by Prasad Ganti
A Journey to Earth’s Extremes to Unlock the Secrets of the Universe by Anil Ananthaswamy
Anil’s book contains different stories relating to physics experiments conducted in different parts of the world, most of them remotely located. Travelling to those desolate places is the adventure part. Also, Anil describes the instruments and the experiments along with the relevant physics. The mix of physics and adventure makes this book very exciting. A background of high school physics is enough to understand the experiments.
He starts with the 60-inch and the 100-inch telescopes at Mount Wilson near Los Angeles built by George Hale at the beginning of 1900s. Peeping through these telescopes, the famous astronomer Edwin Hubble and his equally famous assistant Milton Humason, found out in the early twentieth century that galaxies are retreating from each other. This gave rise to the concept of an expanding Universe. Extrapolating this expansion backwards in time led to the now widely accepted Big Bang theory. Later George Hale built a 200-inch telescope on Mount Palomar, but further south to escape the light pollution caused by the growing city of Los Angeles.
The action then moves to a deep mine in Minnesota at Soudan. At the bottom of this abandoned mine is a very sensitive detector for detecting Cold Dark Matter. It is now postulated that most of the matter in the universe consists of dark matter, which is not visible to us as normal matter consisting of atoms. It does not contain the regular subatomic particles like electrons, protons and neutrons etc. Instead it is speculated to contain a very weakly interacting particle called a neutralino. The sensitive detectors consist of ultrapure germanium and silicon crystals cooled to 40µK, just a shade above the absolute zero of -273°C. The detectors have not detected any neutralinos yet. The search is on!
The action then shifts to Lake Baikal in Russia. It has a neutrino observatory deep beneath the ice. Neutrinos, discovered by the famous physicist Wolfgang Pauli, are copiously generated by our Sun. They move quickly; rarely interacting with any matter in its path. Millions of them pass through our bodies each second, and we don’t even know about them. There are very energetic neutrinos, which are generated in the galactic center. Studying them could give us clues about the formation of galaxies. Neutrinos form a streak of blue light when they hit water. A huge amount of pure water contained in Lake Baikal acts as a natural detector for these rare neutrinos from the center of the galaxy.
Next stop is the Cerro Paranal in the Atacama Desert in Chile. Just 12 km from the Pacific coast, on a 2635-meter high mountain, the Very Large Telescope (VLT) consists of four telescopes, each of 8.2 meters in diameter. The telescopes are used in conjunction with an advanced spectrograph, which can detect different light colors or absence of any color coming from different sources. This is one of the most advanced telescopes in the world used to study the Cosmos.
The next location will most likely house a radio telescope called the Square Kilometer Array. Unlike an optical telescope, which consists of mirrors and lenses, some radio telescopes consist of arrays of radio antennas, all of them connected to a radio receiver. The combined signals are scanned for sources like pulsars and quasars, which emit only radio waves, and no light. Karl Jansky started radio telescopy when he first observed radio signals coming from the center of our galaxy, the Milky Way. A mention is made of GMRT (Giant Meter Radio Telescope), an array of thirty 45-meter diameter dishes each located about 50 miles north of Pune in India. Indian astronomer Govind Swarup built each antenna cheaply from 16 tubular steel frames tied by steel ropes.
The stage now shifts to the most desolate of all places, Antarctica. The experiments, called BESS, are conducted by launching balloons packed with detectors. These detectors look for antimatter. Antimatter particles annihilate each other when they come in contact. It is speculated that there is some antimatter in the universe. Some stars and galaxies may be made of antimatter. Matter and antimatter may have formed in nearly equal amounts during the birth of the universe, and thereafter most of the antimatter got annihilated on contact with matter. A few hundred miles from the balloon launch site, at the South Pole is an experiment called IceCube, which has sensors deep in ice cores, to look for neutrinos. It is similar to the Lake Baikal neutrino observatory, but operating in most extreme conditions.
Next is the very famous huge particle collider in Europe that spans the borders of Switzerland, France, and Italy called Large Hadron Collider (LHC). Consisting of a massive underground ring several kilometers in diameter, it generates the highest energies on the planet to accelerate and collide the protons. Built to understand the beginning of the universe, it looks for a particle known as Higgs Boson, which is also called the God particle, (Incidentally Peter Higgs is an atheist). One of the detectors that looks for the aftermath of the collisions is called ATLAS and consists of massive superconducting magnets. If confirmed, the Higgs Boson will open a new chapter in physics.
Towards the end of the book, Anil also mentions about newer telescopes in space such as Planck, which was launched in 2009 to study the Cosmic Microwave Background radiation in greater detail. Laser Interferometry Space Antenna (LISA), to be launched later this decade to detect gravity waves, will consist of three satellites positioned at the vertices of a triangle a million miles apart. The gravity waves, if detected, would represent a ripple in the fabric of space and time.