WAS EINSTEIN RIGHT? Putting General Relativity to the Test by Clifford M. Will Basic Books, Inc., Publishers New York QC173.6.W55 1986 530.1'1 85-73877 ASTRONOMY WITH BINOCULARS A Practical Guide to Observing the Skies by James Muirden Arco Publishing, Inc. New York QB64.M86 1983 523 83-7099 ISBN 0-668-05832-3 (pbk.) $7.95 "Quasars. Cosmic fireball radiation. Pulsars. Black holes. Gravitational lenses. What do these things have in common? "First, they were all discovered after 1960, during a period of unparalleled advances in the technology of scientific investigation, especially in astronomy. "Second, they have attracted intense popular interest. Just look at the success in recent years of the books (THE FIRST THREE MINUTES). Movies (THE BLACK HOLE), and television productions ("COSMOS") that have presented them to the general public, to say nothing of wristwatches (Pulsar) and television sets (Quasar) that carry some of their names. "Third, Their existence makes us ask the question, "Was Einstein right?" Every item in the preceding list involves Einstein's general theory of relativity in a crucial way. Black holes, the remains of dead, collapsed stars, are an important prediction of the theory; a black hole is thought to be responsible for the astronomical X-ray source Cygnus X1, and they are believed by many to power quasars, the incredibly luminous beacons that we can see almost to the edge of the visible universe. The cosmic fireball radiation is most likely the afterglow of the big bang that began the universe, an event whose understanding requires the theory of relativity. The structure of pulsers, believed to be rapidly spinning neutron stars, is strongly influenced by super-strong general relativistic gravitational forces. Finally, the recently discovered gravitational lenses are galaxies that bend and focus passing light by means of the general relativistic warping of space-time around them. "Modern day astronomers and astrophysicists must use general relativity as a tool in their attempts to comprehend these phenomena. If the theory were incorrect, they would be at a loss; an important underpinning of their models would be weakened. "Of course, there is more at stake in the question "Was Einstein right?" than keeping astrophysicists happy (and employed). General relativity is a fundamental theory of the nature of space, time, and gravitation, and has profoundly influenced how we view the universe. But like any theory of nature, it cannot stand on its own. It must face the test of experiment and observation. No matter how profound it may be, no matter how beautiful or elegant it may appear, it must be discarded if it does not agree with observation. Unfortunately, observations of quasars, pulsars, and the like don't in themselves tell us much about general relativity. The reason is that these objects involve such complex physics that we can't easily distinguish the effects of general relativity from the other forces at work. So to find out if Einstein was right, we look at different kinds of tests. "This book is about those tests. It is about an intensive twenty-year effort, beginning around 1960, to check the predictions of general relativity accurately, and to find new predictions to check." Chapter 1. The Renaissance of General Relativity Chapter 2. The Straight Road to Curved Space-Time Chapter 3. The Gravitational Red Shift of Light and Clocks Chapter 4. The Departure of Light from the Straight and Narrow Chapter 5. The Perihelion Shift of Mercury: Triumph or Trouble? Chapter 6. The Time Delay of Light: Better Late Than Never Chapter 7. Do the Earth and the Moon Fall the Same? Chapter 8. The Rise and Fall of the Brans-Dicke Theory Chapter 9. Is the Gravitational Constant Constant? Chapter 10. The Binary Pulser: Gravity Waves Exist! Chapter 11. The Frontiers of Experimental Relativity Chapter 12. Astronomy after the Renaissance: Is General Relativity Useful? James Muirden's ASTRONOMY WITH BINOCULARS is targeted toward those amateur astronomers who don't have the coins to go out and purchase a telescope, but instead can use binoculars. Binoculars are one of the best tools for observing the heavens. They are relatively inexpensive (compared to a telescope), very easy to use, and powerful enough to offer a real advantage over the naked eye in stargazing. Binoculars give you visual access to all the stars in Tirion's Star Atlas 2000.0, including many deep sky objects, the planets, sun (with solar filters), the moon and other celestial phenomena. The chapter entitled, "Around the Constellations" provides detailed information about colored stars, double stars, clusters, variable stars, nebulae and other objects for each constellation including those visible only in the southern hemisphere. ASTRONOMY WITH BINOCULARS is written with the philosophy that amateur astronomers can do real astronomy with binoculars. Not only does this book give you a lot of useful information about how and what to look at, but it, combined with binoculars, opens up a whole world of observation that you can do independently and for many, many years. -S. Wormley