To date, Google Books has scanned 50,000 books from the 16th and 17th centuries. And by working with great European libraries (Oxford University Library and the National Libraries of Florence and Rome, to name a few), the Mountain View-based company expects to index hundreds of thousands of pre-1800 titles in the coming years.
Traditionally, most historical texts have been scanned in black & white. But these newfangled scans are being made in color, giving readers anywhere the chance to read older books “as they actually appear” and to appreciate the “great flowering of experimentation in typography that took place in the 16th and 17th centuries.”
Some of the foundational texts now available in color include Nostradamus’ Prognostication nouvelle et prediction portenteuse (1554), Johannes Kepler’s Epitome Astronomiae Copernicanae from 1635, and Galileo’s Systema cosmicum from 1641. All texts can be viewed online, or downloaded as a PDF (although the PDF’s lack color)…
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FYI, Galileo’s book is not entitled “Systema Cosmicum”. It is really the fourth part of “Dialogue Concerning Two Chief World Systems”
FYI, Galileo’s book is not entitled “Systema Cosmicum”. It is really the fourth part of “Dialogue Concerning Two Chief World Systems”
Galileo’s law of falling bodies v^2=d is the same as Kepler’s distance law v^2=(1/r). The reason for this is that there are two ways of measuring the same velocity, distance per unit time and time per unit distance, with one measure being the reciprocal of the other. In its elliptical context r+d equals the major axis a constant.
Further to my previous comments, the connection between Galileo’s v^2=d at the empty focus end of the elliptical orbit and Kepler’s v^2=1/r at the Sun focus end is mathematically very interesting and not at all straight forward. Kepler’s version can be adapted for further research purposes by including a constatnt V being the maximum velocity, then the variable velocities can be expressed as V/#r where # is my notation for square root. In this way the same velocity arises on both the accelerating side as well as the decelerating side but in opposite directions. As one of the properties of all perfect ellipses d is the distance from the curve to the empty focus, and r is the distance from the curve to the Sun focus. d+r equals the major axis of the elliptical orbit which I will call A. As a matter of further mathematical interest A/V equals #(r/d) +#(d/r). Just as the variable velocities at the Sun focus end can be expressed as V/#r so the variable velocities at the empty focus end can be expressed according to Galileo’s formula as #d=v where d is the distance from the empty focus to either side of the elliptical curve.
Kepler liked to base his mathematical ideas on the ancient Greeks. This is particularly evident in his little known paper Concerning Conic Sections, part of his book on Optics published in 1604. Kepler supposed that geometric shapes which were conic sections would all have focuses, a concept which he invented and described as being constructed by pins and thread. At first Kepler failed to recognise that foci depended on symmetry not conic sections, and was therefore completely wrong about the connection with conic sections. A more symmetrical shape would be cylindric section an expression which Kepler never uses. However in 1618 Kepler at last found a constructive application for the focus namely as the location of the Sun in the symmetrical planetary orbits, giving rise to Kepler’s distance law which applies throughout the whole universe.
A cylindric section has two foci (f) which relate to the half axes (a and b) as follows f = a -(a^2 — b^2)^(0.5). Kepler recognised that this formula could probably be constructed by pins and thread in his little known work of 1604. A slightly less accurate version of this formula can be used for ellipses. Very few astronomers seem to be aware that an axis can easily be calculated if the other axis and the focus are known.