In physics, sound is a vibration that typically propagates as an audible wave of pressure, through a transmission medium such as a gas, liquid or solid.
But if capitalism had built up science as a productive force, the very character of the new mode of production was serving to make capitalism itself unnecessary.
John Desmond Bernal (1959) Marx and Science. p. 39.
There are solar panels that covert sunlight directly to electricity, and there are others that absorb the sun's rays for hot water. EU-funded researchers have made progress on a solar thermoelectric generator that generates electricity from the sun's heat.