It's About Time (cont'd)
Disorder and Time Travel
Time travel is not something we experience on day to day basis and, therefore, its implications are not plausible and often difficult to grasp. Personally, I always find it helpful to review the case of
Mystery in Flatland when facing the puzzling time travel and its implications. Even if you are familiar with it, it's highly recommended for review every now and then.
When the issue of time-travel is looked at, the possibility of a 'conflict' is, usually, singled out. This refers to a case where a grandfather was killed in the past by his own time-traveler grandchild from the present. Since it happened at a time when the grandfather was at a very young age, the time-traveler grandchild could never be born in the first place.
There is, however, a more revealing example as to why time-travel can't be possible.
It's based on the physics' law dictating that the general disorder (known as Entropy), among the basic particles comprising any object, must increase as a result of any process in the universe. Naturally, as time passes, the disorder increases which makes the universe happy. Going back in time, on the other hand, would decrease the entropy (in other words, increase the order among the particles) something the universe does not permit. It should be clear, therefore, why traveling back in time is not possible.
An example (this example is borrowed from John Gribbins's book: In Search of Schrodinger Cat) will clarify the situation. Consider a stone falling down. When the stone hits the ground its kinetic energy turns into heat. While the stone was still in the air falling, its particles were all aligned with each other traveling in the same direction (ordered). As soon as it hit the ground, all these particles, while still traveling very energetically, did so in random directions to each other (a disorder). Clearly, entropy increased in this process.
So far so good! If we try and apply heat to the stone on the ground, in an effort to reverse the process, we know it would not takeoff in the air. Why? Because that will take it back in time which will put its particles back in order (a decrease of entropy).
As stated above, traveling back in time is not possible which is true for humans and animals, and in fact, for any 'complex' object, where a complex object defined here as an object composed from two or more basic particles. It's as if we are caught helplessly in the stream of time, like a twig in the stream of a river, flowing from the past through the present into the future.
That being the case, what about a single basic particle (such as an electron or a photon) which is not attached to any other? It would be meaningless to speak about a single particle as being aligned, ordered or disordered. After all, what would it be ordered with? Itself? A single particle, therefore, has no effect on the entropy one way or the other and, hence, it's not caught in the stream of time.
Consider a particle that is traveling from point A in space in the future, to point B in space in the past. Must it pass necessarily through the present on its way? Remember that it's not caught in the stream of time and in essence is not bound by time at all. In fact such a particle can jump directly from point A to point B and, hence, it can hop in time rather than mere time-travel. Furthermore, it can do that in, practically, no time so that it would appear to us as being in both places, A and B, at the same time wouldn't it?
Yet, from the particle perspective, being a physical entity, it can't possibly be in two places simultaneously and it must take it some finite -- if not time, then something similar to time -- to hop from point-to-point. For lack of a better term, let's call it 'Particle-Time'.
It would appear that Particle-Time is a dimension which is perpendicular to the conventional time dimension and is the domain where single particles are bound, being liberated from the conventional time domain. If the two dimensions of time are plotted in 'x-y' coordinates, it's easy to visualize that any movement along one axis only, will not register on the other.
We shell see in a minute how a particle, appearing simultaneously in two places (also known as being in a 'Superposition'),
can help to solve the puzzling outcome of the 'Double Slit Experiment' and its bizarre implications. But first, let's look how the ability of a particle to time-travel in general (rather, to time-hop!) can serve to resolve the controversial 'Uncertainty Principle'.
The Uncertainty Principle
The uncertainty principle states that, at any instant, it's possible to determine the position of a particle, (say, an electron in its orbit of an atom) or its momentum, but never both simultaneously.
Assuming we record the position of the electron first. The electron is actually traveling continuously by hopping from one of its allowed positions to another of them throughout. As we have seen above, it 'appears' to exist in all its possible positions simultaneously.
When a position of the electron is actually being determined, it must be at the end of a hop, just landing at this position. The electron is, therefore, momentarily at rest at that instant, just before it commences the next hop. An electron at rest has no velocity --no velocity, no momentum. No wonder its momentum can't be observed since it, quite simply, doesn't have any at that very instant.
Similarly, when we determine the electron's momentum, it must be in the midst of a hop from one of its allowed positions to the next. It's, therefore, between positions and it doesn't have a position, as such, at that very instant. No wonder the position can't be determined here.
It's as if the two parameters of position and momentum are placed at the two ends of a seesaw. When one is 'up' (able to be determined) the other must be 'down' (undetermined).
To better visualize it, consider a bus-route with bus-stops placed throughout. As a bus travels along this route, either its speed can be determined at any instant, or at which assigned bus-stop it stopped (in which case it's at a complete halt and its speed is zero).
If this route is of an irregular shape and if the bus is visiting its stops, inequitably, and in an unordered fashion, so that it can be only determined
by a 'Traveling Salesman', or a similar
statistics; it closely simulates the particle behavior.
It should be easy to visualize, therefore, why a particle position can be determined, or its momentum, but not both.
Similar arguments can help to explain the Double-Slit Experiment. However, there is one more thing we need to consider, in regard to a particle behavior, before we can take a look at this crucial experiment. When faced with a choice to go through one slit or the other, a particle appears to choose both and to alternate between the two in its own time (particle-time). Come to think of it, it's precisely what the electron does in its orbit in the atom, where it alternates from one position to the next throughout its all allowed positions.
