Fun with time travel

 Wormhole drawing from Wikipedia

There has much been written about wormholes being used potentially for time travel and popularized by science movies and novels, Contact, Farscape, Stargate. and Sliders, for examples.    It is a familiar topic of some top physicists and not excluded by the Theory of Relativity.

Create a wormhole, drag one end “E” to a vast gravitational source such as a neutron star and wait.   Time for the dragged end will slow down dramatically in comparison with the other end located far from the gravitational source.   This is due to an intense gravitational field’s effect on time – it slows it down, it doesn’t age as fast as the other end.    Then drag the “slow time” end “E” back to the lab and set it beside the “real time”, “L”, and you have a time machine. with ends labeled E on the slow end and  L on the fast.  

If some future civilization could somehow do such a thing, the speculation is that if someone tossed a ball into the L (Late) end, it will come out the E (Early) end before it goes in the L end.   Time travel, back to the past.

Now that may sound confusing, but consider this.  If the E end were put in the gravitational field on July 11, 2007, it would remain at July 11 until it was removed on July 12 and then be a  day early forever.    A ball put into the L end on July 14 would come out on July 13 at E, and a ball put into the E end on July 14 would come out a day later on July 15 at L.   Both ends are at the same date as you sit there watching it, but an object put into either end responds as if it were moving through time.

Looking into a wormhole  – don’t blame me if you get dizzy.

Now there is a situation that needs some explaining.  The person sitting there observing both ends, which are now together, is living only in the “real time” which we call fast time, but it is early time for himself a day later.   He can see both ends at once and both ends of the wormhole are visible at the same time, the one on the left labeled E and the one on the right labeled L.     Suppose he sees a ball with his signature on it pop out of the hole at E.   That implies that someone (presumably him) will put a ball into the L end the next day.    Suppose he decides to lock the lab and prevent someone from doing that.    Where did the ball come from?

Physicists who may accept the possibility of time travel have taken great pains to explain why an action at L cannot be changed by something coming out of E. For example, you can’t go into the L end and come out of E and prevent yourself from going in.  Or kill yourself in the past, or let the ball you toss in be knocked off course by the ball coming out, or lock the door to prevent the ball from going into the L end.  So the answer to the question, “where did the ball come from” is this:  he can’t prevent the ball from being put in the next day if it has already come out early.  The future is already defined for that event.  If he could prevent the ball from going in, it would not have come out early.  Something would intervene or someone from an parallel universe would have to have done it.  Things that come out the E end define what goes into the L end later.  Future foretold.

It occurs to me that it would be apparent soon after it was created whether and how well it works, and if a person could survive the trip or not. It is clear to most physicists that such a machine cannot go further into the past than when the end was dragged into the gravity source because the dragging can only be done in the present.   Merely dragging it does not open a portal to an earlier time than when it was put into the gravitational source.

To determine if and how well it works, you only need to observe the E end. If a ball comes out, it works for some objects. If hamburger like meat or juices come out wearing a name tag, it would not be wise to later go in yourself.  But you would not be able to prevent someone wearing that tag from going in.   His or her fate is sealed.  If your name is on the tag, give it to your worst enemy quick!

Once the end is dragged away, it might work, but it can only begin then. Lets say that the end E is dragged to the lab and placed beside L before any experimenting is done, and the time differential had been built up to 1 hour between the ends. Soon after the two ends are brought near each other, the physicist standing nearby might see a ball pop out with his signature on it.  “It works!”, he shouts.  At that moment, before he ever starts his experimenting, he knows it works with balls. Then he puts the ball back in. Where did the first ball come from? Who signed it? Does the ball come out again? When?

Some Answers:

The first ball came from someone an hour later who puts in a ball previously signed by the physicist. It is the same ball, but cannot come out unless initiated an hour later by action by someone in the future, acting in their present, sending the ball to their past.

If the ball is put back into L, it can’t come out in the lab at E unless the physicist has waited at least an hour after the portal has been established, finds a ball somewhere, signs it and then puts it into L, such that it comes out while portal E is active and in the lab. The initial appearance of the ball at E requires a corresponding initial action at L an hour later.  Predestination.

If the physicist puts the ball back in immediately, it might come back out, but not in his or her laboratory unless the portal has been open in his lab for at least an hour. For example, the portal is only 5 minutes old when the first ball comes out (implying it was put in an hour from then) and if it is immediately put back in, it would be put in 55 minutes before the original one – before the portal is established and comes out somewhere along the dragged path preceding the first one he saw come out.  

