Time is measured by changes, e.g. heartbeats count instants, moving shadows over a landscape mark the hours, and the births and deaths of our loved ones evidence the passing of the years. Periods longer than a lifetime are increasingly difficult to properly accommodate in our mental space. Indeed, while we describe art movements in terms of centuries, and millennia might give a framework to the duration of a civilization, a block of hundreds of thousands of years lies beyond the magnitude of our imagination. We need tangible changes to understand (how much) time passes. For this reason, when a paleontologist explains that 3.5 billion years elapsed between the first signs of life on Earth and the appearance of the Homo sapiens, we allow our mind to open to a new unit of time.

Similarly, it is difficult to grasp time blocks that are shorter than a heartbeat. Anything happening in less than a thousandth of a second falls under the wide label of “very fast.” But, how many degrees of “fast” are there? The flapping of a bee's wings, the scattering of the pieces of an exploding balloon, the functioning of modern chips, each of these processes is a thousand times faster than the previous, but all are equally indiscernible to our eye–brain system, which is limited to less than a few dozen images per second. However, there is a way of introducing ourselves as natural observers of the super-fast: splitting the whole process into still pictures. Each shot needs to record the entrance of light during a short-enough lapse of time, otherwise we would get a blurred image. Shots, moreover, should come up at a tuned pace, otherwise we would miss some relevant steps while the light is off. A stroboscopic lamp, for instance, with flashes of microseconds shooting at intervals of hundredths of a second, offers a clear sequence of the trajectory of an object as fast as a flying bullet.