Q.1. How did tree ring provide a key to unlocking the secrets of Tunguska?

Question

Q.2. If, as the Russian engineer argued, the event at Tunguska resulted from a nuclear explosion, why would that lead to his conclusion that spaceship was the cause?

Answer 1

I think that since the tree rings are a history of annual growth, by looking at them you can see how the growth pattern was interrupted or distorted and possibly detect traces of radiation at a certain time which correlates to the time of the explosion.

Since the ground was not disturbed like it would have been if a bomb blew up at ground level, and the trees were just blown over without the ground being torn up, he concluded that the explosion must have occurred from above, as though a nuclear explosion was intiated in the sky from an outside source.

Answer 2

I don't know where you got the idea that the "secret" of the Tunguska explosion has been unlocked. There are several theories but none has been proven. The nuclear explosion theory was proffered when a Russian scientist who noticed a similarity between the patterns of devastation between the Tunguska incident and the bombing of Hiroshima and Nagasaki. If your science teacher is telling you it was a nuclear explosion he may be feeding you erroneous information.