kaberett: Toph making a rock angel (toph-rockangel)
[personal profile] kaberett
The age of the Earth and of the Sun and the Universe are central questions for mankind.

Until the 19th century the ages were unknown; however, at that time with the advent of modern time, a significant debate arose concerning the age of the Earth. Geologists with their prestigious leaders Lyell and Darwin defended an old age, estimated to be several tenths of billions of years, while physicists tended to defer to Lord Kelvin who claimed that the Earth was not older than a few tens of millions of years.

Whereas physicists have physical laws and calculations, geologists only have simple observations of geological phenomena: the erosion rates of mountains, sedimentation rates, and the amount of volcanic eruptions today compared to the total amount of volcanic rocks, and maybe just intuition, but geologists were right (Thomson (Lord Kelvin), 1899; Darwin, 1859; Lyell, 1930; Rutherford and Soddy, 1902). The Earth is not 20 to 100 million years old as Kelvin thought, but rather billions of years as Lyell (1930) claimed. the debate was resolved when the physicist Rutherford (1929) used the newly discovered radioactivity for measuring ages of rocks and soon obtained an age of billions of years using the U-He method.

In the middle of this century, Hubble's observations initiated a second debate. This time the target was the age of the Universe (Hubble, 1929). Astronomers and geologists fought about that, and again the geologists were right.
CJ Allègre, G Manhes, C Göpel. 1995. The age of the Earth, Geochim. Cosmochim. Acta 59:1445--1456

(no subject)

Date: 2014-06-06 02:41 pm (UTC)
From: [personal profile] swaldman
Am I right in thinking that Kelvin's estimate was based on "It should have cooled off by now", assuming a hot lump of rock without radioactivity?

(I have a vague memory of something along those lines, and your post brought it to mind)

(no subject)

Date: 2014-06-06 02:52 pm (UTC)
From: [personal profile] swaldman
That makes sense - I'm guessing that at that point nobody realised the interior of the planet was fluid? Since you wouldn't get convection in solid rock... Although I'd have thought that assuming only conduction would give a longer time to cool? (in most areas convection speeds up heat transport, but I'm no geophysicist)

(no subject)

Date: 2014-06-06 03:36 pm (UTC)
From: [personal profile] swaldman
Oh, that's wonderful!
And yes, thank you, what you said makes more sense now :-)

(no subject)

Date: 2014-06-06 03:37 pm (UTC)
hollymath: (Default)
From: [personal profile] hollymath
Aw! This makes me happy.

(no subject)

Date: 2014-06-06 11:22 pm (UTC)
birke: (Default)
From: [personal profile] birke
Diplomacy at its finest!

(no subject)

Date: 2014-06-07 11:38 am (UTC)
sylvaine: Dark-haired person with black eyes & white pupils. (Default)
From: [personal profile] sylvaine
*giggles* Smart man!

(no subject)

Date: 2014-06-06 11:05 pm (UTC)
silveradept: A kodama with a trombone. The trombone is playing music, even though it is held in a rest position (Default)
From: [personal profile] silveradept
The rocks do not, apparently, lie.


kaberett: Overlaid Mars & Venus symbols, with Swiss Army knife tools at other positions around the central circle. (Default)

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