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TRANSCRIPT
Pla
nets
& L
ife
Pla
nets
& L
ife
PH
YS 2
14P
HY
S 2
14
Dr Rob Thacker
Dr Rob Thacker
Dept of Physics (308A)
Dept of Physics (308A)
(Please start all class emails with
(Please start all class emails with ““214:
214:””))
Wh
at
is t
he c
ou
rse r
eall
y g
oin
g t
o b
e
Wh
at
is t
he c
ou
rse r
eall
y g
oin
g t
o b
e
ab
ou
t?ab
ou
t?
��Can we estimate
Can we estimate --
scientifically
scientifically--what the total
what the total
number of civilizations in
number of civilizations in
the galaxy is?
the galaxy is?
��Can we do this for the
Can we do this for the
entire Universe?
entire Universe?
��What do we need to know
What do we need to know
to estimate this number?
to estimate this number?
��Astronomical issues
Astronomical issues
��Biological issues
Biological issues
Th
ese
are
Th
ese
are
excit
ing
tim
es!
excit
ing
tim
es!
First image of an
extrasolarplanet
Liq
uid
Wate
r on
Mars
?L
iqu
id W
ate
r on
Mars
?
Liq
uid
Meth
an
e o
n T
itan
Liq
uid
Meth
an
e o
n T
itan
Cassini-Huygens Probe
Extr
em
op
hil
es
Extr
em
op
hil
es :
Lif
e i
n t
he h
ars
hest
: L
ife i
n t
he h
ars
hest
en
vir
on
men
tsen
vir
on
men
ts
Life aroun
d hydrotherm
al
vents
Diatoms surviving in extrem
e salin
e environm
ents
Terrestrial bacteria survived (dorm
ant)
on the M
oon for 3 years
Exp
licit
cou
rse o
utl
ine
Exp
licit
cou
rse o
utl
ine
0. The Search for Extraterrestrial Life: Overview of the
0. The Search for Extraterrestrial Life: Overview of the
Drake Equation and its motivation
Drake Equation and its motivation
1. Introduction to concepts in Astronomy
1. Introduction to concepts in Astronomy
2. Cosmology & the
2. Cosmology & the Anthropic
AnthropicPrinciple
Principle
How
fund
amental ideas about the C
osmos can
relate to the
How
fund
amental ideas about the C
osmos can
relate to the
developm
ent of life
developm
ent of life
3. Formation and Evolution of Stars
3. Formation and Evolution of Stars
Since we are all star du
st, stars play a critical role in the
Since we are all star du
st, stars play a critical role in the
developm
ent of life
developm
ent of life
4. Formation of Planets & Geophysics
4. Formation of Planets & Geophysics
5. Development of Life
5. Development of Life
Adaptivity
Adaptivityan
d survival
and survival
6. Development of intelligence & technological issues in
6. Development of intelligence & technological issues in
SETI
SETI
Weeks
9-12
Weeks
1-8
Mark
ing
Sch
em
eM
ark
ing
Sch
em
e
��50% Final Exam
50% Final Exam
��25% Mid term
25% Mid term
��20%
20% Homeworks
Homeworks(4 set, approx 1 every 3
(4 set, approx 1 every 3
weeks)
weeks)
��5% in
5% in-- class quizzes (best 3 of 5 chosen)
class quizzes (best 3 of 5 chosen)
��Late assignments receive a 10% per day penalty
Late assignments receive a 10% per day penalty
Cou
rse W
eb
site
Cou
rse W
eb
site
��www.astro.queensu.ca/~thacker/new/teaching/
www.astro.queensu.ca/~thacker/new/teaching/
214/
214/
��Course outline + any news
Course outline + any news
��Lecture notes will be posted there in
Lecture notes will be posted there in pdf
pdfformat
