Uncommon Descent Contest Question 14: Is backwards or forwards time travel really possible?

Super-ordinary events that involve the function of time have been observed: certain quantum events, prophesy and miracles; and, of course, the relativity effects. But these events, while in one sense not ordinary, could be said to be part of the so-called natural world. Time travel seems to human perspective to be most definitely not natural as it involves the manipulation of directional laws of science – gravity always attracts; entropy always increases – and functions that, as far as we understand, are unchanging. Indeed these “constants” are not only directional but they are also related to each other; or alternatively bound together by a collective “theory of everything”. It seems therefore that to travel in time science must discover a new “natural” law – presumably one that is observable only at unusual or extreme physical states such as worm-holes or inside the Hadron Collider; or discover the unified underlying theory of physical matter and the unlikely means to manipulate it! Despite the astounding scientific discoveries in the last 500 years a foundational understanding and eventual manipulation of the laws of physics seems to stretch credulity too far. Not much more than ten years ago “string theory” was thought to be well on the road to such an understanding. Sober reflection discovered flaws; and it was simply based upon speculative mathematical assumptions. What has led us to such strange conjecture, indeed to allow reputable science to go where only philosophers and fiction authors dared to tread? Which modern-era figure is responsible for the present-day farrago of eccentric pop-science that masquerades as legitimate science? It is most probably not the enlightenment philosophers such as Kant or Hume; not the champion of forensic conjecture James Hutton; or the explorer of the unconscious mind Sigmund Freud or even the revered Darwin: it is likely the possessor of the most impressive brain in modern science – Albert Einstein! It is unfortunately Einstein’s scientific legacy that it is feasible to discover esoteric scientific laws far removed from ordinary observation. When light was observed to be bent by a gravitational force in accordance with his ten field equations Albert Einstein single-handedly legitimized not only the incomprehensible but also meaninglessness. Modern science, it seems, is willing to accept the probability of virtually any implausible explanation other than the certain existence of a creator God. GFrancis

Answer is yes and no. It's a bad question; like asking what would happen if you sailed a boat off the edge of the Earth. Time is a scalar quantity and is not internally scalable, like distance. Time "travel" is possible under general relativity, as Feynman indicated. Faster than light has been experimentally replicated. Kip Thorne among others, have advanced the maths involved. Theoretically, 2 wavicles with identical eigenstates will behave identically to any observer regardless of Euclidian or Reimannian space. Will the LHC produce the Higgs boson? I'm with Hawking - he says no. I'm not exactly with him on his 'time tourist' business though. 13 Mapou - you get the prize, in my book. This proposition of singularity is really heresy at best. God has given us time-as-vector so that we may experience our lives and exercise our free will in the present moment. We can however call on God to help heal the past by repentance. Time travel? If you wish. toscents

Mapou at #13: Reminds me of this exchange between Landon and Taylor in the original Planet of the Apes: Landon: "That means we've been away from Earth for 18 months." Taylor: "Our time. I read the clocks. They bear out Haslein's hypothesis. We've been away from Earth for 2000 years, give or take a decade." Taylor: "Still can't accept it, huh? Time's wiped out everything you ever knew. It's all dust." Landon: "Prove it. If we can't get back, it's still just a theory." Taylor: "It's a fact Landon. Buy it. You'll sleep better". Of course, as an ex-farmer and history teacher, I have no idea who would be right :). gleaner63

Tell that to the space traveller who returns to Earth finding his spouse now dead after the passage of 100 years, though he experienced only 1 year (remotely possible due to relativistic time compression in a moving frame). This compression has been confirmed experimentally endless times including having to be compensated for by the GPS system in order to allow high accuracy navigation. magnan

It is a fallacy that we travel forward in time. There is no travel in time in any direction for reasons that I have already mentioned above. There is only the changing present. It is also a fallacy that clock slowing is equivalent to time travel. Clock slowing is just that, clock slowing. Nothing more. To say that clocks slow down because time dilates is nonsense. Time cannot change by simple definition and simple logic. I realize that we've all been taught otherwise but we were taught wrong. The logic is unassailable. Mapou

No one has mentioned that as a practical matter, travel to the future is at least possible by expenditure of enough energy. Einstein showed that at high percentages of the velocity of light time is appreciably slowed relative to the rest of the universe. The space traveller at such velocities would arrive back at his starting point having experienced less subjective time than on the earth left behind. Effectively, time travel into the future. magnan

