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SPU-22: The Unity of Science from the Big Bang to the Brontosaurus and Beyond

SPU-22: The Unity of Science from the Big Bang to the Brontosaurus and Beyond. Lecture 24 30 April 2014 Science Center Lecture Hall A. Last Lecture (Fun: First And Finally). Search for: Extra -terrestrial life ( “ ETL ” )

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SPU-22: The Unity of Science from the Big Bang to the Brontosaurus and Beyond

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  1. SPU-22: The Unity of Science from the Big Bang to the Brontosaurus and Beyond Lecture 24 30 April 2014 Science Center Lecture Hall A

  2. Last Lecture(Fun: First And Finally) Search for: Extra-terrestrial life (“ETL”) - Our solar system (planets and satellites) - Interstellar space (precursors to life) - Planets (and satellites) around other stars Extra-terrestrial intelligent life (“SETI”) - If “they” exist, will they signal us? Will they visit us?

  3. Why Satellites Warm? Some satellites of outer planets are (unexpectedly) warm below surface, and hence possible locales for life: Why warm? Tidal effects are basis: Repetitive spin and orbital motions are accompanied by rubbing of neighboring parts of satellite - see demo - which warm them (energy comes from spin and orbital motion). What about our moon? Tidal effects now much reduced; not so in past. Why?

  4. Europa: Second of the Four Galilean Moons of Jupiter Possible abode for under-surface life? Why might we think so? Tidal warming. Surface relatively free from craters (see next two slides); implies youth of surface. Might be water ocean below surface; oxygen apparently detected in atmosphere

  5. Europa - Galilean Satellite – Relatively Free From Craters

  6. Europa Surface Detail Europa Detail

  7. What About Saturn’s Moons? Is life out of question? Case of Enceladus (analog of Europa): discoveries by the Cassini spacecraft (see next slide). Emerging material may be made of ice; source could be liquid ocean underneath; case is not clear, despite analysis of spacecraft tracking data which yield estimates of detailed gravity field of Enceladus consistent with liquid water of considerable thickness. Energy estimates indicate this activity may be only sporadic

  8. Volcano (Outgassing) on Enceladus

  9. Summary for Solar System Life may exist beyond Earth Satellites of planets may be most likely habitats Sophisticated flagship (= multibillion dollar) missions undertaken; Mars Science Laboratory searching for, but hasn’t found, evidence of life; more missions being planned and, for US, being delayed Our analog very unlikely to be uncovered in solar system

  10. Expanding Our Horizons What does rest of universe have to offer in way of life? (Good question; answer not yet so good.) Start: Name for this field of science, “Astrobiology” (only field I know with no data)

  11. Astrochemistry We start at simple level: atoms and molecules in space How do we know what’s there? Discoveries by radio telescopes. Why radio? Answer: space is cold; peak of black-body (not only CMB!) radiation is in radio part of spectrum

  12. Detection Of Atoms & Molecules In Space Slow start: Hydrogen atom in 1951 (here at Harvard); 0H in 1963 (at MIT); water and ammonia in 1968. Pace soon picked up Spatial location: Most molecules found in star-forming regions Basis for detection: Unique spectral signatures; need laboratory prediction or verification (either can come first); some still unidentified

  13. Status of Discoveries List of molecules found in space now contains about 150 entries: See next slide One point is paramount: domination of carbon-based molecules. Selection effect or real? One claim: discovery of glycine (amino acid) proven wrong. Case of wishful thinking

  14. Molecules in Space 2 atoms:~30 (Many with carbon) 3 “~35 “““ 4 “20 5 “ 16 6 “ 13 (Carbon dominance) 7 “ 8 ““ 8 “ 9 ““ 9 “ 8 ““ >10 “ 10 ““ Total = ~150

  15. Extra-solar Planets: How to Detect? Use big telescopes and look? Why not? Two strikes: dimness and proximity (in angle) to central star Indirect means to fore: 1. Radial velocity (Doppler shift or “wobble”) method; 2. Transit method; 3. Pulsar timing; and 4. Gravitational-lens method (See next eight slides for descriptions of first two methods; last two we will mostly skip.)

