214: planets & life phys 214 · 2007. 4. 25. · kardashev classification a scale proposed by...
TRANSCRIPT
Planets & Life
Planets & Life
PHYS 214
PHYS 214
Dr Rob Thacker
Dr Rob Thacker
Dept of Physics (308A)
Dept of Physics (308A)
thacker@
astro.queensu.ca
thacker@
astro.queensu.ca
Please start all class related emails with
Please start all class related emails with ““214:
214:””
Today
Today’’ s Lecture
s Lecture
��A few
exam details
A few
exam details
��Classification of Alien civilizations
Classification of Alien civilizations
��Kardashev
Kardashev
classification
classification
��Possible human futures
Possible human futures
“Any sufficiently advanced technology is indistinguishable from
magic”
Arthur C. C
larke
Final format
Final format
��Mid term form
at was 30 MC, 2 short answ
er, 1 hour
Mid term form
at was 30 MC, 2 short answ
er, 1 hour
��30
30 m
ins
minsfor MC implies you had 15
for MC implies you had 15 mins
minsper short answ
erper short answ
er��
MC and short answ
er contributed equal m
arks
MC and short answ
er contributed equal m
arks
��Not enough time on the short answ
ers for about 1/3 class
Not enough time on the short answ
ers for about 1/3 class
��Final will be only 25 MC, but 4 short answ
er in 2 hours
Final will be only 25 MC, but 4 short answ
er in 2 hours
��Covers all material in course
Covers all material in course
��25+60=85 total marks
25+60=85 total marks
��For comparison, last years 3 hour exam
had 146 m
arks, if we pror
For comparison, last years 3 hour exam
had 146 m
arks, if we pror ate, that
ate, that
corresponds to 97 in 2 hours
corresponds to 97 in 2 hours
��25
25 m
ins
minsfor MC im
plies about ~24
for MC im
plies about ~24 m
ins
minsper short answ
er question
per short answ
er question
��Have quite a bit m
ore time on each question compared to the mid
Have quite a bit m
ore time on each question compared to the mid term
term
Short answer format
Short answer format
��Choose 4 questions from 6, divided into two
Choose 4 questions from 6, divided into two
sections of three. You m
ust answ
er at least one
sections of three. You m
ust answ
er at least one
question from each section
question from each section
��Individual question form
at is sam
e as m
idIndividual question form
at is sam
e as m
id-- term
term
��One part explanation
One part explanation
��One part calculation
One part calculation
��This time I have given a clear representation of
This time I have given a clear representation of
the marks available in each section, so you can
the marks available in each section, so you can
prioritize if you want to
prioritize if you want to
Advice on short answer
Advice on short answer
��One sentence is enough to get you 1 m
ark
One sentence is enough to get you 1 m
ark ––provided you
provided you
explain a concept/fact clearly and succinctly
explain a concept/fact clearly and succinctly
��The number of marks corresponds to the number of pertinent
The number of marks corresponds to the number of pertinent
facts you need to m
ention/discuss
facts you need to m
ention/discuss
��Doesn
Doesn’’ t hurt to put a couple m
ore if you are not sure you have got
t hurt to put a couple m
ore if you are not sure you have got
everything
everything
��As with the midterm
IAs with the midterm
I’’ ll have a list of possibilities exceeding the available
ll have a list of possibilities exceeding the available
marks
marks
��One short answ
er question has 2/3 of the weight on the
One short answ
er question has 2/3 of the weight on the
discussion, but most are 60/40 split between
discussion, but most are 60/40 split between
discussion/calculation
discussion/calculation
��As I mentioned
As I mentioned ––
you will know how m
any marks are available
you will know how m
any marks are available
��There is also one (and only one) question where there are more
There is also one (and only one) question where there are more
marks available for the calculation
marks available for the calculation
Kardashev
KardashevClassification
Classification
��A scale proposed by the Russian physicist
A scale proposed by the Russian physicist
Nikolai
Nikolai Kardashev
Kardashev
for classifying the
for classifying the
relative advancement of (advanced)
relative advancement of (advanced)
civilizations
civilizations
��The classification works on the basis of
The classification works on the basis of
the total power that can be utilized by a
the total power that can be utilized by a
given civilization
given civilization
��Although there is some debate, humans
Although there is some debate, humans
are not considered to yet be sufficiently
are not considered to yet be sufficiently
advanced to be measured on the first
advanced to be measured on the first
““rung
rung””of the scale
of the scale
��So who is interested in this scale?
