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Time Machines and Time Theory
by Kenneth W. Behrendt
Recently, I decided to ask some people if they could give me a definition of time and I received a variety of answers back that, in the final analysis, did not really define the word. Most people readily agreed that time was something that was measured with a clock, but when it came to defining EXACTLY what that "something" was, their opinons began to vary. One fellow, who was familiar with Einstein's Theory of Relativity, said that time was the "fourth dimension" as though that pronouncement would somehow resolve the matter. There was also some talk about the past and the future and how time seemed to "flow". A few thought the present moment was like a car moving down a road: the stretch of road ahead was the future and the road behind the car was the past. One person pointed out that time was the amount of waiting one had to do between the occurrence of two separate events. As a future event "drew nearer" to the present, one person said that the time to it "grew shorter" and as a past event "receded" into the past, the time to it "grew longer". Thus, I learned that time was a measurable something that could vary in "length" depending on how it was measured. However, after my informal survey of opinions was completed, I could only conclude that the general concept of time is a rather muddled one which most people resolved by trying not to think too much about the subject! In this article, however, I want to explore the concept of time in depth so as to, hopefully, finally determine the true nature of this "something" which seems so mysterious and has perplexed philosophers and scientists throughout the ages.
Much of our difficulty in defining time stems, I believe, from the nature of the words we use to describe it and from the way in which the concept is presented in various literary works, particularly in science fiction stories.
Students of physics eventually learn that all physical units such as those that are used to measure things like force, motion, energy, temperature, pressure, field strength, etc. can ultimately be expressed in terms of only three fundamental "dimensions" which are: mass, length, and TIME. In fact, after one derives an equation in theoretical physics that describes the relationship between the various parameters of a physical system, it is very important to perform what is called "dimensional analysis" on the equation to make sure that ALL of the dimensions of mass, length, and time (which are raised to various powers) that appear on one side of the equation are EXACTLY the same as the dimensions (which are raised to the same powers) which appear on the other side of the equation. If the dimensions and their powers which appear on each side of the equation are not identical then either the equation is invalid or there is a math error somewhere in its derivation.
The dimensions of mass and length are easily understood by most people. Mass is a measure of the QUANTITY of subatomic particles that are present in a piece of matter and length is a measure of the QUANTITY of an arbitrarily defined span of space that can be fitted between two points in space. Time, however, is somewhat different from these dimensions because it involves measuring the QUANTITY of MOTION of the universe that takes place between two EVENTS in the universe in terms of an arbitrarily defined amount of MOTION of some readily observed part of the universe. It is important to remember that when we talk about time and its measurement, we are always really talking about the measurement of MOTION of the universe. For example, when we say that one minute is made up of 60 seconds, we are really just saying that, during the unit of time we call a "minute", the universe undergoes 60 times as much motion as it does during the unit of time we call a "second". The unit of time we call a second was originally selected to approximately equal the amount of motion of the universe that takes place between two successive, readily observed events such as the swings of a clock's pendulum or the pulses of the human circulatory system. Currently, we arbitrarily define a second as 1/86400th of the motion that takes place in the universe between two successive maximum angular displacements above the horizon of the Sun in Earth's sky as viewed from any point on the planet's surface.
Thus, we see that when measuring the time between two events we are considering, regardless of whether these events are natural or artificial, we are really determining how much motion of the universe has occurred or will occur between those events. At this point, the reader may be wondering about just what kind of "motion" of the universe to which I am referring. Obviously, for ancient, pre-technological people on Earth this motion would have been one of the most obvious motions connected with the passage of Earth's days and months: the apparent rising and setting of the Sun and the phases of the Moon. As technology was developed, these motions would eventually be replaced by the SYNCHRONIZED motions of small mechanical devices or by the display pattern CHANGES in miniaturized electronic equipment. Such artificial devices then INDIRECTLY allow the original source motions of the universe that inpired them to be conveniently monitored even when the user does not have access to a clear view of the sky or when the astronomical objects involved in the selected motion of the universe are not visible.
