This site (http://htwins.net/scale2/
) lets you zoom in and out on the universe, from the smallest possible length (the Planck length, the basic unit cell size of the universe) to the largerst. (The size of the universe itself) It's tremendous fun, and it looks like it's been improved some lately so that it's smoother to play with.
Three things really struck me while playing with it. First is that there is a largest and smallest thing on this scroll that was built by humans: the distance from Voyager I to the Sun on the large side, and a Buckyball on the small side. In a way, this illustrates the full range of human capabilities to probe the large and the small.
Second is that when you zoom out, you keep seeing more and more structures at each size; but when you zoom in, you'll find yourself scrolling through a very long desert, from the sizes of the smallest known particles (top quarks) down to the Planck scale, where there's simply nothing. This is the realm where we simply don't know what's there: one of the tasks of high-energy physics is to figure that out. We simply don't yet have the ability to even see
the stuff, much less build anything. It's quite possible, for example, that we'll discover that at one of these scales the universe's nice, simple, four-dimensional structure will fall apart, and we'll discover that we're actually living (for example) stuck to being within some short distance of a four-dimensional wall that lives in a much bigger universe.
The third thing is that one of the entries is "the total distance the Earth has traveled about the Sun." It's obvious that such a distance exists and could be worked out, but somehow it had never occurred to me before to think about the total odometer reading on the planet. (About 450,000 light-years, or about four times the diameter of the Milky Way, if you're interested)
Also, did you know that the Minecraft world is about the size of Uranus? I didn't know that.
h/t +Betsy McCall
for the link.