Wikipedia can be a controversial topic: message-board flamewars pop up with some regularity, with proponents and critics raging about the relative merit of experts versus amateur editors. In an academic setting, Wikipedia is a thorn in the side of many professors who've learned to dread research papers from overly-credulous undergrads who cite Wikipedia as an authoritative source.
However, for a random-fact addict like myself, Wikipedia is a gift from the heavens. Let's take a tour through one of my most recent knowledge browsing expeditions: I started out with a link to Centralia, a town in Pennsylvania, now virtually abandoned due to the vein of coal that is currently on fire, which has been smoldering for more than three decades.
That took me to the article on Mine Fires, which I was shocked to find, are actually relatively common, and can burn for not just decades, but centuries. One mine fire in China has apparently been burning since the 1600s, and China at the moment has hundreds of coal fires running uncontrolled, consuming tens of millions of tons of coal annually (how's about that for greenhouse gas emissions?).
From there, it was a short hop to the article on Peat, which can also burn. Apparently Peat (decayed vegetation matter), covers about 2 percent of the global landmass, and is still used as home heating fuel in parts of Ireland and Finland. The related links sent me to Acid sulfate soil, a form of waterlogged soil, that when exposed to air, creates naturally-occurring sulfuric acid, which can acidify water, killing vegetation and fish, and even undermining the structure of concrete and steel buildings.
Well, I couldn't not investigate what Wikipedia had to say about Waterlogging. I found out that waterlogging can preserve otherwise-perishable artifacts that can tell archeologists much about ancient cultures. Well, on to Archeology! Lots to read (skim) there, but the section on Psuedoarcheology caught my eye. Apparently fictional archeologists don't follow established practice very well (take that, Indiana Jones!).
But it was the link to the article on Xenoarchaeology that really caught my attention. Apparently this is a still-hypothetical form of the field, which will (or may) study the physical remnants of extraterrestrial cultures. The actual field is currently a haven for fringe theorists and pseudoscientists, but the links to xenoarchaeology in science fiction will definitely merit a return visit.
The related topic of The Mediocrity Principle was a fascinating one: initially put forth by Copernicus, the theory states that there is nothing particularly special or unique about Earth, as compared to the rest of the universe. One of the logical conclusions of such a principle was the Drake Equation, which hypothesized the likelihood of an extraterrestrial civilization developing in our galaxy (and the likelihood we would come into contact with it), based on: how many stars are formed, how many have planets, how many of those can support life, how many of those actually do, and the subset who develop intelligent life, and so on.
So, in the space of a little reading and clicking, I went from an abandoned town that's been on fire for decades, to the numeric possibility of alien civilizations. That's why I love Wikipedia.