The Search for Life in the UniverseThe Search for Life in the Universe

Jonathan DursiJonathan Dursi

Introductory StuffIntroductory Stuff

Fill out Questionnaires!Fill out Questionnaires!

● Even if you're not sure you're taking classEven if you're not sure you're taking class● Will discuss them after breakWill discuss them after break● Gives me a chance to know where you're coming Gives me a chance to know where you're coming

fromfrom

What we're going to coverWhat we're going to cover

● Today – Mar 12: Today – Mar 12: The Science behind the SearchThe Science behind the Search

– AstronomyAstronomy– Planet Formation/EvolutionPlanet Formation/Evolution– Origin/Evolution of LifeOrigin/Evolution of Life

● Mar 19— May 14: Mar 19— May 14: The Search, Past and PresentThe Search, Past and Present

– Within our Solar SystemWithin our Solar System– BeyondBeyond

How it's (probably) going to workHow it's (probably) going to work

● Go through most of textbookGo through most of textbook● Read 1-2 chapters ahead of timeRead 1-2 chapters ahead of time● Very short quiz on reading at start of classVery short quiz on reading at start of class● Lectures/discussions (separated by break) to Lectures/discussions (separated by break) to

make sure we understand the materialmake sure we understand the material● Assignment on the material due next weekAssignment on the material due next week● Bonus marks forBonus marks for

– Bringing relevant news/media clippings in Bringing relevant news/media clippings in to classto class

– Other stuff as it arisesOther stuff as it arises● Final project/presentation Final project/presentation

Today we start out slow...Today we start out slow...

● What is the nature of the search for What is the nature of the search for truth?truth?

● What is life?What is life?

The Search for Life in the UniverseThe Search for Life in the Universe

Lecture 1: What is Science?Lecture 1: What is Science?

A Scientific FactA Scientific Fact

● How does the Moon glow?How does the Moon glow?

Science is Not a Collection of `Facts'Science is Not a Collection of `Facts'

● `Facts', by themselves, are dead, empty `Facts', by themselves, are dead, empty statements.statements.

● Statements by themselves are neither scientific Statements by themselves are neither scientific nor non-scientific. (They may be true or false)nor non-scientific. (They may be true or false)

● Science is a process that takes observations of Science is a process that takes observations of our world and ideas, and critically examines our world and ideas, and critically examines them, spitting out new observations and ideas.them, spitting out new observations and ideas.

`Facts' unverified and asserted as `Facts' unverified and asserted as truth is NOT science.truth is NOT science.

● ````... only provided further evidence that a ... only provided further evidence that a technological civilization once existed on Mars technological civilization once existed on Mars and that the artifacts of that civilization are still and that the artifacts of that civilization are still visibly presentvisibly present. '' -- P. Gersten, Formal Action . '' -- P. Gersten, Formal Action Committee for Extra-Terrestrial StudiesCommittee for Extra-Terrestrial Studies

Moon glowMoon glow

● Evidence for: Position of sun, moonEvidence for: Position of sun, moon

– Side of moon facing sun glows, side away Side of moon facing sun glows, side away remains dark.remains dark.

● How can we test that theory?How can we test that theory?

Moon glowMoon glow

● Evidence for: Position of sun, moonEvidence for: Position of sun, moon

– Side of moon facing sun glows, side away Side of moon facing sun glows, side away remains dark.remains dark.

● How can we test that theory?How can we test that theory?

– Should be sharp distinction between lit Should be sharp distinction between lit side and dark sideside and dark side

– Light coming off moon should be `similar' Light coming off moon should be `similar' color to coming off suncolor to coming off sun

These Predictions can be TestedThese Predictions can be Tested

● Side of moon Side of moon illuminated by sun illuminated by sun always shines, other always shines, other side doesn'tside doesn't

● Moon does display a Moon does display a terminatorterminator

● Spectrum of light Spectrum of light from moon can be from moon can be compared to sunlight, compared to sunlight, the two are similarthe two are similar

What is Science?What is Science?````Science is what we have learned about not fooling Science is what we have learned about not fooling

ourselvesourselves.''.''

- Richard Feynman- Richard Feynman

The real purpose of the scientific method is to make sure The real purpose of the scientific method is to make sure Nature hasn't misled you into thinking you know something you Nature hasn't misled you into thinking you know something you

don't actually know.don't actually know.

- Robert M. Pirsig, - Robert M. Pirsig, Zen and the Art of Motorcycle MaintenanceZen and the Art of Motorcycle Maintenance

Science in a NutshellScience in a Nutshell

● Skepticism, Skepticism, SkepticismSkepticism, Skepticism, Skepticism● ``Oh yeah?''``Oh yeah?''● HowHow do we know something? What's the do we know something? What's the

evidence?evidence?● If we If we dodo know it, what new things does it tell us? know it, what new things does it tell us?

Are those new things it tells us true? Are those new things it tells us true?

