There are several tests that have been ongoing over decades doing exactly this. The small loss of current during measurement occurs, but you only engage with the field intermittently, and you can calculate approximately what the loss should be.
Yes it could be some tiny resistance, but the same issue occurs with the resolution/accuracy of the voltage or current measurement you would make.
Exactly my point. You cannot measure that the resistance is exactly zero, you can "only" give an upper bound. The upper bound depends on your approach, but no approach can give you a zero upper bound.
Yes it could be some tiny resistance, but the same issue occurs with the resolution/accuracy of the voltage or current measurement you would make.