11The Science of Life in the Universe (Chap 2 – Bennett/Shostak)28 January 2009 - Lecture 3HNRS 228 - AstrobiologyProf. Geller2Overview of Chapter 2Ancient Debate about Life Beyond Earth (2.1)Greeks and GeocentrismThe Copernican Revolution (2.2)Copernicus, Tycho, Kepler, Galileo, NewtonThe Nature of Modern Science (2.3)The scientific method3Overview of Chapter 2The Process of Science in Action: Understanding Gravity (2.4)Newton’s view of gravityEinstein’s view of gravityString theory view of gravity (not in text)4But First – Writing Science AnswersRegarding answering science questionsComplete sentencesScience reasoningSpecific examplesNumbers/formulas once in a while is niceUse all information givenAnswer can start with words from question5Example QuestionEvaluate the given statement and decide whether it makes sense. Explain your reasoning clearly.Even if we discover a civilization around other stars, we will never be able to talk with them with the same ease with which we carry on conversations with people on Earth.6Sample Answer Given that we discover a civilization around other stars, let’s examine the closest that such a civilization could be from the Earth. The nearest star is 4.3 light years distant from Earth. This means that a two-way conversation would take at least 8.6 years, since no information can travel faster than the speed of light. While this is well within a human lifetime of say 75 years, it is a long time for a conversation. There would be a delay of at least 8.6 years for any two-way conversation between any civilization ever discovered. This does not represent an ease with which we carry on conversations with people on Earth. The maximum distance between any two points on Earth is about 26,000 miles (the approximate circumference of the Earth), much less than the speed of light travels, which is approximately 186,000 miles per second. Therefore, the given statement makes sense.27Another Sample QuestionEvaluate the given statement and decide whether it makes sense. Explain your reasoning clearly.If the universe did not contain stars more massive than our Sun, we couldn’t be here.8Sample Answer Related to Chapter 1 The chemical elements upon which all life on Earth is based upon, includes many elements heavier than lithium, such as carbon, nitrogen, and oxygen. All elements heavier than lithium were produced in stars that died as supernovae, long before our Sun was formed. A star like our Sun, can only form elements up to carbon. Elements beyond carbon require stars that are greater than about 3.8 solar masses. Therefore, the statement given makes sense, since we need heavier stars to make the chemical elements upon which our lives are based. In fact, only the most massive stars, greater than about 10 solar masses, will ever form the chemical elements of iron and those more massive than iron, up to and including uranium. Now, back to Chapter 2…9Universality of Chemistry and Physics?Are laws of physics universal?What do we mean by universal?What do we mean by Laws of Physics?How do we know they operate in the universe?Are laws of chemistry universal?What do we mean by universal?What do we mean by Laws of chemistry?How do we know they operate in the universe?10Universality of Biology?Characteristics (laws?) of biological systems universal?What do we mean by universal?What do we mean by characteristics of biological systems?How do we know they operate in the universe?11Universality of Biology?Reasons for optimismEarly Earth’s innate constituents formed complex carbon-based organic molecules (e.g., carbohydrates, lipids, nucleic acids, etc.)Observation of comparable organics on meteoritesStep from chemistry to biology not difficult (thermodynamically)Life arose very early on Earth (first 10% of time)Conditions on Earth were right even though extremeSuccess of “extremophiles”High probability that principle characteristics of life are universal12Science of Astrobiology (by any other name)ExobiologyBioastronomyAstrobiologyNASA (National Aeronautical and Space Administration)Study of life in the UniverseGenerally accepted components (remember ODDS)Beginnings of life on Earth and its evolutionLife elsewhere in the UniverseFuture of life on Earth and elsewhere313The Beginnings of AstrobiologyMythology (< 600 BC)Thales and Pythagorus (~600 BC – 500 BC)Geocentric view of earth and solar systemComposition of nature: water, fire, earth and airAtomists (~600 BC – 400 BC)Universe composed as noted aboveMultiple worlds with lifeKey ideas of AtomistRandom events elsewhere as on EarthGeocentric viewAtom-like chemistryReally not science – more intuition and philosophy14Historical Debate on Life in Other Worlds: SpeculationMythology (< 600 BC)Atomists (~600 BC – 400 BC)Aristotelians (~400 BC – 300 BC)Christianity (Middle Ages)Transition: Speculation to ScienceCopernican RevolutionRevolution in the Life Sciences and GeologySummary: role of science versus speculation15Speculation ContinuedAristotelians (~400 BC – 300 BC)Plato (400 BC) and Aristotle (350 BC)Rejected atomistsTenets: 4 elements plus “aether”GeocentricismUniqueness of the EarthIntegration into Christianity in 1250 AD by St. Thomas Aquinas16Speculation ContinuedPluralism and Christianity (Middle Ages)Plurality of worlds: many worlds in the UniverseChristian scholars: problemJewish scholars: no problemIslamic scholars: no problemEastern Religions scholars: no firm positionFrom Speculation to ScienceKey to all of the above: speculation not scienceWhy?What events trigger the transition from speculation to science (1450?)17The Road to theCopernican RevolutionKey: “models” of how nature operatesDefine model: conceptual, mechanistic, mathematicalOutline approach: observation followed by constructModels fail (and this is good!!)Ptolemy Model of the Solar System (1150 AD)Geocentric, “circle-upon-circle”, tricks, all paths circularReasonable accuracy of model18iClicker QuestionIn the Greek geocentric model, the retrograde motion of a planet occurs whenA Earth is about to pass the planet in its orbit around the Sun.B the planet actually goes backward in its orbit around