format
��Homeworks
Homeworksand supplementary material will be
and supplementary material will be
posted there
posted there
Book
sB
ook
s
��Main course text:
Main course text: ““An Introduction to
An Introduction to
Astrobiology
Astrobiology””Gilmour &
Gilmour & Sephton
Sephton
��Secondary texts that we will draw from (up to
Secondary texts that we will draw from (up to
you whether you purchase them):
you whether you purchase them):
��““Rare Earth
Rare Earth””Ward & Brownlee
Ward & Brownlee
��““The
The Anthropic
AnthropicCosmological Principle
Cosmological Principle””Barrow &
Barrow &
Tipler
Tipler
A n
ote
ab
ou
t th
e c
ou
rse
A n
ote
ab
ou
t th
e c
ou
rse
��I usually produce
I usually produce exha
ustive
exha
ustivepresentations that should
presentations that should
provide all you need to know about a given subject
provide all you need to know about a given subject
��Unfortunately, since I am writing the presentations in
Unfortunately, since I am writing the presentations in
tandem with teaching, I am unable to provide the
tandem with teaching, I am unable to provide the
presentations before the lecture
presentations before the lecture
��Although they will be available soon after class on the
Although they will be available soon after class on the
website
website
��When relevant, I
When relevant, I’’ ll provide additional links within the
ll provide additional links within the
lecture for you to look at in your own time
lecture for you to look at in your own time
Pse
ud
osc
ien
ce
Pse
ud
osc
ien
ce
�T
he c
on
cep
t of
extr
ate
rrest
rial li
fe (
an
d
inte
llig
en
ce)
is d
eep
ly r
ele
van
t to
man
y a
reas
of
life
�C
on
seq
uen
tly m
an
y p
eop
le a
re p
ron
e t
o o
ver
inte
rpre
tati
on
an
d s
pecu
lati
on
�M
oti
vati
on
s m
ay n
ot
necess
ari
ly b
e s
inis
ter
or
econ
om
ic
�D
eep
ly f
law
ed
id
eas
can
be h
idd
en
in
an
ap
par
entl
ysc
ien
tifi
c a
pp
roach
�D
eep
scru
tin
y m
ay b
e r
eq
uir
ed
to
un
eart
h e
rro
rs
�R
ecen
t exam
ple
: u
se o
f Sh
an
no
n’s
in
form
ati
on
th
eo
ry i
n
Inte
llig
en
t D
esi
gn
arg
um
en
ts b
y D
em
bsk
i(a
n e
ssay b
y
Vic
tor
Ste
ng
er
list
s th
e e
rro
rs i
n D
em
bsk
i’s
arg
um
en
ts)
��T
he c
on
cep
t of
extr
ate
rrest
rial li
fe (
an
d
Th
e c
on
cep
t of
extr
ate
rrest
rial li
fe (
an
d
inte
llig
en
ce)
is d
eep
ly r
ele
van
t to
man
y a
reas
inte
llig
en
ce)
is d
eep
ly r
ele
van
t to
man
y a
reas
of
life
of
life
��C
on
seq
uen
tly m
an
y p
eop
le a
re p
ron
e t
o o
ver
Con
seq
uen
tly m
an
y p
eop
le a
re p
ron
e t
o o
ver
inte
rpre
tati
on
an
d s
pecu
lati
on
inte
rpre
tati
on
an
d s
pecu
lati
on
��M
oti
vati
on
s m
ay n
ot
necess
ari
ly b
e s
inis
ter
or
Moti
vati
on
s m
ay n
ot
necess
ari
ly b
e s
inis
ter
or
econ
om
icecon
om
ic
��D
eep
ly f
law
ed
id
eas
can
be h
idd
en
in
an
D
eep
ly f
law
ed
id
eas
can
be h
idd
en
in
an
ap
par
entl
yap
par
entl
ysc
ien
tifi
c a
pp
roach
scie
nti
fic a
pp
roach
��D
eep
scru
tin
y m
ay b
e r
eq
uir
ed
to
un
eart
h e
rro
rsD
eep
scru
tin
y m
ay b
e r
eq
uir
ed
to
un
eart
h e
rro
rs
��R
ecen
t exam
ple
: u
se o
f Sh
an
no
nR
ecen
t exam
ple
: u
se o
f Sh
an
