1 / 48

S.E.T.I.

ET, where are you? Chapter 12 Day 27. S.E.T.I. Ch. 12 - HW. Due Fri. 29 April 1, 2, 9, 25, 29, 32, 35, 43, 44, 47. Announcements. Final Exam – Tuesday May 5 – 0800 Presentations – Wednesday, April 29 Chapter 13 – HW – due exam time 1, 6, 11, 33, 34, 35, 49, 50, 51, 52, 55.

joanne
Download Presentation

S.E.T.I.

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. ET, where are you? Chapter 12 Day 27 S.E.T.I.

  2. Ch. 12 - HW • Due Fri. 29 April • 1, 2, 9, 25, 29, 32, 35, 43, 44, 47

  3. Announcements • Final Exam – Tuesday May 5 – 0800 • Presentations – Wednesday, April 29 • Chapter 13 – HW – due exam time • 1, 6, 11, 33, 34, 35, 49, 50, 51, 52, 55

  4. The Drake Equation • 1961 – 1st SETI conference, Green Bank, WV • Number of civilizations in our galaxy (or the Universe at large) from which we could potentially get a signal. • Does NOT give a definitive answer. • Rather, it lays out the factors that are important in determining this number.

  5. The Drake Equation • Number of Civilizations = NHP X flife X fciv X fnow • NHP -Number of habitable planets in galaxy • flife -Number of habitable planets that have life • fciv -Fraction of life-bearing planets where a civilization capable of IS communication at some time has arisen. • fnow -Fraction of habitable planets with civilization now, not in the past.

  6. Cosmic Calculation #1 • What is the volume that civilizations could occupy in the galaxy? • Assume limited to the disk. Why? • Metallicity content • Age of stars

  7. Is Intelligence Widespread? • If life is widespread, what about intelligence? • SETI is only successful if THEY communicate. • Homo sapiens have only started to understand the environment and explore the cosmos in the last <500 years. • Suggests a long period of evolution is required to produce technologically intelligent creatures. • Chance events • body plans in Cambrian explosion • K-T extinctor

  8. Convergent Evolution • The tendency of organisms of different evolutionary backgrounds that occupy similar ecological niches to resemble each other. • Large marine predators – dolphins & sharks • Eyesight (eyes evolved eight times).

  9. Encephalization Quotient (EQ)‏ • Raw brain power based on brain mass. • Simple measure • EQ = 1 line – general intelligence • Above line – capable of elaborate behavior • Below line – less mentally agile

  10. Evolution of Intelligence • Humans don't have the largest brains. • Is the largest in relation to body mass.

  11. Early SETI • Marconi (1874-1937)‏ • Tesla (1856-1943)‏ • Both claimed to have heard aliens on the radio. • Probably “whistlers” • Low frequencies which don't penetrate atmos.

  12. Modern SETI - Origins • 1959 – Cocconi & Morrison – Cornell Univ. • Galaxy is older than solar system, so could be civilizations around linger than ours. • Band – set of freqs receiver is sensitive to. • Bandwidth – a particular freq. in the band. • Governed by how much information is xmitted.

  13. Announcements • Final Exam – Tuesday May 5 – 0800 • Presentations – Wednesday, April 29 • Dept. Spring picnic this afternoon • 4:30pm, fairgrounds • Chapter 13 – HW – due exam time • 1, 6, 11, 33, 34, 35, 49, 50, 51, 52, 55

  14. SETI - Today • Categories of Signals • Local communications on other world. • Communications between home world & other site. • Intentional signal beacons. (Project Ozma) • In theory, SETI can detect all three types. 26m dish at NRAO-Green Bank

  15. Our Own Signals • Broadcast in ~1950, just past 50 ly distance. • High power, high-frequency TV • > 2000 stars in this volume. • Star map

  16. A Signal Look for: repetition, prime numbers … 1974 – signal sent to M13 (bad choice in hind sight). – 21,000 ly distant.

  17. SETI - Today • Current SETI projects

  18. Radio –vs.– Optical • Radio is a logical choice since we developed radio capability early (didn’t everyone?) • Dust blocks light in the denser parts of the Galactic plane. • Limits our view to a few hundred parsecs. • Not as big an issue today. • But how? • Laser pulses - doesn’t everyone know Morse code? • Lick – 500 ly search distance • Harvard also has a project going.

