You, me, and everything we generally think of as reality exist on the macroscale. It’s the arena where our senses make sense, where we live our lives and where we can have some intuitive understanding of the world around us. To put it a bit more technically, it’s the arena where things are continuous. Continuity is a big point here so it is worth elaborating for a moment. From my perspective, lounging in the lobby at O’Hare airport waiting for my flight back to Akron to board, the wall across from me is a solid object. It’s a dull blue affair with some errant texture and a light gloss, but for all intents and purposes, I know that it is a solid slab of gypsum with a layer of low quality paint tossed on top by a team of union contractors – 3 to paint, 2 to inspect, 2 to oversee, and one to oversee the overseers, with a few trainees tossed in for experiential learning. I know that if I took a piece and broke it in two, it would largely be the same material. The gypsum would crumble in my hand, but one piece would largely resemble the other. From an engineering perspective, the properties of one piece would be the same as the other, and just the same if we broke the piece down again. Each piece would have the same hardness, the same stiffness, the same strength, the same color, and so on. I could even toss it under a microscope and see the structure in finer detail, but everything would remain independent of size. No matter the size of the piece, it will all be the same regardless, excepting some massive quality control issue that caused a big variation over a larger area.
The pieces that I see and interact with are on the macro-scale. The features I see under a microscope are the micro-scale, and they might give me some idea about why the macroscale behavior is a certain way. Perhaps there is a trace red hue that periodically pops up on the microscope due to an impurity when the paint was mixed. That might be the reason why there is a glint in the color depending on the angle I observe the wall at. Still, nothing too shocking or interesting.
The nanoscale is where things get interesting. In a bureaucratic sense, the nanoscale is usually defined by the nanometer, which is one meter finely divided into 1 billion little pieces. For those of us red-blooded Americans that believe in truth, freedom, and the American system of units, that’s about 25 million inches or 25,000 mils (thousandths of an inch). If it is easy enough to find, I will toss in a nice graphic showing different things at different scales [edit: done!]. A hobbit, for example, is one of the few things that are right at the meter mark (see the attractiveness of feet – they mean something!).
The nanoscale is usually used to differentiate objects that are below 100 nanometers. The problem is that 100 nanometers is meaningless. There is no difference between something that is 99 nanometers and 101 nanometers, in a practical sense. The definition that I prefer is that the nanoscale is the point at which things stop behaving like they should – where the behavior we are familiar with in the “bulk”, macro-scale starts changing. One big problem with this definition is that the length scale of importance depends on what bulk behavior you are interested in, and sometimes also on the rate of testing (viscoelasticity is a great can of worms relevant here). The reason I like this definition is because the potential of nano-science and nano-technology becomes more clear. If we can control the features on a size scale where things start behaving in different ways, then we can start developing new materials and new systems that can do things that conventional materials can’t. We can have colors that never fade over time, or that change given certain stimuli, or that interact with light in a way that aren’t even visible – the famed invisibility cloak at long last. And that is just the start, but I’ll pull back for a minute, catch my breath, and start anew with some more grounded examples.