Is that story correct, the witness account accurate, the theory up-to-date? Here’s where we’ll email people related to the 9/11 story, and post their responses.

• Dr Asif Usmani published a paper in 2003 suggesting that relatively low temperatures (600 to 800 degrees C) could have been sufficient to initiate the WTC collapse. Does he still believe this in December 2005? We asked.
   
• Did Leslie Robertson really say there was “molten steel” at Ground Zero, 21 days after the attack? We decided to find out.
   
• Dr Alison Geyh is supposedly another witness to “molten steel” at the WTC. But it’s not quite as simple as that...
   
• Sarah Atlas was a subject in another “molten steel”-related story. We’ve not been able to speak to her, but the author of the story provided us with some interesting comments.