ISP Astronomy Gary D. Westfall1Lecture 35 Where Have Your Atoms Been? The universe was created in the big bang 13 to 15 billion years ago The hydrogen in the water in your body was created then More complex atoms had to be “cooked” inside stars Several generation of stars had to pass with the most massive stars exploding Interstellar gas was enriched with heavier elements Interstellar dust formed containing these elements

ISP Astronomy Gary D. Westfall2Lecture 35 Local Action About 5 billion years ago, a cloud of gas and dust began to collapse under its own weight and formed our solar system The Earth was formed and its atmosphere allowed liquid water to exist on the surface The chemical makeup of Earth may have been influenced by complex materials from comets Earth’s evolution was punctuated with asteroid strikes Cosmic evolution

ISP Astronomy Gary D. Westfall3Lecture 35 The Copernican Principle The idea that there is nothing special about our place in the universe is called the Copernican principle There are 200 billion stars in the Milky Way and there are 200 billion other galaxies The chances that life is limited to our planet seem small However, science demands proof n The search for extraterrestrial life u Some have been done u More are being done

ISP Astronomy Gary D. Westfall4Lecture 35 The Building Blocks of Life No unambiguous evidence for life beyond Earth has been found Evidence for the building blocks of life has been found n Meteorites have amino acids n Comets show organic molecules n Organic molecules have been found in interstellar gas and dust clouds In the 1950s, Miller and Urey simulated the conditions on an early Earth and produced many of the building blocks of life

ISP Astronomy Gary D. Westfall5Lecture 35 Life in the Solar System Recent work on a meteorite ALH suggested that it contained fossilized life from Mars n Very controversial Recent pictures from the Mars Global Surveyor show evidence for recent water flows less than a million years old n Water flows are thought to have come from underground aquifers n Still under debate Life was observed near black smokers under the ocean sparking interest in observing similar life extraterrestrially

ISP Astronomy Gary D. Westfall6Lecture 35 Possible Water Flow on Mars a)North wall of crater in southern hemisphere b)Nirgal Valles, valley system cut by running water c)Close-up of Nirgal Valles wall d)Gullies on the wall of 20 km wide impact crater in Noachis Terra

ISP Astronomy Gary D. Westfall7Lecture 35 Traveling to Other Stars In our fastest spacecraft, it would take 80,000 years to reach the nearest star If you wanted to reach the nearest star and return in your lifetime, you would need to travel near the speed of light (8 LY round trip) Even with a perfect engine, this trip would take a huge amount of energy n 500,000 years of the US electrical consumption These calculations casts doubt on UFO sightings n There have been no verified UFO sightings

ISP Astronomy Gary D. Westfall8Lecture 35 Communicating with the Stars We have 4 spacecraft that have left the solar system n 2 Pioneers and 2 Voyagers They will take hundreds of thousands of years to even approach another star We put messages on these spacecraft n Each Pioneer carries a gold-anodized plaque with a pictorial message n Each Voyager carries audio-visual recording with photographs and music

ISP Astronomy Gary D. Westfall9Lecture 35 Messages in a Bottle Pioneer’s Message Voyager’s Message

ISP Astronomy Gary D. Westfall10Lecture 35 The Search for Extraterrestrial Intelligence Direct visits are unlikely so we must exchange messages Listening with radio waves is the most likely way of hearing extraterrestrial messages This effort is challenging and success is not likely even if there is extraterrestrial intelligence If we do receive a signal, what should we do?