So who is interested in this scale?
��SE
TI researchers, futurists, science fiction
SETI researchers, futurists, science fiction
authors!
authors!
http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?19
85IA
US..112
..497
K
Type 1 Classification
Type 1 Classification
��Type I
Type I ——
A civilization that is able to harness all
A civilization that is able to harness all
of the
of the power
power
available on a single
available on a single planet
planet
��How m
uch power is that exactly?
How m
uch power is that exactly?
��Sun outputs 4
Sun outputs 4��1010
2626WW
��Fraction reaching Earth:
Fraction reaching Earth: ππrr pp22/4
/4ππddpp22
��So total power= 4
So total power= 4��1010
2626W
W ��
fraction =
fraction =
1.8
1.8 ��1010
1717WW
��1.8
1.8 petaW
atts
petaW
atts! ! ––that is a lot of power
that is a lot of power……
How does our current power
How does our current power
consumption compare?
consumption compare?
��Humans generate about 15 TW of power
Humans generate about 15 TW of power
=15
=15��1010
1212WW
��Quite a bit lower than a Type 1 civilization
Quite a bit lower than a Type 1 civilization
��Can we extrapolate the scale somehow below
Can we extrapolate the scale somehow below
zero?
zero?
��As we
As we ’’ll see, the scale is logarithmic in nature so
ll see, the scale is logarithmic in nature so
we can define a continuous scale of
we can define a continuous scale of Kardashev
Kardashev
classification (K) by
classification (K) by
10
6log10
−=
WK
You can play with the constants
a bit, but this is good enough
So what value do we derive for
So what value do we derive for
Earth?
Earth?
��Log
Log 1
010(15
(15 ��1010
1212)) ≈≈13, hence K=0.7
13, hence K=0.7
��How can we increase our energy gathering up to Type I
How can we increase our energy gathering up to Type I
levels?
levels?
��Since we are talking about energy from the Sun this is (at least
Since we are talking about energy from the Sun this is (at least
in theory) a renew
able resource
in theory) a renew
able resource
��Other than coating the entire surface with a m
anmade
Other than coating the entire surface with a m
anmade
structure(!) giant orbiting solar panels are the least invasive
structure(!) giant orbiting solar panels are the least invasive
approach
approach
��Other suggestions include harvesting energy from
Other suggestions include harvesting energy from
ocean thermal currents
ocean thermal currents
��Seems like an incredibly dangerous idea given the importance
Seems like an incredibly dangerous idea given the importance
of energy circulation in regulating global clim
ate
of energy circulation in regulating global clim
ate
These values are down by 0.1 relative
to the true K
Fiction versus reality
Fiction versus reality
Coruscant(Star Wars)
Earth (Europe)
Type II Classification
Type II Classification
��Type II
Type II ——
A civilization that is able to harness
A civilization that is able to harness
all of the power available from a single
all of the power available from a single star
star
��For the Sun, that would correspond to 4
For the Sun, that would correspond to 4××1010
2626
WW ��K=log
K=log 1
010(4(4��1010
2626)) --6/10=2, so our form
ula works
6/10=2, so our form
ula works
here
here
��How exactly would you go about capturing this
How exactly would you go about capturing this
energy
energy…….?
.?
