I thought that the ground was different from “earth”!
In most electronics, the term "Ground" is widely mis-used to mean the point in the circuit we choose to call "Zero Volts", and use as a reference when measuring voltage elsewhere in the circuit.  We use "Ground" in this sense in portable electronics, cars, and even aircraft, where there is obviously no connection to The Earth.  We should really call this "Ground" Common or Reference, but this mis-use of "Ground" is so deeply entrenched in the industry that there is no hope of changing it.

In AC power wiring, and some radio antenna systems, "Ground" does really imply a connection to The Earth.