What is the meaning of this patient's words to Teddy Daniels?

Question

In Shutter Island, Teddy Daniels (Leonardo Dicarprio) has a fight with a patient loose in the ward C. During this fight, the patient says that he will never leave that hospital.

Billings: Listen! I do not want to leave, all right? I mean why wouldn't anyone want that? I have heard many things here. About the outside world. bout atolls, about the hydrogen bomb tests. You know how a hydrogen bomb works?

Teddy: - I know. With Hydrogen. With hydrogen.

Billings - Ah! that's funny. Other bombs explode, right? but not the hydrogen bomb. It implodes.
It implodes creating an explosion to the thousandth, the millionth degree.(in a louder voice and it resounds).
Do you understand?

Teddy: I understand.

Why was Billings talking about the impulsion reaction of a Hydrogen bomb so specifically and what's funny in it? Why was his last sentence given a higher emphasis?

Answer 1

I would say this is something similar to "Catch 22". Billings is insane but his knowledge of the "outside" reality prove he is sane. But at the same time his grasp make him fear the world while in the hospital he feel safe. Also the hydrogen bomb may seems to be "ad infinitium" weapon as hydrogen is everywhere in the air so "to the thousandth, the millionth degree" would mean the bomb will never stop exploding.

This also strengthens Teddy belief that patients are really normal people held against their will by the staff.

Answer 2

H-bomb discussion was analogous with Teddy's mind of the state. As stated in the dialogue:

Billings - Ah! that's funny. Other bombs explode, right? but not the hydrogen bomb. It implodes.
It implodes creating an explosion to the thousandth, the millionth degree. (in a louder voice and it resounds).

He was the H-bomb here, imploding from inside and creating the explosion more devastating. His inner implosion making him the tik-tok bomb. More dangerous then other mental asylum inhabitants.