As far back as I can remember, I have been deeply fascinated by boundaries between things – and you can generally find me where there are more than one boundary intersecting. In fact, you likely find yourself where different boundaries intersect if you really think about it.
The beach is pretty obvious for anyone as a place where there is a boundary between land and sea – something that I have puzzled over many times, from the whimsical observations of someone who has spent a lot of time at the beach, or even as someone dealing with navigational issues of vehicles that pass through those boundaries all the time. But there is more.
The beach is also a boundary between sea and atmosphere, and between land and atmosphere. It is a boundary between marine life and land life. It allows wonderful views of the evidence of our atmospheric boundaries with what we call ‘space’, with the bending of light on that boundary giving us beautiful colors at… other boundaries when the sun is either at the East or West of the horizon. And the horizon itself is also a boundary.
We treat the ocean and atmosphere separately, largely because studying how the ocean, land and atmosphere interact helps us understand weather. So, really, we have defined a boundary there. So let’s step back a minute. What do we mean when we talk about our planet? When we talk about Earth in this context, we are or should be encapsulating the atmosphere or all in it.
But I could argue that there is more. We have a moon – you may have seen it – and that orbits us, along with our increasing collection of space trash and future space trash. And the gravity of the earth follows an inverse square law as far as we know – it’s reach as far as the imagination can take us, with it’s strength being decreased over that distance. So too, every other object near and far, has that same gravitational attraction.
Suddenly, boundaries make less sense. Boundaries are our way of simplifying things so that we can understand them, but in the process, we tend to define things by their boundaries and forget about what is within the boundaries.