Transcript Are we alone? - School of Physics

Are we alone? The search for life
elsewhere in the universe
Summary lecture
John Webb
Session 2, 2004
Our Place in the Universe
Charley Lineweaver
Where are we?
How old is the Universe?
What is the Universe made of?
Where are we?
How old is the Universe?
What is the Universe made of?
14 Gyr
13.4 +/- 1.6 Gyr
Sievers02
WMAP03
Age of Universe
Lineweaver 1999
Star and Planet Formation
Maria Hunt
Organic Molecules in the
Interstellar Medium
Maria Hunt
School of Physics
UNSW
Chemical Evolution of the Universe
Big Bang
Life
Atoms
Molecules
What Are Organic Molecules?
• Organic molecules are the molecules of life
and contain carbon.
• Only carbon (and perhaps silicon) have a
chemistry complex enough to form life.
What Molecules Are Out There?
• We have found 123 different molecules, with up to
11 atoms
• We see complex organic molecules in molecular
clouds, including alcohol and vinegar.
• We may also have seen the amino acid glycine.
• But, to detect these in molecular clouds with our
radio telescopes on Earth requires incredible
quantities.
How do we “see” molecules?
A Better Place to Look?
• Carbonaceous chondrites are meteorites that
date back to the formation of the solar
system.
• They fall to earth on a regular basis.
• They are found to contain many complex
organic molecules, including amino acids.
• Comets are also remnants of the presolar
nebula.
Carbonaceous chondrite, found to contain organic molecules
with both left and right hand spiral structure
The History of Life on Earth
Malcolm Walters
3 branches:
Bacteria
Archea
Eucarya
Universal tree of life:
- most life is microscopic
- hyperthermophiles at base of tree
- abundant hydrothermal deposits in the rock record
- good but still controversial evidence of life at 3.5Ga
- early Earth like early Mars
The Origin and Evolution of Life
Charley Lineweaver
Stanley Miller 1953
primordial soup
in a warm little
tidal pool
hydrothermal
vents
Where?
Mars
Origin of Life
Evolution of Life
What is Life?
Searching for Extra-solar Planets
John Webb
Methods for detecting extrasolar planets
1. Astrometry (measuring stellar positions)
2. Doppler method (planet and star orbit a
common centre of mass)
3. Gravitational lensing (spacetime distortion)
4. Reflected light (like looking at the planets from
Earth)
5. Eclipse (or occulting or transit) method
Maybe we can
detect an
atmosphere!
~1% relative drop
TPF - terrestrial planet finder
Are We Alone?
• IR interferometer, 5
cooled 3.5m mirrors
• ~75-1000 m baseline
• Separate spacecraft
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for configuration
flexibility
1 milli-arcsec
(mas)
Spectral
Resolution 20-300
Operate at 1 AU for
5 years
Launch date 2011?
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What does 1 mas mean?
If you put TPF on Earth, you could
resolve a man’s face on the Moon!
(For comparison, the AAT could only
just resolve the building we are in).
TPF eliminates light from host
star using “NULLING”
Are We Alone?
3. Time-series as
TPF rotates
1. Simulated target
2. Target through TPF
interference fringes
The Drake equation
Are We Alone?
No. of advanced civilisations which we might contact:
N = (N*f) x (Np/* fsuitable) x (fislifefsmart) x (Ladv/Lmw)
Things we can guess (on the basis of our solar system):
Np/* = no. of planets per star = 9 (as for our Sun)
fsuitable = fraction suitable for life = 1/9
Things we know well:
N* = no. of stars in
galaxy = 300 billion
fislife = fraction of the above WITH life = 1
MW
f = fraction “similar” to
our Sun = 1/3
fsmart = fraction of the above with ADVANCED life = 1
Lmw = lifetime of Milky Way Galaxy; upper limit = age of
universe = 14 billion years
Things we haven’t got a clue about:
Ladv = lifetime of civilisation in its advanced
NB: 1 billion = 1000 million = 109
phase = 200 years (assuming we last that long!)
Artificial Intelligence- Our Future?
Michael Ashley
Overview
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Artificial life
Robotics/nanotechnology
The exponential growth of computing power
The human brain as a computer
Can a computer be intelligent? (Turing test)
The near-term future for life on Earth
Speculations about the long-term future
Exponential growth in computing historical data
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1900 Babbage’s Analytical Engine.
1910 Mechanical calculators
1943 Colossus
1946 ENIAC
1951 Univac I
1960 IBM 1620
1966 IBM 360 model 75
1976 PDP-11
1979 DEC VAX 11/780
1982 IBM PC
1993 Pentium
2002 Pentium 4
Plot of Moore’s Law
Exponential growth - an example
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The Emperor of China was
so impressed with the game
of chess, that he asked the
inventor to name his price.
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One grain of rice on the first square.
Two on the second.
Four on the third.
And so on, doubling with each
square.
The result?
At the half-way point, 4 billion grains
of rice (about one large field).
After 64 squares, you would need a
field twice as large as the Earth’s
surface.
NOTE: no one really noticed the
problem until the half-way point.
And that is where we are with
computers today...
Can we stop the machines?
• In 1962, if you turned off all
the computers in the world, it
would have had little effect.
• In 2004, the same
experiment would have
devastating consequences
(e.g., financial system
collapses, no electricity, no
water, no fuel, no public
transport).