Science in a NutshellScience in a Nutshell

Observations (reality)Observations (reality)

ExplanationExplanation(theory)(theory)

ConsequencesConsequences(predictions)(predictions)

TestsTests

Science in a NutshellScience in a Nutshell

● The universe is understandableThe universe is understandable● Scientific knowledge is foreverScientific knowledge is forever● Scientific ideas are subject to changeScientific ideas are subject to change● Science demands evidenceScience demands evidence● Science explains Science explains andand predicts predicts

How could we test the `Mars Face' How could we test the `Mars Face' Theory?Theory?

How could we test the `Mars Face' How could we test the `Mars Face' Theory?Theory?

Viking, 1976Viking, 1976 Mars Global Mars Global Explorer, 1999Explorer, 1999

Careful ObservationCareful Observation

● Careful observation is the beginnings of all Careful observation is the beginnings of all science.science.

● Observations can be of the world as it is or of Observations can be of the world as it is or of carefully set up situations to see what happens carefully set up situations to see what happens (experiments)(experiments)

● In some sciences experimentation isn't possible In some sciences experimentation isn't possible (astronomy) or is limited (human behavior), and (astronomy) or is limited (human behavior), and only observations are feasibleonly observations are feasible

● Making careful observations isn't as easy as it Making careful observations isn't as easy as it may seem.may seem.

Pseudo-sciencePseudo-science

● Scientific-sounding claims without the evidence Scientific-sounding claims without the evidence and testing to back them up.and testing to back them up.

● Testing a theory doesn't guarantee that it's true, Testing a theory doesn't guarantee that it's true, no matter how many times you get the right no matter how many times you get the right answer.answer.

● But But notnot testing the theory means that there's no testing the theory means that there's no way at all of separating good ideas from way at all of separating good ideas from nonsensenonsense

Pseudo-sciencePseudo-science

● Examples?Examples?

Science in a NutshellScience in a Nutshell

● What are the most important things we can ask What are the most important things we can ask for in a scientific theory?for in a scientific theory?

Science in a NutshellScience in a Nutshell

● What are the most important things we can ask What are the most important things we can ask for in a scientific theory?for in a scientific theory?

● I'd say two things are:I'd say two things are:

– Should be Should be truetrue– Should be Should be usefuluseful – it lets us make – it lets us make

predictionspredictions

Science in a NutshellScience in a Nutshell

● Two are relatedTwo are related● All theories/ideas must constantly be tested.All theories/ideas must constantly be tested.● Fails the test: Must be FalseFails the test: Must be False● Passes the test: True?Passes the test: True?● How do we test a theory/idea/lawHow do we test a theory/idea/law

What Is Science Good At?What Is Science Good At?

What Science is Very, Very Good atWhat Science is Very, Very Good at

● Searching for answers when:Searching for answers when:

– There definitely is an answerThere definitely is an answer– The answer is objective (all rational agents The answer is objective (all rational agents

would agree on the answer)would agree on the answer)● Building ideas to explain these answers.Building ideas to explain these answers.● Questions about our physical Universe are like Questions about our physical Universe are like

this.this.

What Is Science Not Good At?What Is Science Not Good At?

What Is Science Not Good At?What Is Science Not Good At?

● Searching for answers when:Searching for answers when:

– There isn't definitely is an answerThere isn't definitely is an answer– The answer is subjectiveThe answer is subjective

● ReligionReligion● RelationshipsRelationships● Moral decisionsMoral decisions● Science might play a role in these things, but Science might play a role in these things, but

other ways of searching for answers must be other ways of searching for answers must be used too.used too.

What is Science?What is Science?

Science Blends Imagination and LogicScience Blends Imagination and Logic

The Search for Life in the UniverseThe Search for Life in the Universe

Lecture 2: What is Life?Lecture 2: What is Life?

What Is Life?What Is Life?

● What are some properties of life?What are some properties of life?

What Is Life?What Is Life?

● What are some properties of life?What are some properties of life?

– ReproductionReproduction– ``Homeostasis'' (tries to adapt to stay alive ``Homeostasis'' (tries to adapt to stay alive

as environment changes)as environment changes)– Evolution over timeEvolution over time– Eats/breathesEats/breathes– GrowsGrows– COMPLEXITYCOMPLEXITY

Complexity in LifeComplexity in Life

● Even the simplest life form has a lot more going Even the simplest life form has a lot more going on than even fairly complex non-alive thingson than even fairly complex non-alive things

Complexity: To Stay AliveComplexity: To Stay Alive

● 200 years ago, Royal Academy of Science 200 years ago, Royal Academy of Science Fellow Charles Blagden asked two friends to Fellow Charles Blagden asked two friends to help him one afternoon. Blagden took his two help him one afternoon. Blagden took his two friends, a dog, and a raw steak into a room that friends, a dog, and a raw steak into a room that was gradually heated to a sweltering 260 degrees was gradually heated to a sweltering 260 degrees Fahrenheit.Fahrenheit.

● When the men and dog stumbled out after 45 When the men and dog stumbled out after 45 minutes, they were exhausted, dehydrated, and minutes, they were exhausted, dehydrated, and dripping with sweat. The dog was panting hard. dripping with sweat. The dog was panting hard. After a while, they recovered from the heat, and After a while, they recovered from the heat, and looked back in the room to find that the steak looked back in the room to find that the steak was completely cooked.was completely cooked.