“Relics”
episode
The Dyson Sphere
The Dyson Sphere
��The idea for building infrastructure to
The idea for building infrastructure to
encapsulate a star is accredited to the
encapsulate a star is accredited to the
physicist Freem
an D
yson
physicist Freem
an D
yson
��Appeared in an article in
Appeared in an article in Science
Sciencein 1959
in 1959
��Note D
yson did not actually envisage a
Note D
yson did not actually envisage a
hard sphere, rather just a sphere of
hard sphere, rather just a sphere of
collectors floating in space
collectors floating in space
��The original idea has been largely
The original idea has been largely
misinterpreted by science fiction
misinterpreted by science fiction
authors
authors
��A rigid body needs to be extrem
ely
A rigid body needs to be extrem
ely
strong to overcome the gravity if it isn
strong to overcome the gravity if it isn’’ t t
rotating
rotating
��If it does rotate then there will be great
If it does rotate then there will be great
differences in the strains at different
differences in the strains at different
parts of the sphere
parts of the sphere
��Led author Larry
Led author Larry N
iven
Niven
to propose
to propose
making a ring that rotated
making a ring that rotated
““ Ringw
orld
Ringw
orld””series
series
Can we detect Dyson spheres?
Can we detect Dyson spheres?
��If we imagine a Dyson sphere at the Earth
If we imagine a Dyson sphere at the Earth’’ s radius, then
s radius, then
its temperature (assuming incident radiation is re
its temperature (assuming incident radiation is re --
radiated) can be derived in the same way as a planet
radiated) can be derived in the same way as a planet
��As you would expect, for a Dyson sphere at the Earth
As you would expect, for a Dyson sphere at the Earth’’ s s
orbital radius the peak em
ission is in the infrared
orbital radius the peak em
ission is in the infrared
4/1
2
4 *
2 * 4
=
DS
DS
rTR
T
��Unless a D
yson Spheres
Unless a D
yson Spheres
looking very similar to
looking very similar to
collapsing
collapsing protostars
protostars
��Recall, these system
s grow in
Recall, these system
s grow in
temperature until nuclear
temperature until nuclear
ignition is achieved
ignition is achieved
��Early studies thought it would
Early studies thought it would
be impossible to tell them
be impossible to tell them
apart
apart
��Now we think that we can, a
Now we think that we can, a
true Dyson sphere should
true Dyson sphere should
have an alm
ost perfect
have an alm
ost perfect
blackbody spectrum (more so
blackbody spectrum (more so
than
than protostars
protostars ))
��Searches are ongoing, but not
Searches are ongoing, but not
promising as yet
promising as yet
At first we thought
At first we thought ““nono”…”…but
but
maybe!
maybe!
IAC
IAC-- 04
04-- IAA
IAA-- 1.1.1.06
1.1.1.06
SEARCHING FOR DYSON
SEARCHING FOR DYSON
SPHERES WITH PLANCK
SPHERES WITH PLANCK
SPECTRUM FITS TO IRAS
SPECTRUM FITS TO IRAS
��
Dick
Dick
Carrigan
Carrigan
Fermilab
Fermilab
Infrared Processing and Analysis Center, Caltech/JPL.
IPAC is NASA's Infrared Astrophysics Data Center.
http://home.fnal.gov/~carrigan/Infrared_Astronomy/Fermilab_search.htm
How much energy would be
How much energy would be
available to an individual?
available to an individual?
��Let
Let’’ s assume that the civilization is modest in
s assume that the civilization is modest in
size
size ––
say the same as the current Earth
say the same as the current Earth
��10 billion individuals sharing 4
10 billion individuals sharing 4��1010
2626W would
W would
mean each individual had a net energy
mean each individual had a net energy
availability of 4
availability of 4 ��1010
1616W, or 4000 times m
ore
W, or 4000 times m
ore
than the entire world production today
than the entire world production today
��How m
uch
How m
uch ““land
land””would you have?
would you have?
��28 m
illion square
28 m
illion square kilometres
kilometres
��20% of the entire land m
asses on
20% of the entire land m
asses on Earth!
Earth!
