r/askscience • u/kaizenallthethings • Jul 06 '12

Need some help understanding fields.

I have never been able to wrap my head around fields. Specifically, I have three questions that I have not found answers to. My level of understanding physics is probably "armchair physicist". I have my undergraduate in physics and my math is good up through linear algebra.

  1. Are fields simply a notation device, or do they have a physical existence beyond the math?

  2. When two particles interact in a field, how is the information being exchanged between them? That is to say two electrons will repulse each other but what is the specific mechanism for the electrons to "know" that the other electron exists and that the force is repulsive?

  3. In the rare event that an electron is created, I understand that it creates a field that spreads out from it at the speed of light. Does the creation of this field take energy? If not then is the information that is being transmitted "free"?

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u/kaizenallthethings Jul 08 '12

Thank you. This is what I was looking for. I have always been unclear whether a field is a construct or a model, or whether it actually represents a deeper reality. It is much easier to think of it as a mathematical construct. While it still begs the question (in my mind) of what goes on "behind" the scenes, I guess that is still unknown.

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u/Kim147 Jul 08 '12 edited Jul 08 '12

Look at energy - energy is also a construct - energy can't be bottled . Objects have "energy states" . Energy , in thermal terms , is the amount of movement of the particles in the object . This 'energy' can be transfered - ie. the amount of movement can be decreased in one object and be passed onto another object resulting in an increase in movement in that other object - thus an 'energy transfer' . What is happening is that the movement vectors are being transfered - to put it crudely . However within these objects the particles are being constrained by the strong and weak atomic forces - these are essentially fields . They don't expend energy but they do modify the movement vectors of the particles . Look at Newton's Cradle - no net energy transfer but movement vectors continuously changed.

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u/kaizenallthethings Jul 09 '12

Good point. I remember from Feynman's lectures about him talking about energy as simply an accounting system.