How much of “Doctor Who” might really be possible?

Science shows why Doctor Who is so special.

As Doctor Who’s 50th anniversary looms, time travel is everywhere – on the screen, at least. Famously, the Doctor can whizz through the years using a “dimensionally transcendental” machine, the TARDIS, and make changes to the past as and when he likes. But what is time travel – and how much of “Doctor Who” might really be possible?

A handy definition of time travel comes from philosopher David Lewis. Lewis says time travel involves a journey having different durations viewed from outside (in “external time”) or from inside (in “personal time”). Suppose you spend five minutes travelling aboard your machine, as measured by (e.g.) your watch and your memories. On arrival, you find 150 years have elapsed in the outside world. Congratulations, you have time-travelled. Five minutes of your personal time has covered 150 years of external time.

Odd as this sounds, Einstein’s theory of Special Relativity introduced such possibilities to physics in 1905. The theory says: the duration of a process varies with the relative velocity of the observer. The closer that relative velocity gets to the speed of light, the longer the travelling process takes.

Suppose you want to see the Earth a billion years hence, but worry you have only about 50 personal years left. Special Relativity specifies that if you travel very close to the speed of light relative to the Earth, your 50 personal years can cover one billion Earth years.

In backward time travel, personal and external time differ in direction, so journeys end in external time before, not after, they begin; you spend five personal minutes travelling 150 years into the external past. General Relativity suggests that the universe is essentially curved spacetime, which might allow such divergences of external and personal time.

Relativity treats space and time as aspects of a single entity: “spacetime”. One of the more remarkable features of General Relativity is that it allows time and space axes to be interchanged, so one observer’s space axis can be another observer’s time axis.

In 1949, Austrian mathematician Kurt Gödel used General Relativity to describe a universe where intrepid voyagers can go anywhere in (past or future) time without travelling faster than light. Gödel’s universe has no boundaries in space or time, and all the matter in it rotates. But our finite, non-rotating universe is not Gödel’s. Despair not though – simply spin an ultradense, very (maybe infinitely) long cylinder very fast. Spacetime should curve around the cylinder so the direction of the local future partially points into the external past. Such devices are called “Tipler Cylinders”, after physicist Frank Tipler.

Better yet, quantum theory suggests that “wormhole” connections between different spacetime points spontaneously form and break all the time. The chances are that natural wormholes are tiny - vastly smaller even than an electron, (and a billion trillion electrons can fit in a teaspoon). But you could perhaps find (or create) a wormhole big enough and durable enough to let you slip through into the past. Difficult, but theoretically possible.

No, you can’t kill your physics teacher

So perhaps you could travel into the past. But what about paradoxes? What is to stop you assassinating your grandfather or yourself as infants? One answer says: logical consistency.

Classical logic says you cannot consistently kill in infancy someone who achieves adulthood. But, Lewis says, time travel need not involve doing the logically impossible – provided travellers’ actions in the past are consistent with the history whence they come. So you could try killing your baby grandfather, but something would foil you – you would sneeze, or your gun would jam. Lewisian time travel is therefore (classically) consistent, but might look very strange, since seemingly possible actions (like shooting an unprotected infant) would prove impossible.

Another view says that backward time travel requires many worlds – that is, many different but equally real versions of physical reality. Physicist David Deutsch and philosopher Michael Lockwood argue that time travel must involve inter-world travel. If you travel backwards in time, you must arrive in a history different from your native one and so would be quite unfettered by your past once you get there. You could even kill this other history’s counterparts of your grandfather and yourself.

Both these concepts of backwards time travel may disappoint anyone wanting to change the “one and only” past. Conventional logic says time travellers would either help make history what it was (Lewis) or create a different history (Deutsch/Lockwood). However, quantum logic might let travellers change the actual (one-and-only) past.

Suppose we hold that quantum measurements determine (or change) quantities measured, even if those quantities lie in the past. Someone could travel back and “observe” history turning out differently from how it originally was, thereby retrospectively making actuality different from what it had been. What would happen to travellers who rebooted history is not clear, but this model seems closer to the time travel familiar from “Doctor Who” and other fictions. Beware, though, because quantum theory allows no predicting, and still less controlling, of the outcomes of changing the past. There would be no way to foresee the effect you would have on the present.

So classical logic, General Relativity and quantum theory all seem to permit time travel. Classical logic plus General Relativity suggest backward travellers face weird consistency constraints. Many-worlds travellers face no constraints, but get displaced into different histories. Quantum-logic travellers could change the (one and only) past without constraints, but they couldn’t predict or control what they would get.

So far, however, it seems only the Doctor knows how to change the past at will.

Alasdair Richmond received funding from the Arts and Humanities Research Council, to fund one semester of a two-semester leave period that covered the academic year 2008-2009.

The Conversation

This article was originally published at The Conversation. Read the original article.

The eleven incarnations of the Doctor. Image: BBC/Matt Burlem

Alasdair Richmond is a Senior Lecturer in Philosophy at the University of Edinburgh.

