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.
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.
Our perception of passage of time makes us see the arrow of time. Once we know that there is no passage of time then the problem of arrow
of time is half solved. The other half is the wrong expectation that things may happen without cause. Also the question why we do not
remember the future but remember the past becomes redundant when we know that there is no such thing as passage of time. There is only
present and the memory of the observed present we call past.
In summary the arrow of time is due to presence of forces. Motion as well as forces are part of time. The action of forces across gradients sets
the direction of events. We recognize the direction because of experience.
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.
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.
Our perception of passage of time makes us see the arrow of time. Once we know that there is no passage of time then the problem of arrow
of time is half solved. The other half is the wrong expectation that things may happen without cause. Also the question why we do not
remember the future but remember the past becomes redundant when we know that there is no such thing as passage of time. There is only
present and the memory of the observed present we call past.
In summary the arrow of time is due to presence of forces. Motion as well as forces are part of time. The action of forces across gradients sets
the direction of events. We recognize the direction because of experience.