  19. Artifacts • 2001: A Space Odyssey • The TMA is clearly not natural.

  20. Artifacts • Parking spaces – Lagrange points • Manufacturing plants.

  21. Types of Civilizations • Nikolai Kardashev – 20th century Planetary (Type I) – use resources of home planet. Stellar (Type II) – corral resources of home star. Galactic (Type III) – employ resources of entire galaxy. • We’re in the first category. • What would be the hallmark of the third? “Any sufficiently advanced technology is indistinguishable from magic.” – Sir Arthur C. Clarke

  22. Type II Civilizations • Dyson Sphere Freeman Dyson • Could detect the IR radiation

  23. Big Question • What if we succeed in finding another civilization? • Declaration of Principles Concerning Activities Following the Detection of Extraterrestrial Intelligence Sistilli NASA experience Jill Tarter at Arecibo

  24. UFOs • Project Bluebook • Day the Earth Stood Still • War of the Worlds • Mars Attacks

  25. Evidence of Visitation • Roswell, NM • July 8, 1947 • 2009 Conference

  26. Evidence of Visitation • Crop Circles • Abductions “Extraordinary claims require extraordinary evidence.” - Carl Sagan

  27. Ancient Visitations? • Nazca Line Drawings in Peru, ~2000 years ago. • Mayan pyramids • Easter Island heads

  28. If we find them, can we visit? Chapter 13 Interstellar TravelFermi Paradox

  29. Challenges of Interstellar Travel • Pioneer 10, 11; Voyager 1, 2; New Horizons • All five are headed out of Solar System • No place in particular. • All carry messages.

  30. Challenges of Interstellar Travel • Pioneer 10 – headed to Aldebaran • Pioneer 11 - Aquila • At current average speed P10 will rqr 115,000 yrs to reach Alpha Centauri (if it was headed there), the closest star system to us – 4.4 ly • Pioneer 10 plaque

  31. Speed of Light – the Real Issue • Special Theory of Relativity – Einstein • Can't travel through space faster than speed of light. • Closest star system – 8.8 years round trip • Not counting acceleration time. • Energy – even at 10% speed of light, a ship that could carry 5000 people at 18,000 kg/person (Titanic) – 100,000,000 kg. • Using ½mv2 = E ==> 4.5 X 1022 Joules • 100 times the world's annual energy use.

  32. Rockets • Cosmic Calculation 13.1 (pg 442). • Rocket Equation • Rocketry began (in earnest) in the early 1900s • Tsiolkovsky, Goddard, Oberth • The issue is mass ratio ~39 for the most efficient chemical system. Requires multi-stage vehicles to achieve Earth orbit. • A 100-stage Saturn V – ignore all the other issues – could only achieve 0.1% of speed of light (0.001c).

  33. Konstantin Tsiolkovsky Robert Goddard

  34. B.D.B. Mass Ratio – 23.1 13,300 kg to Moon

  35. Rockets • What about non-chemical propulsion? • Nuclear • Fission is only 0.07% efficient, mass conversion. But, dwarfs chemical. • Fusion, 0.7%. • Use reactor to heat a propellant and expel it. • Early NERVA projects were in development in 50s and 60s.

  36. Exotic Nuclear Projects • Project Orion – good use of bombs? • Not the current Orion • ~100 yrs to Alpha Centaurus

  37. Exotic Nuclear Projects • Project Daedalus – BIS • Deuterium pellets – fusion powered • 50 yrs to Barnard's Star.

  38. Exotic Nuclear Projects • Ion engines • Low power (impulse) but long firing (years-decades)‏ • Tested in space – ESA and NASA

  39. Solar Sails • Very large. Probably limited to interplanetary. • Space test planned “soon”. • Lasers?

  40. How about near the speed of Light? • Relativity • Time dilation – time slows down on board the ship as you approach c. • Cosmic calculation • 13.2 (pg 451)‏ • Constant acceleration • 500ly in 12 years • But 500 yrs on Earth

  41. How about near the speed of Light? • Matter – Antimatter propulsion • 100% conversion. • But, how contain it? • IS Ramjets • Collisions

  42. Hyperspace • Relativity • If we can't go at or beyond the speed of light in space, what about bending or folding, spacetime? • Einstein – General theory of relativity. Energy to create a mass to warp space.

  43. Black Holes, Wormholes • How control a BH? • Massive ones might be stable • Torus in core?

  44. Fermi Paradox • If we're not special, then there should be older civilizations in the galaxy. Where are they? • Von Neumann machines – self replicating. • Would other civilizations try to colonize the galaxy? • Coral model • 10% c, 150 years to 5ly • Entire galaxy in 10 Myr • 100 Myr at 1% c

  45. Motives to Colonize • Humans want to explore. Are we unique? • Extinction-proof civilization • Population control? - Not likely.

  46. Fermi Paradox - Solutions 1. We are alone, therefore we are it. 2. Civilizations are common – but no one has colonized the galaxy. A. Technological difficulties. B. Sociological considerations. C. Self-destruction. 3. There is a galactic civilization – they just don't want to deal with us. Zoo hypothesis Sentinel hypothesis

More Related