New adventures of Don Quixote

‘Somewhere in La Mancha…’

‘Where is that, father?’

‘In Spanish they refer to sunspots, son. They are the darker and non-stabilised regions of the photosphere. Their presence was noted by Galileo and their characteristics have been continuously studied. Their apparent movement on the solar disc has allowed the discovery of the Sun’s rotation. Their size is highly variable; they can become visible to the eye, and they offer a great variety of shapes. They take the form of one or several nuclei, very dark, surrounded by a wide, filamentary and radial penumbra. Moving on: in a place whose name I do not care to remember…’

[In the image: President Lincoln reading the Bible to his son, Tad, 1864.]