WHAT IS TIME?
WHAT IS THE CAUSE OF TIME?
drkhan77@yahoo.com
More powerful than all the armies of the world,
is an idea whose time has come.
.......Victor Hugo
PART A
INTRODUCTION
For thousands of years, philosophers and scientists have struggled to understand the phenomenon of time. We have known for the last one hundred years about time dilation or slowing of time with motion and in gravity yet the true understanding of time has evaded us. I am presenting here a clear solution to the enigma of time which brings to light the reason behind many predictions of Special and General Relativity such as why time slows with motion and in gravity? What is the cause of gravity and why it is only attractive? Why is space curved by gravitational fields? Why objects gain mass when accelerated by a force but do not gain mass when falling in gravity? What is the cause of inertia and length contraction and despite the time dilation of the moving twin there is no twin paradox.
Time presents to us in many different ways. We measure time, keep time, meet and greet in time and our daily lives are completely wrapped around the onward rush of time. We perceive time as past present and future. Events in time are always accompanied by the mental image of places suggesting that time is a dimension. This has sprung a whole culture around the concept of time travel leading to numerous science fiction stories, and movies. In physics, time plays a major role in the measurement of motion and forces. The many facets of time should suggest that time is an emergent phenomenon that is arising from some underlying process that we need to identify.
The greatest breakthrough in the understanding of time occurred about a hundred years ago with Einstein's theories of Special and General relativity in which he introduced the concept of slowing of time with motion and in gravity. Einstein also showed that large masses curve space and there is an increase in mass with acceleration by the application of a force. These discoveries of Einstein provide the necessary clues to solving the riddle of time.
MEASURING TIME:
WHAT ARE WE MEASURING?
One of the earliest device to measure time was the sundial; which used the movement of the shadows caused by the sun's motion across the sky as a way to measure time. The use of units like seconds and minutes which are radial angle measurements in geometry may be pointing toward the original connection of time measurements to radial motion of astronomical objects across the sky. Once we started using precise timekeeping devices like digital clocks and time based on atomic oscillations the time's celestial connection was lost. Now devices across the globe can be synchronized with atomic clocks and time has developed a life of its own.
When we measure the speed of a car, we seem to be measuring speed with something abstract called time; we are actually just comparing a known motion (of the sun) with an unknown motion of the car. Time is a way to compare or describe different kinds of motions like the speed of light, how fast heartbeats or how frequently earth spins around its axis. But these processes can be compared directly with the motion of the sun across the sky or another standard motion without making any reference to time. Time may have no independent existence, it may just be a common unit of motion making the world that is constantly changing easier to describe.
TIME CHANGE MOTION AND FORCES
Time is a real phenomenon a continuous change through which we live. Time becomes evident through motion; sunrise, sunsets, night and day, the changing seasons, the movement of the celestial bodies all are indicative of continuous change. The aging process is a reminder that molecular motion and interactions are also at work and are a part of the time. Another important aspect of time is the motion of particles like photon and the motion at atomic and subatomic level. An often overlooked but very important aspect of time is that forces also act in time.
Visualize two objects one moving in an orbit around the other. Now suppose from our distant observation point of a fixed time we observe time to get slower in the area where these two objects are moving. With slower time we expect to see slower motion? We also should observe proportionally weaker gravitational force; otherwise, the objects will get pulled together. If we observed faster time, we expect to see faster motion and stronger gravity to keep the objects from flying apart. While with zero time motion will freeze and gravity will become zero. As this thought experiment also can be extended to particles held together by electromagnetic forces we can say that time involves both motion and forces.
PERCEPTION OF TIME:
THE PAST THE PRESENT
AND THE FUTURE
The present is special; it is the gift of living and feeling the reality of existence. Our interaction with the world in the present creates our memories which then immediately become part of the past. We live in the changing present in which the future continuously unfolds. The present is a fleeting moment; whatever is happening now (present) is confined to an infinitesimally narrow point on the timeline which is being encroached upon by the past and the future.