How much motion of the universe will take place between two events is an important thing for a sentient creature to know. For example, if one knows that an anticipated event will not take place until several days worth of motion of the universe have occurred, then one would realize that one would need, perhaps, to eat a dozen times and have several sleep cycles BEFORE the future event occurred. If, on the other hand, the anticipated future event will not take place until only a few hours worth of motion of the universe has occurred, then one might be able to comfortably forgo both food and sleep before that event. In this example, the person is aware that his body's metabolic processes are just a subset of all of the motions of the universe and that if too much motion of the universe is required before an antipated event occurs, then this also means that excessive motion in the atoms and molecules in his body that underlie his metabolism will also occur. This excessive motion in the atoms and molecules of the person's body will, if uncompensated for with rest and nourishment, lead to the discomfort of fatigue and hunger. Human beings have evolved so as to avoid discomfort and seek comfort and being able to accurately PREDICT the amount of change that will take place in the universe or the "time interval" between two events is an important part of avoiding discomfort.
I have used the phrase "motion of the universe" repetitiously so far in order to try to emphasize to the reader that what we call time is nothing more than the QUANTITY of MOTION and the resulting CHANGE in the POSITIONS of ALL OF THE COMPONENT PARTICLES OF THE COSMOS with respect to each other. For example, when what we call an "hour" of MOTION of the universe has occurred, the Sun seen in Earth's skies will have MOVED through about 15° of arc along its apparent trajectory across the sky. However, it is NOT necessary for any VISIBLE GROSS translational, rotational, or vibrational motions to take place in ANY part of the universe in order for time to be "flowing" or "passing". Without any gross translational, rotational, or vibrational motions, the atoms and molecules of the universe are themselves, at the submicroscopic level, STILL undergoing various types of motions such as molecular translations, rotations, and vibrations and will continue to do so as long as they do not cool to the temperature of absolute zero which is about -459.69° F or -273.16° C. However, even if ALL MEASUREABLE motions of every atom and molecule in the cosmos were to stop and the cosmos did, in fact, suddenly cool to a temperature of absolute zero degrees, time would STILL exist because the perpetual motions of the electons and nucleons within individual atoms continue even if an atom, AS A WHOLE, undergoes no motion. Indeed, and finally, should even the perpetual motions of all electrons and nucleons in the cosmos cease, then the existence of time would STILL be supported by the REMAINING "intrinsic" motions of the "ultimate" particles from which electrons, nucleons, and other subatomic particles are themselves composed! As the reader will realize by now, time and the various levels of motion of the universe which it represents are very difficult to eliminate! In order to eliminate all time everywhere, one would, literally, have to eliminate all of the INFINITE amount of matter and energy from which the comsmos is composed and this is clearly an impossibility.
As we can see from this line of reasoning, there is very little that we can do to affect time throughout the cosmos. Furthermore, there is also nothing that we can do to affect the RATES at which the motions of the cosmos as a whole take place that define the "flow" of time. I am not referring here to the rates of such things as chemical reactions or the speed of an electric motor or internal combustion engine which we obviously can control, but rather to the rates of translational, rotational, and vibrational motions of the electrons and nucleons that compose atoms. I am also especially referring to the rates of motion of the ultimate particle components of subatomic particles themselves. The rates of these motions are, for all practical purposes, beyond the ability of our current science and technology to affect even on the smallest and most local level. These motions are truly the clock at the heart of the cosmos and are currently tamperproof. This is probably a good thing because these most fundatmental motions of the universe are the basic determinants of all of the known laws of physics and chemistry. Their integrity is the only thing that assures eternal stability to the cosmos! The unalterable nature of these fundamental core motions means that during any one second of time as much motion of the universe will occur as during any other second of time. One second of yesterday's time will involve as much motion of the universe as one second of time measured tomorrow.
With these basic concepts of time theory in mind, we are now in a position to begin an analysis of the potential for the development of a so-called "time machine".
