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 due to motion Gravitational shift 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

the Beginning  End of Time Today’s Lecture: purpose & goals AST 1002 Planets, Stars and Galaxies 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 If H o = 70 km/(s. Mpc), what is the age of the Universe, T Hubble ? v = H 0 x d  d = v/H 0 But distance = rate x time (the time here is how long the expansion has been going on  The Age of the Universe)  t Hubble = 1/H 0 ( Mpc ) = 1 sec. Mpc 70 km 10 6 pc ( pc ) 3.26 l.y. ( l.y. ) km = 3.26x10 19 sec 70 = 4.657x10 17 sec ( 3600sec ) 1 hr ( 24 hr ) 1 day ( day ) 1 yr = 1.475x10 10 yr = 14.7 Billion Years!!

At the Beginning Originally all the energy (and matter) of the Universe was condensed into an incredibly small region MUCH smaller than the size of a proton Energy, matter, space and time were all very different than today   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 hot and dense glowed with blackbody radiation but so dense the light kept getting absorbed (opaque) Eventually the Universe cooled enough to form hydrogen atoms 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

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. Cosmic Microwave Background (CMB)

Composition of Light Elements Helium Big Bang model predicts the percentage of light elements Hydrogen ( 1 H), deuterium (heavy hydrogen, 2 H), helium ( 4 He), lithium ( 7 Li), beryllium ( 9 Be), boron ( 10 B and 11 B),… 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 ( 1 H) and helium ( 4 He), with only trace amounts of anything else.  must have cooled from something very hot. Notice no stable mass 5 or 8 isotopes

E N R I C H M E N T 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 ( 1 H) and helium ( 4 He), only trace amounts of anything else. Helium ( 4 He), was enriched in Main Sequence stars Carbon ( 12 C), and the elements up to Iron ( 56 Fe), created in massive Blue Giants and dying Red giant and Supergiant stars The heaviest elements, like Gold ( 197 Au) and Uranium ( 235 U), were created only in supernovae

Formation of Structure (early in the Universe) Normal matter was spread fairly evenly due to interactions and radiation 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 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 H 0 = 70 km/(s Mpc), critical mass density is 8x kg/m 3 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? Answer: Strangely enough… the rate of expansion is speeding up! 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!!)

Life?

Is Life Out There? Actually, so far, we have no direct evidence 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 multiple stars systems Mars Europa, Titan(?) Comets/Asteroids Terrestrial planets/ moons in other systems What evidence do we have of life beyond Earth?

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 hours of observing two nearby stars Project Phoenix privately financed US project search 2 billion channels for each of 1000 nearby stars stars similar to the Sun and at least 3 billion years old about half done – nothing yet

SETI Still Going SERENDIP Project search for signals using regular radio telescope observations from the Arecibo telescope in Puerto Rico you can participate by downloading a screen saver which analyzes SETI data while your computer is idle Allen Telescope Array series of 1000s of small satellite dishes funded by Paul Allen (of Microsoft)

Drake Equation What are the factors to determine the chance there is advanced intelligent life out there? number of stars (T) 200,000,000,000 in our galaxy!! number of planets/moons (n pm ) Recent searches seem to show many number of planets/moons where life does actually start (f l ) carbon chemistry, liquid water, long-lived number of times life becomes intelligent (f c ) (??) length of intelligent civilization that can communicate with stars (L) We’ve only been able to do it for ~40 years – which is totally insignificant!! N = T x n pm x f l x f c x L

Messages from Earth We have tried to communicate with other life Probes Pioneer and Voyager carry plaques and recordings Radio signals been emitting radio signals since the 1940s – “the Honeymooners”, “I Love Lucy” etc. sent several messages Arecibo broadcast – 1974 Encounter 2001