no
n’’ s
in
form
ati
on
th
eo
ry i
n
s in
form
ati
on
th
eo
ry i
n
Inte
llig
en
t D
esi
gn
arg
um
en
ts b
y
Inte
llig
en
t D
esi
gn
arg
um
en
ts b
y D
em
bsk
iD
em
bsk
i(a
n e
ssay b
y
(an
ess
ay b
y
Vic
tor
Vic
tor
Ste
ng
er
Ste
ng
er
list
s th
e e
rro
rs i
n
list
s th
e e
rro
rs i
n D
em
bsk
iD
em
bsk
i ’’ss
arg
um
en
ts)
arg
um
en
ts)
Pse
ud
osc
ien
ce
Pse
ud
osc
ien
ce
�C
lass
ic e
xam
ple
by a
n a
stro
nom
er: P
erc
ival L
ow
ell
(1855-1
916
) w
as
heavil
y i
nfl
uen
ced
by e
arl
ier
com
men
ts b
y S
ch
iap
are
lli
an
d i
nte
rpre
ted
op
tical
illu
sion
s as
bein
g “
can
als
”on
Mars
–d
irectl
y
lead
ing
to t
he a
ssu
mp
tion
of
civ
iliz
ati
on
�O
rson
Well
s th
en
pla
yed
on
th
ese
ass
um
pti
on
s w
ith
th
e
“W
ar
of
the W
orl
ds”
rad
io d
ram
a o
f 19
38
�C
arl
Sag
an
: “E
xtr
aord
inar
y cl
aim
s re
qu
ire
extr
aord
inar
y ev
iden
ce”
�H
ealt
hy s
kep
ticis
m i
s u
ltim
ate
ly t
he m
ost
natu
ral
scie
nti
fic a
pp
roach
��C
lass
ic e
xam
ple
by a
n
Cla
ssic
exam
ple
by a
n a
stro
nom
eras
tron
om
er: P
erc
ival L
ow
ell
: P
erc
ival L
ow
ell
(1855
(1855-- 1
916
) w
as
heavil
y i
nfl
uen
ced
by e
arl
ier
1916
) w
as
heavil
y i
nfl
uen
ced
by e
arl
ier
com
men
ts b
y
com
men
ts b
y S
ch
iap
are
lli
Sch
iap
are
lli
an
d i
nte
rpre
ted
op
tical
an
d i
nte
rpre
ted
op
tical
illu
sion
s as
bein
g
illu
sion
s as
bein
g ““
can
als
can
als
””on
Mars
on
Mars
––d
irectl
y
dir
ectl
y
lead
ing
to t
he a
ssu
mp
tion
of
civ
iliz
ati
on
lead
ing
to t
he a
ssu
mp
tion
of
civ
iliz
ati
on
��O
rson
Well
s th
en
pla
yed
on
th
ese
ass
um
pti
on
s w
ith
th
e
Ors
on
Well
s th
en
pla
yed
on
th
ese
ass
um
pti
on
s w
ith
th
e
““W
ar
of
the W
orl
ds
War
of
the W
orl
ds ””
rad
io d
ram
a o
f 19
38
rad
io d
ram
a o
f 19
38
��C
arl
C
arl
Sag
an
Sag
an
: : ““E
xtr
aord
inar
y cl
aim
s re
qu
ire
Extr
aord
inar
y cl
aim
s re
qu
ire
extr
aord
inar
y ev
iden
ceex
trao
rdin
ary
evid
ence
””
��H
ealt
hy s
kep
ticis
m i
s u
ltim
ate
ly t
he m
ost
natu
ral
Healt
hy s
kep
ticis
m i
s u
ltim
ate
ly t
he m
ost
natu
ral
scie
nti
fic a
pp
roach
scie
nti
fic a
pp
roach
Tod
ay
Tod
ay’’ s
Lectu
res
Lectu
re
��Section 0: Prelude & Motivation: The search for
Section 0: Prelude & Motivation: The search for
extraterrestrial life & the Drake Equation
extraterrestrial life & the Drake Equation
��The Drake Equation
The Drake Equation
��Overview of each of the terms that provides the
Overview of each of the terms that provides the
motivation for the material we will cover in the next 12
motivation for the material we will cover in the next 12
weeks
weeks
��Short biography of Frank Drake
Short biography of Frank Drake
��An artist
An artist ’’s s
conception of our
conception of our
galaxy, the Milky
galaxy, the Milky
Way
Way
��Visible as a bright
Visible as a bright
(diffuse) band
(diffuse) band
overhead on a
overhead on a
clear night
clear night
Asi
de
Asi
de ––
Gala
xie
s are
not
stati
c o
r G
ala
xie
s are
not
stati
c o
r
isola
ted
isola
ted
Movie by John Dubinski(CITA)
Milky Way will collide with Andromeda galaxy in
3 billion years time –here is a simulation
Su
rvey o
f you
r op
inio
ns!