The Double-Slit Experiment
When a single particle is made to travel into the double-slit (or double-hole) setup, it hops from slit-A to slit-B as described above. As if given a choice to go through one slit or the other, it chooses both. Since the particle is not bound by the dimension of time, it does that in practically no time and, hence, 'appears' on both slits at the same time. We know that since it creates interference-fringes on the setup detector or screen. The interference-fringes could only happen if the particle is present on both slits simultaneously and the particle, in essence, interferes with itself (strange as it may sound).
If an observer manages to determine through which slit, uniquely, the particle passed-through at a certain instant, the fringes immediately disappear; which is known as a collapse of the wave function. Actually, the wave function never collapses and the observer doesn't really interfere with the process as such, but rather with that same observer own ability to view the process to its completion. It's like the determination causes a tunnel vision to be developed in which the process is viewed through a too narrow window to see it to its completion where fringes are developed. The rational for this is as follows:
When the observer records the presence of the particle in only one of the slits it means that a snapshot is being taken frozen, not in time (where the particle is present on both slits) but in particle-time where the particle alternates between the slits. (Hence, no interference-fringes to be seen!) It's like taking a frozen-in-time snapshot of a chemical reaction. The picture may not show the end-product of the reaction since it doesn't record the process to its completion. (A Modified Double-Slit Experiment can be used to prove all that.)
So what do you think? Is it crazy enough yet to be true? You may use the link below to communicate your thoughts so it can be posted in the comments section.
There is one more thing I would like to go through before I get out of your hair.
It's known as 'Entanglement' and it could be rather urgent, you see. As we speak, there could be some companies 'on-their-way-up', which are promoting their 'about-to-be-released' software and hardware employing a telecommunications medium which is faster than the speed of light based on the entanglement phenomenon. These hardware and software are most likely nothing but vaporware as you will see soon. (That being said, it must be recognized that it's conceivably feasible, at least in on the face of it, that a single particle ability to time-travel could be exploited in the future to convey a message instantly between two remote points in space. Though... I wouldn't hold my breath if I where you.)
The concept of 'Entanglement' deals with two particles which were once associated with each other, and then flew apart in opposite directions. The two are considered to be entangled for the following reason: if their combined properties are measured when they were still together, it should be possible to infer the properties of either of them by measuring those of the other. At that point, the measured particle mysteriously 'notifies' the other to immediately change its properties in order to hinder the measurements (and comply with the 'Uncertainty Principle').
Since these particles move at the speed of light in the opposite directions, their form of communication must be faster than that. This raises the hope, in some circles, that telecommunications medium faster than light is possible and is just around the corner for commercial implementation.
Notwithstanding the fact that two associated particles do not, necessarily, behave in the same way as a single particle uniquely does (see above), and assuming for a moment that the particles do, indeed, need to communicate with each other. Assuming again that they possess the intelligence to do so and have the sense of 'belonging' and loyalty to their heritage (entanglement?). Why, then, can't they communicate in the past when they are still together?
Ha?? I hear you say: 'how can they possible know they are going to be observed before they are being, actually, observed?' Is that what you are asking? In this case it's perhaps high time to pay a visit to Flatland.
Mystery in Flatland
The following story is not my invention. I heard it told many years ago, alas, I have no recollection by whom. I have tried to search for clues who originated this story or where it was published, but couldn't find anything. If you have any idea please let me know so that a deserving credit can be given. I retell it here from memory and in my own words. So here goes:
Flatland and its inhabitants are of two dimensions. The people of
Flatland live happily in their two dimensional domain having no need nor knowledge of a third dimension with no perception of 'above' or 'below'.
One day, the inhabitants decided to build a facility for safekeeping their treasure. They drew a heavy square perimeter from impenetrable ink enclosing the treasure in the middle.
Some time later, a thief from a three dimensional world arrived in Flatland and removed the treasure form above with no difficulty and without being noticed. When the people of Flatland discovered that the treasure was gone and the perimeter is intact, they stood dumbfounded. How could the treasure disappear? It has remained a mystery to this day. Any explanation that it had been removed from above would have fallen on deaf ears. "What is 'above'? There is no such thing as 'above'!"
The story moves now to our world. The people here also decided to build a facility to hold their treasure. They built a steel and concrete fortified enclosed room with a sophisticated strong safe in it to hold the treasure. When a time-traveler thief arrived, he removed the treasure with no difficulty. How did he do that? He simply removed the treasure before it was put in since a time-traveler is not bound by time and from this time-traveler perspective, 'before' and 'after' have no meaning.
Modified Double-Slit Experiment
Consider a 'Double-Slit Experiment' setup which is made to accommodate two observers simultaneously. The two observers view the experiment independently from one another. Both observe simultaneously a particle traveling into the setup and they do that, obviously, at the same time as it happens (and in the same universe, needless to say).
One of these observers is able to determine through which slit the particle went, the other isn't. If the observer who is not aware, through which slit the particle went, can see the interference fringes while the other witnesses a collapse of the wave function; would you accept, then, that no collapse really took place (and the observer which insists of viewing the fringes, while the particle is only in one slit, simply can't see any)?
If so, you could prove (or disprove, if you so inclined) this theory entirely by designing and building such an apparatus and running the experiment.
Still think it's all crazy? Why not say so?
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My thanks to Paul Abrol for assuming the role of a Sounding Board to the bold ideas presented here, and for editing this blurb.
(Revised since first posted on October, 2007)
Excellent treatise! I enjoyed reading it ... and I hope to time-travel
in the near future!
I thought we are in the near-future already, but could it be the past?? Go figure...
-- A lonely (but essential) particle.