Computation Is Physical
Computation is a physical process. Every bit stored, gate switched, and message sent obeys physics, which both enables and limits computing.
Signals carry information physically. A bit is represented by a physical quantity: voltage, charge, light pulses, or magnetic orientation. Real signals are analog (continuous) but interpreted digitally via thresholding.
| Signal Type | Nature | Function |
|---|---|---|
| Analog | Continuous | Physical world representation |
| Digital | Thresholded | Offers noise immunity |
Small disturbances do not flip bits, ensuring reliability.
Physics Limits & Enables
Physics sets hard limits on computing performance. Switching transistors takes energy and produces heat (), bounding chip speeds. The speed of light limits signal transit across chips, and thermodynamics sets an energy floor for bit erasure.
| Physical Limit | Consequence |
|---|---|
| Heat () | Clock speeds plateaued; chips went parallel |
| Speed of Light | Bounds critical path clock speeds |
Common pitfall: Treating computation as purely abstract. Every bit is embodied physically, and every operation costs energy and time bounded by law.