than gaseous, obv
When you say “all molecules that comprise earth,” are you including every molecule in the atmosphere out to the Karman line?
For what it’s worth this won’t change the result in any meaningful way. Both in terms of atom count and atom mass the atmosphere makes up only a tiny fraction of the earth’s material.
If you’re taking an average by unit of volume, it absolutely matters
By about 4.8 percent.
Of course you also have to include the mars rover and the voyager probe!
You will have a very difficult time finding this. The average temperature of all molecules on earth is absurdly difficult to calculate, nearly impossible to gather data on, and not something that’s very useful for any practical calculations so no one has bothered to do it.
Black body radiation is probably more what you’re looking for, I would suggest starting there.
Why is it hard? At least to get an approximation since you can’t measure everywhere.
We know temperatures of the mantle and both cores. We know their size. We can ignore the crust as a rounding error. This approximation will improve as our measurements get better.
Black body radiation was my thought as well. It may not be the average including the inner layers, but it’s the average at the crust. About -1°F according to Wikipedia.
To add to this, is probably hard because the composition of the interior of the earth is a lot of guesswork. We can only directly observe how much heat is coming out of it.
I don’t think that’s an answer that really exists in any meaningful sense since temperature is a macroscopic phenomenon. When you get down to the scale of the microscopic, i.e. of molecules, then atoms, then particles, you really only have amounts of kinetic energy of said particles, typically measured in the unit electronvolt, or eV.
When said particles interact, they impart kinetic energy to one another, which directly constitutes the thermodynamic fluctuations we see in macroscopic systems.
Put simply, microscopic energy levels create macroscopic temperature readings.
In other words, “temperature” is just a macroscopic reading of collective microscopic energy levels.
tl;dr: Molecules don’t have temperature; they have energy.
Molecules don’t have temperature; they have energy.
You need this distinction when it’s about gas.
Here we are talking solid and fluid matter.
I imagine that if you look up the estimated temp for the Earth’s Mantle, you’ll be pretty close to what the average temp is.
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Hotter than it was last year, and the year before that, and…
Why can’t you take an average of global average ocean, surface, and air temperatures? That seems like it’d be…an okay…estimate…
Cauuse ocean temperature varies greatly with depth, and air temperature with altitude.
After cruising the comments and reading your post twice I propose the following because I’m that asshole today:
Go by layer.
Okay, so, assload insta-death ballpark Celsius in the center, okay fine. Maybe median this one. Then, consider some other identifiable layer(s) between there & surface, with some more eyeballing. THEN, for good measure, as many surface temps you can get for sea/land/air if you have chosen the range to include atmosphere.
Report back. I’m half asleep and haven’t checked my work. Also. I only ever need half a reason to suggest implementing excel to assist in your calculations 😂 I’m so sorry
Average?
The hottest place on earth is the core, about 4400°C to 6000°C(average around 5200°C)
https://education.nationalgeographic.org/resource/core/
A short google point out that the coldest place on earth is Eastern Antarctic Plateau, Antarctica (-94°C)
https://www.newscientist.com/question/coldest-places-earth/#:~:text=1)%20Eastern%20Antarctic%20Plateau%2C%20Antarctica,of%20coldest%20place%20on%20Earth.
And since no living thing is hotter than earth core and no living thing is colder than antarctica(other than my ex), then we calculate the average of this two((5200 + -94)÷2) and we get 2553°C. That’s the average temperature of earth.
That’s a pretty dumb way of calculating average since it’s just the average of the biggest value and the smallest value. That’s neither mean, median, or mode for the whole planet. It needs to be weighted by volume or mass in order to be an accurate average.
It is a half decent Fermi approximation though.
I mean OP asked for average, that’s how average calculated 🤷
Median is impossible to calculate since you need a whole array of data to know what’s in the middle. I think anything other than that is impossible because we need gazillion of data to even getting close to the accurate answer, that’s why all answer out there is usually categorised and in estimate.
That’s not how average is calculated, that would be the average if there were two particles, one 5200 and one -94. The average is the sum of all values divided by the number of values. Not the max plus the min divided by 2.
If only there were some extensive property of matter we could multiply with the temperature to compute a weighted average. That would be massively helpful.
that’s how average calculated
OP has also asked for meaningful
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