Light and Dark: An exploration in science, nature, art and technology
Format: PDF / Kindle (mobi) / ePub
An entertaining, instructive, diverse, and unusual book, Light and Dark: An Exploration in Science, Nature, Art and Technology encompasses a wide range of topics not normally found in one book.
With more than 100 diagrams, graphs, and figures, the subjects discussed include the history of artificial lighting, eclipse cycles, light-sensitive eyeglasses, rainbows, art, bioluminescence, the clock setting at the South Pole, zebra stripe patterns, lighthouses, color perception, the harvest moon, and how information and speech can be conveyed by light from the sun or a laser.
The book encourages readers to take a more careful look at many familiar phenomena, such as the variations in the duration of twilight through the year and the ability of human vision to misinterpret patterns of lines under certain conditions. It describes the anatomical peculiarities of four-eyed fish and explains how the Jewish calendar contrives to follow both solar and lunar cycles. It also presents the reasons why tortoise shell cats are almost always female. Readers are informed where they can see 19th century military equipment that could convey messages rapidly over vast differences.
equinoxes to somewhere near their dates at the time of the Council of Nicea. The outcome of the discussions was a bold and drastic change. Pope Gregory decreed in 1582 that ten adjacent dates should disappear, so that the day after Thursday 4th October became Friday 15th. To maintain the equinoxes at the required dates, he announced shortly afterwards that there should be no leap year at the end of each century unless the year number could be divided exactly by 400. On this basis there are 485
crystals have their hexagonal axis vertical and the Sun is low in the sky, as it inevitably is in Arctic and Antarctic regions, bright patches can be seen in the sky 22Æ to the left and right of the Sun. Such a patch is known as a parhelion or, more often, as a ‘sundog’. A halo and its associated sundogs are shown in ﬁgure 5.16 (colour plate). 102 6 SEEING THE LIGHT 6.1 The human eye The detection of light patterns involves a sequence of processes not only in the eye but also in the brain. The
different hues forming a Maltese cross. The effect lasts only a few seconds, but it can be regenerated in the opposite orientation by switching the polarization direction through 90Æ again or (less effectively) by removing the ﬁlter. The transient nature of this phenomenon may be because the human brain treats the colour pattern as anomalous, in much the same way as the brain compensates for the blind spot on the retina. 6.4 Speed of response Projected movies consist of sequences of still
Heinrich Welker, a German scientist at the SiemensSchuckert laboratory in Erlangen, published a classic paper about a family of materials that are known today as III–V semiconductors. These materials are compounds of metallic elements such as aluminium, gallium or indium (which are in group III of the Periodic Table) with non-metallic elements such as nitrogen, phosphorus, arsenic and antimony (in group V). These compounds contain equal numbers of atoms from group III and from group V. In many of
display with more than 10 000 ﬁreworks took place in 1749 in Green Park, London to mark the Treaty of Aix-la-Chapelle. It took some six months to arrange, giving time for Handel (Georg Friedrich H¨andel before he and his name took British nationality) to compose the music that still accompanies ﬁrework displays more than 250 years later. The music is now much better known than the political and military events that led to its creation. Up to the beginning of the 19th century, ﬁreworks were based