Download Week 2

The search for life in
the Universe
ASTR 201
Friday, September 13, 2013
Outline of Week #2
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What are we searching for?
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Why are we searching now?
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Introduction to Astrobiology
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The Scientific Method
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What are we searching for?
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How do we define life?
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common attributes of bacteria, beetles, mushrooms, a maple tree,
kittens, and your Mom versus a crystal, a fire, or the ocean?
made of cells?
reproduce/spread?
grow?
respond/move?
Necessary and sufficient conditions?
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not just one condition, but need 6 to define life as we know it.
given difficulties in defining life on Earth, then scientific search
for life generally assumes Earth-like as a starting point
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The key properties of life on Earth
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Are your favorite ETs from books & movies
Earth-like?
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A wider variety of possibilities …
?
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Extremophiles on Earth
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What would count as evidence?
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What would count as evidence?
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Fossilized evidence of life
found on Mars
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What would count as evidence?
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Fossilized evidence of life
found on Mars
Fossilized evidence of life
found in a meteorite
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What would count as evidence?
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Fossilized evidence of life
found on Mars
Fossilized evidence of life
found in a meteorite
Evidence of
photosynthesis in
atmosphere of extra-solar
planet
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What would count as evidence?
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Fossilized evidence of life
found on Mars
Fossilized evidence of life
found in a meteorite
Evidence of
photosynthesis in
atmosphere of extra-solar
planet
Signal from alien
civilization (SETI)
Friday, September 13, 2013
What would count as evidence?
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Fossilized evidence of life
found on Mars
Fossilized evidence of life
found in a meteorite
Evidence of
photosynthesis in
atmosphere of extra-solar
planet
Signal from alien
civilization (SETI)
Living organisms found on
a meteorite, comet or
asteroid
Friday, September 13, 2013
What would count as evidence?
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Fossilized evidence of life
found on Mars
Fossilized evidence of life
found in a meteorite
Evidence of
photosynthesis in
atmosphere of extra-solar
planet
Signal from alien
civilization (SETI)
Living organisms found on
a meteorite, comet or
asteroid
Friday, September 13, 2013
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Aliens visit us
What would count as evidence?
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Fossilized evidence of life
found on Mars
Fossilized evidence of life
found in a meteorite
Evidence of
photosynthesis in
atmosphere of extra-solar
planet
Signal from alien
civilization (SETI)
Living organisms found on
a meteorite, comet or
asteroid
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Aliens visit us
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Alien artifacts found on
nearby planet
What would count as evidence?
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Fossilized evidence of life
found on Mars
Fossilized evidence of life
found in a meteorite
Evidence of
photosynthesis in
atmosphere of extra-solar
planet
Signal from alien
civilization (SETI)
Living organisms found on
a meteorite, comet or
asteroid
Friday, September 13, 2013
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Aliens visit us
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Alien artifacts found on
nearby planet
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Living biosystem within
the Solar System
Why are we searching now?
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Debate over life on other worlds is not new
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~300 BC, Greek philosophers debated “What is the Universe made
of?” [Plato, Aristotle, Thales, Anaximander ...] **
atomists
Earth & heavens made of fire,
earth, water, air
Aristotelians
Four elements confined to Earth,
heavens made of ether/quintessence
so long as number of atoms is
each element has its own properties
infinite, then natural to create other (Earth travels towards centre of
worlds and life.
the Universe, fire rises from it),
thus the Earth is the centre and
there are no other worlds.
Friday, September 13, 2013
Is Earth the only “world”?
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Earth was long thought
to be the only “world”
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For thousands of years,
the five naked-eye
planets have been known
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Mercury, Venus, Mars,
Jupiter, and Saturn
However, the nature of
these objects was largely
unknown until the advent
of the telescope
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The Moon as another world
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In 1609, Galileo showed
that the Moon is a world
with mountains, valleys,
craters, etc.
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He also speculated that
the lunar maria might be
oceans of water
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Kepler suggested that the
Moon had an atmosphere
and inhabitants!
