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

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Anybody out there?Life in the UniverseASTRONOMY 3Lesson 26H2OH2O1Depiction of how an Earth-like planet orbiting another star might look like (left), and thebiosignatures (methane, ozone) we could try to detect in its atmosphere (right)
NATURE of the UniverseReview of Lesson 25Astronomy - Life in the Universe• The Universe formed 13.7 billion years ago in the Big Bang. We can observethe cosmic microwave background as the afterglow of the Big Bang.• Small fluctuations in the distribution of dark matter created the seeds for theformation 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 darkmatter, and 74% in the form of dark energy.Review: The Genesis and the Fate of the Universe2
• Life on Earth• Search for Life on Mars• Search for Extra-Terrestrial Intelligence• Summary & Review of Homework 7NATURE of the UniverseToday’s TopicsAstronomy - Life in the Universe3
NATURE of the UniverseLife on EarthAstronomy - Life in the UniverseWhat 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 generationLife reacts to the environment, and adapts to long-term changes by geneticmutations (i.e. evolution)4
The oldest life on Earth evolved 3.5 to 4 billion years ago, i.e. shortly afterEarth had cooled down sufficiently for liquid water (oceans) to existNATURE of the UniverseLife on EarthAstronomy - Life in the UniverseHow did life evolve on Earth?no O2About 3 billion years ago, oxygen-producing blue-algae bacteria(cyanobacteria) evolved, starting to enrich Earth’s atmosphere with O2.5
NATURE of the UniverseLife on EarthAstronomy - Life in the UniverseSingle cell organism evolved by getting larger in size and becominginternally more complex till 1 billion years ago multi-cell organismsevolved. This is also when the oxygen level reached its current value.Life on LandThe first plants on land evolved 500 million years ago, followed by the first landanimals (insects and amphibians) 400 million years ago6

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Term
Fall
Professor
Hansen
Tags
Astronomy, Extraterrestrial life, Homework Review, Universe Astronomy

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