Thursday, 26 February 2009

John Milton, 'Paradise Lost', and General Relativity

'Relative Measurement', Eric Baird, 2009
John Milton (1608-1674) was a linguist, pamphleteer and poet, nowadays best remembered for having written Paradise Lost, first published in 1667.

England in 1667 had been experiencing decades of social upheaval, and an accelerating succession of crises. Oliver Cromwell's side had won the civil war, abolishing the monarchy and executing Charles I in 1649, but Cromwell had then died in 1658, and without Cromwell as a driving force, Parliament had decided to restore the Monarchy, with Charles II being appointed the new king in 1660. Milton had campaigned for religious reform, written campaign material for Cromwell and the Republic, and had held a post in the new regime before going blind. With the Restoration, Milton briefly became a wanted man, and his books were publicly burnt. As England was coming to terms with the abrupt political reversion, it got hit first by the Great Plague of 1665, and then by the Great Fire of London [*] [*] in 1666.

These were, as the saying goes, interesting times.

Paradise Lost, Milton's masterwork, was an epic poem, originally in ten sections, that outlined the rebellion and fall of Lucifer and the subsequent fall of Adam and Eve, in the contemporary poetic equivalent of high-definition widescreen. Milton had something of a talent for visual imagery and a good turn of phrase, and some commentators later ruefully pointed out that Milton seemed to have been influenced by his experiences with the ill-fated English revolution, and not only made the rebellious Lucifer a sympathetic character, but given him some of the the best lines. "Better to reign in hell than serve in heaven", indeed!
The mind is its own place, and in itself
Can make a heaven of hell, a hell of heaven
There are some great phrases in the poem – when we talk about "the fabric" of spacetime, we're arguably borrowing from Milton – but to a physicist, one of the most surprising sections (along with his name-dropping of Galileo) is the bit where Milton writes :
... whether heavn move or earth
Imports not, it thou reckon right.
To a historian, those lines might be taken as an assertation of independence, and a rejection of the notion of centralised supreme power. There's no single authority that decides what is really "moving" and what isn't. No church, no Pope, no religious leader, no monarch.

But to a physicist, they set out the general principle of relativity. When the Earth spins on its axis and loops along its orbit around the Sun, it's convenient to think of the Earth as moving and the background starfield as fixed. But in reality, there's no "special" status accorded to those stars. They're just stars, each following their own line of least resistance as they drift in the wash of their own individual surrounding gravitational tides and currents. It doesn't matter whether we say that the Earth rotates beneath Heaven, or that Heaven rotates around the Earth. If you calculate properly, (said Milton), the answers should be the same in either case.

And if they're not, you've done it wrong.

While Milton was getting his piece finalised and published in 1665-67, the plague had other consequences. Cambridge University sent its students home in the fall of '65, and one these, a previously unremarkable and undistinguished student, chose to make use of the two years of enforced comparative isolation back at his family's farm in the village of Woolsthorpe to work through some ideas on gravity, optics and mathematics. His name was Isaac Newton.

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