Planets & LifePlanets & LifePHYS 214PHYS 214

Dr Rob ThackerDr Rob ThackerDept of Physics (308A)Dept of Physics (308A)

thacker@astro.queensu.cathacker@astro.queensu.ca(Please start all class emails with (Please start all class emails with

“214:”)“214:”)

What is the course really What is the course really going to be about?going to be about?

Can we estimate -Can we estimate -scientificallyscientifically - what - what the total number of the total number of civilizations in the civilizations in the galaxy is?galaxy is? Can we do this for the Can we do this for the

entire Universe?entire Universe? What do we need to What do we need to

know to estimate this know to estimate this number?number? Astronomical issuesAstronomical issues Biological issues Biological issues

These areThese are exciting times! exciting times!

First image of anextrasolar planet

Liquid Water on Mars?Liquid Water on Mars?

Liquid Methane on TitanLiquid Methane on Titan

Cassini-Huygens Probe

Extremophiles: Life in the Extremophiles: Life in the harshest environmentsharshest environments

Life around hydrothermalvents

Diatoms surviving in extreme saline environments

Terrestrial bacteria survived (dormant) on the Moon for 3 years

Explicit course outlineExplicit course outline

0. The Search for Extraterrestrial Life: 0. The Search for Extraterrestrial Life: Overview of the Drake Equation and its Overview of the Drake Equation and its motivationmotivation

1. Introduction to concepts in Astronomy1. Introduction to concepts in Astronomy2. Cosmology & the Anthropic Principle2. Cosmology & the Anthropic Principle

How fundamental ideas about the Cosmos How fundamental ideas about the Cosmos can relate to the development of life can relate to the development of life

3. Formation and Evolution of Stars3. Formation and Evolution of StarsSince we are all star dust, stars play a Since we are all star dust, stars play a critical role in the development of lifecritical role in the development of life

4. Formation of Planets & Geophysics4. Formation of Planets & Geophysics5. Development of Life5. Development of Life

Adaptivity and survivalAdaptivity and survival6. Development of intelligence & 6. Development of intelligence &

technological issues in SETItechnological issues in SETI

Weeks 9-12

Weeks 1-8

Marking SchemeMarking Scheme

50% Final Exam50% Final Exam 25% Mid term25% Mid term 20% Homeworks (4 set, approx 1 every 20% Homeworks (4 set, approx 1 every

3 weeks)3 weeks) 5% in-class quizzes (best 3 of 5 chosen)5% in-class quizzes (best 3 of 5 chosen)

Late assignments receive a 10% per Late assignments receive a 10% per day penaltyday penalty

Course WebsiteCourse Website

www.astro.queensu.ca/~thacker/newww.astro.queensu.ca/~thacker/new/teaching/214/w/teaching/214/

Course outline + any newsCourse outline + any news Lecture notes will be posted there in Lecture notes will be posted there in

pdf formatpdf format Homeworks and supplementary Homeworks and supplementary

material will be posted therematerial will be posted there

BooksBooks

Main course text: “An Introduction Main course text: “An Introduction to Astrobiology” Gilmour & Sephtonto Astrobiology” Gilmour & Sephton

Secondary texts that we will draw Secondary texts that we will draw from (up to you whether you from (up to you whether you purchase them):purchase them): ““Rare Earth” Ward & BrownleeRare Earth” Ward & Brownlee ““The Anthropic Cosmological Principle” The Anthropic Cosmological Principle”

Barrow & TiplerBarrow & Tipler

A note about the courseA note about the course I usually produce I usually produce exhaustiveexhaustive presentations that presentations that

should provide all you need to know about a should provide all you need to know about a given subjectgiven subject

Unfortunately, since I am writing the Unfortunately, since I am writing the presentations in tandem with teaching, I am presentations in tandem with teaching, I am unable to provide the presentations before the unable to provide the presentations before the lecturelecture Although they will be available soon after class on the Although they will be available soon after class on the

websitewebsite When relevant, I’ll provide additional links When relevant, I’ll provide additional links

within the lecture for you to look at in your own within the lecture for you to look at in your own timetime

Pseudoscience Pseudoscience

The concept of extraterrestrial life The concept of extraterrestrial life (and intelligence) is deeply (and intelligence) is deeply relevant to many areas of liferelevant to many areas of life Consequently many people are prone Consequently many people are prone

to over interpretation and speculationto over interpretation and speculation Motivations may not necessarily be sinister Motivations may not necessarily be sinister

or economicor economic Deeply flawed ideas can be hidden in an Deeply flawed ideas can be hidden in an

apparentlyapparently scientific approach scientific approach Deep scrutiny may be required to unearth Deep scrutiny may be required to unearth

errorserrors Recent example: use of Shannon’s information Recent example: use of Shannon’s information

theory in Intelligent Design arguments by theory in Intelligent Design arguments by Dembski (an essay by Victor Stenger lists the Dembski (an essay by Victor Stenger lists the errors in Dembski’s arguments)errors in Dembski’s arguments)