I recall going to see the movie The Time Machine when I was nine years old. It was the George Pal version of the novel written by H. G. Wells and was released to theaters in 1960. Later, during the mid-1960's, I remember seeing it on our first color television. It is a powerful, dramatic story of a 19th century inventor who, out of sheer disgust for the warfare of his era, conceives and constructs a machine that allows him to escape into the "distant" future where he plays a critcal role in saving the "good" remnant of humanity from a horrible existence. This movie and its recent (2002) CGI special effects remake are MUST viewing for all science fiction fans.
Both movies are based on the first novel written by H. G. Wells in 1895 when he was 28 years of age. At the time the novel was written, Wells was recovering from tuberculosis which, in those pre-antibiotic days, required months of isolation and bedrest. We can imagine the boredom he endured as he lay in bed day after day watching the hands of a nearby clock circle around its dial and, at night, viewing the slowly shifting stars of the night sky through his bedroom window. Perhaps he imagined how nice it would be if he could only have a control lever mounted on the side of his bed that he could push forward on and which would then make time OUTSIDE of his bed race ahead so that his remaining months of confinement could be completed in a matter of minutes! This scenario, with a fabulous time machine substituting for a bed, is depicted at the beginning of the novel and, very dramatically, in both movies.
Wells' novel is probably, along with the works of Jules Verne, one of the most important in not only science fiction, but general literature as well. The reason for this is that the language and scenarios it presents have much to do with shaping the currently popular notions of the nature of time. To finally decide just how much of the "Wellsian" approach to time travel is plausible, let us now briefly analyze the concept of a time machine.
Our analysis immediately demonstrates a major obstacle to the operation of such a time machine. In order to "travel" into the future, such a machine would have to be able to do one of two things. Either the machine would have to be able to force the motions of the ultimate particles that compose the subatomic particles in the rest of the universe OUTSIDE of the device to dramatically INCREASE their rates of motion, or, the machine would have to be able to dramatically DECREASE the rates of motions of the ultimate particles that compose the subatomic particles of the machine and its operator's body. I must immediately dismiss the first mode of operation of a hypothetical time machine as being physically impossible. But what about the second mode of operation? Surprisingly, this second mode of operation DOES offer some faint hope for a working time machine.
However, because of the elementary time theory presented earlier in this article, in neither case would it be possible to construct a machine that would allow one to travel BACKWARDS in time so as to be able to journey into the past. This impossibility of backward time travel immediately elimates the annoyingly illogical "time paradoxes" that such travel would give rise to and, of course, invalidates any science fiction stories that use this concept (which is probably over 90% of such stories). This prohibition of backward time travel is also in accord with one of the consequences of Einstein's Theory of Relativity which states that, regardless of the relativistic conditions involved, no cause can ever precede its effect. Thus, causality must always be preserved throughout the cosmos and one should never be able to construct any type of device which would be able to travel back to a state of the universe that existed BEFORE the device was activated to make such a trip.
The only possibility for a working time machine that I can envision would be one that would be able to dramatically slow the rates of motion of the ultimate particles that compose the body of the device's operator. IF this is possible with a stationary machine, then we can imagine what might happen should the rates of motion of the ultimate particles in the operator's body be reduced to 1/100th of their normal values. This would then result in all of the biochemical and physiological processes in the operator's body slowing down to 1/100th of their normal rates. Since all of the mental processes of the operator would now be slowed to 1/100th of their normal rates, he would perceive the processes OUTSIDE of his time machine to be occurring 100 times FASTER than they normally appear to take place. For example, the minute hand on a nearby clock outside of the machine would appear to move from one hour marker to the next in only 36 seconds according to the operator's watch. By pressing his control stick forward, the operator of this hypothetical time machine might further reduce the rates of motion of the ultimate particles composing his body. When these rates reached 1/1000th of their normal values, the operator would perceive of each day outside of his machine as passing in only 1.44 minutes according to his watch whose rate of motion (and, thus, timekeeping) would be the same as that of his greatly slowed physiological processes. At all times, the operator will perceive his own motions and thoughts to be completely normal and the motions of only the outside world to be greatly accelerated when, in reality, it is he whose bodily processes are not normal.
