What is time travel. How is it possible, or is it? These are the questions addressed in this collection of writings, web sites, book, and video.
“Time is of your own making;
its clock ticks in your head.
The moment you stop thought
time too stops dead.”
by Angelus Silesius, a sixth-century philosopher and poet
A number of physicists are exploring the idea of time travel, and determining that it IS possible:
Stanford’s Encyclopedia of Philosophy, which contains some great responses to arguments against time travel. http://setis.library.usyd.edu.au/stanford/archives/fall2001/entries/time-travel-\
K.S. Thorne, Do the laws of physics permit wormholes for interstellar travel and machines for time travel? in Carl Sagan’s Universe , eds. Y. Terzian and E. Bilsen (Cambridge University Press, Cambridge, England, 1997), Chapter 10, pp. 121-134.
“[A]n American theoretical physicist, known for his prolific contributions in gravitation physics and astrophysics and for having trained a generation of scientists. A longtime friend and colleague of Stephen Hawking and Carl Sagan, he is the current Feynman Professor of Theoretical Physics at Caltech and one of the world’s leading experts on the astrophysical implications of Einstein’s general theory of relativity.”
and his book:
K.S. Thorne, Spacetime Warps and the Quantum World: A Glimpse of the Future, in R.H. Price, ed., The Future of Spacetime (W.W. Norton, New York, 2002).
AND, for those of you who don’t like to bother with URLS, some excerpts:
“Despite years of debate, scientists still haven’t completely ruled out the possibility of going back in time. “Many physicists have a gut feeling that time travel to the past is not possible,” said Columbia University theoretical physicist Brian Greene. “But many of us, including me, are impressed that nobody’s been able to prove that.”
“Over the next few years, some experiments hold out a chance of finally being able to show whether or not time can move backward as well as forward. Theoretically, at least, it might be possible for the future to influence the past, said John Cramer, a physicist at the University of Washington. He and his colleagues plan to try just such an experiment next year.
Cramer acknowledged that the concept of retro-causality doesn’t seem to make sense, “but I don’t understand why not.”
Both Greene and Cramer know the science as well as the fiction side of the time-travel issue: Greene is the author of The Elegant Universe, a best-selling book on string theory — but he also played a cameo role in “Frequency,” a time-travel movie released in 2000, and served as a scientific consultant for “Deja Vu.”…
Cramer, meanwhile, has done research into ultra-relavistic heavy-ion physics at CERN and Brookhaven National Laboratory — but he’s also written two science-fiction novels and pens a regular column for Analog magazine called The Alternate View. If his experiments show that retro-causality is a reality — that one event can determine the outcome of another event taking place 50 microseconds earlier — it could lend support to the ultimate alternate view of quantum physics.
“It opens the door to doing all kinds of really bizarre things,” he said.”
“Nature would conspire against changing causality, something Cambridge physicist Stephen Hawking has called the “chronology protection conjecture”: For example, if you tried to shoot your father before you were born, somehow the gun would fail to go off.” http://www.msnbc.msn.com/id/15817394/
OR try Hawking:
“However, in a remarkable paper written in 1905, when he was a clerk in the Swiss patent office, Einstein showed that the time and position at which one thought an event occurred, depended on how one was moving. This meant that time and space, were inextricably bound up with each other. The times that different observers would assign to events would agree if the observers were not moving relative to each other. But they would disagree more, the faster their relative speed.
So one can ask, how fast does one need to go, in order that the time for one observer, should go backwards relative to the time of another observer.
The answer is given in the following Limerick.
There was a young lady of Wight,
Who traveled much faster than light,
She departed one day,
In a relative way,
And arrived on the previous night.
(…lots of physics…)
“But this subject of space and time warps is still in its infancy. According to string theory, which is our best hope of uniting General Relativity and Quantum Theory, into a Theory of Everything, space-time ought to have ten dimensions, not just the four that we experience. The idea is that six of these ten dimensions are curled up into a space so small, that we don’t notice them. On the other hand, the remaining four directions are fairly flat, and are what we call space-time. If this picture is correct, it might be possible to arrange that the four flat directions got mixed up with the six highly curved or warped directions. What this would give rise to, we don’t yet know. But it opens exciting possibilities.
The conclusion of this lecture is that rapid space-travel, or travel back in time, can’t be ruled out, according to our present understanding. They would cause great logical problems, so let’s hope there’s a Chronology Protection Law, to prevent people going back, and killing our parents. But science fiction fans need not lose heart. There’s hope in string theory.”
See the full lecture at:
One of the arguments against time travel is mentioned by Hawking:
“One of these is, if sometime in the future, we learn to travel in time, why hasn’t someone come back from the future, to tell us how to do it.
