Transcript Lecture23
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 205 - Astronomy Gary D. Westfall Lecture 35 1 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 205 - Astronomy Gary D. Westfall Lecture 35 2 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 The search for extraterrestrial life Some have been done More are being done ISP 205 - Astronomy Gary D. Westfall Lecture 35 3 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 Meteorites have amino acids Comets show organic molecules 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 205 - Astronomy Gary D. Westfall Lecture 35 4 Life in the Solar System • Recent work on a meteorite ALH 84001 suggested that it contained fossilized life from Mars Very controversial • Recent pictures from the Mars Global Surveyor show evidence for recent water flows less than a million years old Water flows are thought to have come from underground aquifers Still under debate • Life was observed near black smokers under the ocean sparking interest in observing similar life extraterrestrially ISP 205 - Astronomy Gary D. Westfall Lecture 35 5 Possible Water Flow on Mars a) b) c) d) North wall of crater in southern hemisphere Nirgal Valles, valley system cut by running water Close-up of Nirgal Valles wall Gullies on the wall of 20 km wide impact crater in Noachis Terra ISP 205 - Astronomy Gary D. Westfall Lecture 35 6 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 500,000 years of the US electrical consumption • These calculations casts doubt on UFO sightings There have been no verified UFO sightings ISP 205 - Astronomy Gary D. Westfall Lecture 35 7 Communicating with the Stars • We have 4 spacecraft that have left the solar system 2 Pioneers and 2 Voyagers • They will take hundreds of thousands of years to even approach another star • We put messages on these spacecraft Each Pioneer carries a gold-anodized plaque with a pictorial message Each Voyager carries audio-visual recording with photographs and music ISP 205 - Astronomy Gary D. Westfall Lecture 35 8 Messages in a Bottle Voyager’s Message Pioneer’s Message ISP 205 - Astronomy Gary D. Westfall Lecture 35 9 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? ISP 205 - Astronomy Gary D. Westfall Lecture 35 10