Wednesday, April 27, 2011

Action and Reaction Revisited

Do we do Action which is followed by Reaction or vice versa or they both happen at the same time?
Usually, when we push an object (i.e. Action) we immediately feel the Reaction so the the answer should be that they happen at the same time. Thus the question looks trivial. But further analysis shows this questions isn’t as trivial as it had seemed.
What happens when two interacting objects are at a distance? Like electromagnetic interaction between two objects in the space.
Let us assume an object A emits light towards an object B which is far away. The light emitted will take some time to reach the object B to act on it. So it would be expected that after the light reaches B, it would take the same time for the reaction to act on A. BUT the moment the object A emits light it would experience an opposite push and after some time the light will act on object B! Thus in reality there is an Advanced Reaction! That is reaction is experienced before the action!
This Advanced Reaction has many consequences.
Let us take the example of Gravitational attraction. The gravitational force too would travel at the speed of light and reach the other object after some time. The force F between two objects having mass M1 and M2 separated by a distance of R is given by
  gravity
There would be a force of attraction between an object A and the different objects in the entire universe. Even though the distances between the far away objects maybe humongous still the reaction will be immediate! It does not matter how far an object would be, the object A will get immediate reaction from all the bodies in the universe irrespective of their distance! This immediate reaction can be in turn be used to measure the mass of the universe!
But still an question pops up!
What if a massive  object pops up in space from nowhere? Will it immediately experience the gravitational force from the entire universe or as the gravitational force takes some time to reach the other objects in the universe, the reaction will be delayed?
I guess the reaction from the entire universe will follow instantaneously after the object spawns! This would mean that there is a passive field in the space due to all the massive objects of the universe. The outer boundary of this field will enlarge with time! The reaction on the object will be instantaneous even though its action on the universe will take some time!
Similarly if the Sun disappears from space into nowhere its action will be felt by earth after some time! Earth will continue in its orbit even after 8 mins (i.e. the time light and gravity takes to reach earth).

4 comments:

  1. This immediate reaction can be in turn be used to measure the mass of the universe!,The outer boundary of this field will enlarge with time! Saurabh Misra kya matlab hai in dono statements ka?

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  2. Well the statement that this immediate reaction can be used to measure the mass of universe means that you get the information about the mass of the universe instantaneously through gravity. BUT the information about the mass you get through this technique will be as old as light or gravity takes to travel here.
    and suppose if a new massive object originates from nowhere ( this is possible as 1 particle of matter and 1 particle of anti-matter can come out of nowhere and both experience gravity exactly the similar way) the outer boundary inside which other particles will experience gravity will increase with time. Take an analogy, in the middle of space a bulb is lighted. Then the outer boundary inside which the others can see it glowing will increase with time as light will travel outwards at a finite speed. The same is with gravity! objects will experience gravity the way it will experience a lit bulb!

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  3. This comment has been removed by the author.

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  4. he best post so far...but if only you consider advanced or delayed reaction..but it does explain the 2nd part of the post...

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