• This process will accelerate.
• There will come a point
when the machines are in
control.
• We are becoming more
dependent on computers
with each passing year.
So, we can not stop
them. But this may not
be such a bad thing.
New Aproaches to SETI
Paul Davies
Was it chance or law?
‘Man at last knows that
he is alone in the unfeeling
immensity of the universe,
out of which he emerged
only by chance.’
Jacques Monod
Biological determinism
Life
“The universe is pregnant with life…”
“Life is a cosmic imperative!”
“Life is almost bound to arise… wherever
physical conditions are similar (to Earth).”
Better “message-sending” strategy:
use nanomachines
Self-repairing
Self-replicating
Adaptive
Living cells!
The Anthropic Principle
Joe Wolfe
Weak anthropic principle (WAP)
If we think that our existence requires certain
conditions/laws of nature/... then discovering
that those conditions/laws apply is not
surprising.
Strong anthropic principle (SAP)
Our existence requires certain
conditions/laws. These conditions/laws are
improbable therefore (?) the Universe/laws of
physics are that way in order for us to exist,
therefore .....
Anthropic inconsistencies
Statement of fact:
The laws of physics (& initial conditions of the Universe?) allow:
 stars and planets
 expanding universe
 elements other than H
 evolution of life
The SAP:
Because PexpandPstarsPchemistryPlifePetc = small, someone/thing set up the
Universe this way so that life can appear.
The inconsitency:
If the SAP argument is made by a living being made of chemicals other
than H, living on a planet and powered by sunlight and cold sky, then
Pexpand = Pstars = Pchemistry = Plife = Petc = 1
http://www.phys.unsw.edu.au/~jw/danish.html
Low D anatomy:
everywhere is close to surface
\ diffusion of nutrients & heat possible
large surface:volume ratio
\ intercept large flux of
e.g. light, nutrients, prey
Low D geo(?)graphical zones:
(e.g. littoral zone, dawn zone on Mercury, biosphere)
large gradients (spatial variation) in some of
density and mechanical properties
composition
temperature
radiation intensity
Low D life is not favoured
A Field Guide to UFOs
John Storey
The Evidence
• Millions of sightings
• Eyewitness accounts
• Photographs, videos
• Radar images
• Alien abductions
From the film Men in Black
How far away is it?
• Focus position of eye
(“accommodation”)
• Convergence of eyes
• In front of / behind other things
• Clarity
• Apparent size, based on prior
knowledge
“If an unfamiliar object appears in
the sky several metres away or
more, it is impossible to tell how
far away it is, or how big.”
Is it:
•A fire fly—5 metres away?
•A balloon —500 metres away?
•An aircraft —5 km away?
•Venus —50 million km away?
UFO sightings
•The vague
•The astronomical
•The atmospheric
•The mundane
•Weather balloons
•Space craft (terrestrial)
•The military
•Hallucinations
•Pranks
•Hoaxes
•The unexplained
A few good online references:
The Anthropic Principle
1. In red giant stars with low, medium, and high masses, a change of only 0.4 percent in the
strong nuclear force would have made it impossible for carbon-based life to evolve. Given
even this slight variation, all stars would have produced either carbon or oxygen, but not the
necessary abundance of both elements so critical to organic life.
http://www.space.com/scienceastronomy/astronomy/redstar_carbon.html
2. Interesting article on the Anthropic Principle by Novel Laureate Steven Weinberg:
http://www.nyu.edu/classes/neimark/design.html
3. Article titled “Life, the cosmos, and everything” by Bernard Carr summarising a conference
at the IoA, Cambridge, on the Anthropic Principle/fine tuning in physics:
http://physicsweb.org/articles/world/14/10/3
4. Extract from John Peacock’s book “Cosmological Physics” on the Anthropic Principle:
http://nedwww.ipac.caltech.edu/level5/Peacock/Peacock3_5.html
5. Joe Wolfe’s article “Cosmology, teleology and Danish Grandmothers”:
http://www.phys.unsw.edu.au/~jw/danish.html
Origin of the elements
6. Elementary short article on nuclear fusion in stars and nucleosynthesis:
http://www.enchantedlearning.com/subjects/astronomy/stars/fusion.shtml
A few good online references:
7. NASA introduction to stars of different masses:
http://starchild.gsfc.nasa.gov/docs/StarChild/universe_level2/stars.html
8. Good introductory article by Davison Soper on “The life and death of stars”:
http://zebu.uoregon.edu/~soper/MilkyWay/stars.html
9. Technical article “On the cosmic origins of carbon and nitrogen”:
http://arxiv.org/abs/astro-ph/0004299
Dimensionality
10. Very nice and fairly extensive article, including historical content. Not directly relevant to
“Are we alone” but excellent background material:
http://scholar.uwinnipeg.ca/courses/38/4500.6-001/Cosmology/dimensionality.htm
11. Article on “Spatial Topology” in the context of computer RAM. Not directly relevant to
“Are we alone” but interesting side-issue:
http://www.his.atr.jp/~ray/pubs/zen/node18.html
Bacteria from space
2001 controversy about extraterrestrial bacteria in a meteorite:
http://www.abc.net.au/science/news/stories/s296483.htm
Andrew
Mynott
Philip
Smith