Building Dyson Spheres
Building Dyson Spheres
��Type I Dyson spheres, constructed from
Type I Dyson spheres, constructed from
orbiting panels are surprisingly feasible if you
orbiting panels are surprisingly feasible if you
can find enough m
aterial
can find enough m
aterial
��Type II D
yson are m
uch, m
uch harder to build
Type II D
yson are m
uch, m
uch harder to build
and while you are building them
they are quite
and while you are building them
they are quite
unstable
unstable
��There is a joke
There is a joke ““A society capable of building a
A society capable of building a
Dyson sphere doesn
Dyson sphere doesn’’ t need a D
yson Sphere
t need a D
yson Sphere ””
How thick could a shell be?
How thick could a shell be?
��Let
Let’’ s take all the mass in the planets in Solar System as
s take all the mass in the planets in Solar System as
an example (don
an example (don’’ t ask m
e how we actually get it all!)
t ask me how we actually get it all!)
��about 2.67
about 2.67��1010
2727kg
kg
��Surface area of DS = 2.8
Surface area of DS = 2.8��1010
2323mm
22
��So about 9443 kg per m
So about 9443 kg per m
22
��At a density of 2000 kg m
At a density of 2000 kg m
-- 33means you could only m
ake the
means you could only m
ake the
sphere 4.72 m
eters thick
sphere 4.72 m
eters thick
��Numerous estimates put the required structure thickness at
Numerous estimates put the required structure thickness at
orders magnitude larger levels than this
orders magnitude larger levels than this……
““ A society capable of building a Dyson sphere doesn
A society capable of building a Dyson sphere doesn ’’t need a D
yson Sphere
t need a D
yson Sphere ””
��Having many collectors
Having many collectors
floating around on orbits
floating around on orbits
could theoretically be
could theoretically be
done
done
��Don
Don’’ t have to worry
t have to worry
about one or two
about one or two
enorm
ous pieces of
enorm
ous pieces of
material
material
��Just have to worry about a
Just have to worry about a
lot more smaller ones
lot more smaller ones
Dyson
Dyson’’ s original idea is more
s original idea is more
““tractable
tractable””
Larry
Larry Niven
Niven--Ringworld
Ringworld
��There are a number of problems with
There are a number of problems with
rigid D
yson spheres (sometimes called
rigid D
yson spheres (sometimes called
Type II D
yson spheres)
Type II D
yson spheres)
��Must be strong enough to resist tidal
Must be strong enough to resist tidal
pull from the Sun (even
pull from the Sun (even unobtainium
unobtainium
materials would need to be 100s
materials would need to be 100s m
etres
metres
thick)
thick)
��If you spin it, you create really
If you spin it, you create really
enorm
ous strains (top still feels
enorm
ous strains (top still feels
gravitational pull, equator can be
gravitational pull, equator can be
balanced by centrifugal force)
balanced by centrifugal force)
��Needs to rotate at about 1000 km s
Needs to rotate at about 1000 km s-- 11to
to
give Earth
give Earth-- like gravity
like gravity
��Niven
Niven
made the sensible suggestion that
made the sensible suggestion that
the easiest thing to do is to build a large
the easiest thing to do is to build a large
ring, and then spin that
ring, and then spin that
Type III Classification
Type III Classification
��Type III
Type III ——
A civilization that is able to harness all of
A civilization that is able to harness all of
the power available from a single
the power available from a single galaxy
galaxy
��This power value varies, but was taken by
This power value varies, but was taken by Kardashev
Kardashev
to
to
be 4
be 4××1010
3737WW
��So K=log
So K=log 1
010(4(4××1010
3737)) --6/10=3.1
6/10=3.1
��Such civilizations would have colonized the galaxy and
Such civilizations would have colonized the galaxy and
would be harvesting energy from every star in the
would be harvesting energy from every star in the
galaxy
galaxy
��Presumably this would take an extremely long time
Presumably this would take an extremely long time ……
Type IV civilizations?
Type IV civilizations?
