ALBERT

Note: Contents Preface Background: what you need to know before you start 1 Gravity on Earth: the inescapable force Galileo: the beginnings of the science of gravity The acceleration of gravity is uniform Trajectories of cannonballs Galileo: the first relativist 2 And then came Newton: gravity takes center stage The second law: weight and mass The third law, and its loophole Preview: Newton's gravity Action at a distance The new equivalence principle The gravitational redshift of light Gravity slows time Summing up 3 Satellites: what goes up doesn't always come down Taking motion apart Acceleration, and how to change your weight Getting into orbit 4 The Solar System: a triumph for Newtonian gravity How to invent Newton's law for the acceleration of gravity The orbits of the planets described by Newton's law of gravity What is the value of G? Kepler's laws The Sun has a little orbit of its own Geostationary satellites The gravitational attraction of spherical objects Playing with the orbit program Black holes before 1800 Light is deflected by the Sun's gravity 5 Tides and tidal forces: the real signature of gravity Tidal forces in free fall Ocean tides Tides from the Sun Spring and neap tides What the tidal forces do to the oceans, the Earth, and the Moon Tides elsewhere in astronomy Jupiter gives Mercury's story another twist Triumph of Newtonian gravity: the prediction of Neptune Tiny flaw of Newtonian gravity: Mercury's perihelion motion 6 Interplanetary travel: the cosmic roller-coaster Getting away from the Earth Plain old momentum, and how rockets use it Energy, and how planets never lose it Getting to another planet The principle of the slingshot Using Jupiter to reach the outer planets Slinging towards the Sun Force and energy: how to change the energy of a body Time and energy 7 Atmospheres: keeping planets covered In the beginning . . . ... was the greenhouse . . . ... and then came Darwin The ones that get away The Earth's atmosphere Pressure beats gravity: Archimedes buoys up balloons Pressure beats gravity again: Bernoulli lifts airplanes Helium balloons and the equivalence principle Absolute zero: the coldest temperature of all Why there is a coldest temperature: the random nature of heat The ideal gas An atmosphere at constant temperature The Earth's atmosphere The atmospheres of other planets Quantum theory and absolute zero 8 Gravity in the Sun: keeping the heat on Sunburn shows that light comes in packets, called photons A gas made of photons Einstein in 1905 Gravity keeps the Sun round The Sun is one big atmosphere The Standard Model of the Sun The structure of the Sun How photons randomly 'walk' through the Sun Rotation keeps the Sun going around Solar seismology: the ringing Sun 9 Reaching for the stars: the emptiness of outer space Leaping out of the Solar System How far away are the stars? How bright are stars? Astronomers' units for brightness Standard candles: using brightness to measure distance 10 The colors of stars: why they are black (bodies) The colors of stars Why stars are black bodies The color of a black body Relation between color and temperature: greenhouses again Spectral lines: the fingerprint of a star How big stars are: color and distance tell us the size But why are stars as hot as they are, and no hotter? Looking ahead 11 Stars at work: factories for the Universe Star light, star bright . . . ... first star I see tonight Cooking up the elements The solar neutrino problem Life came from the stars, but would you have bet on it? 12 Birth to death: the life cycle of the stars Starbirth The gravitational thermostat The main sequence Giants Degenerate stars: what happens when the nuclear fire goes out The Chandrasekhar mass: white dwarfs can't get too heavy Neutron stars Fire or ice: supernova or white dwarf Death by disintegration What is left behind: cinders and seeds 13 Binary stars: tidal forces on a huge scale Looking at binaries The orbit of a binary Planetary perturbations Tidal forces in binary systems Accretion disks in binaries Compact-object binaries Fun with the three-body problem 14 Galaxies: atoms in the Universe Globular clusters: minigalaxies within galaxies Describing galaxies Galaxies are speeding apart Measuring the Universe: the distances between galaxies Most of the Universe is missing! Gangs of galaxies The missing mass Radio galaxies: the monster is a giant black hole Quasars: feeding the monster Galaxy formation: how did it all start? Did it all start? 15 Physics at speed: Einstein stands on Galileo's shoulders Fast motion means relativity• Relativity is special The Michelson-Morley experiment: light presents a puzzle Michelson's interferometer: the relativity instrument Special relativity: general consequences The extra inertia of pressure Conclusions 16 Relating to Einstein: logic and experiment in relativity Nothing can travel faster than light Light cannot be made to stand still Clocks run slower when they move The length of an object contracts along its motion Loss of simultaneity The mass of an object increases with its speed Energy is equivalent to mass Photons have zero rest-mass Consistency of relativity: the twin paradox saves the world Relativity and the real world 17 Spacetime geometry: finding out what is not relative Gravity in general relativity is . . . ... geometry Spacetime: time and space are inseparable Relativity of time in the spacetime diagram Time dethroned . . . ... and the metric reigns supreme! The geometry of relativity Proper measures of time and distance Equivalence principle: the road to curvature . .. ... is a geodesic The equivalence principle: spacetime is smooth 18 Einstein's gravity: Einstein climbs onto Newton's shoulders Driving from Atlanta to Alaska, or from Cape Town to Cairo Dimpled and wiggly: describing any surface Newtonian gravity as the curvature of time Do the planets follow the geodesics of this time-curvature? How to define the conserved energy of a particle The deflection of light: space has to be curved, too Space curvature is a critical test of general relativity How Einstein knew he was right: Mercury's orbital precession Weak gravity, strong gravity 19 Einstein's recipe: fashioning the geometry of gravity Einstein's kitchen: the ingredients Einstein's kitchen: the active gravitational mass comes first Einstein's kitchen: the recipe for curving time Einstein's kitchen: the recipe for curving space Einstein's kitchen: the recipe for gravitomagnetism The geometry of gravitomagnetism Gyroscopes, Lense, Thirring, and Mach The cosmological constant: making use of negative pressure The big picture: all the field equations The search for simplicity General relativity Looking ahead 20 Neutron stars: laboratories of strong gravity Nuclear pudding: the density of a neutron star It takes a whole star to do the work of 100 neutrons What would a neutron star look like? Where should astronomers look for neutron stars? Pulsars: neutron stars that advertise themselves The mystery of the way pulsars emit radiation The rotation rate of pulsars and how it changes Puzzles about the rotation of pulsars Pulsars in binary systems X-ray binary neutron stars Gamma-ray bursts: deaths of neutron stars? The relativistic strncture of a neutron star The relation of mass to radius for neutron stars Neutron stars as physics labs 21 Black holes: gravity's one-way street The first black hole What black holes can do - to photons The gravitational redshift Danger: horizon! Getting away from it all Singularities, naked or otherwise What black holes can do ... to orbits Making a black hole: the bigger, the easier Inside the black hole Disturbed black holes Limits on the possible The uniqueness of the black hole Spinning black holes drag everything with them The naked truth about fast black holes Mining the energy reservoir of a spinning black hole Accretion onto black holes The signature of the supermassive black hole in MCG-6-30-15 Wormholes: space and time tubes Hawki