Amount of gold in the world.

The amount of gold produced by man according to yearly quantity records and estimates of the gold production of recent, classical and modern history is a cube about 25 (82 feet) meters on each side. Platinum is even more scarce to the point that all of the platinum in the world would fit in a 6.3 meter (20 foot) cube.
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Ancient Capital Wilted When Water Ran Low

It has recently been uncovered that the ancient city of Angkor, known for its large stone monuments and intricate water system, might have suffered multiple droughts and was possibly ended by one. Studies show that sediment stopped flowing to the end of the canals and rivers during a certain time, and there soil may have been overused due to a growing population, which lead to famine. The ancient Cambodians had many of the water technologies we use today and could be seen as a microcosm to foretell what could one day happen to our society.