The currently accepted time standard is based on the period of oscillations occurring in the atom of the cesium-133 isotope during its transition between two specific energy sublevels of the ground state. By definition, a unit of time – a second – contains 9 192 631 770 periods of such oscillations. To establish the basic unit of length, the same standard is currently used: by definition, a meter is the length of the path traveled by light in a vacuum in 1/299 792 458 seconds.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.