400 Years of Cosmic Discovery Instruments, patterns, and theory Tim McKay Saturday Morning Physics 2/7/09 http://lsa.umich.edu/universe/ Written by: Norriss S. Hetherington W. Patrick McCray http://www.aip.org/history/cosmology/index.htm An Alternate Universe Constructed of two completely separate parts: Heaven and Earth The Earth: made of earth, air, fire, and water. Earth is the realm of transience. The Heavens: perfect, eternally regular, and impossibly remote. The Heavens are realm of the eternal. This is the universe into which Galileo was born… Our Universe A cosmos of infinite Machines we construct connection wander the solar system and beyond. Everything , down to the atoms we’re made of, Our augmented eyes comes from the heavens probe the cosmos in space and time, right back to its Energy floods daily down hot, dense beginning from the Sun, enabling life, then flees back into space Instruments Patterns Theory Instruments Galileo and the telescope • In 1609, Galileo heard rumors of a device for magnifying your view, a “telescope” • He promptly built his own 3x version, then quickly improved it to 30x • This telescope also effectively made his eye larger, gathering more light Portrait by Tintoretto, probably from around 1610-1615 Instruments How does a telescope work? • An “objective” lens (or mirror!) forms an image of distant objects • An “eyepiece” can then be used as a magnifier to allow you to view this image • You only need this eyepiece if you want to view the image with your eye… Image Location What does 3x magnification do for you? What does 30x magnification do for you? Instruments Instruments 1610 Instruments Sunspots in May 1612 Phases of Venus UM Special Collections on the 7th floor of the Hatcher Graduate Library is opening and amazing display of early astronomical texts, instruments, and documents from February 9 – April 11. This will include first editions of Siderius Nuncius, along with the work of Kepler, Copernicus, Brahe, etc. GO SEE THIS! Patterns Kepler divines regularities… • Kepler analyzes planetary observations from Tycho Brahe: 1609 • Finds precise patterns in their motions • Encodes these in three unexplained “laws” – Planets orbit in ellipses with the sun at one focus – Their speeds change, sweeping out equal areas in equal times – Their orbital periods vary like (orbit size)3/2 Newton solves the Theory solar system • Two tasks – Explain all mundane motion with 1687 mechanics – Universal gravity unites apples falling with planets orbiting Blake • The precision of his success was shocking to his contemporaries Nature and nature's laws lay hid in night; God said "Let Newton be" and all was light. Alexander Pope Instruments Newton’s instruments: 1670 Reflecting telescopes The spectrograph “Disperses” light into its constituent colors, here using a prism. Newton also Uses a mirror as the objective, eliminates reassembled these colors… chromatic aberration, allows for very large objectives supported from behind! Fraunhofer and the dark Patterns forest in the Sun: 1814 Joseph Fraunhofer, seeking to understand dispersion in glass and eliminate chromatic aberration, constructed the world’s best spectrographs. He found a forest of hundreds of dark lines interrupting the spectrum of light from the Sun… Patterns K B Partial understanding of Patterns Fraunhofer’s dark forest: 1859 • Kirchoff and Bunsen: interactions between • Specific elements emit light and matter and absorb specific sets – Hot dense object: of frequencies continuous spectrum – Hot diffuse gas: emission line spectrum – Hot dense object surrounded by tenuous gas: absorption line spectrum It’s possible to tell what a distant object is made of! Your basic spectrograph Instruments A prism or diffraction grating “disperses” the light Light comes Light goes in here out here We add a camera here to see A narrow slit for A microscope for us collimation for viewing the dispersed light Spectral lines and Doppler Theory shifting: detecting motion Fizeau Moving Many quasar away spectra faster sorted in order of recession All lines shift to velocity longer wavelength X. Fan, Ariz. Theory Skipping a bit… • Great physics • Involves many fields achievements of the – Thermodynamics 19th and early 20th – Electricity and century magnetism • A thorough predictive – Statistical physics theory of the – Quantum mechanics interaction of light and matter • This knowledge allows • Can predict what light interpretation of the an object will emit or complex spectra of absorb distant objects Cecelia Payne-Gaposhkin promptly put these principles to work… Patterns Cecelia Payne-Gaposchkin finds out Theory what the universe is made of: 1925 Stellar classes (OBAFGKM…) don’t reflect different chemical composition, but just different temperatures She showed that all stars are made primarily of hydrogen and helium: light elements are dominant! This is remarkable. What we are made of is abundant, but rare… Theory The sequence of spectral classifications is a sequence in temperature! Instruments Draper, 1880, from the Harvard Plates Photography exposes a new view of the universe… A. A. Common, 1883 Instruments George Ellery Hale Yerkes 40” Mt. Wilson 60” 1895 1908 Instruments Mt. Wilson 100” Hooker Telescope 1917 Mt. Palomar 200” Hale Telescope Instruments 1948 Brighter “Cepheids“ pulsate more slowly: 1929 Patterns Henrietta Leavitt Patterns • Edwin Hubble and Milton Humason used the 100” to detect Cepheids in nearby galaxies • Meanwhile, Vesto Slipher measured galaxy spectra, 1000 km/s finding that they’re moving Velocity away from us! Distance Einstein’s dynamic universe: 1917 Theory • In general relativity space-time is intrinsically • Matter influences space- time curvature • Space-time curvature tells matter how to move • GR naturally accommodates expanding (or contracting) space-time! R 1 Rg 8GT 2 Seeing the rest… Instruments Sadly, most of the light which arrives from distant objects is absorbed by the atmosphere! Only optical light and radio waves readily penetrate from space to the ground. To avoid this, instruments must be placed above the atmosphere, on mountains, planes, balloons, and satellites. Instruments Fermi GLAST Sputnik ROSAT Multi-wavelength astronomy, like spectroscopy, provides a new view X-ray Extreme UV Ultraviolet X-ray Optical Visible Calcium K Hydrogen Near IR Mid IR Instruments Radio Far IR Radio Infrared M104: the Sombero galaxy Digital detectors collect 40-80x as much light as photographic Instruments plates! 1980 and beyond… This is like making your telescope suddenly 40-80x larger. Computers are completely revolutionary. They allow us to gather massive quantities of data, analyze it precisely, share it Instruments globally, and make precise predictions for complex phenomena Mare Nostrum Supercomputer in Barcelona Patterns 20th century astrophysics • An enormous record of • Major (and many minor) progress, the subject of mysteries remain many talks this term – Dark matter • A solid origin theory for – Dark energy everything we see; the • These are today’s robust hot big bang cosmology patterns for which we • This is an enormous lack adequate achievement, the fruit explanation, like of 400 years of hard Fraunhofer’s dark lines… work Instruments The future? Theory • More of everything, but • Our data will be much not incomprehensively better; more precise, more… deeper, comprehensive • Our map of the universe • Computation will likely is filling in be able to handle the • Its major features will challenge be mapped during our • We will also get some lifetimes wholly new data • Don’t despair, this (gravity waves for leaves plenty to do… example…) Patterns New worlds, new life • Before 1995 we thought • The great triumph of planets must be there, astrophysics is unifying but couldn’t prove it heaven and earth • Now we have found • Life is here, a vibrant, robust physical process, many hundreds, with it should emerge readily thousands to come… • This will be the next • Today we think that life (and last?) great step in must be widespread, unification, so let’s get but we can’t prove it started!