# Force in field? Why isn't it constant?

1. Jul 6, 2013

### Wiz700

Distance is a key variable with fields, however, why is it, in any field(Gravitational,Electric,Magnetic) as "d" increase, F decrease substantially?

Why can't the force x, be constant all around the field. Amazingly, the force is different at each value of d, well in most cases its zero when d is a large number.

2. Jul 6, 2013

### DiracPool

Because its not. Why would you want it to be that way, anyway? The falling off of the strength of the field as the square of the distance is literally what makes the world go round. Atoms wouldn't exist, tissue wouldn't exist, WE wouldn't exist. (I'm starting to sound like a discovery show commentator now :tongue:). Try building a computer simulation of your suggested universe and see how things turn out once you hit "run." Then you'll know why the 1/r^2 law is fine just the way it is.

Well, technically, it is never zero, but it does get vanishingly small pretty fast.

3. Jul 6, 2013

### WannabeNewton

You are thinking of specific field configurations (the Newtonian field, Coulomb field, and magnetic field due to a current wire respectively). The electric field due to an infinite charged plane is uniform, the gravitational field within the Earth is approximately uniform, the magnetic field within an infinitely long current solenoid is uniform etc.

4. Jul 6, 2013

### ShayanJ

Well...DiracPool and WannabeNewton mentioned good points...but I think I still can add sth.
As the last post says,not all fields have the same spatial behavior...and for everyone of them,you can ask why it is like this....and for all of them,there is only one answer:because of the equations governing the fields! And more or less,those equations are determined by experimental data and more fundamental theories.