Biorhythm Graphs

by M. Bourne

Biorhythms may not be very scientific, but it is true that on some days we are full of energy while on other days we find it difficult just getting out of bed. Biorhythms try to explain this by considering the interplay between three cycles: emotional, physical and intellectual.

When a particular cycle is high, it means it is easy to do well in that area (for example, if our intellectual cycle is high, we will do better in examinations). But if we are in the low part of a cycle, it is difficult to do well (we may have more arguments if our emotional cycle is low.)

biorhythms

At birth, each cycle is at 0 (neither positive nor negative). The cycles have different length:

In this Flash interactive, enter your birthday at the top and you can see what is happening in your own emotional, physical and intellectual cycles. It tells you when your "fortunate" and "unfortunate" days will occur. You can also use it to figure out why your friend (or mother) is crabby today!

Loading Flash movie.

Flash source: ztor.com.

These biorhythm cycle graphs are sine curves with the same amplitude, but varying period.

To obtain the graphs, we use:

It is not clear in the Flash interactive how "fortunate" and "unfortunate" days are determined. One possibility is Composite Trigonometric curves, which we meet later. We could add the y-values to give the following (for day 100 to day 150):

biorhythm composite curve

We see that near day 130, all the cycles are against us and we will probably have a terrible day. Two weeks later, near day 145, everything is coming together nicely and we should have an excellent day.

That composite curve (in gray) is the sum of the 3 cycles:

y = sin(2π/23) + sin(2π/28) + sin(2π/33)

It does not appear that the Flash interactive adds ordinates like this.

Disclaimer

I repeat...

Biorhythms are not scientific. However, they are an interesting example of sine curves with different periods.



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