Is it true that nuclear bombs can set the Earths atmosphere on fire.?

yes, we will all be consumed in the final fireball and nothing but ants will survive. ants will rule and evolve to be the next dominant intelligent life as happened once before.

No science professor should be saying this. At the time os the first nuclear test, there was little known about the possible outcome. One SPECULATION was that the atomic blast would cause a chain reaction in the atmosphere and the planet would burn to a cinder. There is no scientific basis for speculation. Your science professor should find facts to tell you. There are plenty of good ones.

Well now let's see ?.....................Hmmmmmmmmmm If all of us ate nothing but beans for about 30 years, then they passed a law making it illegal to fart then we let go at the same time that they droped the big one.......... it could be interesting to say the least !.......... A far more intersting condition for this to pursue would be how could everyone on earth be forced to eat nothing but beans for 30 years and where would all these beans come from ?What are the chances of surviving 30 years without farting ? Then if we can't even get world peace how are we all going to fart simultaneously ? I leave the last question up to you----I know, I know if all the rest can be acheived then it would be easy to get someone to light off the big one just for the hell of it ! Don't hold your breath ! Your nose........................that's another matter.

If we threw all the nukes available the heat would be tremendous. I don't know about an atmospheric fireball, but it sure would be a pretty bad day.

No. During the early days of the Manhattan Project this was a issue that was brought up, but quickly shown to be unphysical. The fear was that if we set off a fission bomb, then we will be releasing enough energy to cause fusion to occur in the atmosphere. These fusion reactions would release more energy leading to more fusion, etc... The problem is that in order for fusion to occur you need extremely hot temperatures(~100 million degrees). And the hotter something is the faster it loses heat and cools. It is a straight forward calculation to show that the atmosphere would cool much faster than any fusion reaction could produce heat, and that the "atmosphere on fire" scenario is impossible.

No. We (various nations) have detonated hundreds of nuclear devices above ground and nothing has ever happened. This WAS a concern during the Manhatten Project days...as your professor said, an EXTREMELY unlikely event. When the Trinity bomb was ignited the scientists weren't exactly sure that it wouldn't happen (even though it was extremely unlikely). No one worries about it now.