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Home , Active SETI, Allen Telescope Array, Biogenesis, Breakthrough Starshot, Fermi paradox, Galactic habitable zone

Northeastern Illinois University

Life in the

Greg Anderson Department of Physics & Northeastern Illinois University

Winter-Spring 2020

c 2012-2020 G. Anderson Introduction to Astronomy – slide 1 / 92 Northeastern Illinois Overview University

Daing Rocks on How Did Life Arise? Life in the Life Around Other SETI Review

c 2012-2020 G. Anderson Introduction to Astronomy – slide 2 / 92 Northeastern Illinois University

Daing Rocks Zircon Dating Sedimentary Grand Canyon

Life on Earth How Did Life Arise? Life in the Solar System Life Around Daing Rocks Other Stars Interstellar Travel

SETI

Review

c 2012-2020 G. Anderson Introduction to Astronomy – slide 3 / 92 Northeastern Illinois Zircon Dating University

Zircon, (ZrSiO4), minerals incorporate trace amounts of but reject lead.

Naturally occuring uranium: • U-238: 99.27% • U-235: 0.72% Decay chains: • 238U −→ 206Pb, τ =4.47 Gyrs. • 235U −→ 207Pb, τ = 704 Myrs. 1956, Clair Camron Patterson dated the Canyon Diablo meteorite: τ =4.55 Gyrs.

c 2012-2020 G. Anderson Introduction to Astronomy – slide 4 / 92 Northeastern Illinois Dating Sedimentary Rocks University

• Relative ages: Deeper layers were deposited earlier • Absolute ages: Decay of radioactive isotopes

old (deposited last)

oldest (depositedolder first)

c 2012-2020 G. Anderson Introduction to Astronomy – slide 5 / 92 Grand Canyon: Earth History from 200 million - 2 billion yrs ago. Northeastern Illinois University

Daing Rocks

Life on Earth Earth History Timeline Late Heavy Bombardment Hadean Greenland Shark Bay Cyanobacteria Life on Earth Q: Earliest Fossils? O2 History Q: Life on Earth How Did Life Arise? Life in the Solar System Life Around Other Stars Interstellar Travel

SETI

Review

c 2012-2020 G. Anderson Introduction to Astronomy – slide 7 / 92 Northeastern Illinois Earth History University Earth Forms (4.6 Ga) in Impact Forms (4.5 Ga) Late Heavy Bombardment Isotopic Evidence (3.8 Ga) Stromatolites (3.45 Ga)

Hadean Archean Proterozoic Phanerozoic 5 4 3 2 1 0 Billions of ago

c 2012-2020 G. Anderson Introduction to Astronomy – slide 8 / 92 Northeastern Illinois Earth History University Earth Forms (4.6 Ga) Oxygen in Atmosphere Impact Forms Moon (4.5 Ga) Late Heavy Bombardment Isotopic Evidence (3.8 Ga) Stromatolites (3.45 Ga)

Hadean Archean Proterozoic Phanerozoic 5 4 3 2 1 0 Billions of years ago

Paleozoic Mesozoic Cenozoic

c OSD C P TR J K Pg N 550 450 350 250 150 50 Millions of years ago c 2012-2020 G. Anderson Introduction to Astronomy – slide 8 / 92 Northeastern Illinois Timeline for Early Life on Earth University

Life arose on Earth soon after the end of late heavy bombardment. • 4.6 billion years ago (Ga) - earth forms • 4.2, 4.4 Ga - evidence of oceans (detrital zircon) • 4.1–3.8 (3.85-3.82) Ga – late heavy bombardment • 3.8 Ga – Isotopic % BIF evidence from Greenland • 3.5, 2.7 Ga – Stromatolites and other fossils. • 2.3 Ga – The great oxygenation event • 2.0 Ga – of Cells with Nuclei () • 1.2 Ga – Evolution of complex multicellular • 0.5 Ga –

c 2012-2020 G. Anderson Introduction to Astronomy – slide 9 / 92

Hadean Earth c Don Dixon Northeastern Illinois Evidence from Greenland (Controversial) University

Greenland is home to some of the oldest rocks on Earth. • Oldest sedimentary rock at Isua 3.82 Ga • Banded formations (BIF), t> 3.7Ga at Isua may suggest life. • 13C depleted graphite found in the Isua schists, similar claims for Akilia 150 km to the SW.

c 2012-2020 G. Anderson Introduction to Astronomy – slide 12 / 92 Fossil Stromatolites Modern stromatolites: Shark’s Bay Northeastern Illinois Cyanobacteria “blue-green algae” University • The fossil record for early life (Stromatolites) goes back 3.5 Gyrs (disputed) [2.7 Gyrs (undisputed). • Early created a great oxygenation event 2.4 Gyrs ago.

