final exam!!!

1. 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:

2. 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

3. AST 1002 Planets, Stars and Galaxies the Beginning&End of Time Today’s Lecture:purpose & goals The “Beginning” The Age of the Universe The “End of Time” Life in the Universe Review for Final

4. Thinking Back in Time • We can calculate the age of the Universe using Hubble’s Law • IfHo = 70 km/(s.Mpc), what is the age of the Universe, THubble? v = H0x d  d = v/H0  tHubble=1/H0 But distance = rate x time (the time here is how long the expansion has been going on  TheAge of the Universe) tHubble=1/H0 1 sec.Mpc 106 pc 3.26 l.y. 1013 km = (Mpc ) (pc ) ( l.y. ) 70 km 3.26x1019 sec 1 hr 1 day 1 yr = = 4.657x1017 sec (3600sec) (24 hr) (365.25day) 70 =14.7 Billion Years!! = 1.475x1010 yr

5. 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

6. 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

7. Cosmic Microwave Background (CMB) • 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.

8. 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.  must have cooled from something very hot. • Notice no stable mass 5 or 8 isotopes Helium

9. 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 E N R I C H M E N T

10. 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

11. 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”

12. 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

13. Enough Matter? • Visible matter (stars in galaxies, & hot gas) • only 2% of critical density; MASS = 0.02 • Dark matterin galaxies • (measured by galaxy rotation curves) • about 10 times as much; MASS = 0.2 • Dark matterbetween 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…

14. 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!

15. Life?

16. Is Life Out There? • What evidence do we have of life beyond Earth? • 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/ moonsin other systems

17. 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

18. SETI • Searchfor 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 to the Sun and at least 3 billion years old • about half done – nothing yet

19. 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 • www.setiathome.ssl.berkeley.edu • Allen Telescope Array • series of 1000s of small satellite dishes • funded by Paul Allen (of Microsoft)

20. 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 (npm) • Recent searches seem to show many • number of planets/moons where life does actually start (fl) • carbon chemistry, liquid water, long-lived • number of times life becomes intelligent (fc) (??) • 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 npmx flx fcx L

21. 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 • Encounter2001