| ARROW OF TIME |
Presence of motion is the most obvious way time is perceived. Normally we do not think of forces as part of time. Once we incorporate
forces into our definition of time the solution to arrow of time becomes feasible. The direction of arrow of time is due to presence of forces with
a statistical touch to it .
Pure motion can be bidirectional. However forces create work against a gradient. Objects fall in gravity. Heat is applied to boil a kettle,
liquids mix, heat dissipates, and batteries lose charge.
The symmetry of time (T-symmetry) can be understood by a simple analogy: if time were perfectly symmetric then it would be possible to
watch a movie taken of real events and everything that happens in the movie would seem realistic whether it was played forwards or
backwards.
For example, a movie showing a cup falling off a table seems realistic when run forwards, but seems unrealistic if run backwards. On the
other hand, a movie of the planets orbiting the sun would look equally realistic run forwards or backwards; either way the orbital motions would
appear to conform to physical laws.
Events requiring a force to produce an action has a strong sense of direction.
Suppose I pick up a rock and throw it and see it fall. Now why I do not ever see a rock suddenly bounce off the ground fly up in the air and land
in my hand which is waiting open to suddenly grasp it. That does not happen as there is no force gradient in the reverse direction. The movie
of planet orbiting the sun looks realistic if run forward or backward as there is no force gradient involved in the different frames of the movie in
either direction.
A hammer smashing a cup of tea to pieces is a cause. While cup of tea spontaneously assembling into a cup and pushing up the hammer
is not cause and effect. This sequence we have learnt by experience that forces produce effects and effects do not usually produce a force.
For cup pieces to assemble into a cup is to expect forces to work against a gradient and motion to reverse without a cause.
Summary
Our perception of passage of time makes us see the arrow of time. Arrow assumes that two points one in future and one in past exists. If we
discard that concept and say only present exists then the arrow collapses to a point and the question why we do not remember the future but
remember the past becomes redundant. For arrow to exist you will have to believe in the block universe where past present and future all exist.
Forces are also part of time and give time its perceived direction. There is also a statistical touch to this argument. Smashing a china with
a hammer means application of force at one point while to assemble the china back in reverse would require application of multiple tiny
forces in reverse in a coordinated and continuous manner which is statistically unlikely. Similarly a stone thrown into a pond produces ripples
which then travel to the edge of the pond. To reverse this would require application of multiple tiny forces at the edge of the pond to produce
multiple synchronised waves moving backward to push the stone back up to the hand of the thrower a statistical impossibility.
forces into our definition of time the solution to arrow of time becomes feasible. The direction of arrow of time is due to presence of forces with
a statistical touch to it .
Pure motion can be bidirectional. However forces create work against a gradient. Objects fall in gravity. Heat is applied to boil a kettle,
liquids mix, heat dissipates, and batteries lose charge.
The symmetry of time (T-symmetry) can be understood by a simple analogy: if time were perfectly symmetric then it would be possible to
watch a movie taken of real events and everything that happens in the movie would seem realistic whether it was played forwards or
backwards.
For example, a movie showing a cup falling off a table seems realistic when run forwards, but seems unrealistic if run backwards. On the
other hand, a movie of the planets orbiting the sun would look equally realistic run forwards or backwards; either way the orbital motions would
appear to conform to physical laws.
Events requiring a force to produce an action has a strong sense of direction.
Suppose I pick up a rock and throw it and see it fall. Now why I do not ever see a rock suddenly bounce off the ground fly up in the air and land
in my hand which is waiting open to suddenly grasp it. That does not happen as there is no force gradient in the reverse direction. The movie
of planet orbiting the sun looks realistic if run forward or backward as there is no force gradient involved in the different frames of the movie in
either direction.
A hammer smashing a cup of tea to pieces is a cause. While cup of tea spontaneously assembling into a cup and pushing up the hammer
is not cause and effect. This sequence we have learnt by experience that forces produce effects and effects do not usually produce a force.
For cup pieces to assemble into a cup is to expect forces to work against a gradient and motion to reverse without a cause.
Summary
Our perception of passage of time makes us see the arrow of time. Arrow assumes that two points one in future and one in past exists. If we
discard that concept and say only present exists then the arrow collapses to a point and the question why we do not remember the future but
remember the past becomes redundant. For arrow to exist you will have to believe in the block universe where past present and future all exist.
Forces are also part of time and give time its perceived direction. There is also a statistical touch to this argument. Smashing a china with
a hammer means application of force at one point while to assemble the china back in reverse would require application of multiple tiny
forces in reverse in a coordinated and continuous manner which is statistically unlikely. Similarly a stone thrown into a pond produces ripples
which then travel to the edge of the pond. To reverse this would require application of multiple tiny forces at the edge of the pond to produce
multiple synchronised waves moving backward to push the stone back up to the hand of the thrower a statistical impossibility.