• Cyanobacteria obtain their energy through photosynthesis, and pro- duce oxygen as a byproduct. • By releasing oxygen into the atmo- sphere, Cyanobacteria allowed for the evolution of more complex life- forms on Earth.

c 2012-2020 G. Anderson Introduction to Astronomy – slide 14 / 92 Northeastern Illinois Q: Earliest Fossils? University

According to fossil evidence, how far back in time did life on Earth exist? A) About 65 million years B) About 545 million years C) About 1.0 billion years D) > 2.7–3.5 billion years or more

c 2012-2020 G. Anderson Introduction to Astronomy – slide 15 / 92 Northeastern Illinois Q: Earliest Fossils? University

According to fossil evidence, how far back in time did life on Earth exist? A) About 65 million years B) About 545 million years C) About 1.0 billion years D) > 2.7–3.5 billion years or more

Fossil stromatolites in Australia are 3.5 Ga.

c 2012-2020 G. Anderson Introduction to Astronomy – slide 15 / 92 Northeastern Illinois History of Atmospheric Oxygen University

• Before 2.3 Ga levels of atmospheric oxygen were to low to sustain aerobic life. • By 0.5–0.6 Ga, atmospheric oxygen was plentiful enough to support complex multicellular life.

c 2012-2020 G. Anderson Introduction to Astronomy – slide 16 / 92 Northeastern Illinois Q: Life on Earth University

You have a time machine with a dial that you can spin to send you randomly to any time in Earth’s history. If you spin the dial, travel through time, and walk out, what is most likely to happen to you? A) You’ll be eaten by . B) You’ll suffocate because you’ll be unable to breathe the air. C) You’ll be consumed by toxic bacteria. D) Nothing: you’ll probably be just fine.

c 2012-2020 G. Anderson Introduction to Astronomy – slide 17 / 92 Northeastern Illinois Q: Life on Earth University

You have a time machine with a dial that you can spin to send you randomly to any time in Earth’s history. If you spin the dial, travel through time, and walk out, what is most likely to happen to you? A) You’ll be eaten by dinosaurs. B) You’ll suffocate because you’ll be unable to breathe the air. C) You’ll be consumed by toxic bacteria. D) Nothing: you’ll probably be just fine.

c 2012-2020 G. Anderson Introduction to Astronomy – slide 17 / 92 Northeastern Illinois University

Daing Rocks

Life on Earth How Did Life Arise? Origin of Life on Earth Hydrothermal Vents How did life arise? Miller-Urey How Did Life Arise? Experiment (1953) RNA World Hypothesis pre-cells DNA DNA Strand Evolution Peppered Moth Q: Natural Selection? Life in the Solar System Life Around Other Stars Interstellar Travel c 2012-2020 G. Anderson Introduction to Astronomy – slide 18 / 92 Northeastern Illinois Origin of Life on Earth University

Last Universal Common Ancestor (LUCA): • All life on Earth shares a common ancestry. • We may never know exactly how the first arose, but laboratory experiments suggest plausible scenarios. Possibilities include: • tidepools • hotsprings • deep sea hydrothermal vents

c 2012-2020 G. Anderson Introduction to Astronomy – slide 19 / 92

Northeastern Illinois Hydrothermal Vents University

Some lines of evidence, including DNA sequencing, suggest the first life earth may have been an which lived in extremely high temperatures near deep sea hydrothermal vents.

c 2012-2020 G. Anderson Introduction to Astronomy – slide 21 / 92 Northeastern Illinois How did life arise? University

1. Simple organic form 2. Replicating molecules (RNA?) evolve and begin to undergo natural selection. 3. Replicating molecules become enclosed within membranes. 4. Some cells evolve modern metabolic processes. 5. Multicellular life evolves

c 2012-2020 G. Anderson Introduction to Astronomy – slide 22 / 92 Northeastern Illinois Miller-Urey Experiment (1953) University

Stanley Miller & Harold Urey’s U. Chicago experiment to simulate conditions on early Earth:

Ingredients for Primor- dial Soup:

• Water (H2O)

• Methane (CH4)

• Ammonia (NH3)

• (H2)

Shocked, heated cooled, ...produced Amino acids: the building blocks for protiens. Modern versions of this experiment have produced even more builing blocks for life.

c 2012-2020 G. Anderson Introduction to Astronomy – slide 23 / 92 Northeastern Illinois RNA World Hypothesis University

The first life on earth used RNA to store genetic information and to catalyze chemical reactions. • Discovery of Ribozymes - RNA can catalyze chemical reactions. • Formation of long RNA strands may catalyzed by clays, salty ice water

c 2012-2020 G. Anderson Introduction to Astronomy – slide 24 / 92 Northeastern Illinois pre-cells University

Clay minerals catalyze formation of membranes around RNA. c 2012-2020 G. Anderson Introduction to Astronomy – slide 25 / 92 Northeastern Illinois Deoxyribonucleic acid (DNA) University

Molecule that encodes the genetic instructions for all living cells.

Double helix composed of the nucleotides. Nu- cleotide = nucleobase + deoxyribose sugar + phosphate group. Nucleobases:

• Guanine (G): C5H5N5O

• Adenine (A): C5H5N5

• Thymine (T): C5H6N2O2

• Cytosine (C): C4H5N3O

c 2012-2020 G. Anderson Introduction to Astronomy – slide 26 / 92

Northeastern Illinois Evolution University

Evolution: The change in the inherited characteristics of biological populations over successive generations.

• All life on earth has decended a common ancestor. • The fossil record shows evolution has occurred through time. • ’s theory of natural selection tells us how this evolution occurs. • This theory was supported by the discovery of DNA: our genetic information is stored in DNA, evolution proceeds through mutations.

c 2012-2020 G. Anderson Introduction to Astronomy – slide 28 / 92 Northeastern Illinois Natural Selection University

Charles Darwin (1809–1882), The Origin of Species (1859). Natural Selection: • Variations exists within all populations of organisms. • More offspring are produced than can possibly survive. • Individuals with certain traits are more likely to reproduce. • Over time the population evolves.

c 2012-2020 G. Anderson Introduction to Astronomy – slide 29 / 92 Northeastern Illinois Evolution of the Peppered Moth University

Peppered Moth (Biston betularia): Studied for 200 years. Two morphs: typica (light) vs carbonaria (dark). In the UK, over time mostly light −→ mostly dark −→ mostly light. c 2012-2020 G. Anderson Introduction to Astronomy – slide 30 / 92 Northeastern Illinois Q: Natural Selection? University

Which of the following best describes natural selection? A) It is the idea that organisms with genetic traits that improve their ability to reproduce are more likely to pass those traits on to future generations. B) It is the idea that the strong survive and the weak die off. C) It is a guess made by scientists about how life develops, but it has no hard evidence to support it. D) It is the idea that organisms naturally increase in complexity and with time. c 2012-2020 G. Anderson Introduction to Astronomy – slide 31 / 92 Northeastern Illinois Q: Natural Selection? University

Which of the following best describes natural selection? A) It is the idea that organisms with genetic traits that improve their ability to reproduce are more likely to pass those traits on to future generations. B) It is the idea that the strong survive and the weak die off. C) It is a guess made by scientists about how life develops, but it has no hard evidence to support it. D) It is the idea that organisms naturally increase in c 2012-2020complexity G. Anderson and intelligence withIntroduction time. to Astronomy – slide 31 / 92 Northeastern Illinois University

Daing Rocks

Life on Earth How Did Life Arise? Life in the Solar System Necessities ? Martian Water History Life in the Solar System Water on Mars Flows Mars Life on Jovian ? Life on Europa? & Callisto Titan Lakes Summary Q: Life in the Solar System? Life Around Other Stars Interstellar c 2012-2020 G. Anderson Introduction to Astronomy – slide 32 / 92 Travel Northeastern Illinois Necessities for Life University

• Energy source – sunlight, chemical reactions, & other internal heat • A liquid medium – water, ...methane? • Essential elements/nutrients – C, H, O, N, P, ...

c 2012-2020 G. Anderson Introduction to Astronomy – slide 33 / 92 NASA: Mars Northeastern Illinois Life on Mars? University

Continuing searches for evidence of past/present life on Mars use both telescopes and missions that have landed on Mars. • Mars had abundant liquid water in the distant past. • Mars still has subsurface water ice – perhaps near sources of volcanic heat. Life near the surface today is unlikely due to cold and extreme radiation.