As outside observers view the machine's operator, they will see him continuously, but he will appear to be moving at only 1/1000th his normal rate of motion. In order to speak to him, their speech would have to be recorded and played back at 1/1000th of the rate as which it was recorded. In order for the machine's operator to speak to people outside of his active device, his speech would need to be recorded and its rate of playback increased by a factor of 1000. If the machine's operator was to thrust his arm and hand outside of the active region of the device, then that part of the operator's body would instantly regain is normal rate of physiological function. It would, in less than a minute of his time, be a biologially dead limb! The reason for this is that, once outside the machine, the limb would only be receiving 1/1000th of the normal rate of blood flow needed to maintain the life of its cells.
The above described hypothetical time machine would need to be protected from the environment during the entire "journey" its operator might use it to make into the future. Ideally, it might be placed in a natural cavern where it would be protected from the weather and disturbance by curious people. If the device uses electrical power to produced the effect that slows down the motions of the ultimate particles which compose the subatomic particles of the operator's body, then a reliable, long-lived power source must be available to it and the best option would seem to be the use of nuclear batteries. It is also important to note that while the ultimate particle motions of the operator's bodily atoms would be greatly reduced during the operation of the machine, large parts of the device would NOT be so affected. In fact, the device might not operator if ALL of its ultimate particle motions were greatly slowed down. For example, the machine will have to have some sort of EXTERNAL clock that measures the cumulative ultimate particle motions of the external universe so that an external computer control will know when to shut the device down after the operator had been in it for, perhaps, a "journey" of several centuries into the future. Such a clock would, most likely, have a highly accurate quartz movement that would be used to control the duration of the journey to within an accuracy of a few minutes of time.
Obviously, all of the materials used in the construction of this hypothetical time machine would have to be ones that could resist corrosion and any deterioration in their structural strength as the centuries passed outside of the device. This suggests the use of thick ceramic materials and metal parts that have been heavily plated with noble metals such as gold or platinum.
One major advantage of this hypothetical time machine is that it does have a sort of built in "failsafe" feature. Should the operator set its controls so that he can complete a journey of, say, one thousand years into the future and something malfunctions that shuts down the power to the chamber containing his body, then the ultimate particles composing his bodily atoms would instantly regain their normal rates of motion. He could then safely exit the device and see if he could diagnose the problem and repair it.
In the event that the quartz movement timer on the machine somehow malfunctioned so that it was unable to reach the preset shutdown time for the machine, then the operator might have to use an emergency shutdown switch inside the chamber that contained his body. If that switch should fail, then he might be tempted to just open a hatch on the device and try to jump free of it. This maneuver would, however, be a fatal one because, as was noted above, if a part of his body hangs outside of the device, then it will receive a blood flow that is far less than that of the remainder of his body which is still inside of the machine. Should the operator's head emerge from the active machine first, he would quickly experience brain death because the bulk of his body still inside the machine's active operator chamber would only be able to supply his brain with 1/1000th of the blood flow needed to keep it alive. Obviously, to eliminate this danger and allow for emergency shutdown of the time machine, several switches wired in series would be needed to prevent the possibility of "runaway" time travel. If such a mishap be unavoidable, however, then the time traveler might have to sit in the active, uncontrollable device for weeks waiting for a malfunction to naturally occur that would shut the machine down so he could safely exit it!
Unlike the time traveler in H. G. Wells classic work, our hypothetical traveler would only be able to make one way journeys into the future. While he would, of course, enjoy the excitement of exploring time as he periodically emerged from his machine and left is remote cavern to, perhaps, visit a local community to see how society and technology were evolving, the knowledge he gained would have no value for the people of the time from which he left. At best, any knowlege he gained would only be of interest to future historians or archaeologists. In each era that he stopped off in, he would be a person out of place (and time), a sort of temporal drifter, who might attract undesirable attention from local inhabitants which might fear his presence or even try to interfer with his journey.
Before concluding this article, I want to briefly mention another method of time travel that emerges from Einstein's Special Theory of Relativity. Although this method is quite impractical for realistic time travel, it is often cited as a solution that is merely awaiting the necessary technology to make it available. Let us first, however, VERY briefly summarize some of the postulates of and consequences of Einstein's great discovery in the realm of physics.
