> the tunnel would be opened up to the outside atmosphere. That would immediately ruin the resonance and all capsules should come to a screeching halt. Correct

> the tunnel would be opened up to the outside atmosphere. That would immediately ruin the resonance and all capsules should come to a screeching halt. Correct me if I'm wrong, but my intuition is that this would also lead to quite a bad explosion. I mean, the amount of energy I imagine it would take to initiate a standing wave between LA and NY should be massive, (and certainly not a small amount to maintain it either, though far less than the initial amount if it truly stores the energy well). But if it is _storing_ this energy, then any rupture should release it quite... quickly. No? A standing wave is not nothing.. it is a huge amount of pressure oscillating back and forth in an underground cavity. A controlled hole in the cavity wall could release it properly, but a crack in the side could effectively lead to rupture, couldn't it? Another thing, if the air pressure inside the tunnel is indeed quite high, the train cars would also need to be pressurized. This leads to some other potential dangers.. not to mention the time to pressurize would be added to the total trip time.