c 2012-2020 G. Anderson Introduction to Astronomy – slide 35 / 92

NASA/JPL: Water on Mars Northeastern Illinois Warm Season Flows University

NASA/JPL: Warm Season Flows, Salty Liquid Brine?

c 2012-2020 G. Anderson Introduction to Astronomy – slide 38 / 92 Northeastern Illinois Warm Season Flows University

NASA/JPL: Warm Season Flows, Salty Liquid Brine?

c 2012-2020 G. Anderson Introduction to Astronomy – slide 38 / 92 Northeastern Illinois Warm Season Flows University

NASA/JPL: Warm Season Flows, Salty Liquid Brine?

c 2012-2020 G. Anderson Introduction to Astronomy – slide 38 / 92 Northeastern Illinois Warm Season Flows University

NASA/JPL: Warm Season Flows, Salty Liquid Brine?

c 2012-2020 G. Anderson Introduction to Astronomy – slide 38 / 92 Northeastern Illinois Warm Season Flows University

NASA/JPL: Warm Season Flows, Salty Liquid Brine?

c 2012-2020 G. Anderson Introduction to Astronomy – slide 38 / 92 Northeastern Illinois Warm Season Flows University

NASA/JPL: Warm Season Flows, Salty Liquid Brine?

c 2012-2020 G. Anderson Introduction to Astronomy – slide 38 / 92 NASA’s Spirit & Rovers: mineral evidence of past liquid water on Mars. Northeastern Illinois Life on Jovian Moons? University

Could there be life on Europa or other Jovian moons? alone has three potential homes for life.

Ganymede Callisto Io Europa

c 2012-2020 G. Anderson Introduction to Astronomy – slide 40 / 92 Europa Northeastern Illinois Life on Europa? University

• Surface mostly solid water ice. • Hypothesis: ocean of liquid water below the surface • Good place to look for life: liquid water + energy from tidal heat- ing.

c 2012-2020 G. Anderson Introduction to Astronomy – slide 42 / 92 Northeastern Illinois Ganymede & Callisto University

Evidence for subsurface oceans on Ganymede, Callisto, but less tidal heating energy available. Did life find a way?

c 2012-2020 G. Anderson Introduction to Astronomy – slide 43 / 92 ’s Enceladus Titan Titan: Liquid hydrocarbons. Northeastern Illinois Summary: Life in the Solar System University

• Could there be life on Mars? - Evidence for liquid water in past suggests that life was once possible on Mars. • Could there be life on Europa or other Jovian moons? - Jovian moons are cold, but some show evidence for subsurface water and other liquids.

c 2012-2020 G. Anderson Introduction to Astronomy – slide 47 / 92 Northeastern Illinois Q: Life in the Solar System? University

After Mars, the next most likely candidates for life in the solar system are A) The of the Jovian . B) The large moons of the Jovian planets. C) The largest asteroids. D) in the Kuiper-belt.

c 2012-2020 G. Anderson Introduction to Astronomy – slide 48 / 92 Northeastern Illinois Q: Life in the Solar System? University

After Mars, the next most likely candidates for life in the solar system are A) The atmospheres of the Jovian planets. B) The large moons of the Jovian planets. C) The largest asteroids. D) Comets in the Kuiper-belt.

c 2012-2020 G. Anderson Introduction to Astronomy – slide 48 / 92 Northeastern Illinois University

Daing Rocks

Life on Earth How Did Life Arise? Life in the Solar System Life Around Other Stars Anthropic Life Around Other Stars Principles Suitable Systems NASA Kepler Kepler Candidates TESS Habitable Identification Steps Planetary Temperatures Circumstellar Habitable Zones HEC ESI c 2012-2020 G. Anderson Introduction to Astronomy – slide 49 / 92 ESI Scatter Northeastern Illinois Mediocrity Principle University

Mediocrity principle: ∼ (): are not privileged observers of the universe. – Hermann Bondi (1948) • We should assume ourselves to be typical in any class that we belong to, unless there is some evidence to the contrary (Garriga and Vilenkin 2008). • Vilenkin 2011 Whitrow Lecture

c 2012-2020 G. Anderson Introduction to Astronomy – slide 50 / 92 Northeastern Illinois Anthropic Principles University