Albert Einstein published his "Special Theory of Relativity" at the beginning of the 20th century and it was a breakthrough in rationalizing certain paradoxical results that had been obtained in various physics experiments conducted in the late 19th century. Basically, his theory starts with only TWO postulates (which are accepted as true and are not themselves derivable from any higher theory). The first postulate is that the velocity of light (which is about 2.99 x l0 to the 10th power centimeters per second in a vacuum or about 186,000 miles per second!) has a CONSTANT value regardless of the motion of an observer RELATIVE (from which the name of the theory derives) to the source of the light. The second postulate is that ALL of the known laws of physics must be the same in a "frame of reference" whether determined by an observer STATIONARY with respect to that frame of reference or determined by an outside observer who is MOVING with respect to the frame of reference.
These postulates seemed obvious to Einstein and, as was briefly mentioned above, neatly explained the strange and unexpected results that were obtained in earlier experiments that had been conducted by other physicists.
Once he had accepted these two basic postulates as true, Einstein was able, through a variety of ingenious "thought experiments", to show what the consequences of these postulates would be. At the beginning of this article it was noted that all of the physical units of measurement (such as of force, velocity, acceleration, etc.) can be rewritten in terms of the fundamental physical "dimensions" of mass, length, and time. Einstein wanted to see what the effects of his two postulates would be on these basic physical quantities and what emerged is considered to be one of the most important theories in all of science. The theory describles exactly what happens to mass, length, and TIME as an object with these properties accelerates so that its velocity begins to approach that of light. The results are rather bizarre and this fact accounts for the great resistance to the Special Theory of Relativity that initially followed its publication. However, during the last century, MANY independent physics experiments have been conducted concerning the Special Theory of Relativity and EVERY one of them has verified the conclusions Einstein reached as to what will happen to the mass, length, and TIME of an object whose velocity approaches that of light (at which point the object is said to have a "relativistic velocity").
As energy is supplied to an object to accelerate it, the velocity of the object will increase, initially, at the SQUARE power of the energy supplied to the object. Thus, when the velocity of the object is low, DOUBLING the amount of energy supplied to it will increase its velocity by a factor of FOUR. However, one of the strange conclusions of the Special Theory of Relativity is that as the object begins to accelerate to velocities that are ever closer to that of light, less and less of the energy supplied to the object will go into increasing its velocity, but will, rather, go into increasing its MASS! The equation that describes this effect indicates that in order to achieve the velocity of light, a material object (that is, one which had some mass to start with when it was at rest) would need to be supplied with an INFINITE quantity of energy and would then, once it reached the velocity of light, possess INFINITE mass! Since this is clearly an impossible situation, the theory proves that no MATERIAL object can ever attain the velocity of light or exceed this velocity. Indeed, to date, no one as ever found or been able to create a material particle that moves at or exceeds the velocity of light.
The fundamental dimension of length is also altered dramatically for objects moving at relativistic velocities. In this case, the Special Theory of Relativity states that lengths will CONTRACT along the direction of motion of an object in motion. For example, if a spacecraft was to fly past the Earth at, perhaps, 0.8 the velocity of light, then earthly astronomers observing the spacecraft's near approach would see it greatly compressed along its trajectory of motion. If it was normally cigar-shaped when LANDED and, thus, stationary with respect to the Earth, it might appear to actually be spherical in shape as it flew past the Earth at relativistic velocities. If the vehicle could achieve 0.99 of light velocity, then the astronomers might see it as an almost flat disc moving past the Earth!
If the astronomers had a telescope with sufficient magnification and resolving power, then they would be able to see inside the craft through a window or porthole in its hull. All objects within the craft, including the crew, would also appear flattened in their direction of motion. Interestingly enough, this length contraction effect is MUTUAL; that is, as the spaceship flies past the Earth, its crew will see the Earth moving at the same speed the craft has only in the OPPOSITE direction. This will make the Earth appear to the crew members to be contracted along its apparent direction of motion. If the spacecraft travels past the Earth at close to light velocity, then our planet might appear to be a thin disc with only two circular sides! BOTH the earthly astonomers AND the astronauts in this thought experiment will perceive themselves as having normal dimensions and claim it is the others that have contracted along their directions of motion. Both astronomer and astronaut are correct in the claims they make even though these claims contradict each other! This mutual distortion effect is not just some sort of optical illusion, but is a REAL PHYSICAL change in shape that is measurable by each observer in the OTHER'S moving frame of reference! As soon as the craft lands back on Earth, this mutual distortion in length along the apparent path of motion disappears as far as the astronomers and astronauts are concerned and each will again view the others as having their normal proportions.