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Bruno burned at the stake
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Percival Lowell’s Mars
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In the late 1800’s, astronomer Percival Lowell made
detailed maps of Mars, identifying numerous “canals”
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He concluded that a Martian civilization had made
these canals to transport water from the poles to cities
close to the equator
Friday, September 13, 2013
In the News
The south pole of Mars shows that
the Red Planet isnʼt always dull,
dusty, and barren
1 By Sebastian Anthony on September 6, 2013 at 9:58 am
What you see is an image of Mars’ south pole,
captured by the European Space Agency’s Mars
Express Orbiter. It is distinctly different from the
dusty, barren, not-attractive landscapes that we
usually associate with the Red Planet, but it’s still
most definitely Mars.
The huge white swirl in the middle is Mars’
permanent southern polar ice cap. It mostly
consists of water ice, like the poles here on Earth.
In the winter, as temperatures fall to around -153
Celsius (-243 F), carbon dioxide freezes, forming a
few-meter-deep layer of dry ice. When the winter
ends and sunlight strikes the dry ice, it sublimates
into gas, creating massive winds that travel at 250
mph (400 kph).
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The Solar System’s habitable zone
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Places to look in the Solar System
Europa
Mars
Titan
Enceladus
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Are there other suns?
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Ancient astronomers
speculated that stars
were like the Sun but
much further away
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Confirmation of this idea
required measurement of
stellar distances
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One technique for
measuring distances is
called stellar parallax
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The first detections of stellar parallax
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Ancient astronomers tried to detect
stellar parallax with the naked eye,
but were unsuccessful
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In 1838, Friedrich Bessel became the
first to measure the parallax of
another star (61-Cygni)
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he found a parallax of 0.3
arcseconds, corresponding to a
distance of about 700,000 AU! (11 LY)
later in 1838, Thomas Henderson
measured a parallax of 0.76” for
Alpha Centauri, placing it only
270,000 AU away (4.3 LY)
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Do other stars have planets?
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Given that the Sun is a fairly ordinary star, it seems
reasonable to imagine that other stars may have planets
too
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However, it is extremely difficult to detect a (relatively)
small, faint planet very close to a bright star
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Despite several decades of effort, no so-called extra-solar
planets had been detected as of the early 1990’s
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However, the first such planet (51 Pegasi) was detected in
1995
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We now know of about 600 extra-solar planets!
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Techniques for finding
extra-solar planets
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How many planets are there in
the observable Universe?
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We will make a very rough estimate of the number of
planets in the observable universe, and for the sake of
argument, let’s be very pessimistic …
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assume that 1% of stars have planets (likely about 1-30%)
assume that each of these stars has only 1 planet
assume our Galaxy contains 100 billion stars
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assume the observable universe contains 100 billion galaxies
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likely to be considerably higher
Together, this implies that the observable universe contains
100 billion * 100 billion * 1 * 0.01 planets
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more likely 200-400 billion
100 billion billion planets in total (1020)
While this calculation is overly simplistic, there clearly is no
shortage of locations in which life may exist!
Friday, September 13, 2013
In the News
905 Planets around 697 Stars
154 Confirmed (Kepler & community)
3,573 Kepler Candidates and Confirmed Planets
Date of last update: 2013-09-05
From the NASA Exoplanet archive at http://exoplanetarchive.ipac.caltech.edu/
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Summary of why search now?
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New discoveries on the environments that host life and
the range in types of life found on Earth suggest that
life is very hardy
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Universe if full of stars, now learning full of planets too.
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Scientific/technological advances make it possible to
search for habitable planets and varieties of life.
Friday, September 13, 2013
Some Review Questions
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Chapter 1, page 14 -
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Could try #1, 4, 12, 17
1. Why are scientist interested in the possibility of life beyond the Earth?
4. What are extrasolar planets? In what way does their discovery make it seem
more reasonable to imagine finding life elsewhere?
12. A habitable planet is (a) a planet that has oceans like Earth, (b) a planet that
has life of some kind, (c) a planet that may or may not have life, but has
environmental conditions under which is seems that life could arise or survive.
17. If we sent one of our current spacecraft to a nearby star (besides the Sun), the
trip would take about (a) a decade, (b) 100 years, (c) 100,000 years.