Even if there were sound reasons for keeping us in ignorance, human nature being what it is, it is difficult to believe that someone wouldn’t show off, and tell us poor benighted peasants, the secret of time travel. Of course, some people would claim that we have been visited from the future. They would say that UFO’s come from the future, and that governments are engaged in a gigantic conspiracy to cover them up, and keep for themselves, the scientific knowledge that these visitors bring. All I can say is, that if governments were hiding something, they are doing a pretty poor job, of extracting useful information from the aliens.”
There are two views on time paradoxes. As Stephen Hawking says:
“A possible way to reconcile time travel, with the fact that we don’t seem to have had any visitors from the future, would be to say that it can occur only in the future. In this view, one would say space-time in our past was fixed, because we have observed it, and seen that it is not warped enough, to allow travel into the past. On the other hand, the future is open. So we might be able to warp it enough, to allow time travel. But because we can warp space-time only in the future, we wouldn’t be able to travel back to the present time, or earlier.
This picture would explain why we haven’t been over run by tourists from the future.
But it would still leave plenty of paradoxes. Suppose it were possible to go off in a rocket ship, and come back before you set off. What would stop you blowing up the rocket on its launch pad, or otherwise preventing you from setting out in the first place. There are other versions of this paradox, like going back, and killing your parents before you were born, but they are essentially equivalent. There seem to be two possible resolutions.” http://www.hawking.org.uk/lectures/warps3.html
One: the alternative universe, from John Gribbon’s page “Everything You Always Wanted to Know About…Time Travel“:
“According to one interpretation of quantum theory (and it has to be said that there are other interpretations), each of these parallel worlds is just as real as our own, and there is an alternative history for every possible outcome of every decision ever made. Alternative histories branch out from decision points, bifurcating endlessly like the branches and twigs of an infinite tree. Bizarre though it sounds, this idea is taken seriously by a handful of scientists (including David Deutsch, of the University of Oxford). And it certainly fixes all the time travel paradoxes.
On this picture, if you go back in time and prevent your own birth it doesn’t matter, because by that decision you create a new branch of reality, in which you were never born. When you go forward in time, you move up the new branch and find that you never did exist, in that reality; but since you were still born and built your time machine in the reality next door, there is no paradox.”
This branch of “research deals with both time, and relative dimensions in space. You could make a nice acronym for that — TARDIS, perhaps?” http://www.lifesci.sussex.ac.uk/home/John_Gribbin/timetrav.htm
The other explanation, in Stephen Hawking’s words is:
” One is what I shall call, the consistent histories approach. It says that one has to find a consistent solution of the equations of physics, even if space-time is so warped, that it is possible to travel into the past. On this view, you couldn’t set out on the rocket ship to travel into the past, unless you had already come back, and failed to blow up the launch pad. It is a consistent picture, but it would imply that we were completely determined: we couldn’t change our minds. So much for free will.” http://www.hawking.org.uk/lectures/warps3.html
Now for the good part – science fiction books!
Here are some books I found that mention time travel – not all are HardSF, but I think you can figure that out by the authors. The best description of time travel’s paradoxes and how they are figured out is in Connie Willis’ To Say Nothing of the Dog. It talks about history reweaving itself back around an event that was changed – so if you changed something in 1812, a change that would have had Bonaparte win the war, time would go backwards far enough and make changes so that the event you “changed” could not have happened – the inn where someone overheard a conversation you made about Wellington and is passed on to Napoleon, instead burns down before you could stop there, etc. It is fascinating. Another good one is Kay Kenyon’s Leap Point.
