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The title can refer to Quantum ElectroDynamics, as in the title of Richard Feynman's popular book on the subject, or it can refer to quod erat demonstrandum (which was to be demonstrated), which logicians use to indicate the conclusion of a proof.

Behold the Feynman diagram, a map of matter neat,

of ghostly Forms in space and time, dancing on aetherial feet.


In indeterminate array across the vacuum they prance,

flickering into and out of existence in the rhythm of the Heisenberg dance.

To and fro they whirl about; to us they seem a blur.

The Forms all melt together; what they are we're not quite sure.

The ghosts themselves are well defined; each we could identify,

but for the fixed amount of substance for which they all must vie.

Borrowing energy against the clock, virtual particles all awhirl,

fill the quantum vacuum with a dizzy Feynmanesque swirl.

The energy makes the ghosts come real; it gives them all their masses,

but like the buckets of a fire brigade from one to another it passes.

Forcefields toss virtual particles to and fro to mediate their forces

and guide real particles in the traverse of their myriad spatial courses.

Chaos seems to reign supreme: nothing here makes sense.

The odds against finding a coherent Reality seem to us immense.

But the whole of Reality coheres under a truly sublime direction:

In deciding what comes real wave interference makes the selection.

A sum over all possible histories clears away the veil.

Everything that can possibly happen, happens at this scale.

Waves of probability roll across a quantum sea

and where they reinforce each other something will come to be.

Join those things into bodies bigger and slower and indeterminism fades away.

Fuzziness dissipates and Newton's determinism comes into play.

Thus we gain a sensible world, one easy for us to conceive

to guide our learning in baby steps, lest we not believe,

that the Reality that feels so firm to us is more like fog or smoke,

that the solidity that we feel underfoot is just the Creator's little joke.


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