Scrutable

https://www.reddit.com/r/dataisbeautifu ... this_is_a/

Looks super unlike any map of earth I've ever seen. I guess the role of tectonics is pretty key for creating earth-like continents?

It always amazes me that tectonics was still controversial within my mum's lifetime. By the time I did geography at school it was just a fact, with no mention that the boffins had only figured it out a few decades ago.

Bird on a Fire wrote: ↑

Mon Jun 28, 2021 1:22 am

It always amazes me that tectonics was still controversial within my mum's lifetime. By the time I did geography at school it was just a fact, with no mention that the boffins had only figured it out a few decades ago.

My 1963(ish) Britannica mentions it as a theory, and says something about it being diffcult to suggest a plausible source of energy for something of that scale. The author of that article hadn't realised there were huge quantities of fissile elements quietly fissing away down there.

basementer wrote: ↑

Mon Jun 28, 2021 2:38 am

Bird on a Fire wrote: ↑

Mon Jun 28, 2021 1:22 am

It always amazes me that tectonics was still controversial within my mum's lifetime. By the time I did geography at school it was just a fact, with no mention that the boffins had only figured it out a few decades ago.

My 1963(ish) Britannica mentions it as a theory, and says something about it being diffcult to suggest a plausible source of energy for something of that scale. The author of that article hadn't realised there were huge quantities of fissile elements quietly fissing away down there.

We need rockdoctor or someone, but I thought most of the heat was primordial?

There are three main sources of heat in the deep earth: (1) heat from when the planet formed and accreted, which has not yet been lost; (2) frictional heating, caused by denser core material sinking to the center of the planet; and (3) heat from the decay of radioactive elements.

From here:

https://www.scientificamerican.com/arti ... s-core-so/

Kelvin's calculation of the age of the earth gave too short a time by a few orders of magnitude because he didn't account for heat from radioactive decay.

shpalman wrote: ↑

Mon Jun 28, 2021 7:29 am

Kelvin's calculation of the age of the earth gave too short a time by a few orders of magnitude because he didn't account for heat from radioactive decay.

According to Steve Novella at SGU the main factor was actually that he didn’t account for the fact that the earth is cooling mainly by convection rather than conduction. The story about radioactive decay is commonly repeated but doesn’t stand up. Now I haven’t got the data and methods to double check this, but it sounds plausible.

First segment in this show: https://www.theskepticsguide.org/podcasts/episode-825

Grumble wrote: ↑

Mon Jun 28, 2021 7:57 am

shpalman wrote: ↑

Mon Jun 28, 2021 7:29 am

Kelvin's calculation of the age of the earth gave too short a time by a few orders of magnitude because he didn't account for heat from radioactive decay.

According to Steve Novella at SGU the main factor was actually that he didn’t account for the fact that the earth is cooling mainly by convection rather than conduction. The story about radioactive decay is commonly repeated but doesn’t stand up. Now I haven’t got the data and methods to double check this, but it sounds plausible.

First segment in this show: https://www.theskepticsguide.org/podcasts/episode-825

I would assume that convection is faster within a fluid than conduction would be.

Bird on a Fire wrote: ↑

Mon Jun 28, 2021 1:22 am

https://www.reddit.com/r/dataisbeautifu ... this_is_a/

Looks super unlike any map of earth I've ever seen. I guess the role of tectonics is pretty key for creating earth-like continents?

It always amazes me that tectonics was still controversial within my mum's lifetime. By the time I did geography at school it was just a fact, with no mention that the boffins had only figured it out a few decades ago.

Yes, Dad told me that he saw it in the first copy of New Scientist as an interesting theory

Speaking of, what the heck happened to rockdoctor? He needs to come back sharpish.

jimbob wrote: ↑

Fri Jul 02, 2021 4:38 pm

Grumble wrote: ↑

Mon Jun 28, 2021 7:57 am

shpalman wrote: ↑

Mon Jun 28, 2021 7:29 am

Kelvin's calculation of the age of the earth gave too short a time by a few orders of magnitude because he didn't account for heat from radioactive decay.

