Was ist Zeit? - Das ewige Rätsel.

Even if we don't understand Einstein's theories, we can all see empirically that the way we think about time depends on the way we occupy it. At the end of the 19th century, French philosopher Paul Janet, for example, explained the widespread feeling that time accelerates with age. In 1962, French speleologist Michel Siffre spent two months 130 meters underground in total isolation and succeeded in demonstrating that the human internal clock moves much more slowly than their supposedly objective measures of time. Today, these are based on extremely precise instruments, such as the atomic clock at the Paris Observatory, with its 9 billion 192 million 631,770 oscillations per second. The latest in a long line of scientific achievements.