It's About Time (cont'd)
'What is
this?'
Disorder and Time-Travel
Time travel is not something we experience in everyday life. Therefore, its implications often seem implausible and difficult to grasp. Personally, I find it helpful to revisit the case of
Mystery in Flatland when confronting the puzzling implications of time travel.
Even if you are familiar with it, it is worth reviewing from time to time.
When discussing time travel, the possibility of a "conflict" is often raised. The classic example involves a time traveler killing his own grandfather in the past before the traveler's parent is born. If the grandfather dies young, the traveler could never be born in the first place.
However, there is an even more revealing reason why time travel into the past can't be possible.
Physics dictates that the general disorder—known as entropy—among the particles comprising any object must increase as a result of any process in the universe. As time passes, disorder increases, which seems to satisfy the universe quite nicely. Going back in time, on the other hand, would decrease entropy (in other words, increase order among particles), something the universe does not appear to permit.
An example borrowed from the book "In Search of Schrodinger Cat" by John Gribbin clarifies this idea.
Consider a stone falling to the ground. When it hits the ground, its kinetic energy turns into heat. While the stone is falling, its particles are largely aligned and moving in the same direction—ordered motion. Once the stone strikes the ground, those particles continue moving energetically but now in random directions relative to each other—disorder. Clearly, entropy has increased.
So far, so good. If we attempt to reverse the process by heating the stone on the ground, we know it will not leap back into the air. Why not? Because doing so would effectively—reverse the flow of time—and restore the ordered motion of its particles—reducing entropy.
s stated above, traveling backward in time is not possible for humans, animals, or any complex object. Here, a complex object is defined as anything composed of two or more basic particles. We are all, in a sense, caught helplessly in the stream of time like twigs in a river, flowing from the past through the present into the future.
But what about a single basic particle, such as an electron or photon, that is not attached to anything else?
It is meaningless to speak of a single particle as ordered or disordered. After all, what would it be ordered with? Itself?
A single particle therefore does not affect entropy one way or another. Consequently, it's not be caught in the stream of time at all—and hence, is even capable of time travel.
Particle 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 simultaneously wouldn't it?
From the particle's perspective (being a physical entity) it cannot truly occupy two places at once. It also must require some finite interval to hop from point-to-point—not necessarily time as we know it, but something analogous.
For lack of a better term, we can 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.
This idea may help explain why particles sometimes appear simultaneously in two places—a state known as superposition—and may shed light on the puzzling results of the Double-Slit Experiment.
But first, let us examine the controversial Uncertainty Principle.
The Uncertainty Principle
The Uncertainty Principle states that, at any instant, it is possible to determine either the position of a particle (such as an electron in an atom) or its momentum—but never both simultaneously.
Suppose we determine the electron's position first.
The electron is continuously hopping from one allowed position to another (when viewed in particle-time). From our perspective in conventional time, it appears to exist in all its allowed positions simultaneously.
When its position is measured, the electron must be at the end of a hop—just arriving at that location. At that instant it is momentarily at rest before beginning the next hop. A particle at rest has no velocity; without velocity, it has no momentum.
Therefore, its momentum cannot be observed because, at that instant, it simply does not have any.
Conversely, when we measure the electron's momentum, it must be in the middle of a hop between positions. At that moment it does not occupy a specific position, so its position cannot be determined.
It is as if position and momentum sit at opposite ends of a seesaw. When one is up, the other must be down.
A simple analogy might help.
Imagine a bus route with stops along the way. At any given moment, you can either measure the bus's speed while it is traveling or identify the stop where it has halted. But if it is stopped, its speed is zero.
If the route is irregular and the bus visits stops in a complex and unpredictable sequence—something like the classic traveling-salesman problem—it begins to resemble particle behavior.
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 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 enters a double-slit apparatus, it hops between slit A and slit B as described earlier. Faced with the choice of passing through one slit or the other, it effectively chooses both.
Because the particle is not bound by conventional time, these hops occur instantaneously. To us, it appears as though the particle passes through both slits simultaneously.
We know this because an interference pattern appears on the detector screen. Such interference can only occur if the particle is effectively present at both slits, interfering with itself—strange as that may sound.
If an observer determines that the particle passed through only one slit, then the observation is effectively being made in particle-time. In that frame, the particle is alternating between slits and therefore appears at only one slit at any given moment.
In that case, no interference fringes appear. This is what is commonly described as the collapse of the wave function.
However, if the observer cannot determine which slit the particle passed through, the observation occurs in conventional time. The particle appears to be present at both slits simultaneously, and the interference pattern emerges.