The concept of extraterrestrial life The concept of extraterrestrial life (and intelligence) is deeply (and intelligence) is deeply relevant to many areas of liferelevant to many areas of life Consequently many people are prone Consequently many people are prone

to over interpretation and speculationto over interpretation and speculation Motivations may not necessarily be sinister Motivations may not necessarily be sinister

or economicor economic Deeply flawed ideas can be hidden in an Deeply flawed ideas can be hidden in an

apparentlyapparently scientific approach scientific approach Deep scrutiny may be required to unearth Deep scrutiny may be required to unearth

errorserrors Recent example: use of Shannon’s information Recent example: use of Shannon’s information

theory in Intelligent Design arguments by theory in Intelligent Design arguments by Dembski (an essay by Victor Stenger lists the Dembski (an essay by Victor Stenger lists the errors in Dembski’s arguments)errors in Dembski’s arguments)

Pseudoscience Pseudoscience

Classic example by an Classic example by an astronomerastronomer: Percival : Percival Lowell (1855-1916) was heavily influenced Lowell (1855-1916) was heavily influenced by earlier comments by Schiaparelli and by earlier comments by Schiaparelli and interpreted optical illusions as being interpreted optical illusions as being “canals” on Mars – directly leading to the “canals” on Mars – directly leading to the assumption of civilizationassumption of civilization Orson Wells then played on these assumptions Orson Wells then played on these assumptions

with the “War of the Worlds” radio drama of with the “War of the Worlds” radio drama of 19381938

Carl Sagan: “Carl Sagan: “Extraordinary claims require Extraordinary claims require extraordinary evidenceextraordinary evidence”” Healthy skepticism is ultimately the most Healthy skepticism is ultimately the most

natural scientific approachnatural scientific approach

Classic example by an Classic example by an astronomerastronomer: Percival : Percival Lowell (1855-1916) was heavily influenced Lowell (1855-1916) was heavily influenced by earlier comments by Schiaparelli and by earlier comments by Schiaparelli and interpreted optical illusions as being interpreted optical illusions as being “canals” on Mars – directly leading to the “canals” on Mars – directly leading to the assumption of civilizationassumption of civilization Orson Wells then played on these assumptions Orson Wells then played on these assumptions

with the “War of the Worlds” radio drama of with the “War of the Worlds” radio drama of 19381938

Carl Sagan: “Carl Sagan: “Extraordinary claims require Extraordinary claims require extraordinary evidenceextraordinary evidence”” Healthy skepticism is ultimately the most Healthy skepticism is ultimately the most

natural scientific approachnatural scientific approach

Today’s LectureToday’s Lecture

Section 0: Prelude & Motivation: The Section 0: Prelude & Motivation: The search for extraterrestrial life & the search for extraterrestrial life & the Drake EquationDrake Equation The Drake EquationThe Drake Equation

Overview of each of the terms that provides Overview of each of the terms that provides the motivation for the material we will cover the motivation for the material we will cover in the next 12 weeksin the next 12 weeks

Short biography of Frank DrakeShort biography of Frank Drake

An artist’s An artist’s conception of conception of our galaxy, our galaxy, the Milky Waythe Milky Way

Visible as a Visible as a bright bright (diffuse) band (diffuse) band overhead on a overhead on a clear nightclear night

Aside – Galaxies are not Aside – Galaxies are not static or isolatedstatic or isolated

Movie by John Dubinski (CITA)Milky Way will collide with Andromeda galaxy in3 billion years time – here is a simulation

Survey of your opinions!Survey of your opinions!

Three choices: Number of civilizations in the Milky Way galaxy

is 1 Number of civilizations in the Milky Way is

greater than 1 but we just haven’t detected them

Number of civilizations in the Milky Way is greater than 1 and they are already here

At the end of the course we’ll revisit this survey

Three choices: Number of civilizations in the Milky Way galaxy

is 1 Number of civilizations in the Milky Way is

greater than 1 but we just haven’t detected them

Number of civilizations in the Milky Way is greater than 1 and they are already here

At the end of the course we’ll revisit this survey

Estimating the number of Estimating the number of civilizations we can detectcivilizations we can detect

Suppose over the Suppose over the entire lifetimeentire lifetime of the Milky of the Milky Way galaxy Way galaxy NNtotaltotal civilizations are created that civilizations are created that broadcast their existence (at different, but broadcast their existence (at different, but perhaps overlapping, times)perhaps overlapping, times)

