Recursion

Recursion is a fundamental property of reality. The laws of physics operate on the present instant to produce the next. Although the progress of time from one instant to the next for us seem seems to be continuous but is not. There is some minimum time interval, probably near the Planck time. 

The resolution of the Ultraviolet catastrophe was to assume that there is a finite minimum frequency. Without that assumption, the energy would become infinite as the wavelength decreases to zero. Length, time, and energy all had to have some minimum quantity, called quanta. The size of the minimums just had to be finite - not zero. The size turns out to be some 35 orders of magnitude smaller than our familiar world. 

Some very simple recursive systems display complicated, even unpredictable behavior. Conway's Game of Life is an example well worth the time to investigate. If you want a deep dive into the concepts, I recommend a book, A New Kind of Science by Stephen Wolfram.