The conclusion is that the observer does not truly influence the outcome of the experiment. It merely appears that way depending on how the observation is made.
(A Modified Double-Slit Experiment could be designed to test this idea.)
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.
Hardware, Software and Vaporware
Before concluding, there is one more concept worth examining.
It's known as "Entanglement".
Some establishments and companies are promoting the idea that they are in the process of developing faster-than-light telecommunications and quantum computers with their special hardware and software. They base it on a phenomenon of entanglement. These claims must be plain vaporware as discussed further.
Entanglement Shmentanglement
The entanglement concept is the outcome of an attempt to overcome the restriction imposed by the uncertainty principle, dictating that the a single time-traveling particle's two parameter—location and momentum—can't be simultaneously determined. This attempt—known as the EPR Paradox — proposes a pair of particle which, originally, are attached to each other and then got separated. It suggests that after separation, each of these particles can be tested for a different parameter and, therefore, the two parameters can be known for the combined pair and, hence, overcome the imposed restriction.
In order to accommodate the HPR's proposal and yet maintain the dictate of the uncertainty principle, it has been suggested that the particle which is tested first notifies the other that it just have been tested. Upon receiving this message the second particle immediately changes its untested parameter in order to fail the entire process of testing.
It argued that the two particles are "entangled" and that is the reason they are able to communicate with each other, even though they are separated and are farther apart from each other—traveling in opposite direction. Since these particle are traveling in the speed of lights, it implies that the communications between them must be faster than that.
That presents a dilemma since it violates the principle of classic-physics, maintaining that noting can travel faster then light. Nevertheless, it elicits the claim that it's possible to develop computers, known as quantum-computers, which will operate faster than light propagation. It also expected to enable telecommunications at that ultra-fast speed.
The fact is that the uncertainty principle refers to only a single unattached-particle which uniquely can travel in time. The proposal of a pair of particles traveling together, in a similar manner, meant to challenge this principle. However, two associated particles constitute in fact a complex-object (as discussed above), and as such, aren't able to travel in time to begin with; hence, the HPR's proposal—is in fact "dead on arrival".
Notwithstanding, assuming for a moment that the two attached-particles, indeed, can travel in time just the same. Assuming again that they possess the intelligence to communicate with each other, have the sense of loyalty to their heritage, as well as, to each other (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 tested before they are actually being tested"? Is that what you are asking? In this case it's perhaps high time to pay a visit to Flatland.
(Hint: time-travel particles do not need faster than light medium to communicate with each other—they are able to go back in time to do that.)
Mystery in Flatland
This story is not my invention. I heard it many years ago but unfortunately cannot recall the original source.
Flatland is a two-dimensional world. Its inhabitants live entirely within two dimensions and have no concept of a third dimension—no sense of "above" or "below."
One day they build a secure vault to store their treasure. They draw a thick square boundary of impenetrable ink around the treasure.
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'!"
Now imagine a similar situation in 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.
Back to: Disorder and Time-Travel
Modified Double-Slit Experiment
Imagine a double-slit experiment observed simultaneously by two independent observers.
Both see a particle entering the apparatus at the same moment (and in the same universe, needless to say). However:
• One observer can determine which
slit the particle passes through.
• The other observer cannot.
If the second observer sees interference fringes while the first observes wave-function collapse, then no real collapse has occurred. Instead, the first observer simply cannot see the interference pattern because the observation occurs in particle-time.
Such an experiment could potentially confirm—or refute—this entire interpretation.
Back
Conclusions
If these interpretations hold:
• Explanation involving multiple
universes are unnecessary.
• The Uncertainty Principle remains intact.
• An observer does not interfere with an
experimental outcome simply
by observing it.
• Descriptions based on the EPR Paradox
and entanglement are implausible
and far-fetched.
In short, the notion of quantum computers and faster-than-light telecommunication are noting more then a pie in the sky.
Still think it's all crazy? Why not say so?
Add a comment via:
telejt[delete_me]@shaw.ca
Acknowledgement
My thanks to Paul Abrol for assuming the role of a Sounding Board to the bold ideas presented here, and for editing this blurb.
Joel Tepper
(Revised since first posted on October, 2007)
comments
Excellent treatise! I enjoyed reading it ... and I hope to time-travel
in the near future!
Regards,
-- Paul
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I thought we are in the near-future already, but could it be the past?? Go figure...
-- A lonely (but essential) particle.
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P.S. See anther famous myth of quantum
physics known as "tunneling" while you at it:
Is there a light at the end of the tunnel?
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