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Rodman Seminar Oct 11, 2005

Rodman Seminar Oct 11, 2005. Today: Life beyond the Solar System. Intelligence. Definition = technology. On Earth: At least one species Several almost there Most not there If intelligent life elsewhere, Where to look? What to look for?. Is intelligence likely or unlikely?

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Rodman Seminar Oct 11, 2005

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  1. Rodman Seminar Oct 11, 2005 Today: Life beyond the Solar System

  2. Intelligence Definition = technology. On Earth: • At least one species • Several almost there • Most not there If intelligent life elsewhere, • Where to look? • What to look for? Is intelligence likely or unlikely? What factors are important?

  3. Intelligent life : Drake Equation [Proposed by Frank Drake in WV, 1960]

  4. Intelligent life : Drake Equation

  5. N* : # stars in our galaxy Roughly 100 billion stars Average separation: a few LY = few 100,000 AU Sun

  6. fC : fraction with planets Must detect indirectly: (so far) Planet gravity acts on star Starlight alternately blue- then red-shifted  About 150 discovered so far, all gas giants in 15% of stars surveyed.

  7. Extrasolar planets Sizes of planet systems discovered so far  Tend to have: Jupiter-sized planets close to stars Eccentric orbits Not like our S.S?

  8. Extra-Solar Earths Can’t detect them yet: • Too faint compared to star: • Wobble effect on star too small. If we find them, possible life signs? • O2 in atmosphere • Planet color (oceans, vegetation) • Pollution? • Transmissions?

  9. fHZ : fraction with planets in HZ Need liquid water. Depends on distance from star: Too distant  too cold • H2O only as ice • Mars-like Too close  too hot • H2O only as gas • Venus-like Planet must be in this region for right Temp

  10. Habitable Zones Zone location depends on star size. Stars heavier than Sun burn out quickly. Stars smaller than Sun are dim and unstable.  Cooler – Star Temp – Hotter 

  11. Habitable Zones

  12. Habitable Zones Common or rare? Our Solar System: 1 to 3 planets inside fHZ near 1? Other systems: Giant planets close to stars + eccentric orbits = Earthlike planets unlikely? fHZ near 0?

  13. Habitable Zones Galactic HZ:

  14. Too dangerous Reasonably safe & stable Enough heavy elements Element poor Habitable Zones Galactic HZ:

  15. fL :fraction with life Our S. S. example only example: On Earth, life developed early  fL = 1 ? Or include failures on Mars, Europa  fL = 1/2, 1/3 ? Or life on Earth a fluke  fL near 0 ?

  16. fI : fraction where life becomes intelligent Earth only example: What factors were important? Evolution  moves toward intelligence? fI = 1 ? Or, only 1 species out of all life on Earth? fL near 0 ? Or are several species close?

  17. L: civilization lifetime Considerations: • For us, at least ~ 100 years. • Typical or much much longer? • Considerations Do we destroy ourselves? Can we handle natural catastrophes?

  18. Drake Equation Estimates could give N = 1 to N = 107. Number not as important as the process  guides thinking about SETI.

  19. ETI Cocconi & Morrison (1959) suggest searching is possible. SETI begun to search radio frequencies around “water hole”: Project Ozma: 1960 Tatel Telescope, WV

  20. SETI What do we look for? ‘Leakage’ Ex: radio/TV signals. Weak, limited to nearby. Getting weaker with tech advances. ‘Hello’ Intentional transmissions  Can see greater distances. Recently: Optical SETI – search for laser pulses. Our transmission toward M13

  21. SETI Various SETI programs at major telescopes over past 40 years. New dedicated telescope: ATA Allen Telescope Array, 300+, 5 m dishes Under construction Puerto Rico, 300 m dish

  22. SETI • Several projects funded by NASA until 1993 • Political pressure, other NASA projects. • “Giggle factor” • Restarted with private funding. • Project Phoenix • SETI Institute • NASA today: Origins Program • Goal “To explore the universe and search for life.”

  23. SETI Search for signals from ETI (radio or optical) No detections yet. Some strong, strange signals,  but none repeatable. Progress: have searched only a fraction of Galaxy. Probability of success low or high? Worth doing? Is this science? Ohio State, 1977

  24. SETI@Home

  25. SETI Progress

  26. Fermi Paradox Where is everyone?

  27. Fermi Paradox Average distance between stars = few LY Travel time: 100 years? Rebuild and launch next ship: few 100 years? = Time to colonize galaxy: few million years much less than age of Galaxy using known technology

  28. Fermi Paradox Possible solution #1: • We are alone.

  29. Rare Earth • Unique coincidences on Earth: • In the Sun’s Habitable Zone for a long time. • In Galactic Habitable Zone for a long time. • Right size to keep enough atmosphere. • Has a large Moon. • Jupiter protection from impacts. • Chemical conditions just right – narrow range needed?

  30. Fermi Paradox Possible solution #2: • We aren’t alone, other factors at work. • Colonization not popular? • Interstellar travel not feasible? • Zoo hypothesis. • They are here.

  31. Interstellar Travel Nuclear detonations Nuclear fusion

  32. Interstellar Travel Fusion with ramscoop Light sail

  33. Interstellar Travel Other Issues: Timescales – decades to centuries Generation ships? Suspended animation? Send genetic material only? Hazards Small impacts with dust, meteoroids Radiation damage

  34. Interstellar Travel More exotic methods • Example: wormholes

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