Here’s a list (URL below) + some additions of my own:
The Avatar by Poul Anderson
Tau Zero by Poul Anderson
The Corridors of Time by Poul Anderson
The End of Eternity by Isaac Asimov
Pebble in the Sky by Issac Asimov
In the Garden of Iden (The Company) by Kage Baker et al (series)
Manifold: Time by Stephen Baxter
The Time Ships by Stephen Baxter
The Fall of Chronopolis by Barrington J. Bayley
Looking Backward by Edward Bellamy (1888)
Timescape by Gregory Benford – “the best of the modern time travel novels, even though only subatomic tachyons do the traveling”
Kindred by Octavia Butler
Pastwatch by Orson Scott Card (series)
The Light of Other Days by Arthur C. Clarke and Stephen Baxter (“remote viewing” through a worm hole of other times)
Time’s Eye (A Time Odyssey) by Arthur C. Clarke and Stephen Baxter
Timeline by Michael Crichton
The Watch by Dennis Danvers
Time and Again by Jack Finney
1632 by Eric Flint
The Man Who Folded Himself by David Gerrold
The Accidental Time Machine by Joe Haldeman
The Door Into Summer by Robert Heinlein
The Proteus Operation by James Hogan
Leap Point by Kay Kenyon
Somewhere In Time by Richard Matheson (basis of the movie with Christopher Reeve and Jane Seymour – not HardSF)
World Out of Time and Rainbow Mars by Larry Niven
The Time Traders by Andre Norton (read the original version)
Door Number Three by Patrick O’Leary
Century Rain by Alastair Reynolds
The Didymus Contingency: A Time Travel Thriller by Jeremy Robinson ( a thriller – not HardSF)
End of an Era by Robert Sawyer
Flashforward by Robert J. Sawyer
Up the Line by Robert Silverberg
Our Children’s Children by Clifford Simak
Ilium by Dan Simmons (and others)
Chronospace by Allen Steele
Island in the Sea of Time by S. M. Stirling
Bones of the Earth by Michael Swanwick
Gunpowder Empire by Harry Turtledove (1st in the Crosstime Traffic series)
The Time Machine by H.G. Wells
The Doomsday Book and To Say Nothing of the Dog by Connie Willis
Much of this list came from:
and myself Del.icio.us.ing and Amazon tagging.
I also found:
The Best Time Travel Stories of the 20th Century: Stories by Arthur C. Clarke, Jack Finney, Joe Haldeman, Ursula K. Le Guin, by Harry Turtledove and Martin H. Greenberg
The Best Time Travel Stories of All Time by Barry N. Malzberg, Philip K. Dick, and Robert Silverberg
Travels Through Time (Science Fiction Shorts) by Isaac Asimov, Martin Harry Greenberg, Charles G. Waugh, and Thomas Leonard
Time Machines: The Greatest Time Travel Stories Ever Written by Bill Adler
Time Machines: Time Travel in Physics, Metaphysics, and Science Fiction by Paul J. Nahin and K.S. Thorne (Non-fiction)
And some more NF references from Brian’s Views on Time Travel and Interdimensional Voyages: http://www.brianbosak.com/
1) Bagnall, Phil , Where have all the time travelers gone? New Scientist July 6 1996, v151
2) Deutsch, David, & Lockwood, Michael , The quantum physics of time travel, Scientific American March 1994, v270
3) Parsons, Paul , A warped view of time travel, Science October 11 1996, v274
4) How to murder your grandfather and still get born, The Economist January 20 1996, v338
“This site was used by the TV show “NOVA” on PBS CH11 Chicago” (which I have a link to elsewhere).” http://www.brianbosak.com/
Interestingly, according to the book I’m Working on That by William Shatner, in his chapter on time travel, he says that Hugo Gernsback, the SF editor of Amazing Stories, et al, first posed a question to his readers in 1929 about time travel and interaction between future visitors and the people of that time. He supposedly posed the grandfather paradox, and there is a direct quote from his “letter’ to the readers. This is in open opposition to Wikipedia’s article on it, which states that the first mention of it was René Barjavel in his 1943 book Le Voyageur Imprudent (The Imprudent Traveller): http://en.wikipedia.org/wiki/Grandfather_paradox
I highly recommend Shatner’s book (as I have before) for the science illiterate. It contains chapters on time travel, black holes, transporters, holodecks, and all those cool gadgets like communicators. And he went to the leading people in the field for the information. Like in the time travel one, he used Kip Thorne who holds the Feynmann Professor of Theoretical Physics at the California
Institute of Technology.
Also of interest would be: Time Travel: A Writer’s Guide to the Real Science of Plausible Time Travel (Science Fiction Writing Series) by Paul J. Nahin
According to the link above (under the list of books), the author says: “The definitive book on time travel, its mathematical theory, its possibilities in modern Physics, and its literary exploration is
Time Machines: Time Travel in Physics, Metaphysics, and Science Fiction, by Paul Nahin [New York: American Institute of Physics, 1993].”
