I wondered aloud about what the flares were made of. The ensuing conversation went something like this:
Guy: "They're made of thermite. Same thing they used to bring down the twin towers."
Me: "Oh yeah?"
Guy: "Totally dude. They found molten iron at ground zero. Molten iron, I shit you not. That stuff melts at 1500 degrees Celsius."
Me: "Well, that makes sense, a plane full of jet fuel crashed into the building."
Guy: "No, it doesn't make sense man. Jet fuel burns at 1000 degrees Celsius. It couldn't possibly have melted the iron. Thermite, that's what did it."
Me: "Hhhhmmmm. I'm sorry, but I don't think jet fuel burns at any specific temperature. I believe it depends on the rate it burns and how fast the heat is carried away."
Guy: "No way man, you should look it up."
Guess what, we were both right!! At least about the jet fuel/iron part. I had reasoned that if you get enough fuel and burn it in a small area where most of the heat can't escape (like a fueled-up plane burning in a building maybe), the fire could get as hot as it damn well pleased. This is true in certain cases. However, I forgot about our good friend oxygen. If you ignite a fuel in air, taking no special measures to supply the fuel with something for it to react with (usually oxygen), then the energy from the fuel can be released only as fast as the flames can pull in oxygen. So, jet fuel does "burn at 1000 degrees celsius" under these conditions, which would not be hot enough to melt iron (which does melt at 1500 degrees celsius). A more complete explanation of this and the ensuing building collapse is laid out here by this MIT engineer, Thomas Eager.
So how did molten iron get to ground zero? I have no idea, dummy! Ask the internet! My guess though is the deconstruction crew melted the steel beams of the collapsed buildings in order to remove the debris, and that is the molten iron he is talking about. The full conspiracy theory can be found here.
Why is that guy so convinced the molten iron can only be explained by thermite?? Well, let's talk about what thermite is. To make thermite you mix aluminum (Al) powder with rust (iron oxide, Fe2O3) powder, and heat it up (way up). To heat it hot enough for the reaction to start, people typically insert a piece of burning magnesium metal into the aluminum/rust mixture. DISCLAIMER: Don't Try That at Home! If you do though, send me a picture. When you heat the mixture up, you are giving the system enough energy so that the oxygen atoms can remove themselves from the iron atoms and attach themselves to the aluminum atoms. This makes aluminum oxide (Al2O3) and iron (Fe). Now since oxygen prefers to be attached to aluminum atoms rather than iron atoms, this reaction also makes a buttload of heat. Essentially you are burning the aluminum atoms, only instead of using oxygen as the oxidant, you are using rust. As you can see, making thermite is not complicated. Probably the hardest thing about it is finding the aluminum. If you want to prepare for the apocalypse, I would stash away some aluminum powder and a butane lighter, just in case. This, I imagine, is why conspiracy theorists suspect thermite in the twin towers collapse--it is the easiest, most low-budget way to make molten iron, and molten iron can do a lot of crazy things.
For instance, watch this cool mythbusters video where they ignite a bunch of thermite on this car: