I'm not a physicist. If I weren't so lazy and I had unlimited time perhaps I would become one so I could answer a question that's been bothering me for a while. Only today this question occurred to me in a different form than it had previously.

Does the future exist?

When I read Stephen Hawking's book A Brief History of Time, and in particular where he describes how time can be thought of as another dimension with space comprising space-time, I started to imagine the implications this would have if the universe had an actual creator.

My initial conclusion was that if space-time is tangible and if the universe was created by an entity which must necessarily exist outside of the universe and that creator has the ability to observe all of the universe then all of the following must be true.

  1. The creator would be timeless from our perspective, being outside of space-time.
  2. The creator would observe all points in space-time simultaneously, including (assuming the historical accuracy of the Bible or Qur'an for a moment) the "original sin" event, the death of Jesus, the birth of Mohammed, and my death. In effect, the creator might be called omniscient about events in the universe.
  3. The creator would have dictated the nature of space-time so not only would it be observed but it would also have been designed. In effect, free will could not exist. An omniscient creator and free-will are mutually exclusive.

Unfortunately, I don't know how physicists really understand space-time. I know that it is theorized that traveling to some point in non-contiguous space-time is possible in one direction (the past) but probably not the other (the future). Logically, if the future does not exist then one cannot travel there. However, if the future does exist, if space-time is complete and tangible, then our speculations about determinism are no longer so speculative. The events which happen at any point on the space-time continuum are set and the idea of free will (however you define it) is obsolete.

I invite discussion and, hopefully enlightenment, from people who have a different perspective and a better education. I personally don't think that space-time is complete or that time exists in both directions based on what I've learned so far.

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@John D,

Hmmmmmm. Why would you conclude there is a great sky daddy who exists outside "space-time?" I don't see any reason to think there is any creator. Isn't it okay to just believe the universe exists? Why did something have to make it? Why does there have to be "intelligence" behind the universe?

I do not conclude that the universe has a creator. I am only describing the implications for our understanding of reality under a set of conditions. Consider it a thought experiment. The rest of your response seems based on this misunderstanding.
Stephen Hawking discusses the uncertainty principal in his book as well. It seems like a strong argument for a scientific understanding of the nature of time and uncertainty of the future, as opposed to a more philosophical understanding.

My initial thoughts assumed that space-time is complete, i.e. the future is set. It was wrong to assume this and now I'm simply trying to find the understanding that best makes sense to me for why that assumption is wrong.

When I hear various explanation like the one you describe above I picture time as a tree of possibilities or time-lines. Either there exists a single possible sequence of events that is predetermined and unchangeable or there exists many possible sequences determined by events which occur at any point in time. These 2 possibilities limit the views we have of determinism.

The uncertainty principal seems to suggest that the tree of possible time-lines is certainly a valid solution, that different possibilities can coexist simultaneously (in different dimensions as some people describe it).
I agree that the sci-fi treatment of time travel is ridiculous. I can rarely stand to watch a movie or tv show about it because of the naive understanding the writers have about the subject.

I do not agree that our best understanding of what we perceive as time is good enough to make blanket statements about it. Even the best physicists apparently don't really know if time exists or what it is. It's all conceptual and since we all have different consciousnesses we all have slightly different conceptions, I suppose.

It seems we agree, though, that the future does not exist.
I disagree.

Einstein's Theory of General Relativity allows for the general possibility of time travel.

The General Possibility of Time Travel in General Relativity
http://plato.stanford.edu/entries/time-travel-phys/
Time travel has recently been discussed quite extensively in the context of general relativity. Time travel can occur in general relativistic models in which one has closed time-like curves (CTC's). A time like curve is simply a space-time trajectory such that the speed of light is never equalled or exceeded along this trajectory. Time-like curves thus represent the possible trajectories of ordinary objects. If there were time-like curves which were closed (formed a loop), then travelling along such a curve one would never exceed the speed of light, and yet after a certain amount of (proper) time one would return to a point in space-time that one previously visited. Or, by staying close to such a CTC, one could come arbitrarily close to a point in space-time that one previously visited. General relativity, in a straightforward sense, allows time travel: there appear to be many space-times compatible with the fundamental equations of General Relativity in which there are CTC's. Space-time, for instance, could have a Minkowski metric everywhere, and yet have CTC's everywhere by having the temporal dimension (topologically) rolled up as a circle. Or, one can have wormhole connections between different parts of space-time which allow one to enter ‘mouth A’ of such a wormhole connection, travel through the wormhole, exit the wormhole at ‘mouth B’ and re-enter ‘mouth A’ again. Or, one can have space-times which topologically are R4, and yet have CTC's due to the ‘tilting’ of light cones (Gödel space-times, Taub-NUT space-times, etc.)

General relativity thus appears to provide ample opportunity for time travel. Note that just because there are CTC's in a space-time, this does not mean that one can get from any point in the space-time to any other point by following some future directed timelike curve. In many space-times in which there are CTC's such CTC's do not occur all over space-time. Some parts of space-time can have CTC's while other parts do not. Let us call the part of a space-time that has CTC's the “time travel region" of that space-time, while calling the rest of that space-time the "normal region". More precisely, the “time travel region" consists of all the space-time points p such that there exists a (non-zero length) timelike curve that starts at p and returns to p.


I am not a physicist myself and reading books on pure physics can be a bit of a challenge. A "readable" version (which I read some years back) is one from J. Richard Gott III, Time Travel in Einstein's Universe: The Physical Possibilities of Travel Through Time.
http://en.wikipedia.org/wiki/J._Richard_Gott
http://vinkovic.org/Projects/PopularScience/Gott_interview/J.Richar...
http://preposterousuniverse.com/writings/gottreview.html

Read also Ronald Mallet's research for a time machine built around Einstein's theory.
http://www.phys.uconn.edu/~mallett/main/time_travel.htm
I don't know - I'll let you know in a minute.
Yes - it does.
LMAO. Wait...nope, I'm still not there yet.
Seriously though, there are respected physicists that that think that time itself doesn't exist - or more correctly is an illusion.

Julian Barbour wrote an interesting book on the topic, and his work is mentioned here:

http://www.newscientist.com/article/mg19726391.500-is-time-an-illus...
Thanks for the pointer.
Awww, you beat me to it. I was going to say "Not yet"
I'm not as well versed in Physics as I would like but I do follow Dr. Michio Kaku and he has a great show on the Science Channel were he created a theoretical time machine. According to him, if we get close enough to the event horizon of a Black hole and stayed close to it with out getting sucked in, we (theoretically) could go into the future as time moves at a slower rate in the event horizon. So once we got out you would have lived a few minutes but in normal space time would have moved at a faster rate. The only problem with this method as he points out is that it's a 1 way trip to the future. So he discarded it and used another law of physics for his purpose, my apologies as I can't remember what was the final design, but I think he used warm holes.

Here are some of his videos I found on Youtube of him discussing this topic.



This does not qualify as traveling into the future, in my opinion. By your explanation it merely takes advantage of time dilation to allow you to travel through time at a slower rate than some other entity so that when you again matched speed you would be in that other entities "future". We have already conducted experiments and have many practical real world examples demonstrating time dilation. No black hole is required. If this counts as time travel then we're using incompatible definitions.

A worm hole is one of the theorized methods that I'm familiar with which should permit actual time travel, but not into the future as far as I'm aware.

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