Part I: Reality has rules

Matter and energy#

Computers exist inside the same universe as everything else. They are made of physical matter which behaves according to physical laws. At this level, we’re dealing with:

• Atoms arranged into materials, with electrons bound to those atoms.
• Energy differences that allow electrons to move.
• Heat produced as a result of energy dissipation.

Why this layer matters#

Nature provides us with something crucial: physical behaviour that is predictable at the scale at which most technological devices are built. If electrons behaved randomly, computation would be impossible. Individual particles do not need to behave with perfect certainty. What matters is that large collections of them respond consistently enough, within known tolerances, for engineers to build reliable structures.

Computing depends on the fact that certain materials conduct electricity while others resist it, and that energy differences produce repeatable outcomes. This layer doesn’t solve any computational problem yet, it’s only a precondition: having a physical substrate that can be controlled reliably enough to build higher-order behavior.

Conductors, insulators and control#

Conductor materials allow electrons to move somewhat freely, while insulator materials strongly resist electron movement. This depends on the atomic structure of the material.

Electrons, however, do not move arbitrarily. They move only when the surrounding conditions allow it: when energy is supplied and a viable path exists. This is what electricity is: the controlled movement of electric charge through matter under energy differences. Making something happen always requires energy, and part of that energy also ends up as heat. These physical costs constrain everything that comes later.

The layers above and below#

Strictly speaking, there is more beneath this layer: quantum mechanics, fundamental physics, and unresolved questions about the nature of reality itself. We are not going there, though.

The next layer will assume that physical behavior can be made predictable enough to act like a switch. The next part examines how matter is turned into semiconductors, and how those semiconductors are used to build transistors: physical devices that make controlled electrical switching possible.