The most bizarre consequence of the Special Theory of Relativity is what it predicts MUST happen to the time for processes to occur in two different reference frames that are moving, especially at relativistic velocities, with respect to each other so that observers in each system will observe the same consistent physical laws in BOTH systems. In this case, the theory predicts that the apparent time for physical processes to take place will "dilate" or expand so that an outside observer will see processes seem to take longer and longer to occur as the relative velocity of a system or reference frame he has under observation approaches the velocity of light. It will appear to the observer that time in the observed moving reference frame has slowed down and, if it was possible for the system to reach the velocity of light (which is not possible as was stated earlier), then all time and all motion in the observed system would appear to come to a complete halt.
Again, as in the case of length contraction, this effect of time dilation is NOT an illusion, but a REAL PHYSICAL effect! And again, this effect is MUTUAL. Observers in each of two different reference frames moving at relativistic velocity with respect to each other will claim that their "flow" of time is normal and that it is the other reference frame that is experiencing time dilation. And again, observers from two such systems in motion with respect to each other will, paradoxically, BOTH be right about the claims they make!
Once again, let us consider the thought experiment wherein a spaceship leaves Earth and begins traveling around our solar system at near light velocity. As it travels about, Earth based astronomers use their powerful telescopes to follow its progress and note that time aboard the craft is extremely dilated. The astronauts appear almost motionless. Occasionally, when the spaceship flies nearer the Earth, the astronauts use their own onboard telescope to observe that life on a flattened Earth seems to be moving in slow motion...perhaps they notice that it takes a week of ship time for the Earth to complete a single rotation. This tour of the solar system is continued for several weeks of the ship's time at which point it is decided by the crew that they will return to Earth and land their ship.
Upon arriving back on Earth, the spaceship crew will have a surprise waiting for them. While the crew has only aged a few weeks as indicated by their ship's clocks and calendars, the people they left behind on Earth may have aged anywhere from a few years to a few decades depending on how close to the speed of light the ship was able to travel and Earth's clocks and calendars will be years to decades AHEAD of those of the spaceship!. The crew of the spacecraft has, effectively, traveled forward in terms of Earth's time because the crew members have not aged at the same rate as the astronomers they left behnd when they first began their tour of the solar system. While it is true that both the astronauts AND the astronomers both saw the other's rate of time flow slow down, the relative motion of the spacecraft with respect to the Earth AND the rest of the universe forces the slowed rate of ship time flow to prevail when both the spacecraft and the Earth finally come to rest with respect to each other. Once again, this time dilation effect is REAL and has been observed in many physics experiments involving various electrically charged subatomic particles that have been artificially accelerated to relativistic velocities using machines known as "accelerators". The results of these experiments in particle physics are further verification of the reality of the paradoxical predictions of the Special Theory of Relativity.
In the above though experiment, our spaceship was obviously functioning as a time machine and could allow its crew to move ahead in Earth's time by years to decades depending on the ship's velocity for each week of shipboard time that passed. The reader unfamilar with the many problems of spaceflight may believe that the time dilation effect predicted by relativity theory provides a practical solution to engaging in time travel. Unfortunately, it does not. The best space technology we now possess will only allow us to accelerate a MASSIVE object to a velocity of about 50,000 miles per hour which is equivalent to about 13.89 miles per SECOND. Since the velocity of light is about 186,000 miles per second, this means that our best current techology would only get our spaceship time machine up to a velocity that was 1/13,391 th of the velocity of light...less that 0.01% of the velocity of light! For all practical purposes, our fastest spaceship is standing still compared to the motion of light and any time dilations that would be produced aboard it as it travels at its maximum velocity would be negligible as far as allowing its crew to "journey" into the future.
