1. Astronomy 3040 Astrobiology Spring_2016 Day-18

2. The Drake Equation 1961 – 1 st 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.

3. The Drake Equation Number of Civilizations = N HP X f life X f civ X f now N HP -Number of habitable planets in galaxy f life -Number of habitable planets that have life f civ -Fraction of life-bearing planets where a civilization capable of IS communication at some time has arisen. f now -Fraction of habitable planets with civilization now, not in the past.

4. 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

5. 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

6. 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).

7. 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

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

10. 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.

11. 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.

12. 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

13. SETI - Today Categories of Signals 1. Local communications on other world. 2. Communications between home world & other site. 3. Intentional signal beacons. (Project Ozma) In theory, SETI can detect all three types. 26m dish at NRAO-Green Bank

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

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

16. SETI - Today Current SETI projects

17. 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.

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

19. Artifacts Parking spaces – Lagrange points Manufacturing plants.

20. Types of Civilizations Nikolai Kardashev – 20 th 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

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

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

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

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

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

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