How does he know that it was graphite?
Best Answer
We don't have the perspective of Legasov in the photo you show here, we are behind him looking ahead at the path of the helicopter, while he is more able to look down. Helicopters often have windows that extend quite low. It's possible he is able to look down at an angle on the roof of the building they are approaching.
Graphite is a very dark, almost black rock-like material. I think we are meant to presume from his statement, that he can see a significant amount of black colored debris on the roof of the building. Concrete is the other rock-like material he is likely to see, but that is relatively light colored.
Pictures about "How does he know that it was graphite?"
Sources: Stack Exchange - This article follows the attribution requirements of Stack Exchange and is licensed under CC BY-SA 3.0.
Images: Pok Rie, Jim Fawns, Anthony, Craig Adderley