What Does a Person Leave Behind? — Information Is What Reduces Not Knowing

The director's question

This thought stayed with me for a long time while I prepared the film. I could accept that atoms scatter; a carbon atom is just a carbon atom, whoever's body it was in. But the face in the photograph and the recorded voice were still there. Perhaps remembering someone is also a way of having a little of them written into me. Could physics call this information too?

Science's answer — information is what reduces not knowing

Yes, all of it is information. And science can even measure it.

Think of twenty questions. Each yes-or-no answer halves the possibilities, so twenty questions can pick one out of more than a million. Tossing a coin and learning heads or tails is also learning exactly one yes-or-no answer's worth. Scientists made a unit for that much and named it one bit. It is also why computers store everything as 0s and 1s: a single 0 or 1 is one yes-or-no answer. So information is the amount by which what you did not know is reduced. Its formal name: bits and information entropy.

Tool The Binary Board — Counting with Eight Switches Eight switches to flip yourself. Press +1 and watch the carry happen; build a target number; see your own name become a row of on and off. Knowing by reading and knowing by pressing are different things.

Seen this way, photos, voices and writing all go on the same scale. A phone photo is millions of bits; a song, tens of millions. You could count what one person leaves behind in bits.

But this kind of information has a weakness: you can read it, and it fades. Photos bleach, tapes stretch, memories blur. Physics also has information of the opposite kind, which never disappears but cannot be read. That is part 6.

Those who asked first

The American mathematician Claude Shannon, working out how to send speech down telephone lines with fewer errors, was the first to define information mathematically. For Shannon, information was not meaning but surprise. An answer you always guess tells you nothing new; the less expected an answer, the more it tells you.

The physicist John Wheeler went further and said that everything comes from information: not matter first with information written on it, but perhaps information first. This is not proven science but a physicist's imagination, and the Science Atlas always labels such lines that way.

A little further in

What we do not know yet

Where and in what form memories are stored in the brain is not fully known. What is known is that memory is not a photograph taken once and filed. Each time we recall, it is rebuilt and stored again. So the me in someone else's memory is not the original but a version they have rebuilt many times.

In the film

The film's physicist, David, says: “A life can leave a pattern.” A pattern is an arrangement, and an arrangement is information. Up to that sentence, the film and science say the same thing.

The film holds two kinds of memory: one rebuilt over two thousand years through countless voices and writings, and one no hand has touched. If memory is rebuilt every time it is recalled, the two must differ, and that gap gives the film its tension.

The question that remainsOf the bits I will leave behind, which could pass on without anyone rebuilding them?