7/8/22

I found this to be an excellent survey of how our conception of the universe has changed over the last couple of millenia, and how these shifts relate to technological change (in the instrument of the telescope).

The book is concise, erudite, entertaining and incredibly informative. However, I suspect that some scientific literacy is needed from the reader to get the most out of this work. Don't let that put you of though - I reckon the primary point of the narrative is forcibly established even without recourse to prerequisite knowledge.

I won't be parted with my copy. ( )

History of the telescope as it changed over time and changed science and the questions asked by science. Great topic, OK delivery.
Read Aug 2006 ( )

Panek claims that the telescope was “the first instrument ever to extend one of the human senses” (46 & 72). The book suffers from a lack of illustrations: when Panek talks about Galilean versus Keplerian telescopes, we ought to be able to see the difference. Panek traces the development of telescopes and what each phase meant to knowledge.
Almost immediately after its invention in Holland in 1608, Galileo began using and perfecting the telescope which came to be known by his name—with a convex objective lens and a concave eyepiece. Starting in 1609 he saw many more stars in familiar constellations, mountains of the moon, that planets were not pinpoints of light but disks, and that Jupiter had moons. Published Sidereus Nuncius (24 pp.) in 1610—the first evidence that Copernicus’s model of the solar system (1543) was correct. The telescopio was named at a dinner given for Galileo in 1611 by the Academy of the Lynx-Eyed. In 1613, Letters on Sunspots gave Galileo’s observations of the phases of Venus and his coming out for the Copernican model.
The Galilean telescope narrowed the field as magnification grew—Galileo couldn’t get it beyond about 30 diameters and couldn’t figure out the appearance of Saturn because of the telescope’s limitations. Kepler suggested a better design in 1611: let the the convex objective lens converge the light and then magnify it with another convex eyepiece.
Christian Huygens saw the rings of Saturn in 1656 and three years later pointed out that a measuring device—a micrometer—could be put where the objective image focuses before it’s magnified by the eyepiece. William Gascoigne had noticed this in the 1640s. Crosshairs were first used by Jean Picard in 1667. These were first steps to the measurement of size and distance of celestial bodies. They enabled first a more accurate measurement of earth’s size; then, by shooting a planet from widely separated places on earth, an observer calculated the distance of Mars, and, by extension, the distance of the sun. Once lenses had been perfected enough, from the distance of the sun observers used parallax to measure the distance to a star—two measurements six months apart from the extremes of earth’s orbit (1830s).
Newton theorized that a reflecting telescope would get past the aberration problem in lenses. William Herschel got a mirror up to 48 inches (silvered glass wasn’t invented until 1856, so the first reflectors all had metal mirrors) and discovered Uranus in 1781.
Once David Gill attached a camera to a telescope (1882), many more stars became visible, and new developments right up to the Hubble Space Telescope extended the number of galaxies (not just stars) from 10 to 50 billion (1996); then, when the team looked more closely at the data, to 100 billion.
In 1859, a spectroscope was used to determine the chemical composition of the sun; five years later, William Huggins’s spectroscope answered the question what a nebula was (one line in the spectroscope: gas) So the main questions about the stars (What are they? How far away are they? How many are they?) got answered. The next question—what are they doing?—took a hundred years. Huggins suggested in 1868 that light from stars moving away should shift toward the red end of the spectrum—a kind of Doppler effect of light. People began to notice such red shifts after the turn of the twentieth century. Then in 1929 Edwin Hubble observed that the farther away galaxies were, the greater their red shift—thus the faster they were going.
Just about the time the Palomar 200-inch reflector was going on line (1948), radio telescopes were just beginning—a branch of telescopy where the idea of seeing was expanded into the invisible range of radiation. This opened up telescopy looking for all kinds of electromagnetic radiation and the discovery of pulsars, quasars, and black holes. ( )