Lecture 26 - Anybody out there - Life in the Universe

Lecture 26 - Anybody out there - Life in the Universe -...

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Unformatted text preview: Anybody out there? Life in the Universe ASTRONOMY 3 Lesson 26 H 2 O H 2 O 1 Depiction of how an Earth-like planet orbiting another star might look like (left), and the biosignatures (methane, ozone) we could try to detect in its atmosphere (right) NATURE of the Universe Review of Lesson 25 Astronomy - Life in the Universe The Universe formed 13.7 billion years ago in the Big Bang. We can observe the cosmic microwave background as the afterglow of the Big Bang. Small Fuctuations in the distribution of dark matter created the seeds for the formation of galaxies and clusters of galaxies. The Universe is expanding at an accelerated speed. Normal matter makes up only 4% of the Universe. 22% is in the form of dark matter, and 74% in the form of dark energy. Review: The Genesis and the ate of the Universe 2 Life on Earth Search for Life on Mars Search for Extra-Terrestrial Intelligence Summary & Review of Homework 7 NATURE of the Universe Todays Topics Astronomy - Life in the Universe 3 NATURE of the Universe Life on Earth Astronomy - Life in the Universe What is life? Life builds complex structures (like cells) out of simpler materials (air molecules, water, nutrients, ...) Life is self-replicating, i.e. genetic information is passed on to the next generation Life reacts to the environment, and adapts to long-term changes by genetic mutations (i.e. evolution) 4 The oldest life on Earth evolved 3.5 to 4 billion years ago, i.e. shortly after Earth had cooled down sufFciently for liquid water (oceans) to exist NATURE of the Universe Life on Earth Astronomy - Life in the Universe How did life evolve on Earth? no O 2 About 3 billion years ago, oxygen-producing blue-algae bacteria (cyanobacteria) evolved, starting to enrich Earths atmosphere with O 2 . 5 NATURE of the Universe Life on Earth Astronomy - Life in the Universe Single cell organism evolved by getting larger in size and becoming internally more complex till 1 billion years ago multi-cell organisms evolved. This is also when the oxygen level reached its current value....
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Lecture 26 - Anybody out there - Life in the Universe -...

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