<p>There is no thermal expansion of the Earth. On the contrary, the Earth is very gradually cooling, and therefore shrinking, but so gradually that the effects are imperceptible and perhaps in the short term unmeasurable. You can see the process at work on Mars, which has over the course of 4.5 billion years lost much of its internal heat owing to its smaller size and greater distance from the sun. The result is that volcanism has ceased and the planet has a much thicker crust, but the core is still molten. Therefore Mars must have shrunk a little, but we don't know exactly how much because we have no precise measurements from four billion years ago.</p>

<p>Gravitational flexion ie. tides in the Earths outer regions caused by the moon, as well as decay of radioactive elements in the core and mantle, generate heat which reduces the rate at which the Earth cools. The Earth's loss of heat is so gradual that its interior still won't be completely inert when the sun expands to become a red giant in 5 billion years time. The Earth will then stop cooling and the surface will be scorched and probably melted, but it's nothing to worry about because 5 billion years is an almost unimaginably long time. Humans will have gone to join the dinosaurs billions of years earlier.</p>

CC BY-SA 4.0
2019-11-22T23:31:39.270Z
I guess what I'm really interested in is how much of Earth's radius can be attributed to its internal heat. I suppose this would be very difficult to know without, say, putting Earth somewhere else for several billion years and closely watching it. But, the Earth is made of rock and metal inside predictable conditions. Is it impossible to know this?
BMF
CC BY-SA 4.0
2019-12-23T10:17:26.277Z
What recent volcanism? The Martian volcanoes have been extinct for many millions of years.
Michael Walsby
CC BY-SA 4.0
2019-12-23T10:59:30.407Z
20 million years is not what I'd call recently. I recently dislocated my shoulder. I wish it had ben 20 million years ago, as that would have made me the longest-lived man in history and the longest lived vertebrate in the universe.
Michael Walsby
CC BY-SA 4.0
2019-12-23T16:09:36.967Z
@BMFForMonica actually it is fairly easy to answer as thermal expansion is pretty straightforward and predictable. we know what the earths composition is so the rest is just math. Feel free to ask it as a new question.
John
CC BY-SA 4.0
2019-12-23T16:42:53.457Z
@John Why a new question? This question asks for just that. Well, maybe my wording is a bit funny.
BMF
CC BY-SA 4.0
2019-11-22T23:08:04.490Z
2019-11-22T23:08:04.490Z
Michael Walsby
<p>Matter tends to change its volume in response to changes in temperature--or, hot things tend to be expanded. Is the thermal expansion of Earth significant?</p>

<p>That is, is it significant when compared against a cooler or perhaps internally-inert Earth?</p>

CC BY-SA 4.0
2019-11-22T23:39:01.100Z
It's complicated. Here is [one paper](https://www.jstor.org/stable/25427823?seq=1).
Keith McClary
CC BY-SA 4.0
2019-11-22T23:39:49.040Z
@KeithMcClary I'll read into it, thanks!
BMF
CC BY-SA 4.0
2019-11-23T12:14:28.620Z
Matter also tends to change its volume in response to pressure. So as you go deeper into the Earth, increase in temperature would cause expansion while increase in pressure would cause compression. I'm not saying the later process would completely counterbalance the former (silicate compressibility is pretty low), but that would be another parameter to take into account...
Jean-Marie Prival
CC BY-SA 4.0
2019-11-23T12:43:05.287Z
@jmprival and an increase in pressure results in an increase in temperature which works to counteract compression... Yikes.
BMF
<geophysics>
Thermal expansion of Earth
BMF
# Thermal expansion of Earth

(Asked by: username_0 on 2019-11-22)

Matter tends to change its volume in response to changes in temperature--or, hot things tend to be expanded. Is the thermal expansion of Earth significant?

That is, is it significant when compared against a cooler or perhaps internally-inert Earth?

**Tags:** geophysics

> **Comments:**
> **username_1**: It's complicated. Here is [one paper](https://www.jstor.org/stable/25427823?seq=1).  
> **username_0**: @username_1 I'll read into it, thanks!  
> **username_2**: Matter also tends to change its volume in response to pressure. So as you go deeper into the Earth, increase in temperature would cause expansion while increase in pressure would cause compression. I'm not saying the later process would completely counterbalance the former (silicate compressibility is pretty low), but that would be another parameter to take into account...  
> **username_0**: @jmprival and an increase in pressure results in an increase in temperature which works to counteract compression... Yikes.  

---

## 1 answers

### Answer by username_3 on 2019-11-22. Score: -1

There is no thermal expansion of the Earth. On the contrary, the Earth is very gradually cooling, and therefore shrinking, but so gradually that the effects are imperceptible and perhaps in the short term unmeasurable. You can see the process at work on Mars, which has over the course of 4.5 billion years lost much of its internal heat owing to its smaller size and greater distance from the sun. The result is that volcanism has ceased and the planet has a much thicker crust, but the core is still molten. Therefore Mars must have shrunk a little, but we don't know exactly how much because we have no precise measurements from four billion years ago.

Gravitational flexion ie. tides in the Earths outer regions caused by the moon, as well as decay of radioactive elements in the core and mantle, generate heat which reduces the rate at which the Earth cools. The Earth's loss of heat is so gradual that its interior still won't be completely inert when the sun expands to become a red giant in 5 billion years time. The Earth will then stop cooling and the surface will be scorched and probably melted, but it's nothing to worry about because 5 billion years is an almost unimaginably long time. Humans will have gone to join the dinosaurs billions of years earlier.

> **Comments:**
> **username_0**: I guess what I'm really interested in is how much of Earth's radius can be attributed to its internal heat. I suppose this would be very difficult to know without, say, putting Earth somewhere else for several billion years and closely watching it. But, the Earth is made of rock and metal inside predictable conditions. Is it impossible to know this?  
> **username_3**: What recent volcanism? The Martian volcanoes have been extinct for many millions of years.  
> **username_3**: 20 million years is not what I'd call recently. I recently dislocated my shoulder. I wish it had ben 20 million years ago, as that would have made me the longest-lived man in history and the longest lived vertebrate in the universe.  
> **username_4**: @BMFForMonica actually it is fairly easy to answer as thermal expansion is pretty straightforward and predictable. we know what the earths composition is so the rest is just math. Feel free to ask it as a new question.  
> **username_0**: @username_4 Why a new question? This question asks for just that. Well, maybe my wording is a bit funny.  

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