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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The Jewish lawyers who reinvented justice

Two new books explore the trials of Nazis – and asks how they changed our conception of justice.

In August 1942, Hans Frank, Hitler’s lawyer and governor general of occupied Poland, arrived in Lvov. “We knew that his visit did not bode well,” a Jewish resident later recalled. That month, writes Philippe Sands, Frank gave a lecture in a university building “in which he announced the extermination of the city’s Jews”.

Frank and other leading Nazis were tried at Nuremberg after the war. It was, writes Sands, “the first time in human history that the leaders of a state were put on trial before an international court for crimes against
humanity and genocide, two new crimes”.

For Sands, this is the story of some of the great humanitarian ideas of the 20th century. A T Williams, however, is more sceptical. For him, the search for justice after 1945 was a wasted opportunity. “It began,” he writes, “as a romantic gesture. And like any romance and like any gesture, the gloss of virtue soon fell away to reveal a hard, pragmatic undercoat.” Did the trials of 1945 and beyond provide any justice to the victims? How many more deaths and tortures were ignored and how many perpetrators escaped?

Together these books ask important questions. Were the trials and the new legal ideas – international human rights, war crimes, genocide – among the crowning achievements of our time, the foundations of how we think about justice today? Or were they, as Williams concludes, “an impersonal and imperfect reaction to human cruelty and human suffering”?

Williams won the Orwell Prize for political writing in 2013 for A Very British Killing: the Death of Baha Mousa. His new book reads as if it were several works in one. Each chapter begins with the author visiting the remains of a different Nazi concentration camp – intriguing travelogues that might have made a fascinating book in their own right. He then looks at what happened in these camps (some familiar, such as Buchenwald and Dachau; others barely known, such as Neuengamme and Neustadt). The single reference to Nikolaus Wachsmann’s KL: a History of the Nazi Concentration Camps, published last year, suggests that it came out too late for Williams to use.

A Passing Fury starts with an atrocity at Neuengamme, near Hamburg, where, in the last days of the war, the concentration camp’s inmates were put to sea by Nazis in the knowledge that they would almost certainly be killed by Allied bombers. Williams buys a pamphlet at the visitors’ centre on the site of the camp. It informs him: “Almost 7,000 prisoners were either killed in the flames, drowned or were shot trying to save their lives.” His interest in the subsequent trial leads him to look at other Nazi trials after the war. His central argument is that these were not a victory for rational and civilised behaviour – the widespread assumption that they were, he writes, is simply a myth.

Williams has plenty of insights and is especially good on the Allies’ lack of manpower and resources in 1945. There was also enormous pressure on the prosecutors to gather information and go to trial within a few months. The obstacles they faced were huge. How to find witnesses and make sure that they stayed for the trials, months later, when they were desperate to be reunited with their families or to find safety in Palestine or the US?

The lawyers also felt that they were “operating in a legal void”. These crimes were unprecedented. What should the SS men and women be charged with? “They needed new terms,” writes Williams, “a completely fresh language to express the enormity of all that they were hearing.” This is exactly what the Jewish lawyers Hersch Lauterpacht and Raphael Lemkin, who play major roles in Sands’s book, were providing – but they are almost completely absent here.

Williams is also troubled by what he sees as flaws in the British legal system. Defence lawyers focused ruthlessly on the inconsistencies of witnesses, forcing them to recall the most terrible ordeals. One particularly devastating account of a cross-examination raises questions about the humanity of the process. The disturbing statements of British lawyers make one wonder about their assumptions about Jews and other camp inmates. “The type of internee who came to these concentration camps was a very low type,” said Major Thomas Winwood, defending the accused in the Bergen-Belsen trial. “I would go so far as to say that by the time we got to Auschwitz and Belsen, the vast majority of the inhabitants of the concentration camps were the dregs of the ghettoes of middle Europe.”

Williams has put together an original polemic against our assumptions about these trials, including those at Nuremberg. Sands, a leading lawyer in the field of war crimes and crimes against humanity, presents a completely different view of Nuremberg and the revolution in justice it introduced. His is a story of heroes and loss.

Lvov is at the heart of Sands’s book. Now in Ukraine, the city changed hands (and names) eight times between 1914 and 1945 – it is known today as Lviv. This is where his grandfather Leon Buchholz was born in 1904. Leon had over 70 relatives. He was the only one to survive the Holocaust.

In 1915, Hersch Lauterpacht came to Lvov to study law. He became one of the great figures in international law, “a father of the modern human rights movement”. Six years later, in 1921, Raphael Lemkin also began his law studies in Lvov; in 1944, he coined the term “genocide” in his book Axis Rule in Occupied Europe.

Both Lauterpacht and Lemkin, like Leon, lost members of their family during the Nazi occupation of Poland. Sands interweaves the stories of these three Jews and how their lives and their ideas were affected by what happened in Lvov. This is an important question. We forget how many of the greatest films, works and ideas of the postwar period were profoundly affected by displacement and loss.

East West Street is an outstanding book. It is a moving history of Sands’s family and especially his grandparents but, at times, it reads like a detective story, as the author tries to find out what happened to his relatives, tracking down figures such as “Miss Tilney of Norwich”, “the Man in a Bow Tie” and “the Child Who Stands Alone” – all involved in some way in a mystery surrounding the author’s mother and her escape from pre-war Vienna. But Sands’s greatest achievement is the way he moves between this family story and the lives of Lauterpacht and Lemkin and how he brings their complex work to life.

There is a crucial fourth figure: Hans Frank, the Nazi lawyer who was responsible for the murder of millions. Sands uses his story to focus his account of Nazi war crimes. Frank was brought to justice at Nuremberg, where Lauterpacht and Lemkin were creating a revolution in international law. Lauterpacht’s emphasis was on individual rights, Lemkin’s on crimes against the group.

This is the best kind of intellectual history. Sands puts the ideas of Lemkin and Lauterpacht in context and shows how they still resonate today, influencing Tony Blair, David Cameron and Barack Obama. When we think of the atrocities committed by Slobodan Milosevic or Bashar al-Assad, it is the ideas of these two Jewish refugees we turn to. Sands shows us in a clear, astonishing story where they came from. 

This article first appeared in the 19 May 2016 issue of the New Statesman, The Great Huckster