I have a few questions about earthing in electrical systems. 1) How can earth be used as a "conductor"? I googled its resistance and it turns out that earth resistance is not that large and it can be reliably used as a conductor. For example, I read it can be used as a return conductor in single wire power system, HVDC etc. Is this true? How can earth act as a conductor in long distance HVDC transmission lines? Which properties of earth are involved here? 2) When we plug the tester in the live (hot) terminal on the switchboard, we see the neon bulb glowing. I know that the current flows to the ground through our body. But how does this current flow even when we are standing on insulating materials like concrete floor, a stool or when we are sitting on a matress etc? Also, as we go upstairs in our apartment, the distance between the switchboard and ground increases. But we still get a current through the tester when we are on higher floors. How is this possible? I read that the stray capacitance of our body is involved here but no explanation was given. Please explain this. 3) In residential wiring, neutral wires are grounded at a particular location. Is that the only ground present in the whole residential circuit? (I should mention that I am from India and we have 230V, 50Hz supply with one hot and one neutral.) Thanks a lot in advance!