Your meter is too sensitive. It reads voltage while having a very very tiny current flow through it. The long unconnected wire you're measuring is coupling to other current carrying wire in your house. While there may be some voltage there, if you put any sort of load on the circuit it would disappear.

stray voltage shows up at the strangest locations. My garage roof (asphault shingles) has a 3 volt charge with respect to an electrical ground wire.
Now how do you ground a shingle roof???

"stray voltage shows up at the strangest locations. My garage roof (asphault shingles) has a 3 volt charge with respect to an electrical ground wire.
Now how do you ground a shingle roof???"

Phantom voltage is not exactly the same thing as stray voltage.

Phantom voltage has a very high source impedance that only a decent digital meter can detect.
It cannot deliver any significant current since the source impedance is so high, and is not a danger.

Stray voltage is often associated with defects or errors in grounding and neutral connections.

If your neighbors neutral is broken, the neutral current may return through water pipes from one house to another. the pole.

It is a relatively low impedance source and can deliver enough voltage and current to be dangerous.

It is one of the reasons to be very careful about making alterations to the grounding electrodes conductors and water pipe bonds.

If you open the connection and stray voltage is present you may find that one side of a supposed 'ground' connection has significant voltage.

Before opening grounding electrode connections placing a clamp on ammeter around them is worth the few seconds.