I thought I'd tackle another hard science subject of the future - quantum computing. But I realized you first have to know about a whole new way of thinking. Thinking in quanta.
So, first comes quantum theory.
Best known -or better: least unknown- is the field of quantum mechanics.
In essence, quantum mechanics is just a mathematical description on how matter and waves (read: radiations like light). On macroscopic scale, these effects are seldom observed, but at extremes (microscopic, or very high or low temperatures or energies) some odd observations can be made.
Max Planck observed that some physical quantities can only be changed by discrete amounts, called quanta, which are multiples of the Planck constant, instead of varying in a continuous way.
A bound electron, for example, can only change within certain energy states. The difference in energy between these states is the quantum involved.
A second observation made was that the matter and wave-like behavior seem to overlap. A particle (like an electron) can behave like a particle, and eg. collide, but also has a wave-like property, and can therefore interfere with other particles/waves.
A third effect involved is Heisenbergs uncertainty principle, where you can, on microscopic scale, not say what the total characteristic of this particle/wave is: if you observe it as a particle, you wont get information on it's energy, but only on its (probable) position, and vice versa: if you observe the wave, you can get info on everything but the position. You see the dilemma. It's like a spooky thing that forever slips through your fingers.
(I know, some physicists will now start grumbling and protesting. But I'm not writing a college text here. I'm trying to explain the whole thing in less than 400 words....)
The previous is called the wave-particle duality. Physicists tend to describe a particle as a wave packet.
The rest is higher mathematics, witch I'm not totally familiar with, and interested persons should start a degree in physics to understand this.
The biggest consequence is that it is like a particle can be at the two places at the same time, or have different 'appearances at the same time. And this stays, until the moment someone comes in and takes a look at it. and suddenly, PING!!!! its just in one place, one state, behaving like we know it.
De concept of being in many places and/or states at the same time is important, as long as there is no observer. It means nothing is definite until somebody takes a better look at it.
The consequences are enormous, also on philosophical terrain. Does nothing exist (in one definite state, that is) if there's nobody around?
But as up to today, nothing really challenged the theory, and observations have been made that suggest the thruthworthiness of the hypothesis.