Present resembles the sharp point of a recording laser or needle; it may be the mental awareness of recording of memory as it is being perceived and inscribed into our neurons. Unlike the present, we see past and future as a measurable duration of time. Past historical events, a meeting, or a wedding reception are all measurable duration or extensions in time, just like a recording on tape. This similarity suggests that the past is more like a recorded memory, while future can be compared to an unrecorded tape.
Another interesting observation pointed out by the philosopher Mc' Taggart was that historical events also have the same time characteristic as stories that are creations of the human imagination. Both stories and historical events contain the time concepts of earlier, the later, the past the present and the future suggesting that the past is nothing more than a memory of events.
Future appears to be a projection created by our past experiences stored in our memory. The fact that present which gives us the most realistic feel of time cannot be measured while inaccessible past and future can be measured as duration suggests that our perception of time as a place where we could possibly go, that is the dimensional view of time is an illusion.
IS THE BLOCK UNIVERSE
DESCRIPTION OF TIME CORRECT?
Every past or possible future event also has a place like feeling to it, as if it may be possible to go there. This dimension-like view of time has spawned numerous science fiction stories and movies on time travel. This view of time suggests that dinosaurs are still alive and roaming the earth in some other time dimensions; it also suggests that there are multiple copies of us and the whole universe smeared across multiple dimensions of time.
In Special Relativity (SR) the block universe view of time arises from an interpretation of the Lorentz transformation equation known as the Rietdijk-Putnam argument (or the Andromeda paradox.) By this innovation of SR, just walking on the earth toward or away from the Andromeda Galaxy which is 2.5 million light years away, we can shift our line of simultaneity so that our time can be in sync with either past or future of beings living somewhere in the Andromeda Galaxy. This interpretation of SR suggests that past and future exists as a part of the block universe.
Lorentz transformation is interesting but has not been proven experimentally and this interpretation of SR cannot be verified. Other SR predictions such as slowing of time and gain in mass with motion can be derived without Lorentz transformation and are experimentally verifiable. In the block-universe time is already laid out as multiple slices of time-scape similar to landscape and it is obvious that there cannot be free will. This has led to some innovations or variations in the theme of the block universe in which the future is changeable. If time-scape is already laid to an infinite future then what caused it to be laid out and what causes our conscious experience to move through this time-scape? also why we cannot willfully move our consciousness anywhere anytime?
The time concept of the block universe leads to some interesting conclusions. The universe should have numerous future civilizations millions or billions of years more technologically advanced than us. At least some of these civilizations should be capable of traveling through the block universe and we should have seen some evidence for that unless there is some law of the universe which prohibits time travel. Block universe also leads to the possibility of time travel paradoxes like the grandfather paradox in which a person travels to the past and kills his grandfather thereby changing the future so that the time traveler would not exist and thus not travel to the past to kill his grandfather.
THE INSTANTANEOUS BIG BANG ORIGIN OF THE BLOCK UNIVERSE
If the universe with its past, present, and future exists as a part of time-scape in the block universe. Then all of the time-scape from the big bang to the infinite future should have begun at the instant of the Big Bang.
The universe is thought to have originated in an event called the Big Bang about 13 billion years ago. We live in an expanding universe and the galaxies are receding from each other as a part of the universal expansion. Microwave background radiation which is a relic from the Big Bang has been studied by many NASA and European satellites. There is no doubt in the minds of physicists and astronomers that Big Bang occurred. Similarly, the concept of time being a block universe is considered a natural outcome of the Lorentz transformation. However, we seem to have overlooked that the concept of a block universe in which the past, the present and all of the future is laid out as a time-scape may be at odds with the origin of the universe in the Big Bang.
In the block universe view of time everything, every event exists simultaneously. If the universe from its beginning to its distant infinite future exists as a part of time-scape of the block universe then all of the time-scape from the big bang to the infinite future should have begun in the Big Bang. This basically means that all of the history leading to the infinite future was created in a flash at the time of the big bang. There is no escape from this conclusion unless we discard the block universe view of time or the origin of the universe in the Big Bang. These two concepts appear to be mutually exclusive.