Su
rvey o
f you
r op
inio
ns!
�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
Est
imati
ng
th
e n
um
ber
of
Est
imati
ng
th
e n
um
ber
of
civ
iliz
ati
on
s w
e c
an
dete
ct
civ
iliz
ati
on
s w
e c
an
dete
ct
��Suppose over the
Suppose over the entire lifetime
entire lifetimeof the Milky Way galaxy
of the Milky Way galaxy
NNtotal
totalcivilizations are created that broadcast their
civilizations are created that broadcast their
existence (at different, but perhaps overlapping, times)
existence (at different, but perhaps overlapping, times)
��Suppose civilizations broadcast for
Suppose civilizations broadcast for TTyears, and the
years, and the
lifetime of the Milky Way is
lifetime of the Milky Way is TTMW
MWyears
years
��Each broadcast lasts a fraction
Each broadcast lasts a fraction T
/T
T/TMW
MWof the lifetime of
of the lifetime of
the Milky Way
the Milky Way
��Thus
Thus on average, a
t an
y one time
on average, a
t an
y one time , we can expect to detect
, we can expect to detect
NN= = NN
total
total��(( T
/T
T/TMW
MW) = (
) = (NNtotal
total//TTMW
MW) ) ��
TT= = R
TRT
where we define
where we define RRto be the
to be the rate at which civiliza
tions are
rate at which civiliza
tions are
created
created
Hu
mo
ur
Hu
mo
ur :
Defi
nit
ion
of
Civ
iliz
ati
on
?: D
efi
nit
ion
of
Civ
iliz
ati
on
?
��Reporter:
Reporter: ““What do you
What do you
think of Western
think of Western
Civilization?
Civilization? ””
��Ghandi
Ghandi : : ““I think it would be
I think it would be
a good idea!
a good idea! ””
Th
e b
asi
s of
the D
rak
e E
qu
ati
on
Th
e b
asi
s of
the D
rak
e E
qu
ati
on
��The simple equation
The simple equation N
=RT
N=RTis starting point of the
is starting point of the
Drake Equation
Drake Equation
��Calculation of the rate of creation of broadcasting
Calculation of the rate of creation of broadcasting
civilizations is obviously extremely hard, and influenced
civilizations is obviously extremely hard, and influenced
by many factors
by many factors
��Number of stars in the galaxy
Number of stars in the galaxy
��Number of habitable planets
Number of habitable planets
��Number of times life develops on these planets
Number of times life develops on these planets ……
among
among
other things
other things
��The broadcasting time of these civilizations is probably
The broadcasting time of these civilizations is probably
equally hard to estimate, but can be left as a single
equally hard to estimate, but can be left as a single
number
number
Th
e D
rak
e E
qu
ati
on
(19
61)
Th
e D
rak
e E
qu
ati
on
(19
61) T
pp
pn
pR
N
RT
N
ci
lE
p×
××
××
×=
⇒
=
*
The Drake equation expands out the rate of creation
of broadcasting civilizations as follows
So that R is factorized into the product
ci
lE
pp
pp
np
RR
××
××
×=*
Let’s look at each of these variables in the next overheads
R*
R* ––
rate
of
form
ati
on
of
stars
in
th
e
rate
of
form
ati
on
of
stars
in
th
e
Mil
ky W
ay
Mil
ky W
ay
��R* is the number of stars per year formed in the
R* is the number of stars per year formed in the
Milky Way
Milky Way
��Not easy to measure though
Not easy to measure though
��CanCan’’ t see stars forming easily (don
t see stars forming easily (don’’ t suddenly turn
t suddenly turn
on)
on)
��Milky Way includes a lot of dust that obscures the
Milky Way includes a lot of dust that obscures the
sight lines
sight lines
��We
We ’’ll examine this in detail in weeks 3
ll examine this in detail in weeks 3-- 44
pppp
––P
rob
ab
ilit
y o
f p
lan
ets
fo
rmin
g
Pro
bab
ilit
y o
f p
lan
ets
fo
rmin
g
aro
un
d a
su
itab
le s
tar
aro
un
d a
su
itab
le s
tar
��Until very recently we had little idea what this number
Until very recently we had little idea what this number
might be
might be
��The discovery of
The discovery of extrasolar
extrasolarplanets has given us the
planets has given us the
first data relevant to estimating this variable
first data relevant to estimating this variable
��Planets are detected due to a miniscule wobble in the star as
Planets are detected due to a miniscule wobble in the star as
the planet orbits around it
the planet orbits around it
��So far we have only been able to detect very large planets
So far we have only been able to detect very large planets
��The future for research in this field is exceptionally
The future for research in this field is exceptionally
exciting!