• : Even if intelligent life only occurs on only one planet in a trillion, those are the planets that observers will find themselves on. Thus, our location in the universe is necessarily privileged. • Survivor bias: logical errors made by focusing on civilizaton/life/planets that made it past some selection process and overlooking those that did not.

c 2012-2020 G. Anderson Introduction to Astronomy – slide 51 / 92 Northeastern Illinois Galactic Habitable Zone University

c 2012-2020 G. Anderson Introduction to Astronomy – slide 52 / 92 Northeastern Illinois Suitable Star Systems University

Constraints: • Old enough to allow time for evolution (rules out high-mass stars - 1%) • Stable orbits (might rule out binary/multiple star systems - 50%) • Exclude red dwarfs? () • Size of habitable zone: region in which a planet of the right size could have liquid water on its surface. Billions of stars in the seem at least to offer the possibility of habitable worlds.

c 2012-2020 G. Anderson Introduction to Astronomy – slide 53 / 92

Northeastern Illinois TESS University

Transiting Survey Satellite (TESS) • Launched April 18, 2018. • Two- survey of over 200,000 stars. • Expected to to discover thousands of exoplanets.

c 2012-2020 G. Anderson Introduction to Astronomy – slide 56 / 92 Northeastern Illinois Habitable Exoplanets University

• A potentially habitable exoplanet is an extra-solar planet that might support life. e.g. liquid water. – It does not necessarily have life. • Operational definition: a planet with the right size and orbit to support liquid surface water. • Habitable Exoplanets Catalog

c 2012-2020 G. Anderson Introduction to Astronomy – slide 57 / 92 Northeastern Illinois Identification Steps University

Steps for Identifying Potentialy Habitable Worlds

1. Physical indicators: orbital distance, size, temperature, ... 2. Chemical indicators: liquid water, dioxide, ... 3. Biological indicators: proxies for life – oxygen, methane, ...

c 2012-2020 G. Anderson Introduction to Astronomy – slide 58 / 92 Northeastern Illinois Planetary Temperatures University

800 b b Blackbody 700 b With Albedo b Observed 600

500 b b 400 100◦ C b “Goldilocks zone” (liquid water at 1atm) b 300 b ◦ b 0 C

Temperature (K) b b 200 b

b b b 100 b b b b 0 ' ♀ ♁ ♂ X Y Z [ Me V E M J S U N

c 2012-2020 G. Anderson Introduction to Astronomy – slide 59 / 92 Northeastern Illinois Circumstellar Habitable Zones University

M e rc ur y

Venus Earth

Mars Solar System

c 2012-2020 G. Anderson Introduction to Astronomy – slide 60 / 92 Northeastern Illinois HEC University

c 2012-2020 G. Anderson Introduction to Astronomy – slide 61 / 92 Northeastern Illinois (0 ≤ ESI ≤ 1) University

Not Earth Like Mars Earth Kepler-438b

0 0.2 0.4 0.6 0.8 1.0 KOI-433.02 m

n x − x wi/n ESI = 1 − i io  xi + xio  Yi=1

Property Referencevalue xio weight wi Radius r⊕ 0.57 Density ρ⊕ 1.07 Escape velocity v⊕ 0.70 Surface Temp 288 K 5.58

There is not a scientific concensus advocating use of the ESI.

c 2012-2020 G. Anderson Introduction to Astronomy – slide 62 / 92

Northeastern Illinois Kepler-186f University

The first known Earth-size exoplanet to lie within a habitable zone. star Kepler-186. d = 490 ly. c 2012-2020 G. Anderson Introduction to Astronomy – slide 64 / 92

Northeastern Illinois University

Daing Rocks

Life on Earth How Did Life Arise? Life in the Solar System Life Around Other Stars Interstellar Travel Voyager’s Interstellar Travel Golden Record Pioneer Voyager Distant Spacecraft Daedalus Starshot

SETI

Review

c 2012-2020 G. Anderson Introduction to Astronomy – slide 67 / 92 Voyager’s Golden Record

Northeastern Illinois Distant Spacecraft University NASA Launch Distance Current Probe Date in2014 Speed 1972 112 AU 12 km/s 1973 91 AU 11 km/s 1977 130 AU 17 km/s 1977 107 AU 15 km/s v = 17km/s ≈ 5.6 × 10−5c At the speed of Voyager 1 At v =0.1c • 1 light year ∼ 20, 000 years. • one light year ∼ 10 years. • α Cen ∼ 100, 000 years. • nearest stars ∼ decades. • ↔ Milky Way ∼ 2 Gyrs. • ↔ Milky Way ∼ 1 Myrs.

