Why not the standard dictionary definition of "7. Physics A region of space characterized by a physical property, such as gravitational or electromagnetic force or fluid pressure, having a determinable value at every point in the region." ?
... other than it doesn't exist, but it is observable and measurable : ) Is that a contradiction? Well not really, because you don't actually measure and observe the field.
By this same reasoning wouldn't you also say that distance does not exist? (I seriously want to know your response to this.)
And I think you are in error or at least sly in stating that we don't actually measure the field. We don't measure light, either, we measure it's intensity. (Or its frequency or polarization.) But that doesn't mean that it doesn't exist!
For that matter, we can't observe light either -- we only observe what it does to things it hits or otherwise interacts with.
Unless you're talking about a realm which entirely different from the standard realm (which which case you should say that 'There is simply no quick and dirty answer to what a field is in thus-and-such-a-strange-realm.' There certainly IS a very nice quick definition of what a field is in the normal realm.
Just like the fact that we don't observe light but it's effects, and we don't measure light but it's intensity, the same is true for an electric or magnetic field. In an electric field, the strength of the electric field can be measured at any point by the force that it exerts on an electron. Millikan of course used this in his oil droplet experiment. So how can you say that a field cannot be measured?
When you create a field it propagates at the speed of light to infinity.
I think you're being overly dogmatic here. For example, an electric field can be set up completely and entirely contained inside a metal enclosure. For example, if you welded shut a metal box with a 9v battery inside, there would be an electric field inside which would not propagate to infinity.
In other words when you look at the Sun, you are seeing it about 7 minutes behind where it actually is
Please help me out here. If the sun orbited the earth, I'd say you're right. But considering that the earth is rotating while being bathed in the sun's rays, I don't see how you can be right.
I remember well as a child playing in the summer with the garden hose. I would stand there and swing it back and forth as fast as I could, and I could see that the stream of water traveled away from me in a sort of arc. As I did this near a fencepost, I could see that by the time the water hit the post, I wasn't aiming at the post anymore.
But now imagine if I was just standing still pointing the stream of water at the post, but the post was turning -- an observer on the post, as soon as he comes around to my side, will see me exactly where I am because that's where I've been.
Please explain why the sun is about 7 minutes ahead of where it appears. (I honestly want to understand this one, too.) And this one shouldn't require QM, QED, or Relativity to understand!)
I think I know what your problem is. I'd say you think the sun orbits the earth and that you don't know what a field is :-)
Thanks,
-Jesse
From a photons perspective, distance does not exist nor does time. Distance and time contract as you approach the speed of light, they are variables.
And I think you are in error or at least sly in stating that we don't actually measure the field. We don't measure light, either, we measure it's intensity. (Or its frequency or polarization.) But that doesn't mean that it doesn't exist!
Certainly Light (photons) exist. I never said that they didn't.
So how can you say that a field cannot be measured?
Again, what are you measuring?
Please explain why the sun is about 7 minutes ahead of where it appears. (I honestly want to understand this one, too.) And this one shouldn't require QM, QED, or Relativity to understand!)
This is getting tedious, but I will make one last effort. Lets take your garden hose example, but instead of spinning you are in the back of a fire truck spraying the water off to the side as it speeds down the road. Objects that are close to the truck get sprayed almost immediately as the truck passes. Objects that are further away take longer to get sprayed. Now If I am the object that is close to the the truck and I point to the source of the water I am pointing at the truck. If I am farther away, when I get sprayed and point to the source of the water I will be pointing behind the truck.
It is exactly the same concept if the observer is spinning and you with the hose let out a single burst of water when the observer is facing you. If you are close you will hit the observer squarely between the eyes. If you are far away you will hit the observer on the back of the head. Now if you are shooting photons, the observer will 'see' you 180 degrees off from where you actually are.
Now can you try and answer the question? If you have a problem may I suggest turning to Feynman 12-4, Fundamental Forces. Fields.