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 All physics is fields. I wouldn't even
 know how to do any calculation without
 fields. I mean essentially everything
 everything in modern physics relies
 on fields and they're extremely
 powerful exactly because you can
 describe a lot with just one field. 
 In physics a field is something very real.
 In fact for modern physicists fields are
 currently the correct point of view from
 which to understand the real world.
 Fields are quantities distributed
 through space and space-time where every
 point has a distinct value. For instance
 the temperature in this landscape is a
 field where every point in space has a
 temperature value. This is a scalar field
 because temperature is fully described
 by a single quantity. On the other hand
 wind is a vector field where every point
 has two values the wind speed and the
 wind direction. Because fields are
 represented mathematically they can be
 added or averaged together to give
 general views of the field like in this
 global temperature map or this one that
 shows wind velocities.
 Yet as useful as fields are they are far
 more than practical tools. The first time
 I actually managed to get a clear
 description of a field in my own mind is
 when I did an experiment of putting two
 magnets and all iron filings around
 it. So you can clearly see the lines of
 force because the iron filings are like
 test particles here which are following
 the field lines or the force lines in
 the field. So they orient themselves in
 these kind of patterns and you can see
 in the direction of their orientation
 the direction of how a test particle
 would move in the field. Even though we
 often represent fields as being flat
 objects spread out in space a field like
 the magnetic field created by this
 magnet occupies the space all around it
 as we can see if we pause this splash of
 iron filings midair. Or even more vividly
 in a spectacle of the Northern Lights.
 But what do modern field theories tell
 us about reality that older theories do
 not?
 In high school you don't see the reason
 the fields are useful and the reason
 they're useful is when you look at 
 things that are moving - we're always
 talking with static things when you're in high school
 and so that the useful
 difference is that if you move a
 charge and you ask - how do things
 respond to that motion that's where the
 field comes in. Now when we're figuring out
 what the fundamental forces are we are
 doing fields and nobody tries not to do
 fields. Fields are it. And so 
 we talk about fundamental forces but
 what we really mean are fundamental
 fields. Fields occupy space
 store and transfer energy and momentum
 and even curve space-time. Einstein's
 theory of general relativity is a type
 of field theory of gravity where the
 field is the degree of curvature in
 space-time created by the presence of
 energy or mass. It is a field theory of
 gravity that reflects reality in every
 way we've been able to test including
 the nature of black holes and how light
 bends around stars and galaxies. All of
 the different forces all the different
 interactions including electromagnetism
 and gravity and the weak and strong forces
 are mediated by fields which basically
 means that something happens here and
 then there is kind of a disturbance in
 the field that propagates at this speed
 of the field usually it's the speed of
 light. Quantum field theory uses fields
 to describe not only fundamental forces
 but it tells us that fundamental
 particles are oscillations of particular
 fields. So we can understand a field as a
 collection of vector points in
 space-time and then this collection of
 vector points of space-time will have
 collective excitations and then
 this collective excitations will have a
 particular energy and will have a
 particular momentum and as we know from
 our wave-particle duality we can
 describe a excitation which has a
 particular energy and a momentum as a
 particle. The field is really the
 fundamental concept and then the
 particle is one way of looking at the
 field - a force is another way of
 looking at fields there's not an dichotomy
 between forces and particles any more.
 And in fact quantum field theory is
 literally the most well-tested theory in
 all of science and all of its
 predictions have been shown to be true.
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