 In this video, we'll introduce the concept of fields, which are very useful tools for many areas of physics. When we think about fields, we may think of something physical that has a value at every possible position, or we may think of some nice grass with maybe a few sheep. Let's go on with the second thought. On our field, there may be several woolly sheep that are happy and randomly oriented enjoying their grass meal on their patch of grass. Now let's imagine that some hay mysteriously appears in the sheep field. Sheep love hay, so I'm told, so they get very excited. The sheep that are closest to the hay can see and smell the hay the best, so they really, really want to get to the hay. Sheep that are further away can't smell the hay as well, so they want the hay, but not as much as the sheep that are closer. Now, let's take away the sheep, and instead imagine how much a sheep would want the hay at each point on our field. Closer to the hay, as we saw earlier, the sheep will want the hay more. If we include a second hay bale, we can imagine that sheep closest to the second hay bale are more likely to want to move toward that hay bale, unless the first hay bale is much bigger and juicier. So, as you may have guessed, we've just described a field. The sheep's desire to go and eat hay is that something physical, and how much and what direction the sheep want to move to the hay is the value. At every possible position on our grassy field, there is a value for where and how much a sheep will want to move to eat hay. Fields can be scalar fields, which have a single number or scalar value at every point, or they can be vector fields. As you might expect, vector fields therefore have a vector at every point. You'll be shocked to hear that I haven't commonly heard of physics research related to sheep's desire to eat hay being made in fields. In physics, something physical that has a value at every possible position is more typically useful when applied to pressure fields, electric fields, magnetic fields, fluid flow fields, and gravitational fields, which is what we'll be looking at in more detail.