final exam Today we will discuss Cosmology and the Big Bang Wednesday we will finish the Big Bang have a short discussion of Life in the Universe and review for the final exam Remember Cosmological Redshift We now know 3 kinds of redshift Doppler shift Gravitational shift due to motion due to distortion of space time by mass Cosmological shift due to stretching of space not due to relative motion as space stretches the wavelength stretches and becomes longer AST 1002 End of the Beginning Planets Stars and Galaxies Time Today s Lecture purpose goals 1 The Beginning 2 The Age of the Universe 3 The End of Time 4 Life in the Universe 5 Review for Final Thinking Back in Time We can calculate the age of the Universe using Hubble s Law v H0 x d v H0 tHubble 1 H0 d But distance rate x time the time here is how long the expansion has been going on The Age of the Universe If Ho 70 km s Mpc what is the age of the Universe THubble tHubble 1 H0 1 sec Mpc 106 pc 3 26 l y 1013 km 70 km Mpc pc l y 19 sec 1 hr 1 day 1 yr 4 657x1017 sec 3 26x10 70 3600sec 24 hr 365 25day 1 475x1010 yr 14 7 Billion Years At the Beginning Originally all the energy and matter of the Universe was condensed into an incredibly small region Energy matter space and time were all very different than today MUCH smaller than the size of a proton what we call matter was then almost entirely energy gamma ray photons need a new theory of everything to understand not yet possible 11 dimensional space models are very weird During early expansion space time and gravity became separate from energy and mass particles and antiparticles were being created from energy and annihilating into energy all the time Glow of the Universe The early Universe was very dense radiation getting absorbed Eventually the Universe cooled enough to form hydrogen atoms glowed with blackbody but so dense the light kept opaque hot and blackbody radiation could now travel freely That time called recombination of the Universe Light from that time should be all around us and be detectable 3K background radiation Cosmic Microwave Background This light should be cosmologically redshifted Mostly into microwave region CMB was first seen in 1960s Pensias Wilson Bell Labs won Nobel prize in physics for this twenty years after prediction COBE satellite mapped the CMB measured the spectrum wonderful match between theory and data Temperature 2 73K cooled glow from recombination era Incredibly uniform across sky CMB Composition of Light Elements Big Bang model predicts the percentage of light elements Hydrogen 1H deuterium heavy hydrogen 2H helium 4He lithium 7Li beryllium 9Be boron 10B and 11B elements formed before recombination out of cooling extremely hot plasma created out of light percentages depend upon density and temperature of early Universe and how fast it cooled Observed percentages agree with Big Bang model predictions Almost all that was created as hydrogen 1H and helium 4He with only trace amounts of anything else Helium must have cooled from something very hot Notice no stable mass 5 or 8 isotopes Big Bang model predicts the percentage of light elements observed percentages agree with Big Bang model predictions Almost all that was created in the Big Bang was hydrogen 1H and helium 4He only trace amounts of anything else Helium 4He was enriched in Main Sequence stars Carbon 12C and the elements up to Iron 56Fe created in massive Blue Giants and dying Red giant and Supergiant stars The heaviest elements like Gold 197Au and Uranium 235U were created only in supernovae ENRICHMENT Formation of Structure early in the Universe Normal matter was spread fairly evenly Dark matter was not distributed smoothly WMAP and Boomerang follow ups of COBE show the seeds of that nonuniformity clumps remained Expansion spread things out due to interactions and radiation but gravity held large clumps of dark matter together Dark matter attracted normal matter source of galaxies and structure Fate of the Universe The Universe is expanding But gravity should be pulling it back in So what should the Universe s fate be Continue expanding forever Have expansion keep getting slower forever and stop at infinite time Expansion stops and eventually Universe collapses upon itself These possibilities are called open universe ends in cold dark blackness flat universe closed universe ends in blinding white light Big Crunch Enough Matter The amount of matter in the Universe helps determine its fate if there is enough mass gravity wins given H0 70 km s Mpc critical mass density is 8x10 27 kg m3 define MASS as the actual density of mass in the Universe divided by the critical density MASS 1 is an open universe MASS 1 is a flat universe MASS 1 is a closed universe Enough Matter Visible matter stars in galaxies hot gas only 2 of critical density MASS 0 02 Dark matter in galaxies measured by galaxy rotation curves about 10 times as much MASS 0 2 Dark matter between galaxies measured by watching galaxies fall inward in galactic clusters and from gravitational lensing raises total to 30 of critical density MASS 0 3 We do not observe enough matter to cause the Universe to be closed But it s not the end of the story Is the Expansion Slowing Down Use Type 1a supernovae a standard candle use brightness to determine distance use redshift to determine speed compare them data lies below prediction galaxies are speeding up Answer Strangely enough the rate of expansion is speeding up Life Is Life Out There What evidence do we have of life beyond Actually so far we have no direct evidence Earth of life beyond Earth What possibilities are there Requires complex carbon chemistry only around population I stars in liquid water narrow temperature range btwn melting boiling points of water Requires long lived worlds probably not around blue giant stars or in binary or Mars multiple stars systems Europa Titan Comets Asteroids Terrestrial planets moons in other systems The Search for Life We search for intelligent life using radio waves radio waves travel far distances at the speed of light not produced by most stars seems fairly easy to develop technology possible to communicate information Numerous large radio telescope arrays around the world SETI Search for ExtraTerrestrial Intelligence SETI There are numerous programs First search Project Ozma was in 1960 200 hours of observing two nearby stars Project Phoenix privately financed US project search 2 billion channels for each of 1000 nearby stars stars similar