��Suggestions have been m
ade to extend the scale to
Suggestions have been m
ade to extend the scale to
include
include
��utilizing either the power of a
utilizing either the power of a supercluster
supercluster
of galaxies 10
of galaxies 104242W
W
��harnessing the power of the entire Universe
harnessing the power of the entire Universe
��See Frank
See Frank Tipler
Tipler ’’ss““The Physics of Immortality
The Physics of Immortality ””
��maybe Type IV
classifications should be lim
ited to
maybe Type IV
classifications should be lim
ited to
civilizations that can
civilizations that can ““control the laws of physics
control the laws of physics ””
��Perhaps we lim
it this to civilizations that can spaw
n new
Univer
Perhaps we lim
it this to civilizations that can spaw
n new
Universese’’ s as
s as
in the
in the Biocosm
Biocosm
hypothesis
hypothesis
��To us, such civilizations would be indistinguishable
To us, such civilizations would be indistinguishable
from deities
from deities
Kardashev
Kardashev& Dyson
& Dyson’’ s s
projections
projections
��Kardashev
Kardashev
& D
yson m
ade some guesstimates of
& D
yson m
ade some guesstimates of
when humans would transition between each
when humans would transition between each
type of civilization
type of civilization
��Guesstim
ates assume that energy production grows
Guesstim
ates assume that energy production grows
exponentially, but with a low growth factor
exponentially, but with a low growth factor
��Type I
Type I ––2200 AD
2200 AD
��Type II
Type II ––
5200 AD
5200 AD
��Type III
Type III ––7800 AD
7800 AD
��However,
However, Kardashev
Kardashev
neglects relativity, so in fact Type III
neglects relativity, so in fact Type III
must at minim
um be millions of years aw
aymust at minim
um be millions of years aw
ay
See interview with MichioKaku-"H
ow Advanced Could They Be?". A
strobiology Magazine.
Will humans actually get to Type I
Will humans actually get to Type I
status?
status?
��Technological Singularity? (
Technological Singularity? ( V
inge
Vinge, , Kurzweil
Kurzweil ))
��If we build systems that are as intelligent as humans are they
If we build systems that are as intelligent as humans are they
destined to m
odify them
selves to become increasingly
destined to m
odify them
selves to become increasingly
efficient and m
ore intelligent?
efficient and m
ore intelligent?
��Runaw
ay growth of intelligence?
Runaw
ay growth of intelligence?
��AI pundits suggest this could occur by 2030
AI pundits suggest this could occur by 2030-- 2040
2040
��They assume though that M
oore
They assume though that M
oore’’ s Law
(computer power
s Law
(computer power
essentially grows exponentially) will continue
essentially grows exponentially) will continue ––it looks like it
it looks like it
won
won’’ t beyond 2015 (but we don
t beyond 2015 (but we don’’ t know yet!)
t know yet!)
��Some people are genuinely worried about this
Some people are genuinely worried about this
��Bill Joy (Sun M
icrosystem
s co
Bill Joy (Sun M
icrosystem
s co-- founder) wrote an extensive
founder) wrote an extensive
article in W
ired m
agazine in 2000
article in W
ired m
agazine in 2000 ““Why the future doesn
Why the future doesn’’ t t
need us
need us ””
Summary of lecture 31
Summary of lecture 31
��Kardashev
Kardashev
classification classes civilizations according
classification classes civilizations according
to their power utilization
to their power utilization
��At present humans do not yet rate as a 1 on this scale
At present humans do not yet rate as a 1 on this scale
��Type I civilizations utilize all of the power of their star
Type I civilizations utilize all of the power of their star
arriving at the planet
arriving at the planet
��Type II civilizations utilize all of the power of their star
Type II civilizations utilize all of the power of their star
��Dyson sphere is one way to do this
Dyson sphere is one way to do this
��Type III civilizations utilize all the power of a galaxy
Type III civilizations utilize all the power of a galaxy
��Presumably this requires galactic colonization and m
ust take a l
Presumably this requires galactic colonization and m
ust take a l ong
ong
long
longtime
time ……
Thank you!
Good luck in the exam!