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Lecture11_iks-rev0.pdf - 2019-06-13 Announcements...

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2019-06-131AnnouncementsAssignments;Online Q&A SessionsAssignments #5 & #6:both DUE Tuesday June 18 (before midnight)Online Q&A Sessions (using [Bb Collaborate] on Quercus):Friday @ 7-8 pm;Sun @ 4-5 pmFinal ExamDate:Wednesday June 19, 9:00-12:00 noonLocation: SF3202 (Sanford Fleming building, 10 King's College Rd.,Toronto, Ontario)~76 MC questions (76%),~8 short-answer Qs (24%)[pencil, ruler, calc]CoversENTIRE COURSE(i.e.- review and understand lecture notes,recommended readings in textbook, assignments, etc.)Recap from Lecture 10 (Kepler): First 1235exoplanet candidates, with Sun+Jupiter+Earthshown for comparison
2019-06-132Recap from Lecture 10 (Kepler results)Harvard study in Jan. 2013 concluded there is a high precentage(17%) ofEarth-likeplanets.AST251Life on Other WorldsLecture 11ETs: How Many? How to Find /Visit? Are We Alone?Extra terrestrial intelligenceProspects there are ETs[how to estimate?]Communication with ETs[is it possible?]Interstellar Travel[not yet, maybe never?]Extra terrestrial intelligence“So where are they?[a very good question!]Ch.20 (+ maybe some 21)
2019-06-133The 'Rare Earth' HypothesisThe rare EarthMost scientists expect there are large numbers of terrestrial-sizeplanets with conditions sufficiently similar to those on Earthto lead to the formation of life elsewhere.Usually, it is agreed thatsimple life formsmay be relatively easilyto get started; but some argue thathigher level life like that onEarth exists because of“incredible luck”.The“rare Earthhypothesis” states thatsimpleLife might becommon, BUTadvancedLifesimilar to that on Earth isextraordinarily rare, and could have happened only through avery unusual set of fortunate circumstances.
2019-06-134The“rare Earth” arguments1.“Galactic HZ”:Earth-like planets can form incertain parts of the Galaxy: If too far from thecentre, then too little heavy elements; if too close tothe centre, then too many devastating Supernovaexplosions that would destroy life.2.Earth is special in havingplate tectonicswhichenables the CO2cycle to operate and hence ensuresclimate stability.... but we dont know how common plate tectonics is in Earth-size planets3.Therole of Jupiterin deflecting & swallowing comets and planetoidswhich otherwise would strikethe Earth. If the Solar System had a “hotJupiter” close to the Sun,there would be no defense against them.... yes, but we dont know yet how common hot Jupiters really are(recall thebiasesin extrasolar planet detections!)The rare Earth arguments4.There is“justright” amount ofwateron Earth.... but life on Earth is very adaptable (as long as there is somewater)5.Earth has abig Moonwhich prevents it from experiencing chaoticand unpredictable rotation axis tilt variations (as with Mars). It's onlybecause of the Moon that Earths climate is stable for long duration.

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Term
Winter
Professor
Kante
Tags
Extraterrestrial life, Extrasolar planet, Rare Earth hypothesis, SETI

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