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!