Question: do you thingk that computers would be some day be able to operate without electricity?

Simone Sturniolo answered on 16 Jun 2013:

Interesting question! Computers use electricity for many things. Some are “accessories” (for example, cooling fans, or the screen), but also their core, the CPU, runs on electricity. The CPU does not use electricity only as a source of power though: its main use is to create “signals” that are used to make operations and communicate messages. Think of it as an abacus: a single electric pulse could mean “one”, two electric pulses could mean “two”, and so on (it’s a bit more complex than that, but you get the point). In this sense, electricity could well be replaced. For example, someone is thinking about replacing it with light, because its much faster and would make the computer work better. The problem is that it is easy to manipulate electricity, a bit less to do so with light. Lots of talented people are working on making this idea a reality though, and I think it will eventually happen in our near future. Other scientists are studying “quantum” computers – these would be even odder beasts, but basically they would use subatomic particles to communicate signals. They sound like sci-fi, but there is a company that claims they have built one already! If it’s true, that would be absolutely great – a quantum computer would be super-fast compared to our actual ones.
So, to answer your question: is it possible to build a computer that does not use electricity for its calculations? Yes, probably it is, and we have a few ideas about how to do that. But is it possible to build a computer that does not use electricity or any other source of power at all? I don’t think so. A computer always does a “work” after all – it runs calculations for us – and this means we have to “pay” for that work, that is, we have to use energy! It does not need to be electric – our brains are a very complex kind of computer after all, and they work on the energy they can extract from whatever we eat. It’s not electric, but it’s always energy!