exciting!
��There is hope of building a telescope that can image
There is hope of building a telescope that can image
Earth
Earth-- sized planets around 2020
sized planets around 2020
��We
We ’’ll look at planets in weeks 5
ll look at planets in weeks 5-- 88
nnEE
––avera
ge n
um
ber
of
suit
ab
le
avera
ge n
um
ber
of
suit
ab
le
pla
nets
in
hab
itab
le z
on
es
pla
nets
in
hab
itab
le z
on
es
��It is widely believed that planets that are
It is widely believed that planets that are ““too hot
too hot ””or or ““too cold
too cold””
cannot develop life
cannot develop life
��As with Goldilocks & the Three Bears
As with Goldilocks & the Three Bears ––things have to be
things have to be just right
just right
��Thus there is an expected region of space
Thus there is an expected region of space ––a ha
bitable zone
a ha
bitable zone--in
in
which stellar radiation heats a planet up to a surface temperatu
which stellar radiation heats a planet up to a surface temperature
re
that is
that is ““acceptable
acceptable””
��Morrison &
Morrison & Cocconi
Cocconi(1959) formally presented the idea in an
(1959) formally presented the idea in an
early SETI paper
early SETI paper
��Recent discoveries of
Recent discoveries of ““extremeophile
extremeophile””creatures adapted to high
creatures adapted to high
temperatures have questioned the accuracy of this assumption
temperatures have questioned the accuracy of this assumption
��We
We ’’ll come back to this in weeks 7
ll come back to this in weeks 7-- 88
ppll––
pro
bab
ilit
y o
f li
fe d
eve
lop
ing
pro
bab
ilit
y o
f li
fe d
eve
lop
ing
��Very difficult to address this question
Very difficult to address this question
��Although the exact origins of life are far from clear, it is
Although the exact origins of life are far from clear, it is
widely believed that the steps involved are
widely believed that the steps involved are
��Origin of biological monomers
Origin of biological monomers
��Origin of biological polymers
Origin of biological polymers
��Evolution of molecules to cells
Evolution of molecules to cells
��We know from the Miller
We know from the Miller-- Urey
Ureyexperiment in 1953 that
experiment in 1953 that
we can form organic monomers in atmospheres
we can form organic monomers in atmospheres
containing water, methane, ammonia and hydrogen
containing water, methane, ammonia and hydrogen
��Other steps remain
Other steps remain shrowded
shrowdedin controversy
in controversy
��We
We ’’ll look at this in weeks 9
ll look at this in weeks 9-- 1111
ppii––
pro
bab
ilit
y o
f in
tell
igen
t li
fe
pro
bab
ilit
y o
f in
tell
igen
t li
fe
develo
pin
gd
evelo
pin
g
��Another poorly understand variable
Another poorly understand variable
��It may be possible that simple single cell life is
It may be possible that simple single cell life is
extremely common, but complicated
extremely common, but complicated multicellular
multicellularlife is
life is
extremely rare due to a coincidence of circumstances
extremely rare due to a coincidence of circumstances
required for it
required for it
��This is really the thrust of the
This is really the thrust of the ““Rare Earth
Rare Earth””hypothesis
hypothesis
��Complex Eukaryotic cells are widely believed to be
Complex Eukaryotic cells are widely believed to be
fundamental to the development of intelligent life,
fundamental to the development of intelligent life,
while the evolution from prokaryotic cells is poorly
while the evolution from prokaryotic cells is poorly
understood at best
understood at best
��We
We ’’ll look at this in weeks 10
