A metal wire can be an #antenna.

an #antenna can be a metal wire.

the longer the wire, the longer the #wave length (frequency) being picked up by the wire. This is because the wire in an #antenna is divided in 2 parts, -+. When it receives a #wave, the top and bottom of the #wave make both ends of the metal also - or +. The difference in polarity between the two parts determines the strenght of the #current.

And measuring the resulting #current ~ measuring the #radio #wave.

An analogy would be:

A #wave and a #yacht. When the bottom of the #wave passes the front or back, it goes down. When the top passes, it goes up.

But because of its weight, it is difficult for the #yacht to react to the #wave. When the #wave has the right length, the front and back find themselves in the top and bottom of the #wave respectively, enduring equal opposite forces, making the #yacht tilt optimally and thus react the fastest at the #wave.

Now we don't want another Titanic, so we hope the #yacht remains steady. But for #radio signals, we measure the #current (tilting of) in the #antenna (the #yacht) to pick up the #wave. And thus the #wave length needs to allow for the top and bottom to pass the opposite ends of the #antenna at the right time, to stimulate as much electrical #current (flowing from - to +) as possible.

Now the neat thing is that to pick up a #current, extremely little energy needs to be used. Maybe none. Now the less neat thing is that to amplify it so we can hear it, we need more energy. But I don't think it needs so much. Especially when we put the audio next to our ear, as low volume levels can still be heared.