advertisement

• Special theory of relativity (1905) • general theory of relativity Dept of Phys M.C. Chang Space and time Newton Post-Newton Inertial frame and noninertial frame The velocity of light C=299792458 m/s 100+200=300 C+C=2C? The velocity of light is the same to all observers (in inertial frames) Simultaneity There is no unique “now”. Time dilation (a moving clock ticks slower) ct’ ct ct’ vt An optical clock (ct )2 (vt )2 (ct ')2 In 1971, experimenters from the U.S. Naval Observatory undertook an experiment to test time dilation . Eastward Journey Westward Journey Predicted -40 +/- 23 ns + 275 +/- 21 ns Measured -59 +/- 10 ns + 273 +/- 7 ns The twin paradox Length contraction (a moving object shrinks) Relative point of view The barn-pole paradox Relativistic mass (a moving object becomes heavier) Nothing moves faster than the speed of light The most famous formula in the world Nuclear fusion 由氘及氚組成的靶 deuterium tritium L. Livermore National Lab. 核融合設施 (NIF) • Special theory of relativity • general theory of relativity (the theory of gravity, 1916) Objects of different weights fall at the same speed The principle of equivalence = The bending of light by gravity Gravitational lens Relativity in GPS (Global Positioning System) with on-board atomic clocks USD 350 Accuracy: 30 nanosecond → 15 meters Gravity slows down a clock (g/4) Relativistic effect: Faster by -7+45=38 microsec per day = an error of 11 km! Gravity balanced by pressure Black hole Gravitational collapse will always occur on any star over 5 solar masses, inevitably producing a black hole a space-time singularity Schwarzschild radius (1916) Detecting gravitational wave LIGO Laser Interferometer Gravitational Wave Observatory, Hanford, WA + Livingston, LA Lisa (launch > 2018 ) Laser Interferometer Space Antenna a resolution of 20 picometers over a distance of 5 million kilometers !! 20xx? The milky way Our galaxy 2.6 ± 0.2 million times the mass of the Sun • 2.5 MLYs away • 0.2 MLYs in diameter • 10^12 stars Cluster of galaxy Large-scale structure of the universe (each blue dot is a galaxy!) "Space is big. Really big. You just won't believe how vastly, hugely, mind-bogglingly big it is." The Hitchhiker's Guide to the Galaxy Shape of the universe http://abyss.uoregon.edu/~js/cosmo/lectures/lec15.html Einstein’s field equation Λ>0 leads to repulsion Cosmological constant (<-> vacuum energy) Red shift Hubble’s law (1929) 1 pc=3.26 ly (The name was given by Hoyle, 1950) From Mather’s slide Oldest galaxy known Age ～ 13 billion yrs Penzias and Wilson 1978 Background radiation (COBE satellite) 1% TV static Dipole due to earth motion 10-3 Galactic plane 10-5 The universe at age 389000 years Mather & Smoot 2006 COBE (launched 1989) WMAP (launched 2001) angular resolution～ 0.3° Space travel Caution: Slippery ahead The matricide (or grandpa) paradox Thank you