SLOWING OF TIME IN
THE BLOCK UNIVERSE
Next time you look at a tall building or a mountain imagine that time is running more slowly even slightly so near the bottom of these structures than at the top. The stability of these structures depends on the fact that space-time is continuous between areas of slower and faster time. Being slow in time does not lead to lagging behind and disappearing into the past. Imagine if the bottom of a mountain or a building vanished into the past.
Theory of relativity predicts slowing of time with motion and gravity. These predictions have been confirmed in particle accelerators as well as gravity experiments. If there is a block universe why particles and masses with slower time do not disappear into the past? In gravitational fields space is clearly continuous between areas of slower and faster time. Black holes with their intense gravity that bring time to a screeching halt do not disappear from our present into the past.
We need to have clarity in our minds as to what slowing of time means in a block universe. Slowing of time without sliding into the past or the future suggests that time is a process and not a dimension and there is no block universe.
MOTION FORCES
AND THE ARROW OF TIME
Arrow requires two points in time that can exist only in the block universe. The time-scape in the block universe is already laid out and our conscious experience of time is only toward the future. The question, therefore, remains why arrow of time does not point toward the past? If future and the past already exist (as in the block universe) why we only remember the past and not the future?
Unrestricted by the block universe view of time we are free to consider time as a process so that there is no past or future only our perception of time which we call the present. If as shown earlier, time is the presence of motion as well as forces, then forces provide the necessary gradient for the direction of time. There is also a statistical touch to this argument; smashing a glass with a hammer means an application of force at one point while to assemble it back in reverse would require the coordinated application of multiple tiny forces in a reverse and continuous manner which is statistically unlikely. Similarly throwing a stone into a pond creates ripples which then travel to the edge of the pond.
To reverse this process it would require simultaneous application of multiple tiny forces at the edge of the pond to produce multiple synchronized waves moving backward to the area of splash where the stone pushed up by the ground at the bottom of the pond will be waiting to be thrown out into the hand of the thrower, a statistical impossibility. The direction of time in a block universe is difficult to explain as times-scape is already laid out and our conscious experience could have run in any direction. Without the burden of the block universe arrow of time is no enigma, it is just a process that is a natural outcome of a cause, effect, and probability.
SUMMARY
1. We measure time by comparing one standard motion like the suns movement across the sky against another motion like that of a car. Clocks are used as intermediaries for convenience. Time may not have any independent existence, the motion could have been compared directly suggesting that time is a process that is linked to motion.
2. Motion alone is not enough to explain time. Forces also appear to be part of time. Arrow of time is difficult to explain in the block universe where every event is already laid out. Arrow of time is however easily explained if we consider time as a process which includes motion as well as forces.
3. Perception of time as past present and future gives us the feeling of passage of time, as well as the block universe view of time. Time can be compared to recording devices, the present is just where the events and their perception is being recorded into our memory. The perception of time as a record is also apparent in the similarity of time characteristic of past present and future that exists in historical events as well as stories. The fact that the present which gives us the most real feeling of time cannot be measured while the inaccessible past and future can be measured as duration suggests that the way we perceive time is an illusion.
4. Slowing of time in motion and gravity does not lead to disappearance into the past as should happen in a block universe. Absence of time travelers from futuristic advanced civilizations is also against the concept of the block universe.
5. The concept of origin of the universe in the Big Bang is at odds with the block universe view of time. If the block universe which is supposed to be laid out as a time-scape (from the past to the present to the infinite future) exists and began in big bang then it would mean that all of the time up to the infinite future would come into existence in the instant of the big bang. To truly comprehend this, big bang should be renamed "Instantaneous big bang origin of the whole block." This idea is truly preposterous.
6. Slowing of time in gravity and in motion as well as the ultimate speed limit c provides the necessary clues to understanding the cause of time however we need to first convince ourselves that time is a process that is linked to motion and forces and the block universe view of time is not correct.
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