  16. Cartoon For Radial-Velocity Method:M x Rs= m x Rp(X = Center of Mass)

  17. Radial Velocity Method:Problem With Web

  18. Effect On Radial Velocity Of Inclination Of Orbit To Line- Of-Sight

  19. Example Of Radial Velocity Vs. Time

  20. How To Determine Mass Of Planet? Use formulas: 0. M x Rs = m x Rp(mass of each object x its distance from center of mass is same) • Vmax x Ps = 2πRs (zero inclination) • Rp3 = [GM x Ps2/4π2] and bit of algebra to obtain: m ≥ M2/3 x Ps1/3 x Vmax/[2πG]1/3 where “≥” accounts for non-zero inclination

  21. Cartoon Of Transit Method

  22. Conditions To Observe Transit(Looking Into Paper)

  23. Example Of Transit Data

  24. Comparison Of Two Methods Radial Velocity Method: Favors massive, “close-in” planets, with line-of-sight from earth in plane of planet’s orbit. Estimates of mass, not size, of planet Transit Method: Favors large, “close-in” planets, with line-of-sight from Earth in plane of planet’s orbit. Estimates of size, not mass, of planet (look at fraction of starlight blocked by planet during transit)

  25. How is Search Progressing? 1989 discovery of possible planet around sun-like star, via radial velocity method (why “possible”?) 1992 discovery of two planets around pulsar: major “shock.” Gravitational effects between two planets made detection/discovery unambiguous. (How?) 1995 discovery of first planet around sun-like star, with radial-velocity method as in 1989 1998 discovery of first planet around sun-like star via transit method Dam broke, starting in 1995. About 1,500 extra-solar planets now known, thanks mainly to Kepler - Method 2 - mission (see next slide); show has just begun!

  26. KEPLER

  27. Kepler And Planned Missions Kepler: Launched 3/7/2009; 1-m diameter telescope; field-of-view 100 square deg (what’s that?); stares at c. 150,000 stars; earth-trailing orbit; orbital period c. 373 days K2: Continuation of Kepler without pointing at same stars (reaction wheels failed on Kepler) TESS (Transiting Exoplanet Survey Satellite): All sky; monitor 500,00 stars; expect 500 earth-sized planets to be discovered; scheduled for launch 8/8/17

  28. What Have We Learned? We have data which allow estimates of masses, radii (and hence densities), as well as characteristics of orbits of many of extra-solar planets and some information on their atmospheres (far from all information for each) New information, some startling, flows in almost on daily basis. It is hard to keep up

  29. Biggest Surprises Many Jupiter-sized (and larger) planets Many, including Jupiter-sized, with remarkably short orbital periods, some of only very few days Some planets in very eccentric orbits Clear biases at work: Name two

  30. What About Life? No detections yet (if there were one, you would have heard!) What do we look for? Earth-like planets in “habitable zone” (see next slide), with atmospheric spectral signatures indicative of molecules that we associate with life, such as O2-- -- very anthropomorphic (parochial?) approach What about satellites? None yet detected around extra-solar planet

  31. Habitable Zone What is it? How do we identify these habitats? Do they have atmospheres? Do these atmospheres have oxygen? (Recall why relevant)

  32. Planets’ Positions Relative ToHabitable Zone (HZ)

  33. Kepler 186f Star: ~0.5 mass of sun; ~0.5 radius of sun; surface temperature ~60% of sun’s Planet: 1.1 radius of earth; unknown mass; in habitable zone Distance of system from earth: ~150 pc

  34. Search For Extraterrestrial Intelligence Search for purposeful signals Cocconi and Morrison (1959): Suggested looking for radio (spectral “line”) signals from hydrogen. Now have Allen Array of 42 radio telescopes in California (there were intermediate efforts) Townes (1970s): Suggested looking for (“narrow-band”) laser signals. Now have 1.8m diameter optical telescope in Harvard, MA observing for signs of such signals See next two slides

  35. Allen Telescope Array

  36. Harvard SETI Optical Telescope

  37. Where Are They? (Deep Question) Why have no extraterrestrials visited us (see next slide for one possibility of such visitors)? Possible reasons: They don’t exist They die out too fast; hence, no overlap They are not interested in communicating or in travelling. (Even light travel time is rather long.)

  38. Suppose We Reliably Discover Extraterrestrial Intelligent Life Such an event, which would likely be spread in time to be reasonably certain of reliability, could conceivably occur within your lifetimes. What then? Could we exchange visits? Could we communicate via electromagnetic signals? Listen and ye shall hear

  39. Goals for the Course (Achieved? You Decide!) Understand and remember: 1. What science is and how it “works,”and colossal scales it encompasses 2. Positive feedback loop between science and technology 3. Effects on other fields of advances in one 4. Key difference between experiments and studies of past 5. Need to seek basic evidence underlying claim or conclusion 6. Importance of asking (good) questions

  40. Grand Finale Magician’s trick!

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