The two pendula (left and right) are identical, apart from their initial conditions (initial conditions are the way in which a system is started). The initial conditions for the double pendulum are the starting angles of each arm, and their initial speeds. The starting angles are the same in each case, but the initial speeds are as shown. |
Initial speeds, left: | Initial speeds, right: |
main arm = 400.0 degrees/sec | main arm = 400.1 degrees/sec |
secondary arm = 0.0 degrees/sec | secondary arm = 0.0 degrees/sec |
This is the so-called "butterfly effect" which is also often exhibited by the Earth's atmosphere. This makes it difficult to make medium-to-long term weather forecasts. |