[vimeo] Dr. Sean Carroll talks bout how time travel would possibly work in the context of Einstein's theory of general relativity, including the hypothetical idea of wormholes connecting distant regions of space. Dr. Carroll also explores the logical structure of time travel, and what it implies about predestination and free will. In the end, time travel is probably not possible, but by taking the idea seriously we help understand how the universe works.
Sean Carroll studies the structure and evolution of the universe in his quest to learn about its fundamental physics. His interests these days are on inflation, the arrow of time, and what happened at or before the Big Bang. His research involves dark matter and dark energy, modified gravity, topological defects, extra dimensions, and violations of fundamental symmetries. Dr. Carroll is a Senior Research Associate in Physics at the California Institute of Technology where he investigates the theoretical aspects of cosmology, field theory, and gravitation. His most recent book is "From Eternity to Here: The Quest for the Ultimate Theory of Time", a popular book on cosmology and the arrow of time and is a contributor to the blog Cosmic Variance. He received a B.S. in astronomy and astrophysics from Villanova University and a Ph.D. in astronomy from Harvard University.
4 Comments
MichaelLThere is another solution that allows for time travel and does not involved paradoxes.
Simplifying it, it goes like this:
1. Nothing can go faster than the speed of light, but we can travel as close to it as possible, neglecting the technological issues.
2. You engineer a wormhole, a Time Tunnel into the past using some sort of as-yet unknown technology.
3. Entering the wormhole at one end with your space/time machine, you emerge ten years in the past (say from 2011 to 2001), TEN LIGHT YEARS AWAY from earth.
4. Immediately, you set out to return to earth at the speed of light (less an infinitesmal amount).
5. You would arrive back at earth in 2011 just seconds/minutes/hours after you entered the Time Tunnel the first time. Because you emerged so far from Earth there was/is nothing you could have done to change or affect your past. You couldn't kill your parents in the past, you couldn't have stopped yourself from entering the Time Tunnel...
I suspect that we'll find that time travel via wormholes is possible but that wormholes will only form in such a way that the two ends cannot lead to paradoxes being created.
This means that we will still never be able to travel to see dinosaurs. Travel back in time 65 million years and you will emerge 65 million light-years away. Travel back to earth and you will still only arrive just after you entered the other end of the time tunnel.
Hence we will also never see future time travelers in our time, including killer cyborgs from the future.
GenjiKilpatrickThat light cone and black hole diagram was one of the craziest things to finally have explained. =]
Amazing Sift!!
siftbotMoving this video to kulpims's personal queue. It failed to receive enough votes to get sifted up to the front page within 2 days.
budzosI've always wondered if you would not just pop up in the middle of empty space if you time travelled without compensating for the fact that the earth is moving through at what like 1500 M/s through the solar system? And the solar system is orbiting the galactic centre. And the galaxy is moving away from all other galaxies (or vice-versa) as spacetime itself apparently expands. It all depends on how you think about frame of reference WRT your model of time-travel.
Like in Back to the Future, they travelled 30 years at a time. And they appeared to "portal/shunt" as opposed to "tunnel". It seems to me on a gut level like a portal or shunt would probably just dump you into empty space a fraction of a light year behind or ahead of the solar system if you jumped 30 years. A wormhole (Doctor Who or Bill and Ted style) is easier to imagine as being connected to the same "place" (according to what frame of reference I can't mentally peg down) in both times.
>> ^MichaelL:
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