In the 1920s, a generation before the coming of solid-state electronics, one could look at the circuits and see how the electron stream flowed. Radios had valves, as though electricity were a fluid to be diverted by plumbing. With the click of the knob came a significant hiss and hum, just at the edge of audibility.

Particle physicists may freeze a second, open it up, and explore its dappled contents like surgeons pawing through an abdomen, but in real life, when events occur within thousandths of a second, our minds cannot distinguish past from future.

For much of the twentieth century, 1984 was a year that belonged to the future - a strange, gray future at that. Then it slid painlessly into the past, like any other year. Big Brother arrived and settled in, though not at all in the way George Orwell had imagined.

For the modern physicist, reality is the whole thing, past and future joined in a single history. The sensation of now is just that, a sensation, and different for everyone. Instead of one master clock, we have clocks in multitudes.