Suppose civilizations broadcast for Suppose civilizations broadcast for TT years, years, and the lifetime of the Milky Way is and the lifetime of the Milky Way is TTMWMW years years

Each broadcast lasts a fraction Each broadcast lasts a fraction T/TT/TMWMW of the of the lifetime of the Milky Way lifetime of the Milky Way

Thus Thus on average, at any one timeon average, at any one time, we can , we can expect to detectexpect to detect NN = = NNtotal total ( (T/TT/TMWMW) = () = (NNtotaltotal//TTMWMW) ) TT = = RTRT

where we define where we define RR to be the to be the rate at which rate at which civilizations are createdcivilizations are created

Humour: Definition of Humour: Definition of Civilization?Civilization?

Reporter: “What do Reporter: “What do you think of Western you think of Western Civilization?”Civilization?”

Ghandi: “I think it Ghandi: “I think it would be a good would be a good idea!”idea!”

The basis of the Drake The basis of the Drake EquationEquation

The simple equation The simple equation N=RTN=RT is starting point is starting point of the Drake Equationof the Drake Equation

Calculation of the rate of creation of Calculation of the rate of creation of broadcasting civilizations is obviously broadcasting civilizations is obviously extremely hard, and influenced by many extremely hard, and influenced by many factorsfactors Number of stars in the galaxyNumber of stars in the galaxy Number of habitable planetsNumber of habitable planets Number of times life develops on these planets… Number of times life develops on these planets…

among other thingsamong other things The broadcasting time of these civilizations The broadcasting time of these civilizations

is probably equally hard to estimate, but can is probably equally hard to estimate, but can be left as a single numberbe left as a single number

The Drake Equation The Drake Equation (1961)(1961)

TpppnpRN

RTN

cilEp

*

The Drake equation expands out the rate of creationof broadcasting civilizations as follows

So that R is factorized into the product

cilEp pppnpRR *

Let’s look at each of these variables in the next overheads

R* – rate of formation of R* – rate of formation of stars in the Milky Waystars in the Milky Way

R* is the number of stars per year R* is the number of stars per year formed in the Milky Wayformed in the Milky Way

Not easy to measure thoughNot easy to measure though Can’t see stars forming easily (don’t Can’t see stars forming easily (don’t

suddenly turn on)suddenly turn on) Milky Way includes a lot of dust that Milky Way includes a lot of dust that

obscures the sight linesobscures the sight lines We’ll examine this in detail in weeks We’ll examine this in detail in weeks

3-43-4

pppp – Probability of planets – Probability of planets forming around a suitable forming around a suitable

starstar Until very recently we had little idea what this Until very recently we had little idea what this number might be number might be

The discovery of extrasolar planets has given The discovery of extrasolar planets has given us the first data relevant to estimating this us the first data relevant to estimating this variablevariable Planets are detected due to a miniscule wobble in Planets are detected due to a miniscule wobble in

the star as the planet orbits around itthe star as the planet orbits around it So far we have only been able to detect very large So far we have only been able to detect very large

planetsplanets The future for research in this field is The future for research in this field is

exceptionally exciting!exceptionally exciting! There is hope of building a telescope that can There is hope of building a telescope that can

image Earth-sized planets around 2020 image Earth-sized planets around 2020 We’ll look at planets in weeks 5-8We’ll look at planets in weeks 5-8

nnEE – average number of – average number of suitable planets in suitable planets in

habitable zoneshabitable zones It is widely believed that planets that are “too hot” It is widely believed that planets that are “too hot”

or “too cold” cannot develop lifeor “too cold” cannot develop life As with Goldilocks & the Three Bears – things have to be As with Goldilocks & the Three Bears – things have to be

just rightjust right Thus there is an expected region of space – Thus there is an expected region of space – a a

habitable zonehabitable zone - in which stellar radiation heats a - in which stellar radiation heats a planet up to a surface temperature that is planet up to a surface temperature that is “acceptable”“acceptable”

Morrison & Cocconi (1959) formally presented the Morrison & Cocconi (1959) formally presented the idea in an early SETI paperidea in an early SETI paper

Recent discoveries of “extremeophile” creatures Recent discoveries of “extremeophile” creatures adapted to high temperatures have questioned the adapted to high temperatures have questioned the accuracy of this assumptionaccuracy of this assumption

We’ll come back to this in weeks 7-8We’ll come back to this in weeks 7-8

ppll – probability of life – probability of life developingdeveloping

Very difficult to address this questionVery difficult to address this question Although the exact origins of life are far from Although the exact origins of life are far from

clear, it is widely believed that the steps clear, it is widely believed that the steps involved areinvolved are Origin of biological monomersOrigin of biological monomers Origin of biological polymersOrigin of biological polymers Evolution of molecules to cellsEvolution of molecules to cells