According to Steve Novella at SGU the main factor was actually that he didn’t account for the fact that the earth is cooling mainly by convection rather than conduction. The story about radioactive decay is commonly repeated but doesn’t stand up. Now I haven’t got the data and methods to double check this, but it sounds plausible.

First segment in this show: https://www.theskepticsguide.org/podcasts/episode-825

I would assume that convection is faster within a fluid than conduction would be.

Depends on the fluid, surely?

I'd never appreciated that Kelvin's calculation was based on the temperature gradient at the surface, I'd assumed it was a calculation of heat loss (and convection would accelerate that).
Kelvin and Perry, earlier.

shpalman wrote: ↑

Fri Jul 02, 2021 5:38 pm

I'd never appreciated that Kelvin's calculation was based on the temperature gradient at the surface, I'd assumed it was a calculation of heat loss (and convection would accelerate that).

kevin-and-perry.jpg

Kelvin and Perry, earlier.

I hadn't thought of it until now, but pretty much that.

jimbob wrote: ↑

Fri Jul 02, 2021 5:43 pm

shpalman wrote: ↑

Fri Jul 02, 2021 5:38 pm

I'd never appreciated that Kelvin's calculation was based on the temperature gradient at the surface, I'd assumed it was a calculation of heat loss (and convection would accelerate that).

kevin-and-perry.jpg

Kelvin and Perry, earlier.

I hadn't thought of it until now, but pretty much that.

Convection would accelerate it - which only shows how slow it is.

Grumble wrote: ↑

Fri Jul 02, 2021 7:49 pm

jimbob wrote: ↑

Fri Jul 02, 2021 5:43 pm

shpalman wrote: ↑

Fri Jul 02, 2021 5:38 pm

I'd never appreciated that Kelvin's calculation was based on the temperature gradient at the surface, I'd assumed it was a calculation of heat loss (and convection would accelerate that).

kevin-and-perry.jpg

Kelvin and Perry, earlier.

I hadn't thought of it until now, but pretty much that.

Convection would accelerate it - which only shows how slow it is.

Exactly, so it would give a younger age for the Earth, wouldn't it?

nezumi wrote: ↑

Fri Jul 02, 2021 4:49 pm

Speaking of, what the heck happened to rockdoctor? He needs to come back sharpish.

I'm always here. Watching

rockdoctor wrote: ↑

Wed Jul 07, 2021 5:39 pm

nezumi wrote: ↑

Fri Jul 02, 2021 4:49 pm

Speaking of, what the heck happened to rockdoctor? He needs to come back sharpish.

I'm always here. Watching

Gneiss

basementer wrote: ↑

Mon Jun 28, 2021 2:38 am

Bird on a Fire wrote: ↑

Mon Jun 28, 2021 1:22 am

It always amazes me that tectonics was still controversial within my mum's lifetime. By the time I did geography at school it was just a fact, with no mention that the boffins had only figured it out a few decades ago.

My 1963(ish) Britannica mentions it as a theory, and says something about it being diffcult to suggest a plausible source of energy for something of that scale. The author of that article hadn't realised there were huge quantities of fissile elements quietly fissing away down there.

I did geology at uni in 1973 when it had been pretty much proved by Dan Mackenzie, who was one of the academics there. Prior to that it was considered interesting that Africa and south America fitted together, but when they started looking at the topography of the ocean beds, and particularly saw that the magnetic field orientations in the rocks where completely symmetrical leading away from the central ridge, that pretty much nailed it

shpalman wrote: ↑

Fri Jul 02, 2021 5:38 pm

I'd never appreciated that Kelvin's calculation was based on the temperature gradient at the surface, I'd assumed it was a calculation of heat loss (and convection would accelerate that).

kevin-and-perry.jpg

Kelvin and Perry, earlier.

Little known fact: William Thompson named the units of absolute temperature after the River Kelvin flowing past Glasgow University, because it is absolutely freezin'.

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