At this point, the reader may suggest that all that would be required to remedy this velocity problem would be to equip the spaceship with some sort of exotic nuclear or ion propulsion system that could operate CONTINUOUSLY at low thrust so as to, eventually, accelerate the ship until it finally achieved the relativistic velocities needed to make forward time travel possible. Again, there is a problem that makes this solution unuseable.
There are reliable calculations which indicate that a conventional spacecraft would not be able to exceed a velocity of about 20,000 kilometers per second or about 12,500 miles per second. At this velocity the spacecraft would be impacting so much interstellar gas and dust that ALL of the thrust of its engines would have to be used to counter the drag on the ship's hull caused by this material and no further acceleration would be possible. At this velocity, a collision with a single micrometeorite the size of a pea would, most likely, destroy the entire spacecraft! At a maximum velocity of only 12,500 miles per second, our hypothetical spaceship time machine would only be moving at about 1/15 th or 6.7% of the velocity of light. The equations of Special Relativity Theory indicate that such a very low relativistic velocity would only dilate time aboard the spacecraft by about 0.23 % which is virtually negligible. For every 168 hour week spent aboard a spacecraft limited to moving at about 12,500 miles per second, the crew would find that they only "traveled" about 23 MINUTES into the future each time they landed the craft back on Earth! If all of the astronauts left Earth at the age of 18 and each managed to live to be 100 years old before they decided to land back on Earth, then they would find themselves to have to have traveled forward in time by about only 68 days...a little over two months time. It would hardly seem worth being cooped up inside a small spaceship for 82 years for so short a trip into the future!
From the above, the reader can appreciate why I am not a advocate of the various relativity approaches to time travel. They are not now and, most likely, never will be a practical solution to engaging in forward time travel.
While there can be no doubt that the Special Theory of Relativity is one of the most important contributions to the structure of modern science because of its revelation about the time dilation effect noted by OUTSIDE observers of reference frames moving at relativistic velocities, the theory fails to ask and answer an even more fundamental question about this strange effect: why should the motion of a system cause time to slow down in that system? Just stating that this effect MUST exist so that the laws of physics can be described with the same equations for two reference frames in uniform (i.e., unaccelerated) motion with respect to each other is really not a satisfying answer.
It is my belief that this effect of time dilation is somehow connected with the same effect that causes the MASS of objects to increase as they are accelerated toward the velocity of light. Perhaps as kinetic energy is imparted to an object to accelerate it and this energy begins to show up as an ever increasing mass of the object as its velocity approaches that of light, that increase in mass somehow causes the rates of motion of the ultimate particles which compose the object to begin slowing down. This effect then is relayed throughout ALL of the subatomic particles, atoms, and molecules that compose the object. If the object is a living organism such as a human being, then his entire metabolism will slow down INCLUDING the neurological processes responsible for cognition and thought. Since ALL parts of a person's body experiencing such time dilation are equally affected, that person is completely unaware that all of his bodily processes have slowed down. He feels completely normal, but becomes aware of his situation only after he becomes motionless with respect to the rest of the cosmos and can then measure the physical differences that have accumulated between himself and the rest of the cosmos due to the prior DIFFERENCE in the rates of motion of the ultimate particles that compose his body and the ultimate particles that compose the rest of the cosmos.
In order to make a kind of "monodirectional" Wellsian type time machine possible and practical, we need a way of producing the same kind of time dilation effect predicted by the Special Theory of Relativity for moving objects, only WITHOUT the necessity of accelerating the body of the time traveler to near light velocities. POSSIBLY, at some time in the future, a chance discovery in a physics laboratory will provide a clue as to how to artificially create localized time dilation using some combination of electric, magnetic, or electromagnetic fields. But, should that discovery ever be made, the time traveler would still have to cope with all of the problems discussed for such devices in the earlier part of this article.
