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ASTR/GEOL 3300: ET Life

ASTR/GEOL 3300: ET Life. Logistics: Final exam is Monday December 13! Bring your notes, books, etc. 1:30 – 4:00 pm here. Final papers due to me electronically AT THE FINAL EXAM before 5pm ! Our Last Day IS THIS FRIDAY: Pick up old work & paper reviews!!!!!!

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ASTR/GEOL 3300: ET Life

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  1. ASTR/GEOL 3300: ET Life • Logistics: • Final exam is Monday December 13! Bring your notes, books, etc. • 1:30 – 4:00 pm here. • Final papers due to me electronically AT THE FINAL EXAMbefore 5pm! • Our Last Day IS THIS FRIDAY: • Pick up old work & paper reviews!!!!!! • We will finish our discussion of interstellar travel. • Then, Fermi’s Paradox • Implications of the Search • UFOs

  2. Pick up more reviews please Brandt, Grudzinski, Gray, Okonowsky, Townsend, Trohman, Ely, Uhle, Collette, Kaspyrzk, Rynning, McCollom, McNeill, Watson, Hazlitt, Fairbanks, Hecht, Lewis, Melville

  3. Matter/Antimatter • Isp ~105 - 107 • Might work at ~100% efficiency, mass required is reasonable • No real designs, many enormous hurdles (containment, production, radiation, efficiency) • 100 billion dollars for 1 mg!

  4. RECALL • This is for a 1000 year, one-way voyage to the nearest star. • Are there ways to do this without carrying the propellant with you? • Space is not quite empty

  5. Relativity and other weirdness • No matter who you are or where you are, how fast you’re moving and in what direction, the speed of light in vacuum always appears the same to you. • Whoa, but this has been verified many times • You can’t go more than 3 x 108 m/s • The faster you move, the slower time passes • The faster you move, the more massive you get

  6. 4 ly 10 ly 50 ly 150 ly 20,000 ly 2,000,000 ly 106 ly Perceived travel times To where? How long (to traveler) ? How far? • Alpha Centauri • Epsilon Eridani • Deneb • Pleides • Center of Milky Way • Andromeda galaxy • Virgo cluster • 2.5 y • 5 y • 10 y • 15 y • 21 y • 28 y • 30 y

  7. The Scientific Method (Chapter 2) • Science seeks natural explanations for observed phenomena: • Explanations rely solely on natural causes. • "Miracles" are not allowed. • Science advances by developing and testing hypotheses (models). • A scientific model must make testable predictions. • If tests show that the predictions are false, the model must be revised or abandoned. • Occam's Razor: • The simplest scientific model that fits all the observations is most likely the right one.

  8. Incorrect Scientific Practice • Pseudoscience ("false science"): • Masquerades as science, but does not follow the scientific method. • Commonly based on adherent belief. • Cannot be shown to be false to the satisfaction of practitioners. • Unfortunately, there are many, many, many examples.... "Extraordinary claims require extraordinary evidence." - Carl Sagan

  9. The Cosmic Calendar The Universe Is Old, So… • First civilizations might have arisen ~5 Byr after galaxy formed: • Mid-June on CC. • If 1/1,000,000 stars has civilization, a new civilization arises each 60,000 yr! • Each 3 min on CC. (Book says Aug. 14)

  10. Fermi’s Paradox:Where Is Everybody?

  11. The Coral Model of Galactic Colonization • Coral Model: • Advanced beings (or self-replicating machines) are sent from home planet to build colonies; • Each colony sends out more colonies. • Entire galaxy is colonized “quickly”: • ~105 yr at 0.9 c • ~107 yr at 0.1 c • ~108 yr at 0.01 c

  12. Where Is Everybody?Possible Solutions to Fermi’s Paradox • We are alone: • Civilizations are very rare & we may be the first. • Civilizations have not colonized: • Technological difficulties: • Interstellar travel is too hard or expensive. • Sociological considerations: • Other societies choose not to colonize. • Self-destruction: • Civilizations do not survive long enough to colonize. • Civilizations do not wish to reveal themselves: • Zoo Hypothesis: • They are watching us… • Sentinel Hypothesis: • Devices are standing by until we’re ready…

  13. Implications of the Search

  14. Intelligent Life: Poll • When will humans find convincing evidence of intelligent extraterrestrial life? • In the next 20 years. • In the next century. • In the next millennium. • In the even more distant future. • Never--there is probably no other intelligent life out there to find.

  15. Microbial Life: Poll • Will humans eventually find convincing evidence of microbial extraterrestrial life in our solar system? • Yes, probably just at Mars. • Yes, probably just at Europa. • Yes, at Mars & Europa (at least). • There is probably no microbial extraterrestrial life in our solar system. • I just don’t know.

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