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Time Travel: Possible, or Impossible?

Jack Hokikian, Ph.D. is the author of The Science of Disorder, an excellent book, especially the chapter on he Second Law of Thermodynamics. This essay expands on that chapter; what exactly does the law have to do with the possibility of time travel. The answer is here.

Recently, time travel has received much attention in the media. Books and articles have been written on the subject purporting that time travel is possible and consistent with the laws of physics, and that Albert Einstein supposedly was in agreement with this assessment. [1] This essay examines the situation and reaches a definitive conclusion whether time travel is possible or impossible as far as physics is concerned.

Two statements of Einstein are often quoted, which presumably support the view that traveling into the past is possible. One quotation of Einstein comes from a condolence letter offering comfort to the son and sister of his longtime friend and engineer Michelangelo Besso: “In quitting this strange world he has once again preceded me by just a little. That doesn’t mean anything. For we convinced physicists the distinction between past, present, and future is only an illusion, however persistent.” [2] Some scientists have speculated that this remarkable statement was also a comfort to its author, who died a month later in April, 1955. [3]

Einstein was alluding to the fact that nearly all laws and equations of physics, including his theory of relativity, quantum theory and Newtonian mechanics are time-reversible. They make no distinction between future and past.

Does this mean that physics is telling us we live in a reversible world and that the passage of time is merely an illusion? The Second Law of Thermodynamics—the Law of Increasing Entropy—holds the answer.





Alright If I ever have access to time travel in my lifetime, I will travel back and tell you all about it in a comment on this string.

I think what is more likely is that time is not as we perceive and that we are currently in the future as much as we are the past or the present.

Then again, I am not a physicist.

This was interesting - especially about the K-mesons being the first non-time reversible particles discovered --- only after Einstein's time but he already surmised the irreversibility of time.

As far as whether time travel is possible or not, I always think of Hawking's statement that he assumes it isn't because we aren't overrun with tourists from the future.

But - I like to think of time as RedSeven described it - more like Vonnegut's Trafalmadorians described it...and you concentrate on the good times.

This reminds me - did anyone see Primer? Interesting time travel movie.

Not being overrun by time tourists wouldn't account for short term time travel, say the ability to go back 10 minutes in time and intervene.

I found the Second-Law argument against time travel to be insufficiently fleshed out to be coherent. To state the time travel isn't possible because it requires that a system 'run backwards' so as to decrease its entropy isn't sufficient. If time travel could occur in such a way that local decreases in entropy occur (i.e., in the neighborhood of 'you', the time traveller) but that the entropy of the universe still increases (i.e., increase in entropy elsewhere in the universe outweigh such local decreases) then the Second Law would seem to be obeyed.

Of course all the causality objections stand. Furthermore, I'm not sure how the past can be allowed to increase in mass/energy by virtue of one's having travelled there – in other words, does time travel have to involve a swap of matter/energy with the past in order to avoid a violation of the First Law of Thermodynamics?

I looked at Hokikian's book at Amazon by browsing its contents and I'm pretty skeptical at of everything after Chapter 3 - I'd be suspicious of Jeremy Rifkenesque bullshit overwhelming the physics from there on out. I also can't resist taking a cheap shot: did you ever notice that truly great scientists (or even people in other specialties like economics) never attach 'Ph.D.' to their name even on a popularly oriented book? I don't think you'll find books by Carl Sagan Ph.D. or Richard Dawkins, Ph.D., or Richard Feynman, Ph.D.

Tim The PH.D comment (actually valid point, I think) reminded me when I worked at a start-up where the CEO addressed people who had PH.D's as Doctor - our head of PR and head of business development. THAT was amusing...Also - did you see "Primer?" If so - what did you think?

I didn't see Primer - perhaps I'll rent it.

just a cursory grunt:

Go"del closed timelike loops are Penrose triangular, if maximally bulging...

I know, I know GEBen Sie mir ein Break! Jawohl,


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