1. Origins of Life Physics 102 Goderya Chapter(s): online Learning Outcomes: 1,11,10,11,12

2. What is life?

3. Information Storage and Duplication All information guiding all processes of life are stored in long spiral molecules of DNA (Deoxyribonucleic Acid) Basic building blocks are four Amino acids: Adenine, Cytosine, Guanine, and Thymine Information is encoded in the order in which those amino acids are integrated in the DNA molecule.

4. The Miller Experiment Miller Experiment in 1952: Simulating conditions on Earth when life began ~ 4 billion years ago: Water (oceans), primitive atmosphere gases (hydrogen, ammonia, methane), and energy from electric discharges (lightning). Experiment produced some of the fundamental building blocks of life: amino acids, fatty acids, and urea.

5. Three Questions About the Evolution of Life 1) Could life originate on another world if conditions were suitable? 2) Will life always evolve toward intelligence? 3) How common are suitable conditions for the beginning of life? Miller experiment etc. indicate: probably yes. If intelligence favors one species over another: probably yes.  Investigate conditions on other planets and statistics of stars in our Milky way

6. Some Requirements of Life Liquid water (for chemical reactions and as transport medium). Atmosphere (to avoid rapid vaporization of water; gasses needed for organic compounds) Moderate temperatures (keep water liquid; avoid disintegration of organic compounds; activate complex chemical reactions) Time for life to evolve from simple organic compounds into higher life forms: several billion years.

7. Life in Our Solar System Other planets or their moons are unlikely to have ever provided suitable conditions for life. Meteorite ALH84001,0 probably originated on Mars. Most promising candidate: Mars. Possibly some evidence of past life on Mars, but questionable. Claimed traces of microscopic fossils may well be regular mineral formations in the rock.

8. Requirements for Life in Other Planetary Systems Planetary systems are probably common. Stable orbit around the star  consider only single stars. Time for evolution  consider only F5 or less massive stars. Moderate temperatures  Life zone around the star

9. How do we communicate with other intelligent life? Source: NARO-VLBA Mauna Kea Hawaii

10. Communication with Distant Civilizations Direct space travel to other stars not feasible due to large distances (long travel times). Viable alternative: Radio communication. Even for radio communication: Long answer times due to light-travel time. Messages can be arranged in blocks of certain length that is a product of two prime numbers  Only two ways to arrange them in a rectangle.

11. The Arecibo Message At dedication of Arecibo Radio Observatory, blocks of 1679 pulses were emitted, which can be arranged in only two ways: Resulting 23 x 73 grid contained basic information about our human society. 23 rows of 73 or 73 rows of 23.

12. The Search for Extraterrestrial Intelligence (SETI) In addition to sending messages to possible extraterrestrial civilizations, there are also programs to listen for intelligent messages from space: SETI. Signals would be overwhelmed by background noise SETI program is highly controversial because of the uncertain prospects of positive results. Only certain wavelength ranges are suitable for this search.

13. The Drake Equation Factors to consider when calculating the number of technologically advanced civilizations per galaxy: N c = N * · f p · n LZ · f L · f l · F S Most of the factors are highly uncertain. Possible results range from 1 communicative civilization within a few dozen light years to us being the only communicative civilization in the Milky Way.

14. What if life is not carbon based? What other chemical element is a viable candidate for life? Theories and Hypothesis.