Welcome to Part II of our story. The picture above shows Charles Greely Abbot reading his pyrheliometer. I enjoy pictures of how science was done in earlier eras!
The discussion and mathematical problems in the attached pdf file are from some course materials I used a while back. I thought it easiest to simply put it in pdf format so I didn't have to rework things to accommodate web format limitations. They illustrate Abbot's method in computing the solar constant. (In another part we will use Abbot's methods to calculate the Sun's luminosity and temperature.) We begin by giving the same example used by Abbot to describe his techniques. It shows his first step in determining the solar constant. He took data for just one wavelength through varying zenith angles as the Sun moved across the sky and was thus observed though varying thicknesses of the atmosphere. This was difficult, time-consuming work, and he repeated this step many times over many days (and years) for each of 44 separate wavelengths to get the Sun's total radiation curve.
I found it rewarding to sift through Abbot's reasoning. In my experience, the best way to learn anything in the history of science is to work through actual historical problems. So that is the method here, using Abbot's actual data. I've graphed results, too, as Abbot did.
I'll give you a heads up that there is some math involved! It is pretty straightforward, though, and if you take the time to work through it, you will be on your way to becoming an amateur solar scientist! So, brush up on your logarithms and have at it!
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