How many years are required for a chunk of thermally insulated granite to increase 490°C in temperature (assum

Question

Radioactive decay of granite and other rocks in the Earth's interior provides enough energy to keep the interior molten, heat lava, and provide warmth to natural hot springs. This is due to the average release of about 0.03 J per kilogram each year. How many years are required for a chunk of thermally insulated granite to increase 490°C in temperature (assume the specific heat of granite is 800 J/kg °C)?

Answer 1

Garret is indeed missing something. He forgot to multiply by the temperature change. 490 * 800 / 0.03 = 13,066,667 years. It always helps to check your units!

Lord Kelvin in the 1800's calculated that the earth should have cooled too much for volcanoes to occur in less than 40 million years, even if it started out in a molten state. This caused Darwin to go to his death bed doubting his theory of evolution. The fact that this was due to no one knowing about radioactivity then is a subtlety conveniently overlooked by Creationists who love to trumpet Darwin's doubts.

Answer 2

This looks really simple:

800 J/kg °C
0.03 J/kg

t = (800 J/kg*°C) / (0.03 J/kg*yr) = 26,666 years.

Am I missing something?

[EDIT]
Yup. Guy after me was right - Even though I wrote out the units I forgot the °C. Should've been 26,666 yr/°C, and then multiplied by the 490 °C, etc. etc. etc...

But he's wrong about that Darwin nonsense. Darwin was indeed wrong. The world was, indeed, created by God. But not by design. It was sneezed out of God's nose precisely 67 years ago, and in 3 years the world will end by the hand of "The Great and Terrible Tissue." Everything before then is artificial memories written out in divine mucus. ;)

Damn blasphemer.
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