Periodicity in Nature 1

• Periodic phenomenon: one that repeats itself at regular intervals
• Examples of periodic phenomena in nature
  • Day/night cycle (rotation of earth)
  • Season (revolution of the earth)
  • Tides
  • Pendulums and other swinging movements
  • Ocean waves
  • Birth/marriage/death cycle
  • Menstrual cycle
  • Eating and sleeping cycle
  • Heartbeat and breathing
  • Locomotion (gaits)
  • Animal calls
  • Musical rhythm
  • Linguistic rhythm
  • Dribbling, juggling
  • Calendars
  • Fashion cycles, for example, skirt lengths or necktie widths
  • Economic and political cycles, for example, boom and bust economic periods, right-wing and left-wing political tendencies
• Every periodic phenomenon involves
  • One or more variables which characterize the repeating phenomenon (displacement, speed, light intensity, pitch, loudness, wakefulness, necktie width)
  • A period (T): the length of time required for one repetition of the process (one cycle); a frequency (f), the number of repetitions (cycles) per unit of time
    f = 1/t