There are many approaches toward understanding the phenomenon of time. We perceive time as past present and future. In
physics time plays a major role in measurement of motion and forces. Einstein’s relativity introduced the concept of slowing of time in
motion and gravity.
MEASURING TIME: THE SUNDIAL
One of the earliest device to measure time was sundial 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 measuring time independent of the celestial connection 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.
|More powerful than all the armies of the
world, is an idea whose time has come.
We perceive time as past present and future. We relate events to places as well as time; this gives us a feeling that time is
more like a place and gives support to the block universe view of time. 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 the mental awareness of recording of memory
as it is being inscribed into our brain. A person who 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 event it does not seem to enter our past memory.
Unlike the present the past and future are 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 the 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
suggests that the way we perceive time ( present-ism or the block universe view ) is an illusion.
1 We measure time by comparing one standard motion against another. Time may not have any independent existence.
Time and clocks are used for convenience. The motion could have been compared directly.
2. Motion alone may not be enough to explain time. Forces also appear to be part of time. Arrow of time may be explained by
presence of forces.
3. Perception of time as past present and future gives us the illusion of the passage of time as well as the block universe
view of time. Above it is shown that this perception may just be an illusion and time is more like memory and recording devices.
The similarity of time characteristic of past present and future in historical events and made up stories also suggests that our
perception of time is an illusion and this aspect of time is also like a record.
4. Slowing of time in motion and gravity does not lead to disappearance into the past as should happen if there was
block universe. Absence of time travellers from futuristic advanced civilizations is also against the concept of the block universe.
The block universe of time in physics derives its support mainly by lack of simultaneity and Lorentz transformation
equations which we will examine next.
WHAT IS TIME AND WHAT CAUSES TIME?
1. "Time!" What are we really measuring?
2. Time motion and forces.
3. Perception of time as past present and future.
4. Time memory and recording devices.
5. Block universe and time in historical events and stories.
6. What to expect when there is slowing of time in the block universe?
7. Forces in addition to motion and probability can explain the arrow of time.
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 infinite number 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 in time 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.
SLOWING TIME IN A BLOCK UNIVERSE
TIME 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 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 forces to keep the objects from flying apart. While with zero time motion will freeze and force
will become zero. The increase or decrease in strength of forces 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 force 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.
PERCEPTION OF TIME: PAST PRESENT AND FUTURE
Theory of Relativity predicted slowing of time with motion and gravity. These predictions were soon confirmed in particle
accelerators and gravity experiments. Twin paradox discussions may have served as a distraction from obvious question that
arises; 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. Slowing of time without sliding into the past or the future suggests
that time is a process and not a dimension. This may be a significant point against the block universe view of time when taken
together with other aspects of time described on this page. Block universe derives its support from Lorentz transformation equations
which have never been proven experimentally.
MOTION FORCES AND ARROW OF TIME
Arrow requires two points in time that can exist only in the block universe. Arrow assumes that the two points’ between past
present or future exist, it also assumes that time only involves motion. Presence of forces as a part of time changes this equation as it
provides the necessary gradient for the direction in time. There is also a statistical touch to this argument; smashing a glass with a
hammer means application of force at one point while to assemble it back in reverse would require 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 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.
Time presents to us in numerous ways which possibly creates difficulty in understanding this phenomenon. We are immersed in
time yet we do not fully understand it. We know that time is closely linked to motion as well as forces. Theory of relativity introduced
the concept of slowing of time with motion and gravity. This breakthrough could have led to further progress in understanding of time
and possibly the cause of time however almost 100 years have passed without substantial progress.