2 billion years from now, the Milky Way will collide with the Andromeda Galaxy. This video from NASA shows a simulation (it also talks about star formation and the creation of the elements during intergalactic collisions).
The precious metals are those few that are not gasses, and not reactive. Of these, only gold (Au) and silver (Ag) are not extremely rare and hard to extract and work.
A while back, I posted a radio article by Planet Money on why gold is so valuable, and has been used for money for so long (God, Glory and GOLD: but why gold?). They’ve now created a nice video explaining the same thing. Though there’s less detail, the dramatic visuals (of the reactivity of sodium for example) make it quite interesting.
Chemical Galaxy II: A new vision of the periodic system of the elements by Philip Stewart.
Periodic Table of the Elements - a traditional view by Wikimedia Commons User:Cepheus.
The traditional periodic table of the elements breaks the elements into rows as their chemical and physical characteristics repeat themselves. But since the sequence of elements is really a continuous series that gradually increases in mass, a better way of displaying them might be as the spiral, sort of like the galaxy.
When the chemical elements are arranged in order of their atomic number, they form a continuous sequence, in which certain chemical characteristics come back periodically in a regular way. This is usually shown by chopping the sequence up into sections and arranging them as a rectangular table. The alternative is to wind the sequence round in a spiral. Because the periodic repeats come at longer and longer intervals, increasing numbers of elements have to be fitted on to its coils. …
The resulting pattern resembles a galaxy, and the likeness is the basis of my design. It seems appropriate, as the chemical elements are what galaxies are made of.
The ‘spokes’ of the ‘galaxy’ link together elements with similar chemical characteristics. They are curved in order to keep the inner elements reasonably close together while making room for the extra elements in the outer turns.
While the spiral version of the periodic table is not used a lot, it is scientifically valid. There are other ways of representing the spiral and the periodic table itself. It all depends on what you want to show.
Benfey's spiral table first appeared in an article by Glenn Seaborg, 'Plutonium: The Ornery Element', Chemistry, June 1964, 37 (6), 12-17, on p. 14. (via Wikimedia Commons)
Indeed, Mendeleev’s monument in Bratislava, Slovakia has the elements arranged as the spokes in a wheel.
Monument to the periodic table and Dmitri Mendellev (photo by mmmdirt, caption via Wikipedia).
NPR’s Planet Money has a nice story on why gold is used for money. They take the entire periodic table of elements and eliminate the ones that don’t work because they’re too reactive, a gas, too common, or too toxic. You’re left with five precious metals, rhodium, palladium, silver, platinum and gold, but only one of them has a low enough melting temperature so that it can be worked easily and is not ridiculously rare.
Also, Tony Clayton has a wonderful webpage on Metals Used in Coins and Medals. It has some fascinating details about the history of these metals and their alloys in coinage. For example, “In Old English the Latin word aes was rendered as brass, thus the use of the word brass to mean money still found today, especially in Northern England. “