In other words, if less than an hour, it must come out somewhere along the path that the port E was dragged through, and thus his evidence would be lost in space. In addition, an unsigned ball must be found, signed and put into the portal L prior to putting the first ball back in. To fail to do so would have meant the initiating event never happened and he/she would have no knowledge of it, much less a signed ball to admire.

The physicist must wait until enough time has elapsed that the time differential from E to L has elapsed (in this case 1 hour) to avoid losing the ball. The physicist must also initiate the process with a newly signed ball. This requires an hour’s wait the first time, but might not if, say two hours (or 48 hours) elapsed before the initial action is taken.

Then putting the ball back in would enable it to come around again and not be lost in space. However he would first have to find a ball and sign it to start the original process and such an action would have already resulted in earlier balls pouring out of the E end. 

Major Problem 

There is a major problem brought to light right here, but it was a problem from the beginning and just now evident.  Lets say that he just got the portals working and they are side by side.  He has a signed ball on the table waiting for the hour to elapse and a signed ball unexpectedly comes out of E.  Now he has two signed balls!   Matter Created?   Energy created?   Violations of energy conservation all over the place!   Can he go into the ball manufacturing business by putting the balls back in quickly and getting a never ending supply of perfectly identical balls?   I don’t think so!  If he could, he should find a large carat diamond and switch to that.   They would pour out of E by the shovel full after a few minutes!  First 1 then 2 then 4 then 16 until they started to pile up and he is shoveling them back in as fast as possible.   Not going to happen!   Whatever happens, energy, and thus mass, and thus new balls (or diamonds) are not got going to be created.  No matter what. 

The answer may be that the ends cannot be placed close enough together that light can go from one to the other within the time frame of the experimental time warp.  That would put a real damper on the project, although it would work as a good portal between far flung space stations.  Set two of them up with a time delay of the light travel time and have one with E at one end and L at the other, then a second set of L at the first end and E at the other.  Then someone could go from one star to the other and back in a matter of seconds, round trip.   The traveler could never be in the same place at the same time.

Lets say this is one sharp physicist that thought that this paradox of having matter creation would prevent it from working at all, so he put his original signed ball into a box and never opened it.   Did it cease to exist?  Can he use the ball that came out of E to put back into L an hour later?   If so, who signed that ball and when?  He only has one ball to deal with and he carefully reuses it no often than once an hour but we still have a major problem to deal with when he opens that box.    Actually the answer to all these is this:  If he puts the first signed ball into the box, seals it, and never opens it, he will never get a signed ball out of E the first time.  

We just can’t deal with that situation logically.  So lets move on to another scenario and see if we do any better.   Suppose somehow the balls can co-exist and if you put one in now, it comes out an hour earlier, no problem.  Suppose our physicist is very conservative, thinks about things thoroughly and decides in advance to wait 3 hours before putting in the first ball. If he actually did wait for the 3d hour, it would come out at the 2d hour.   It would still be matter created because he has at that time still not put the first one in, so he has two.  The happy physicist thinking “this is neat!” might be tempted to put both back in immediately.   He can’t.  Somehow he can’t because to do so would have meant that he would have had 3 at the first hour (the original plus the 2 from the second hour) and he did not.    As soon as one comes out, the future of the portal at L is fixed for that event.   Unless parallel universes come into play.  The portals in different but parallel universes.   You would never know unless the laws and/or sequence of history were different and your ball came back signed by someone else. 

Each appearance implies that the future event will take place.  If a new ball  appears at hour 2 at E,  that ball is destined to be put into L an hour later. 

The above sequence may seem like the past is forcing the future to comply with past events.   Deterministic.  Maybe that is already happening.  Everything we do is pretty much dictated by our past actions.   We have very little room to maneuver.  

“Whenever the future repeats itself the price goes up.*”   Maybe we just can’t afford a time machine.  

 * The original version of this quote is more than 4000 years old!  Future foretold!

Time machine lost! 

When it comes down to the bottom line, a time machine for travel into the past is an energy and matter creator and would have to violate a fundamental law.  Travel into the future also violates the same law because matter and energy in the past “disappears” when it enters the portal. 

During the transition from the past to the future, the universe would have less matter and energy than before. 

Sorry folks, but we aren’t going either way.

Oldtimer

(Reliving the past)