On our last day in Tokyo we went down to the Odaiba area. Great idea! Odaiba is basically Tokyo’s giant amusement park. In contrast to some of the narrow streets back in town, Odaiba is expansive, and has well-designed everything. There is the Museum of Emerging Science and Innovation. It has displays of robots, cat brains, the space station, genetically-engineered plants, model demonstrations of concepts from quantum mechanics, and best of all: a fully-working mechanical model of the internet.
Time is traditionally accounted for by counting periodic motion of a planetary mass in the solar system. One rotation of Earth is a day, one revolution about the sun is a year. In the current era, it has its progress tracked by atomic clocks, the principles of which is founded upon the periodic motion of subatomic particles. I recall learning at one point in school that the relevant international standard is based on energy transitions of a particular isotope of caesium, and identifying over nine billion periods of its radiation as one second.