ll look at this in weeks 10-- 1111
ppcc
––p
rob
ab
ilit
y o
f in
tell
igen
t li
fe
pro
bab
ilit
y o
f in
tell
igen
t li
fe
bro
ad
cast
ing
bro
ad
cast
ing
��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 and
Others may be (understandably) paranoid and
choose not to broadcast
choose not to broadcast
��Humans have released signals purposefully, but
Humans have released signals purposefully, but
we do not send them continuously
we do not send them continuously
��We
We ’’ll look at this in more detail in week ~12
ll look at this in more detail in week ~12
TT––
life
tim
e o
f th
e b
road
cast
life
tim
e o
f th
e b
road
cast
��Are intelligent civilizations destined to have a
Are intelligent civilizations destined to have a
short lifetime?
short lifetime?
��If they develop technologies to leave their
If they develop technologies to leave their
planetary system does T become exceptionally
planetary system does T become exceptionally
large? Billions of years?
large? Billions of years?
��If they can leave their planetary system how long
If they can leave their planetary system how long
would they take to colonize a galaxy?
would they take to colonize a galaxy?
��We
We ’’ll look at this issue in week ~12
ll look at this issue in week ~12
Fra
nk
Dra
ke
Fra
nk
Dra
ke
��Frank Drake was born in
Frank Drake was born in
Chicago on May 28, 1930
Chicago on May 28, 1930
��Graduate work at Harvard,
Graduate work at Harvard,
later became professor at
later became professor at
Cornell
Cornell
��Conducted first radio search
Conducted first radio search
for ETI in 1960:
for ETI in 1960: ““Project
Project
Ozma
Ozma ””
��Instrumental in the
Instrumental in the
conversion of the
conversion of the Arecibo
Arecibo
Observatory into a radio
Observatory into a radio
telescope for astronomy
telescope for astronomy
��““The father of SETI
The father of SETI ””
Ho
w m
an
y c
ivil
izati
on
s in
th
e
Ho
w m
an
y c
ivil
izati
on
s in
th
e
ob
serv
ab
le U
niv
ers
e?
ob
serv
ab
le U
niv
ers
e?
Lp
pn
GRp
Ni
lE
b=
The standard Drake Equation assigns a probability to whether the
civilization broadcasts. If we just wish to estimate the number of
civilizations we can remove this factor and replace the broadcasting
time, T, with the lifetime of the civilization, L.
Secondly, assuming all galaxies to be the same (which we’ll see is
far from true), we need to multiply by the number of galaxies inthe
observable Universe, G
We’ll look at measuring G in the next couple of weeks.
Is t
he D
rak
e E
qu
ati
on
& t
he s
earc
h
for
ET
I sc
ien
tifi
c?
�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?
Su
mm
ary
of
lectu
re 1
Su
mm
ary
of
lectu
re 1
��The Drake Equation provides a useful frame
The Drake Equation provides a useful frame
work for discussing the search for ETI
work for discussing the search for ETI
��Nonetheless, many of the parameters are difficult to
Nonetheless, many of the parameters are difficult to
measure and at worst impossible to
measure and at worst impossible to
��We can measure many of the astronomical parameters,
We can measure many of the astronomical parameters,
such as the rate of formation of stars
such as the rate of formation of stars
��Parameters relating to the origin of life are very uncertain
Parameters relating to the origin of life are very uncertain
Next
lectu
reN
ext
lectu
re
��Fundamental concepts in Astronomy
Fundamental concepts in Astronomy
��Angular measurements
Angular measurements
��Astronomical distances & units
Astronomical distances & units
��Celestial sphere & motions
Celestial sphere & motions