Theory of relativity (SR) holds the key to the phenomenon of time, yet more than a century has passed since publication of SR without any significant progress in understanding of what really is time.
“Till Death Do Us Part”
The stark reality of time is in the grief which death of a loved one brings; the time in life which we would rather have as an illusion. We feel the passage of time in the present which is flowing into the memories of the past as we venture into the unknown future. Present is the most real perception of time however almost all of what we perceive as the present is already past.
The present is a fleeting moment; whatever is happening now (present) is confined to an infinitesimally narrow point on the time line which is being encroached upon by what we think of as the past and the future. Present resembles the sharp point of a recording laser or needle; it may be mental awareness of the recording of memory as it is being inscribed into our brain. A person goes to an event but falls asleep would have no recollection of it as if the event did not exist in his past. Unless we are consciously aware of an eventit does not seem to enter our past memory.
Unlike the present we see past and future as measurable durations of time. Past historical events, a meeting, or a wedding reception, are all measurable durations or extensions in time, just like a recorded material on tape. This similarity suggests that past is just a recorded memory, while future can be compared to an unrecorded tape. Historical events have in them the same time characteristic as stories that are just creations of human imagination. Both contain in them the time concepts of earlier, the later, the past present and the future; this again suggests that past really is similar to memory of events.
Future appears to be a projection created by our past experiences stored in our memory. The fact that the present which gives us the most real feel of time cannot be measured while the inaccessible past and future can be measured as durations strongly suggest that the way we perceive time is an illusion.
TIME AS A BLOCK UNIVERSE
"People like us who believe in physics know that the distinction between the past, the present and the future is only a stubbornly persistent illusion" Albert Einstein
Every event in time has a place like feeling to it, giving support to the block universe view of time in which time is fixed and laid out like a time-scape. In the block universe past, present and future exist together superimposed in different dimensions. This view of time suggests that dinosaurs are still alive and roaming the earth in other time dimensions; so are multiple copies of us and the whole universe. This view is reinforced by Einstein’s General Relativity (GR) in which time extends as the fourth dimension from the past to the future. Lack of simultaneity in Einstein's SR and an interpretation of the Lorentz transformation equation also promote this view to explain the Andromeda paradox as an alternative reality existing in a different time dimension.
Time in the block universe is laid out as time-scape similar to landscape; future and past already exists and there cannot be a free will. Even in the smallest duration of time in a block universe there should be infinitenumber of copies of everything including the whole universe. Block universe leads to a few problems and paradoxes. How do we explain the origin of universe as all parts of the block universe exist all the time? If there is a big bang in block universe then even now it exists. If time-scape is already laid out then what causes us to move through this time-scape? How does our consciousness move across time? What makes it move and why we cannot willfully move it anywhere anytime?
If concept of block universe is correct then there should exist future civilizations millions or billions of years more technologically advanced then us. At least some of them should be capable of time travel. We should have seen some evidence for that, unless there is some law of the universe which prohibits time travel. Then there is the possibility of time travel paradoxes including 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.
MEASURING TIME: THE SUNDIALS
One of the earliest devices to measure time was sundials; which used suns motion as a standard of measurement for time. The use of units like seconds and minutes which are radial angle measurements in geometry points toward the original connection of time measurements to radial motion of astronomical objects across the sky. Once we started using accurate time keeping watches, clocks and digital devices capable of independently measuring time we lost the celestial connection of time and time developed a life of its own.
When we measure the speed of a car, we are just comparing its motion to the motion of the hands of the clock and also indirectly to the fractional motion of sun across the sky. 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 speed of light, how fast heart beats or how frequently earth spins around its axis. But these processes could be compared directly without making reference to time. Time may have no independent existence it may be just a common unit of motion making the world that is filled with motion easier to describe.
TIME CHANGE AND MOTION
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 is indicative of continuous change. The aging process is a reminder that molecular motion and interactions are also at work and are a part of time. Other important aspect of time is presence of motion of particles like photon and the motion at the atomic level.
Imagine two objects one moving in orbit around the other in space. 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. 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.
The increase or decrease in strength of gravity is only in relation to our fixed time from where we are making the observation. From the point of view (time) of the orbiting objects neither motion nor gravity has changed. 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.