Forwards time travel is trivial - we do it all the time. Even going, say, 100 years into the future doesn't violate any laws of physics. All you have to do is hop on a rocket and accelerate away from the Earth at 1g for about 5 years, turn around and spend another 5 coming back. You could also find yourself a nice black hole and do a few low orbits around it and have the same effect. Now going back in time is the trickier part... Ellis

Hm, "time travel" could be mis-interpreted. As I understand it, he argues that information traveled backwards to before The Fall. I guess the God Particle could have been involved. :-) Heinrich

Denise, I’d love to share my theory here, but since I am fairly certain that I am the only person that has ever seen this in the Word, at least among the living and posting thoughts online, I am keeping it to myself for a future book.

I believe Dr. Dembski has also argued for time travel in one of his books (which one should go out and buy, of course). Heinrich

The answer is no because motion in time, in any direction, is self-referential. Velocity in space is given as v = dx/dt. Velocity in time would have to be given as v = dt/dt, which is nonsensical. It's very simple, really. It follows that nothing can move in Einstein's spacetime. And this is the reason that Sir Karl Popper comapred Einstein to Parmenides of Elea who maintained that motion was impossible. Popper called spacetime, Einstein's block universe in which nothing happens. Source: Conjectures and Refutations. Google it. PS. As you can tell, there is only the present and spacetime is a fictitious math construct. It does not exist. So, any physicist (e.g., Hawking) who claims that time travel is possible according to General Relativity is either a liar or a crackpot. Enjoy. Mapou

It seems to me that we are always traveling forward in time. Mung

wagenweg @3: You are joking, right? :-)) Kontinental

Denise, I'd love to share my theory here, but since I am fairly certain that I am the only person that has ever seen this in the Word, at least among the living and posting thoughts online, I am keeping it to myself for a future book. I know, sounds like a cop-out. I would be open to sharing it with you privately. For those that missed my first post. I believe there is a crystal clear example of time travel in the Bible. So clear that when I explain it to you you'll slap yourself for not having seen it before. I have shown it to about a dozen people, and the reaction is the same each time, and no one needs to be "convinced" It's just obvious. Gods iPod

Reality is an ongoing existence or continuum, and we measure that ongoing reality by units of length which we call time. Whatever happened in the past, that section of reality/time continuum no longer exists. If one wanted to travel somewhere that doesn't exist -- that would be impossible since there is nowhere to go. You can move forward in time, or rather with time. In fact at every moment you are moving forward with time through the space time continuum. I guess the real question is: can you move faster forward in time than everything else? Again, there would be nowhere to go. Everything in existence is part of the space time continuum, i.e. part of and taking up space while experiencing a continuation of existence. If by some means one would be able to move faster on the continuum than everything else, one would find oneself in a future on the space time continuum which the rest of existence hasn't caught up with, and would therefore not be there, nothing would be there. Since "nothing" by definition doesn't exist, therefore the future doesn't exist, therefore you cannot go there. mentok

Is backwards or forwards time travel really possible, even for particles? Why or why not? What are the consequences if it is true? As I am merely an Athletic Trainer and not a physicist, my attempt at an answer may be rather amusing to those who are, so enjoy! I have two approaches that say, “Yes, time travel is possible especially for particles.” First, from what I think I’ve learned from reading this blog is that matter/particles are made up of information. If in fact all things are made up of information and assuming that time itself is also made up of information, it would be possible at some point be able to manipulate the information of time itself allowing for transference of data of particles from one position on the time continuum to another position on the continuum such as is the case with information now geographically, for example emails or facsimiles. Secondly, in the case of an omniscient Intelligent Designer (IDer) who obviously knows all things past present or future, it is again reasonable to think that the fact that the IDer is able to know all things past present and future suggests that the manipulation of that information in time can also be possible. However the IDer would have to be independent of time and the information within it. If he were not, then he would not be able to manipulate that information without effecting his own circumstances. Although a feeble attempt, I can at least say I tried. Thanks for the blog!! I enjoy it!! wagenweg

Yes. And I can prove it from the Bible alone :) Gods iPod

Is backwards or forwards time travel really possible, even for particles? Why or why not? What are the consequences if it is true?

No, it's impossible. First, because it violates conservation of energy; second, because we would have noticed time travelers by now - and we haven't. If it is true, I will invest all my money in a time traveling company. But since I don't, that proves that it's impossible. Think about it. IrynaB