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Why Richard T Kelly's The Knives is such a painful read

It is well known that Stendhal compared politics in a novel to a gunshot in the middle of a concert  this novel of modern British politcs is more like a mirror being shot at.

It is well known that Stendhal compared politics in a novel to a gunshot in the middle of a concert: a noise harsh but not dynamic, and with no resemblance to any instrument in the orchestra. What is often forgotten is that his enduring soundbite started life on the losing side of an argument. In The Red and the Black, Stendhal says that he is tempted to present a page of dots rather than subject the reader to an interlude of dreadful speechifying. His fictional publisher replies by asking him to square that with his earlier description of a novel as “a mirror going along a main road”. If your characters don’t talk politics, the publisher concludes – in a scene that does some damage in its own right to Stendhal’s realist aspirations – then your novel will fail to provide an honest reflection of Frenchmen in the year 1830.

Richard T Kelly’s new novel bets everything on this position. Kelly wants to show that a political novel – even one with characters who give political speeches and conduct discussions about policy – doesn’t need to be an ear-bashing polemic or a scuzzy piece of genre writing, but can succeed as a work of realism no less than the story of a provincial dentist’s mid-life crisis, or an extended family crumbling at Christmas.

Kelly is more a descendant of Trollope and Dickens than of Stendhal. His first novel, Crusaders (2008), a consciously neo-Victorian portrait of Newcastle in the 1990s, featured a Labour MP, Martin Pallister. The Knives is a sequel of sorts – a long, dense novel about a Conservative home secretary (Pallister is his shadow) which arrives at a moment when we are thinking about domestic politics, political process, Westminster bartering and backstabbing, and the role of the home secretary.

Kelly begins with a note explaining that The Knives is “a work of fiction . . . make-believe”, and it is true that any resemblance between David Blaylock and the real-life recent occupant of his post is scuppered in the prologue – a long gun battle in the Bosnian countryside with virtually no resemblance to Theresa May’s tenure at the Association for Payment Clearing Services. Yet the novel contains plenty of allusive nudging. Kelly’s member for Teesside may not be standing in for the member for Maidenhead, but a prime minister who is “primus inter pares” of a group of “university contemporaries and schoolmates” rings some bells. There are also borrowings from Robert Peel and Tony Blair, as well as a quotation from Trollope and a discussion of Coriolanus (“He wouldn’t last five minutes”).

As the novel begins, Blaylock is widely respected, has even been named Politician of the Year, but he is also surrounded by possible pitfalls: the presence in Britain of foreign nationals with charge sheets, the proliferation of radical Muslim clerics, the debate over ID cards, mounting questions over his record on unemployment, immigration, human rights. There is also an ex-wife whose work as a barrister converges on Home Office business. The Knives is a full-bodied account of Blaylock’s day-to-day business, in which the relationship between journalism and realism, research and description, is generally fruitful. Kelly’s mirror travels through meeting halls and community centres, down “the plum carpet of the long corridor to the cabinet anteroom”. The problem is that Kelly is too effective – too diligent – and the book is detailed to a fault, at times to the point of mania.

His habits in general tend towards overkill. As well as his note to the reader, he introduces the book with a trio of epigraphs (Joseph Conrad, Norman Mailer, Norman Lewis) and a not-inviting list of dramatis personae – 60 names over two and a half pages, in some cases with their ages and nicknames. Virtually all of these figures are then described fully in the novel proper. One character is compared to a thinker, a dancer, a Roman and a pallbearer in the space of a single paragraph.

Stendhal took his publisher’s advice but did not ignore his own instincts: having accepted that politics might have a place in a realist novel set in Paris in 1830, he is careful to give us an extract from Julien’s 26 pages of minutes. Kelly gives us the minutes. But it isn’t only world-building that detains him. Early in the book, out jogging, Blaylock passes “a young blonde” who is “wand-like from behind”: yet only by virtue of “a conjuror’s trick – a stunning trompe l’oeil – for from the front she was bulgingly pregnant, to the point of capsizing”. Almost every sentence carries a couple of excess words.

In Kelly’s universe, hubbubs emanate and autumn insinuates and people get irked by periodic postal admonishments. At one point, we read: “The likelihood that they worsened the purported grievances of said enemy was not a matter one could afford to countenance.” In a dinner scene, “brisket” is served by the “briskest” of waiters. There are tautological similes, dangling modifiers (“A vicar’s daughter, Geraldine’s manner was impeccable”), truisms (“The law was complex”), fiddly phrases (“such as it was”, “all things considered”), Latin tags and derivations, and every conceivable shade of adverb. When Kelly’s phrasing reaches for the mock-heroic, it often comes back to Earth with too great a thud: “Blaylock, tired of the joust, accepted the black ring-binder.” All this verbiage obscures the novel’s function of bringing the news – or rather, the truth behind the news – and the cumulative effect is grating, even painful, like a mirror being shot at.

Leo Robson is the New Statesman’s lead fiction critic

The Knives by Richard T Kelly is published by Faber & Faber (475pp, £12.99)

Leo Robson is the lead fiction reviewer for the New Statesman.

This article first appeared in the 18 August 2016 issue of the New Statesman, Corbyn’s revenge