c 2012-2020 G. Anderson Introduction to Astronomy – slide 70 / 92 Art: Spacecraft Northeastern Illinois Starshot University

Breakthrough Starshot: R&D proposal for proof-of-concept light spacecraft capable of traveling to . • Light-driven nano-spacecraft • Speed 15% – 20% lightspeed. • Travel time 20–30 years • Starshot

c 2012-2020 G. Anderson Introduction to Astronomy – slide 72 / 92 Northeastern Illinois University

Daing Rocks

Life on Earth How Did Life Arise? Life in the Solar System Life Around Other Stars Interstellar Travel Are We Alone? SETI aliens Watterson SETI Allen Array Just an Estimate EQ Fermi’s Paradox Q: Q: Galactic xkcd Possible Solutions Great c 2012-2020 Filters G. Anderson Introduction to Astronomy – slide 73 / 92 (Hard Steps)

Northeastern Illinois SETI University

The Search for Extraterrestrial Intelligence • Passive SETI (SETI) – the search for extraterrestrial intelligence. – Ongoing: , SERENDIP, ... • Active SETI aka METI – attempts to send messages to intelligent life. METI: Messaging to ExtraTerrestrial Intelligence. e.g., signals, physical messages: the , ....

c 2012-2020 G. Anderson Introduction to Astronomy – slide 76 / 92 Northeastern Illinois Arecibo Message University

FM radio broadcast from Arecibo in 1974. 73 × 23 binary digits. Beamed for three minutes towards M13, 25,000 light years away.

c 2012-2020 G. Anderson Introduction to Astronomy – slide 77 / 92 SETI: Allen Telescope Array Frank Drake Northeastern Illinois Drake Equation University

Number of communicating civilizations in our :

N = R∗fpnefℓfifcL

R∗ = rate of in Milky Way.

fp = fraction of stars with planets.

ne = number of planets that could support life per star with planets.

fℓ = fraction of those planets where life develops.

fi = fraction of planets with life that develop intelligent civilizations.

fc = fraction of civilizations that develop . L = length of time for which civilizations release detectable signals.

c 2012-2020 G. Anderson Introduction to Astronomy – slide 80 / 92 Northeastern Illinois Just an Estimate University

Estimates based on available data:

• R∗ ≈ 7/year (NASA & ESA)

• fp ≈ 1 (microlensing surveys)

• fp · ne ≈ 0.4

• fℓ ≈ 1?? (EARLY life on Earth)

• fi · fc ≪ 1 (we evolved only recently) • L & 420 years? L N ≈ 7 ∗ 0.4(fi · fc)L = 1176(fi · fc) =? 420

c 2012-2020 G. Anderson Introduction to Astronomy – slide 81 / 92 Northeastern Illinois Mass vs Body Size University

4 b b 10 3 b 2/ b

b b b b b b b b b b b 3 b b b (Body Mass) b 10 b b ∝ b b b b bb b b b bb b b b b

b b b b Brain Mass b b 2 b b b 10 b b b b b b b b b b b b b b b b b b b 1 b b b b b b b b 10 b b b bb b b b b b b b b b b b b b b 0 b

Brain Mass (g) 10 b b b b hominids 10−1 b H sapiens b b other 10−2 10−3 10−1 101 103 105 Body Mass (kg)

c 2012-2020 G. Anderson Introduction to Astronomy – slide 82 / 92 Northeastern Illinois ’s Paradox University

Where are they? • Our is young. There are billions of older stars. • The size and age of the uni- verse/galaxy suggest techno- logicially advanced civiliza- tions should exist. • Colonization of the galaxy should only take tens of mil- lions of years.

c 2012-2020 G. Anderson Introduction to Astronomy – slide 83 / 92 Northeastern Illinois Q: Fermi Paradox University

What is the Fermi Paradox?

A) Galactic civilizations, like ours, seem forbidden by the laws of physics.

B) Interstellar travel is possible yet would take an infinite amount of time because of relativistic time-dilation.

C) We would be unable to detect an Earth-like planet even at a distance of a few light years.

D) Reasonable assumptions predict that a galactic should have already arisen in the Milky Way. Yet, we have absolutely no evidence for it.