There are also a variety of other modes proposed for time travel which occasionally surface in the literature of the subject which I will just collectively lump together as "suspended animation modes". They involve either completely stopping a person's metabolism by cooling his body to temperatures near absolute zero (-459.69°F) using liquid nitrogen vapors or just greatly slowing down a person's metabolism by putting him into a drug induced coma while using ice paks to lower his core body temperature to tens of degrees below its normal temperature (about 98.6°F). Once in such a state, the person would either not age or do so at a much slower rate so that when he was eventually revived, he would perceive himself to have jumped forward into the future.
About the first suspended animation mode of time travel mentioned above, I can only note that much experimentation in cryogenics research involving both dead and living organisms has been conducted since the early 1960's and, so far, no one has been sucessful in reanimating or reviving a HIGHER organism that had been cooled to such low temperatures. I doubt if the process will ever be made workable because, even when attempts are made to "perfuse" the organism with a substance such as ethylene glycol in an attempt to saturate the bodily cells with an antifreeze that will prevent ice crystal growth as body fluids freeze, the fact is that the antifreeze does not reach all of the structures within a cell uniformly. Upon freezing, ice crystals do still form and critically damage delicate structures and membranes within the cells. When later attempts are made to thaw out such an organism, the then warm remains tend to form a kind of "soup" made up of damaged cells incapable of living again.
The second mode of suspended animation time travel does give one a better chance of being revived than cryogenic suspension at liquid nitrogen vapor temperatures, but it is still a very risky procedure that requires continuous monitoring by medical personnel. As with any kind of an induced coma, the risk of PERMANENT damage to the body and brain increases with the length of time spent in such a state. While this technique is useful in certain types of surgery, I do not see it as feasible for a time traveler wanting to journey decades or centuries into the future.
Finally, I shall conclude this article with a summary of what I have come to believe is the true nature of time.
I have come to realize that our perception of time is rather delusional in nature. There really is NO such thing as past or future states of the cosmos that somehow NOW coexist with the present state and to which we can instantly travel with a time machine. We basically live only in a present state of the cosmos whose component particles are constantly changing positions with respect to each other according to the various laws of physics.
The basic physical processes of the cosmos take place with rates of motion that are ultimately determined by the rates of motion of the ultimate particles from which the entire cosmos is constructed. Thus, when we measure the "time" that takes place between two events in the cosmos, we are, usually without even realizing it, actually measuring the QUANTITY of MOTION that occurred in the individual ultimate particles of the cosmos during the "temporal interval" between the two events. Since we can not directly view and measure the motions of these submicroscopic ultimate particles, we substitute some other physical process for them whose motion we can easily observe and whose motion is CONSISTENTLY synchronized with the motion of the ultimate particles...we use a reliable timepiece such as a clock or watch.
Since we will NEVER be able to control the rate and direction of the motions of the infinite number of ultimate particles that compose the cosmos while simultaneously perserving the rate and direction of the motions of our own bodily ultimate particles, it is IMPOSSIBLE to build a machine that would allow us to travel backward in time. However, it MAY someday be possible to create a monodirectional Wellsian type time machine that would allow its operator to greatly suppress the motions of the ultimate particles that compose his body so that he would not appreciably age while the cosmos outside of the chamber containing his body continued to change at its usual rate which is controlled by the precise and eternal motions of its unaffected ultimate particles.
Should working time machines ever become possible, the operator of such a device would need to seriously consider whether or not he would be able to make and keep the commitment to engage in IRREVERSIBLE, one way travel to future states of the cosmos and what value such exploration would have to the people he might meet along the way. His adventures and the knowledge gained from them would be of no use to the people he left behind, but might be of some benefit to future historians or archaeologists.
Finally, it should be remembered that, although a temporal explorer may be able to overcome the prison of time that limits those who do not possess his technology, he would still be subject to the same AGING processes that they experience. Should some future time traveler spend twenty years of his life exploring the future, then he will be twenty years older when he ceases his exploration. Unfortunately, the ability to travel through time, interesting as it might be, does not bestow immortality upon a time traveler and, in time, he will eventually suffer the same fate as those he has left behind in the distant past...
(Note: this article completed August 22nd, 2003)
COSMIC VAULT GIFT SHOP