I stumbled across this discussion while searching for some information about the heat capacities of different steel alloys, but was bored at the time and proceeded to read the thread.
In case anyone happens to read this again, and for some reason finds crazymike's oft-repeated but mostly misunderstood points to be worth bothering to consider, I'll give an overview of why mike has failed to convice me.
I'd first like to note the nature of the open-minded scientist's discussion. More often than not, a disagreement is met with, "Oh you just don't believe me because I totally blew your mind by turning your world upside down, man! You've got to escape the paradigm!" Or something like that. And the reference to some "hard-core physics" website just blew me away, because, as Maddox says, "Hey, this article is great but you know what would make it better? If I could read another article in the middle of it."
In addition, no plausible motive has been given for anyone to have gone to the length of getting some kind of massive laser to finish what the planes started. Wouldn't it have been enough for thousands to die and the buildings to slowly burn down or be condemned? Was there some top-secret x-files type conspiracy leader watching the planes crash who said, "well, that was pretty good, but it needs some more 'punch.' Break out the IR lazer!"
As for the "melting steel" argument, steel does become more malleable as it reaches elevated temperatures, long before it actually reaches a melting point. One grade actually undergoes a phase transformation at about 1333 degrees Farenheit (that's around 723 C I believe), which is characterized by its increased softness and toughness. Other grades of steel, with different carbon contents and different alloyed metals, do have higher phase transformation temperatures, but we're talking a maximum difference of a few hundred degrees Farenheit in the extreme for the kinds of steel that were in the towers. All it would take for a beam to begin to buckle is a decent-sized spot of austenite, and once it started buckling, you have the friction caused by shear stress within the beam adding to the thermal energy of the system, which spawns more phase changes, which causes more failure.
There were many more factors in the collapse of these buildings, but I think I've demonstrated that you at least know jack about metallurgy, government conspiracies, and reality in general, crazymike. I hope you get to read this. Looking forward to your reply. Will it have a listing of all of your points to date? I hope so! That would totally change my mind.