Going to be a bit pedantic here but you absolutely can have 0 Voltage. Voltage is the potential energy created by a difference in charge between 2 points. If you have a mass with sufficient free mobile charge, when you inject additional charge into it, it will rearrange the charge within itself to cancel out in injected charge resulting in 0 Volts of potential. This is the principal that a ground connection works on and why you don't have voltage inside of metal conductors, just on the surface.
If you have any conductive bar or wire of sufficient size you can safely touch both ends (and measure zero volts across them. If you stretch those conductors over miles and miles of distance, it gets harder to reference the end to both grounds at the same time. And getting a good ground can be hard. There are numerous stories of "stray voltage" making cattle jumpy, etc.
Of course if you coil up that conductor and pass a magnet by it you're going to get shocked ;)