Complexity in LifeComplexity in Life

● Life has to be able to have complex interactions Life has to be able to have complex interactions with the matter that comprises it.with the matter that comprises it.

● Interactions: four fundamental forcesInteractions: four fundamental forces

– ElectromagneticElectromagnetic– GravitationalGravitational– Strong & Weak nuclear forcesStrong & Weak nuclear forces

● Chemistry – how our forms of life operate – is Chemistry – how our forms of life operate – is dictated by electromagnetic forces (electrons)dictated by electromagnetic forces (electrons)

Chemistry of LifeChemistry of Life

● Chemistry has as building blocks the elements Chemistry has as building blocks the elements around us.around us.

● Sun: Everything's Hydrogen, Helium, Oxygen, Sun: Everything's Hydrogen, Helium, Oxygen, Carbon, small traces of other stuff.Carbon, small traces of other stuff.

● Earth: Richer in heavier stuff (Iron, Silicon,...)Earth: Richer in heavier stuff (Iron, Silicon,...)● Other stars, planets likely to be similar (more on Other stars, planets likely to be similar (more on

that in a couple of weeks.)that in a couple of weeks.)● Of these building blocks, what chemicals can Of these building blocks, what chemicals can

build complex chemistry?build complex chemistry?

Chemistry of life: CarbonChemistry of life: Carbon

● Of plentiful stuff, Carbon (alone) can build very Of plentiful stuff, Carbon (alone) can build very complex moleculescomplex molecules

Chemistry of life: Water?Chemistry of life: Water?

● Water is essential to life on earthWater is essential to life on earth● Thought that life began in the water (more on Thought that life began in the water (more on

that in later lectures)that in later lectures)● Why is water so important?Why is water so important?

Chemistry of life: Water?Chemistry of life: Water?

● For chemical life, need a way to get chemicals to For chemical life, need a way to get chemicals to different part of the bodydifferent part of the body

● Water is a very powerful solvent.Water is a very powerful solvent.

– Dissolve chemicalDissolve chemical– Allow transport through body in liquid Allow transport through body in liquid

formform● Very few liquid solvents as powerful, or as Very few liquid solvents as powerful, or as

common. common.

Limitations of waterLimitations of water

● If life depends on water, then very strict limit on If life depends on water, then very strict limit on where life can bewhere life can be

● Can't be anywhere colder than freezingCan't be anywhere colder than freezing● Can't be anywhere hotter than boilingCan't be anywhere hotter than boiling● Other liquid solvents have different Other liquid solvents have different

freezing/boiling points, but problem remainsfreezing/boiling points, but problem remains● Hard to see how chemicals can be efficiently Hard to see how chemicals can be efficiently

transported through a body otherwisetransported through a body otherwise

More Exotic forms of life?More Exotic forms of life?

● Gas in these clouds Gas in these clouds dense by interstellar dense by interstellar space standards, but space standards, but barely exist by barely exist by terrestrial standardsterrestrial standards

● ~billion times less ~billion times less dense than Earth's dense than Earth's atmosphereatmosphere

● Difficult for there to be Difficult for there to be complex interactions complex interactions going on in there.going on in there.

More Exotic forms of life?More Exotic forms of life?

● Why stick with life like Why stick with life like on Earth?on Earth?

● Or on planets?Or on planets?● Molecular clouds are Molecular clouds are

known to have water, known to have water, methane, even organic methane, even organic chemistry. chemistry.

● Could life begin there?Could life begin there?

Gravitational Life?Gravitational Life?

● Same problemSame problem● Mostly `not there'Mostly `not there'● Very simple structuresVery simple structures● Change only occurs Change only occurs

over hundreds of over hundreds of millions of yearsmillions of years

● Even if alive, we could Even if alive, we could never communicate or never communicate or interact with theminteract with them

Nuclear-force Life?Nuclear-force Life?

● Nuclear forces only Nuclear forces only significant on very significant on very small scales/high small scales/high densitiesdensities

● Neutron starsNeutron stars● Any life that did exist Any life that did exist

would be small/fast that would be small/fast that we couldn't interact we couldn't interact with it.with it.

What sort of life are we interested in?What sort of life are we interested in?

● In our own solar system, even bacteria fossils In our own solar system, even bacteria fossils would be enormous find.would be enormous find.

● Have some chance of looking at nearby planetsHave some chance of looking at nearby planets● For life outside our solar system, won't be able to For life outside our solar system, won't be able to

visit for foreseeable futurevisit for foreseeable future● Only way to recognize life is to receive signalsOnly way to recognize life is to receive signals● Life must be intelligent enough to communicate Life must be intelligent enough to communicate

with us in a way we can recognizewith us in a way we can recognize

Readings for Next WeekReadings for Next Week

● This week's lectureThis week's lecture

– Chapter 1Chapter 1– Chapter 7 (pp. 163 – 167)Chapter 7 (pp. 163 – 167)– Chapter 10Chapter 10

● Next weekNext week

– Chapter 18Chapter 18