IN SUMMARY: TIME HAS MANY FACETS
Time is a real however it has many facets and it may not be possible to nail down our perception of time to one phenomenon. We feel the flow of time from the unknown future to the fleeting moments of the present and in the memories of the past. The flow of time persists in stories and recorded historical events suggesting that past is just a recorded memory. The present which gives us the real feel of time cannot be measured while past and future have measurable durations comparable to recorded and unrecorded tapes again suggesting the connection of time to memory and that the feeling of the passage of time is an illusion. Measurement of time seems to involve comparing a known motion with an unknown motion. The feeling of flowof time possibly emerges as our mind tries to make sense of the world filled with motion and change. Time ismost likely is a concept created by our mind by merging consciousness, memories, anticipation, perception,change and motion. There however is a real underlying process and there is a cause for this process the exposition of which will bring us to a better understanding of the phenomenon of time.
IDEAS THAT CAN HELP IN THE UNDERSTANDING OF TIME
The road to understanding time is relativity and the concept of time dilation is an important milestone. To find out the cause of time we need to know why time slows in motion and around large masses. One of the most dramatic aspects of the universe is that it is expanding and the presence of motion, forces and curved space-time happens in the expanding space. Conceptually it is easier to derive space curvature in an expanding universe as an area of slower expansion. This is one of the crucial concepts that were missing from Einstein’s vocabulary till many years after he developed GR. Einstein’s GR with the universal force of gravitation predicted that universe could not be static; it has to be either expanding or contracting. Einstein however introduced a fudge factor in his equations to keep the universe from expanding or contracting choosing a static universe.
Michelson and Morley experiment demonstrated that the speed of light is unaffected by the motion of the earth. If light moved in a fixed background of space or aether then the constancy of the speed of light was inexplicable unless large masses completely dragged aether. Presence of such a medium through which huge planetary and solar masses could move with perfect ease cannot be explained. Einstein did away with this issue by calling ether superfluous, however GR brings suspiciously ethereal terms such as warping or curving of space, black holes in space and frame dragging back into mainstream physics; it appears that we have just changed the name of aether to space.
The constancy of the speed of light, lack of simultaneity and the Lorentz transformation equations lead to the block universe interpretation of time. It can be easily demonstrated that Einstein’s famous time dilation equation the Lorentz factor actually depends on the preservation of simultaneity therefore Lorentz transformationequation in its present form is not correct. This point will be discussed in detail later. Einstein believed that acceleration was the cause of time dilation in moving objects as this is the main difference that can be seen between travelling and stay home twin in the famous twin paradox thought experiment. Einstein equated acceleration in gravity with that in accelerated motion in his famous equivalence principalbringing time dilation into gravity. It is clear however from particle accelerators that acceleration plays no role in time dilation of moving particles. Time dilation in motion can be precisely calculated with velocity only; similarly gravitational time dilation can be calculated from escape velocity and not necessarily from gravitational acceleration.
We do not need particle accelerators to tell us that acceleration cannot be the cause of time dilation. In twin paradox thought experiments the acceleration and deceleration of the travelling twin can be made brief or instantaneous and then the only difference between the two is the uniform velocity of the travelling twin. One of the reasons for the existence of the twin paradox is the insistence of SR that rest and motion are the same and motion is only relative however presence of centrifugal force in rotating objects suggests that motion and rest are not equivalent.
Discovery of cosmic back ground radiation; zero point energy along with space curvatures of GR makes it difficult to think of space without some sort of structure. The other side of the coin is the ease with which massive objects move through space with zero resistance, and the constancy of the speed of light in moving objects like earth. Any new development in relativity will have to reconcile all these difficulties and precisely show it to be superior to relativity while keeping the predictions of relativity. Many unnecessary concepts in relativity have hampered the true understanding of time. The answer to this conundrum lies in the simple ideas developed by Lorentz, Einstein and others of his time.
Author has submitted an article with the following title:
" MOVING OBJECTS ALSO CURVE SPACE EXPLAINING LENGTH CONTRACTION, TIME DILATION AND OTHER PREDICTIONS OF RELATIVITY" to “PHYSICS ESSAYS” for publication.
This article builds basis for the understanding of time by clearing up incorrect concepts in relativity and removing paradoxes and problems. It will take them from 3 to 4 months to publish it on line. Please come back and check for a link to the article.
More powerful than all the armies of the world, is an idea whose time has come. ........Victor Hugo