We know from the Miller-Urey experiment in We know from the Miller-Urey experiment in 1953 that we can form organic monomers in 1953 that we can form organic monomers in atmospheres containing water, methane, atmospheres containing water, methane, ammonia and hydrogenammonia and hydrogen

Other steps remain shrowded in controversyOther steps remain shrowded in controversy We’ll look at this in weeks 9-11We’ll look at this in weeks 9-11

ppii – probability of – probability of intelligent life developingintelligent life developing

Another poorly understand variableAnother poorly understand variable It may be possible that simple single cell life It may be possible that simple single cell life

is extremely common, but complicated is extremely common, but complicated multicellular life is extremely rare due to a multicellular life is extremely rare due to a coincidence of circumstances required for itcoincidence of circumstances required for it This is really the thrust of the “Rare Earth” This is really the thrust of the “Rare Earth”

hypothesishypothesis Complex Eukaryotic cells are widely believed Complex Eukaryotic cells are widely believed

to be fundamental to the development of to be fundamental to the development of intelligent life, while the evolution from intelligent life, while the evolution from prokaryotic cells is poorly understood at bestprokaryotic cells is poorly understood at best

We’ll look at this in weeks 10-11We’ll look at this in weeks 10-11

ppcc – probability of – probability of intelligent life broadcastingintelligent life broadcasting Some advanced civilizations may not use Some advanced civilizations may not use

communication equipment along the communication equipment along the (electromagnetic) lines we envisage(electromagnetic) lines we envisage

Others may be (understandably) paranoid Others may be (understandably) paranoid and choose not to broadcastand choose not to broadcast

Humans have released signals Humans have released signals purposefully, but we do not send them purposefully, but we do not send them continuouslycontinuously

We’ll look at this in more detail in week We’ll look at this in more detail in week ~12~12

TT – lifetime of the – lifetime of the broadcastbroadcast

Are intelligent civilizations destined Are intelligent civilizations destined to have a short lifetime?to have a short lifetime?

If they develop technologies to leave If they develop technologies to leave their planetary system does T become their planetary system does T become exceptionally large? Billions of years?exceptionally large? Billions of years? If they can leave their planetary system If they can leave their planetary system

how long would they take to colonize a how long would they take to colonize a galaxy?galaxy?

We’ll look at this issue in week ~12We’ll look at this issue in week ~12

Frank DrakeFrank Drake Frank Drake was born Frank Drake was born

in Chicago on May 28, in Chicago on May 28, 1930 1930

Graduate work at Graduate work at Harvard, later became Harvard, later became professor at Cornellprofessor at Cornell

Conducted first radio Conducted first radio search for ETI in 1960: search for ETI in 1960: “Project Ozma” “Project Ozma”

Instrumental in the Instrumental in the conversion of the conversion of the Arecibo Observatory Arecibo Observatory into a radio telescope into a radio telescope for astronomyfor astronomy

““The father of SETI”The father of SETI”

How many civilizations in How many civilizations in the observable Universe?the observable Universe?

LppnGRpN ilEb

The standard Drake Equation assigns a probability to whether thecivilization broadcasts. If we just wish to estimate the number of civilizations we can remove this factor and replace the broadcastingtime, T, with the lifetime of the civilization, L.

Secondly, assuming all galaxies to be the same (which we’ll see isfar from true), we need to multiply by the number of galaxies in the observable Universe, G

We’ll look at measuring G in the next couple of weeks.

Is the Drake Equation & the search for ETI scientific?

It is a statistical equation Not a fundamental law such as F=ma

Is it testable? No Alternative proposals are equally

untestable If we cannot test the underlying

hypotheses of the Drake Equation, is searching for ETI really a science?

Summary of lecture 1Summary of lecture 1

The Drake Equation provides a useful The Drake Equation provides a useful frame work for discussing the search frame work for discussing the search for ETIfor ETI Nonetheless, many of the parameters are Nonetheless, many of the parameters are

difficult to measure and at worst difficult to measure and at worst impossible toimpossible to

We can measure many of the astronomical We can measure many of the astronomical parameters, such as the rate of formation of parameters, such as the rate of formation of starsstars

Parameters relating to the origin of life are Parameters relating to the origin of life are very uncertainvery uncertain

Next lectureNext lecture

Fundamental concepts in AstronomyFundamental concepts in Astronomy Angular measurementsAngular measurements Astronomical distances & unitsAstronomical distances & units Celestial sphere & motionsCelestial sphere & motions