Expert: Philip A. Stahl - 3/23/2009

Question
Hello Mr. Stahl;
My brother in law and I were in a discussion about time travel.  I had heard (though I don't remember where) that a university in the US had devised a working theory about travelling back in time.  While I believe this is, or will be, possible for us, I wanted to know if someone did do this, which universe would they be in?  Would they be in their own or possibly in a parallel universe?  Do you feel that there is a type of natural law to prevent one from altering their own past and causing the grandfather paradox?  Thank you for your time in this matter,
Mike


Answer
Hello,

Let's order the answers in the order of your questions:

i)I think the university you may be referencing is the University of Connecticut which at one time had a budget developed for an initial phase of a time machine experiment. It had been designated:the  "Space-Time Twisting by Light" (STL) project.

This was reported in Dr. Ronald Mallet's book, 'Time Traveler' (2006, Thunder's Mouth Press)

ii-iii) Which universe it would be to is still speculative. David Deutsch has a "multi-verse" theory (infinite number of universes co-existingside by side- see his book, 'The Fabric of Reality') and it could be that one of them is a likely destination for any would be time travelers - especially to avoid Hawking's Chronology Protection Hypothesis (preventing anyone from going back in time to kill a grandfather and thereby create the well known 'grandfather paradox' which should prevent the traveler's existence in the first place)

iv) The Hawking Chronology Protection Hypothesis is not a "natural law" but it does make sense, to protect against causal anomalies and prevent time-like events from crossing paths.

If you want to learn much more I suggest getting Mallet's book which is very readable. Apparently he goes down in history as the first astrophysicist to actually propose a serious time travel device. (Note: I did not say a 'workable' device, in the sense of achieving its ends. On that I remain highly skeptical)