Chapters 17,18: Cosmology and Life in the Universe Nearly every speck of light in the image is a galaxy.

Chapters 17,18: Cosmology and Life in the Universe A map of the distribution of galaxies seen out of the plane of the Milky Way

Chapters 17,18: Cosmology and Life in the Universe Is the universe infinite or closed. Olbers’s Paradox says in must be finite because if it was infinite then every direction one looked in space would ultimately land on the surface of a star and the whole sky would be as bright as the Sun’s surface.

Chapters 17,18: Cosmology and Life in the Universe Hubble’s Law states that Recession velocity = H o X distance Where H o is the Hubble constant Since velocity is distance/time, if we assume the universe has been expanding since the Big Bang then we can invert the equation for Hubble’s law and calculate how long it has been since the Big Bang. Time since Big Bang = 1/H o gives 14 billion years

Chapters 17,18: Cosmology and Life in the Universe At a time 1/Ho the universe began in an event we call the Big Bang But like living on the surface of a balloon, we can see no beginning.

Chapters 17,18: Cosmology and Life in the Universe Also, as the balloon expands we see all parts reseeding from all others. This explains why we see all the other galaxies speeding away from us.

Chapters 17,18: Cosmology and Life in the Universe The expanding universe also caused the wavelengths of radiation from the Big Bang to be red shifted. We see this today as the microwave background radiation.

Chapters 17,18: Cosmology and Life in the Universe Classical thought says depending on how much matter there is in the universe we have three possible outcomes. Modern evidence points to a fourth outcome, an accelerating expansion.

Chapters 17,18: Cosmology and Life in the Universe 1) too little mass means we expand forever (death by ice) 2) too much mass and we get the big crunch (death by fire) 3)just the right amount and we eventually stop expanding (also death by ice) 4)But truth is an increasingly expanding Universe. How can this be?

Chapters 17,18: Cosmology and Life in the Universe Currently astronomers cannot find enough mass to close the Universe. The increasingly expanding Universe suggests we have negative energy and/or anti-gravity. This is a very active area of research.

Chapters 17,18: Cosmology and Life in the Universe As the Big Bang occurred we went from a radiation dominated universe to a matter dominated universe

Chapters 17,18: Cosmology and Life in the Universe Hydrogen and Helium are the only two atoms made during the Big Bang. All other elements were manufactured in by the stars and supernovae explosions. The ration of Helium to Hydrogen is an important constraint to current theories. It is difficult to tell if spacetime is curved because the distances mw can measure are so small compared to the universe

Chapters 17,18: Cosmology and Life in the Universe Somehow dark mater caused the ordinary mater in the Universe to be clumpy.

Chapters 17,18: Cosmology and Life in the Universe Is there anybody out there?

Chapters 17,18: Cosmology and Life in the Universe

While we can recreate amino acids under early Earth conditions, we have not been able to “create” Life. Radio astronomers can detect complicated molecules in dark molecular clouds. Miller-Urey experiment

Chapters 17,18: Cosmology and Life in the Universe Organic mater is found in meteorites. And life is found to grow where we never thought it could exist.

Chapters 17,18: Cosmology and Life in the Universe Different star have different ranges of habitable zones

Chapters 17,18: Cosmology and Life in the Universe number of technological, intelligent civilizations now present in the Galaxy rate of star formation, = averaged over the lifetime of the Galaxy fraction of stars X having planetary systems average number of habitable X planets within those planetary systems fraction of those X habitable planets on which life arises fraction of those X life-bearing planets on which intelligence evolves fraction of those intelligent-life X planets that develop tech- biological society average lifetime of a technologically X competent civilization. Drake’s Equation

Chapters 17,18: Cosmology and Life in the Universe Many astronomers think the best place to look for ET is in the water hole part of the electromagnetic spectrum.