A Crack in Everything by Marcus Chown

Author:Marcus Chown
Language: eng
Format: epub
ISBN: 9781804544303
Publisher: Head of Zeus

a A celestial object with an “apparent magnitude” five times larger than another is 100 times fainter. The faintest star visible to the naked eye has a magnitude of about 6 while the apparent magnitudes of the full Moon and the Sun are -12.7 and -26.7, respectively. This means the Sun shines about a million times brighter than the full Moon.

b The spectral lines created when an electron drops to the first, or lowest, energy level are not visible to the naked eye. These “Lyman” lines are in the ultraviolet.

c In a hydrogen atom, the single electron can either have the same quantum “spin” as the single proton or the opposite spin (naively, the spins can be thought of as either a clockwise or anticlockwise rotation). The state in which spins are aligned has a very slightly greater energy than that in which they are not aligned. So, if the atom drops from the higher to the lower energy state, the excess energy is shed as “photon”. This has a wavelength of 21 centimetres.

d Sagittarius A* would later be identified as a 4.2-million-solar-mass black hole at the heart of the Milky Way.

e The discovery of cosmic radio waves was not the only major astronomical discovery made at Bell Labs’ Holmdel site. In 1964, Arno Penzias and Robert Wilson would discover the “cosmic background radiation”, the “afterglow” of the Big Bang fireball in which the universe was born 13.82 billion years ago. See my book, Afterglow of Creation (Faber & Faber, 2010).

f Grote Reber reconstructed his 31-foot dish radio telescope at the National Radio Astronomy Observatory at Green Bank, West Virginia, where it can be seen by visitors. https://public.nrao.edu/gallery/grote-rebers-telescope-and-the-green-bank-science-center/

g Pawsey, on a tour of the US, first used the term “radio astronomy” in a letter to Edward “Taffy” Bowen, director of the Radiophysics Laboratory in Sydney on 14 January 1948. The term was quickly adopted. In August 1948, Martin Ryle in Cambridge published a popular article in British Science News entitled “Radio Astronomy”.

h An interesting application of this effect may be observed when a helicopter flies above the sea near a radio transmitter. The helicopter receives two signals: one signal directly from the transmitter and a second signal after reflection from the sea. As the helicopter rises the phase difference between the two signals will alter and the helicopter will pass through regions of maxima and minima. See “Lloyd’s Mirror”, https://www.schoolphysics.co.uk/age16-19/Wave%20properties/Interference/text/Lloyds_mirror/index.html

i Parkes played a key role in the Apollo 11 Moon landing on 20 July 1969 as well as the rescue of the stricken Apollo 13 spacecraft in 1970. Bolton was portrayed by Sam Neill in the 2001 Australian movie The Dish.

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