Actually, as has been pointed out many times around the internet, the vaccuum problem is not as simple as described. The biggest problem I've seen is that of t

Actually, as has been pointed out many times around the internet, the vaccuum problem is not as simple as described. The biggest problem I've seen is that of thermal stabilisation to prevent metal expansion and contraction. That makes tubes in open air a particularly infeasible proposition without masses of insulation. Bridges are already difficult enough as it is, without things traveling over 1000km/h Or, to directly address this: * We have the ability to evacuate air from a tube, to low air pressure levels. We can evacuate tubes, but they tend not to be very long. About the only very long tubes we have evacuated are CERN and it's predecessors, and I think they got around the issue by building it underground.