Friday, September 13, 2013
Astrobiology
- Given
that we have not yet found life beyond Earth, the
search for such life is obviously very challenging
- simply pointing telescopes at the sky hasn’t been successful
- there is a need for good strategies in deciding how best to
increase our chances of finding life elsewhere
- The
science of Life in the Universe is called Astrobiology
- The
primary goals of astrobiology include
- understanding
the conditions necessary for life on Earth (and
possibly the conditions required for life in general)
- looking for places in the universe which have these conditions
- trying to actually detect extraterrestrial life
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Fields related to astrobiology
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Astronomy & Planetary Science (where to search)
Physics & Chemistry (universality of the Laws)
Biology (define life)
Geology (define habitable)
Engineering (build equipment, rockets, etc.)
Mathematics, Statistics, Computer Science (modelling)
Philosophy
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Is biology also universal?
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Is biology also universal?
Transition from chemistry to
biology occurs under many
condition (extremophiles),
and quickly (like early Earth)
Extremophiles on Earth
Friday, September 13, 2013
Text
Fossil evidence of blue-green
algae (cyanobacteria) were
producing oxygen (contributing
to our atmosphere) for at least
2.7 billion yrs.
also complex molecules in the ISM.
Where will we discover new life?
1. In a test tube?
2. Bacterial goo on Titan?
3. Biomarkers in an exoplanet atmosphere?
4. Calling us up on an interstellar laser phone?
Chances of finding microbial life seem good,
yet that predated intelligent life on Earth by
3-4 billion years.
Friday, September 13, 2013
The Scientific Method
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How do we distinguish between good & bad science?
accept,
observe
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guess
testable
prediction
revise, or
discard
flashlight example
can still fail since rarely have all the facts, or the data you
really want, and scientists are human (intuition, beliefs ...)
not all knowledge is science
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Friday, September 13, 2013
Observe
Occam’s Razor
Verifiable
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“Only a Theory”
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What does that mean exactly?
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Does it mean it’s just a guess?
a guess is more like a hypothesis than a theory.
A theory is an idea that is based on several verifiable
observations, and has been tested and confirmed by others,
giving it broad support.
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Theory of Evolution
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Theory of Gravity
Friday, September 13, 2013
Some More Review Questions
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Chapter 1, p 14
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Could try #6, 14, 20
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Chapter 2, p46
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Could try #4, 5, 12, 14, 15
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Science or Nonscience: test statements #19-28.
Friday, September 13, 2013
Some Review Questions
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Chapter 1, p 14
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Could try #6, 14, 20
6. What do we mean by “universality” of physics and chemistry? Although we do
Chapter
2, p46biology is similarly universal, what evidence makes it seem
not
know yet whether
that it might be?
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Could try #4, #5, #12, #14
Accordingor
to current
scientific test
understanding,
life on #19-28.
Earth (a) was exceedingly
14.
Science
Nonscience:
statements
improbably, (b) arose quite soon after conditions allowed it, (c) may have been
inevitable, but took billions of years to arrive.
20. Failure to find life on any other world would mean (a) the whole subject had
been a waste of time, (b) we must have done something wrong, since life has to
exist beyond Earth, (c) we have learned important lessons about the conditions that
made life on Earth possible.
Friday, September 13, 2013
Some Review Questions
12. What is the difference between a hypothesis and a theory in science?
14. What is Occam’s razor?
Given an example of how it applies.
15. Why doesn’t science accept personal testimony as evidence? Explain.
4. Who first proposed the Earth is a planet orbiting the Sun, and roughly when?
Why didn’t this model gain wide acceptance in ancient Greece?
5. Briefly describe and contrast the different views of the atomists and the
Aristotelians on the subject of extraterrestrial life.
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Chapter 2, p46
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Could try #4, 5, 12, 14, 15
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Science or Nonscience: test statements #19-28.
Friday, September 13, 2013
For Week #3
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Review Chapter 3 from the textbook *
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Assignment 1 will be posted on Tuesday
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Familiarize yourself with course website
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Lecture materials are posted online
http://www.astro.uvic.ca/~venn/a201.html
Friday, September 13, 2013