A physicist working on the possibility of travel into the past has to be careful not to be labelled a crank or accused of wasting public money on science fiction fantasy. Nevertheless, it is an important question. Professor Stephen Hawking, interview Horizon: The Time Lords, BBC 1996
To make time travel possible one seems to need both general relativity which describes the large-scale structure of the universe and quantum mechanics which governs very small scales. These two theories are inconsistent with each other as they stand so we need to find a new theory that combines them. ibid.
Time travel might be possible. But if that is the case, why haven’t we been overrun by tourists from the future? ibid.
Time: will it ever come to an end? Where does the difference between the present and the past come from? Why do we remember the past but not the future? Stephen Hawking, A Brief History of Time, TV 1991
Time will not reverse direction when the universe begins to contract. ibid.
Sadly, it looks like time travel to the past is never going to happen. A disappointment for dinosaur hunters and a relief for historians. Stephen Hawking’s Universe: Into the Universe: Time Travel: Is Time Travel Possible? Discovery 2010
Relativity theory says in general that once you’ve made a time machine you can never use it to go backwards in time before the period it was made. Professor Kip Thorne
If backward time is possible, what does Nature do about the so-called Grandfather Paradox? Kip Thorne
Once it appeared time machines were a real possibility we then had to face the question of paradoxes. Of going back in Time and changing history. And thereby causing the foundations of Physics to crumble beneath us. Kip Thorne, interview Horizon: The Time Lords, BBC 1996
We believe that the river of time can have whirlpools. Whirlpools by which you may be able to go back and meet your parent before you were born. Or perhaps even fork into two rivers by which you can alter the past to create an alternate universe. Professor Michio Kaku
But one day if somebody knocks on your door and claims to be your great great great great great great great granddaughter coming from the future going backwards in time to meet her illustrious ancestor – don’t slam the door. Michio Kaku
Einstein’s friend, Kirt Godel, who was one of the most famous mathematicians of the twentieth century, found a solution to Einstein’s equations, where Time travel to the past is possible. Richard Gott
So we always knew that if you could travel faster than the speed of light, you could travel back in Time. Richard Gott
If I turn the device on today, and I leave it on for a hundred years, then someone a hundred years from now could travel back seventy-five years, fifty years, twenty-five years all the way back to the time I turned the machine on. But they can’t travel earlier than that because the device didn’t exist earlier than that. Ronald Mallett, University of Connecticut
We run into trouble with cause and effect ... Travelling into the future is possible, but suppose you want to come back again? Isaac Asimov, Horizon: It’s About Time, BBC 1980
But Physics does put a limit on how far back any time tourist could travel. Horizon: The Time Lords, BBC 1996
Everyone assumed Time flowed in a straight line. But what if it didn’t? What if Time could loop round like eddies in water? [Kurt] Godel suggested if you could make Time loop round like that, then you could reach the Past. You wouldn’t need to travel faster than the speed of light. You could take a short cut. Horizon: Time Trip, BBC 2003
The Paradoxes when we meddle with the past ... If Time Travel is possible Nature must have a way round the contradiction. The Universe s5e4: Time Travel, History 2010
Nature prevents paradoxes ... It can’t be done. A different idea is the strange idea of multiple universes. A third solution to the Paradox Problem is the notion that if time travel is possible you just won’t be able to change the past when you get there. ibid.
Are the doors to the past firmly closed? The Science of Doctor Who, Brian Cox BBC 2013
Time travel into the future is possible, but is it a one-way trip? Morgan Freeman’s Through the Wormhole s1e4: Is Time Travel Possible? Science 2010
We can’t turn back the clock. But we will keep trying. ibid.
As they sang the words of this noble chorus the Tories seemed to become inspired with lofty enthusiasm. It is of course impossible to say for certain, but probably as they sang there arose before their exalted imagination, a vision of the Past, and looking down the long vista of years that were gone, they saw that from their childhood they had been years of poverty and joyless toil. They saw their fathers and mothers, wearied and broken with privation and excessive labour, sinking unhonoured into the welcome oblivion of the grave. Robert Tressell, The Ragged Trousered Philanthropist
It has been said that though God cannot alter the past, historians can; it is perhaps because they can be useful to Him in this respect that He tolerates their existence. Samuel Butler, English novelist, 1835 -1902
For my part, I consider that it will be found much better by all Parties to leave the past to history, especially as I propose to write that history. Winston Churchill
They [Allies] forged a coherent memory of the War. It is the memory of the Good War which we have lived with for fifty years. But in the process the victors buried those fragments that didn’t fit. The Living Dead I: On the Desperate Edge of Now, BBC 1995
The Allies selected certain memories: they used them to build the official version of the Good War. ibid.
The Nazis’ project was far more than a simple reawakening of history. Their aim was to use the power of the past to transform those they governed into new and better people. ibid.
We live, said one, on the desperate edge of now. ibid.
The Allies forged a simple, powerful story. But the memories and experiences that didn’t fit the story were quietly discarded and forgotten. ibid.
The Germans called it Zero Hour: the destruction of all belief in the past. ibid.
What frightened Jackson [prosecutor] was the link between the political ideas that Goering was explaining to the court and the terrible crimes the Nazis had committed. ibid.
What was buried at Nuremberg was any idea of examining why Nazism had happened in the first place. What the social and political forces were that had led ordinary people to such savagery. ibid.
The students were convinced that what the had uncovered was a hidden continuity with the Third Reich. Beneath the facade of a liberal democratic country the fascist state had continued run by the very same men and women who had run Hitler’s regime. ibid.
They were known as the Red Army faction. The Red Army faction embarked on a series of bombings and shoot-outs with the police. Their strategy was to use violence to provoke the state into exposing its true identity. But as the violence escalated, some of the terrorist leaders began to have doubts. ibid.
The Cold War – it is about a group of scientists who believe that they had found for the first time ever a way of controlling the human mind. They were convinced they had discovered how to change human memory. Adam Curtis, The Living Dead II: You Have Used Me As A Fish Long Enough, BBC 1995
Their certainty and optimism turned to paranoia. They found themselves in a strange world in which nothing could be trusted, not even their own memories. ibid.
Penfield invited a psychiatrist called Ewen Cameron to come and join him in Montreal. Cameron was fascinated by Penfield’s work. He believed that if it was possible to change memories, one could produce better, more rational human beings. ibid.
In a Gothic mansion overlooking Montreal: it was both a psychiatric clinic and a centre for research. His [Cameron’s] aim was to find ways of changing the memories in the minds of his mentally ill patients. ibid.
Memory became a weapon in a confrontation between Russia and America. ibid.
Cameron had begun a series of experiments to try and brainwash the memories in his patients. He called it psychic driving. ibid.
He [Cameron] had published a paper about his work called Brainwashing Canadian Style. ibid.
The CIA decided to fund Cameron’s experiments. They wanted to find a way of controlling human beings by reprogramming their memories. ibid.
Cameron’s experiments weren’t working out quite as he expected … He couldn’t find a way of replacing them with new memories. His patients were completely free of their past and of all the emotions that went with it. ibid.
The CIA were terrified that the Russians might also be working to produce a programmed assassin. They decided to continue funding Dr Cameron; whether he was creating healthy human beings or not was now irrelevant. The perfect assassin would be programmed for one simple task, and the fewer memories and emotions involved the better. ibid.