E) The Drake equation predicts that there should be no intelligent life in the Milky Way. Yet, we exist.

c 2012-2020 G. Anderson Introduction to Astronomy – slide 84 / 92 Northeastern Illinois Q: Fermi Paradox University

What is the Fermi Paradox?

A) Galactic civilizations, like ours, seem forbidden by the laws of physics.

B) Interstellar travel is possible yet would take an infinite amount of time because of relativistic time-dilation.

C) We would be unable to detect an Earth-like planet even at a distance of a few light years.

D) Reasonable assumptions predict that a galactic civilization should have already arisen in the Milky Way. Yet, we have absolutely no evidence for it.

E) The Drake equation predicts that there should be no intelligent life in the Milky Way. Yet, we exist.

c 2012-2020 G. Anderson Introduction to Astronomy – slide 84 / 92 Northeastern Illinois Q: Galactic Civilizations University

If there are other civilizations at present in the Milky Way Galaxy, which statement is almost undoubtedly true?

A) They are far more technologically advanced than we are.

B) They are anatomically much like us, with two arms, two legs, two eyes, and two ears.

C) They have social structures that are completely different from our own; for example, different types of ”family” units, and so on.

D) For fun, they enjoy ”buzzing” to Earth and temporarily abducting people, showing a clear preference for people located in less-developed rural areas.

c 2012-2020 G. Anderson Introduction to Astronomy – slide 85 / 92 Northeastern Illinois Q: Galactic Civilizations University

If there are other civilizations at present in the Milky Way Galaxy, which statement is almost undoubtedly true?

A) They are far more technologically advanced than we are.

B) They are anatomically much like us, with two arms, two legs, two eyes, and two ears.

C) They have social structures that are completely different from our own; for example, different types of ”family” units, and so on.

D) For fun, they enjoy ”buzzing” to Earth and temporarily abducting people, showing a clear preference for people located in less-developed rural areas.

c 2012-2020 G. Anderson Introduction to Astronomy – slide 85 / 92

Northeastern Illinois Possible Solutions University

• N > 1: Aliens exist, there IS a galactic civilization – They are sending signals, but we don’t know how to listen. – They have no desire to communicate. – Its dangerous to communicate – The

• N ≪ 1: Hypothesis, We are alone. – Intelligent tool making life rarely evolves. – Advanced civilizations destroy themselves on short timescales. c 2012-2020 G. Anderson Introduction to Astronomy – slide 87 / 92 Northeastern Illinois Great Filters (Hard Steps) University

Cyanobacteria Combigenesis Civilization Biogenesis Eukaryotes Metazoans

dP dt

−5 −4 −3 −2 −1 0 1 Billions of Years (Ga)

Brandon Carter: http://arXiv.org/abs/0711.1985v1

r−1 n−r ˙ n! t (τe − t) P (r)= n (r − 1)!(n − r)!τe

c 2012-2020 G. Anderson Introduction to Astronomy – slide 88 / 92 Northeastern Illinois Further Study University

• Patterson’s Paper • International Commission on Stratigraphy (ICS) • Early Earth (Elements Magazine) • Exploring Origins (Boston Museum of ) • SETI, SETI at Home • The Drake Equation • Drake Equation Calculator • The Eerie Silence: Renewing Our Search for Alien Intelligence, . • Five or Six Step Evolution, B. Carter. • The

c 2012-2020 G. Anderson Introduction to Astronomy – slide 89 / 92 Northeastern Illinois University

Daing Rocks

Life on Earth How Did Life Arise? Life in the Solar System Life Around Other Stars Interstellar Travel Review SETI

Review Review I Review II

c 2012-2020 G. Anderson Introduction to Astronomy – slide 90 / 92 Northeastern Illinois Review I University

• How old is the Earth? • Where might life have first evolved on Earth? • When did life appear on Earth? • How old are the oldest fossils? • When did oxygen first appear in Earth’s atmosphere? • What was the Cambrian explosion. • What is evolution? How does natural selection work.

c 2012-2020 G. Anderson Introduction to Astronomy – slide 91 / 92 Northeastern Illinois Review II University

• Other than Earth, where might we find life in our solar system? • Are we more likely to find life on a planet orbiting a big star or a small star? • What is an operational definition of a habitable zone? • Have we found exoplanets in habitable zones? • What is the Drake equation? • What is the Fermi paradox? • What are some solutions to the Fermi paradox.

c 2012-2020 G. Anderson Introduction to Astronomy – slide 92 / 92