“Besides the definitive analysis by Paul Nahin, other worthwhile non-fiction sources (critical and scientific) include:
Origins of Futuristic Fiction by P. K. Alkon [Athens GA: University of Georgia, 1987]
New Maps of Hell by Kingsley Amis [New York: Harcourt Brace Jovanovich, 1960]
When It Comes to Time Travel, There’s No Time Like the Present by Isaac Asimov [New York Times, 5 Oct 1986, Sec.2, pp.1&32]
Faster Than Light by Isaac Asimov [Asimov’s Science Fiction Magazine, Nov 1984]
Time Travel by Isaac Asimov [Asimov’s Science Fiction Magazine, Apr 1984]
Impossible, That’s All by Isaac Asimov, in “Science, Numbers and I [New York: Doubleday, 1968]
The Time Machine: an Ironic Myth by B. Bergonzi [Critical Quarterly 2, Winter 1960, pp.293-305]
Physics and Fantasy: Scientific Mysticism, Kurt Vonnegut, and Gravity’s Rainbow by Russell Blackford [Journal of Popular Culture 19, Winter 1985, pp.35-44]
Science Fiction: The Early Years by E. F. Bleiler [Kent OH: Kent State University Press, 1990]
“Time” special issue with many essays [Daedalus, Spring 2003]
Why Time Flows: the Physics of Past and Future by Thomas Gold [Daedalus, Spring 2003]”
See the same site for a list of Time Travel movies with reviews, etc.
which includes two of my favorites: Somewhere in Time, and A Sound Like Thunder, but forgets Butterfly Effect.
And from U of Mich’s “Science of Film Site: Promise of Time Travel”
Cannon, Damian. La Jetee, Movie Reviews UK. (12 Monkeys was based on this short film)
Lefcowitz, Eric. A Brief History of Time Travel, Retro Future. (6/14/99)
And then there’s NOVA’s site on time travel:
Here’s their list of web links AND non-fiction books, including Kip Thorne’s book (Kip Thorne was THE guy Shatner went to to help him with the section on Time Travel in I’m Working On That.
Web Links Time Travel
This well-organized site, an excellent introduction to time travel, is designed for people with various levels of scientific knowledge. The site includes some of the mathematics that may support time travel as well as information on black-hole theory and the theory of relativity.
Virtual Trips to Black Holes and Neutron Stars http://antwrp.gsfc.nasa.gov/htmltest/rjn_bht.html
This site offers virtual trips via MPEG movies to neutron stars and black holes. Most movies are accompanied by a written description. The site also offers plenty of GIFs, a FAQ page, and links to other astronomy sites.
The Time Travel Research Center
This intriguing site offers authoritative studies on the history and philosophy of time, the physics of time travel, and experiments in time travel. Gain access to the Tri Star System, the world’s largest
information database of science, technology, and research related to time travel, and shop for time-travel-related products in the on-line store.
Brian’s Views on Time Travel and Interdimensional Voyages
This page offers a paper that discusses the possibilities of time travel and covers the subjects of time dilation, wormholes, and the grandfather paradox.
The Theory Of Elementary Waves – Part 1
This site further develops the theory of time travel. It examines some of the basic principles of quantum physics, including the theory of elementary waves.
Books Black Holes and Time Warps: Einstein’s Outrageous Legacy by Kip S. Thorne, Norton, 1994
In a book the Wall St. Journal called an “engrossing blend of theory, history, and anecdote,” Kip Thorne, the Feynmann Professor of Theoretical Physics at the California Institute of Technology,
discusses everything from black holes to wormholes, with the final chapter devoted to time travel. The book’s glossary is excerpted in Timespeak.
Time: A Traveler’s Guide by Clifford A. Pickover, Oxford University Press, 1998
Pickover, the lead writer for Discover Magazine’s brain-boggler column, eases the reader into the arcane theory behind time travel with amusing fictional narratives, in which two people in a Museum of Music in New York experiment with time. See Traveling Through Time for
A Brief History of Time: The Illustrated, Updated, and Expanded Edition by Stephen Hawking, Bantam Books, 1996
Physics and the nature of time conveyed with the remarkable wit, clarity, and patience of the foremost theoretical physicist since Einstein. Illustrated with striking color imagery.
Time Machines: Time Travel in Physics, Metaphysics, and Science Fiction by Paul J. Nahin, Springer-Verlag New York, 1993
Paul Nahin doesn’t write like an engineering professor, but that’s what he is (at the University of New Hampshire). With often amusing references to novels, comics, and sci-fi films, Nahin takes on the daunting topic of time machines with erudition and flair.
Faster: The Acceleration of Just About Everything by James Gleick, Pantheon Books, 1999.
In his latest work, James Gleick explores our increasingly speed-driven world. He specifically investigates the newest paradox of time: as technology accelerates, offering more time-saving devices, the notion of haste only increases. From atomic clocks, to answering machines, to the bunkers of war, Gleick approaches the subject from diverse perspectives.
A few quotes on time travel:
“I wouldn’t take a bet against the existence of time machines. My opponent might have seen the future and know the answer” – Stephen Hawking
“Time present and time past are both perhaps present in time future. And time future contained in time past.” – T.S. Elliot
and from one of my favorite poets: