Study Points• What is the Copernican Principle?• What are the basic requirements for life as we know it?• Describe the characteristics of a habitable environment• What biomarkers do we look for in the search for

evidence of life beyond our solar system?• What is the Fermi paradox, and what are some possible

solutions to it?• List efforts to communicate with other civilizations

(listening and talking)

Life in the Universe• Astrobiology

• Are we alone in the universe?

• Searching for LifeNASA Graphic Novels about Life in the Universehttps://astrobiology.nasa.gov/resources/graphic-histories/

Lucky Accidents from last lecture

1. Density fluctuations need to be “just right”• Too small: Gravity too weak and no galaxies form• Too large: Black hole universe with radiation not

allowing humans

2. Finely balanced between expansion and contraction

3. Matter needed to be greater than anti-matter for matter to take over and us to exist

4. The force of gravity has to be just right to form stars of our Sun’s mass

5. And many more perfect balances…

Slido.com Class Poll

• Enter code: #K261

• Answer this:

• Do you think life exists outside of Earth?

The Copernican Principle*• Earth is not a privileged/special place in the universe*

• Not the center of the solar system

• Not the center of the universe

• Not the only planet

• Many stars like our Sun

• From Galileo to Hubble, science proves the universe is much bigger than us

• So why should we be the only planet with life?

• Yet to be answered: Is organic biochemistry likely or unlikely in the universe?

Requirements for Life:What makes life possible?

• All life we know uses the same basic elements*• Carbon

• Hydrogen

• Nitrogen

• Arranged in amino acids: the building blocks of life

• Amino acids based on carbon bonds (organic molecules)

• Biology also requires liquid water*

• Energy input*

• Oxygen

• Phosphorus

• Sulfur

Where do we find these materials?

Everywhere!

Complex organic molecules found near galactic center

Trillions of times Earth’s water in

giant dust clouds

Glycine (amino acid) and phosphorus found on Rosetta

Comet

What makes Earth good for life?

• Moderate temperatures

• Stable for a long time (a few billion years)

• Magnetosphere protects us from harmful radiation

• Moon makes tides (allows for slow transition from water to land)

• Moon protects us from asteroids

• So does Jupiter

• Star not too hot (short-lived), not too cool and stormy

• Solid surface

• Rocky composition means elements are plentiful

But maybe nice isn’t necessaryExtremophiles have been found living at:

• -13° F• 250° F• 1000 times normal pressure

• 1000 times human radiation tolerance• pH equivalent to bleach• 10 million times more acidic than human

blood

Characteristics of a Habitable Environment

What do we look for?

• Liquid water *

• Energy *

• Base materials *

• Stable environment *

Habitable does NOT mean inhabited

Possible Habitable Environments

Current Best Bets in Our Solar System• Mars• Europa – moon of Jupiter• Enceladus – moon of Saturn• Titan – moon of Saturn

Current Best Bets: Mars• Recurring slope lineae:

where water still flows

• Mudstone: rocks that formed in or under water

Curiosity rover also found organic molecules and pockets of methane

Life underground? On the surface? Currently looking…

Current Best Bets: Europa and Enceladus

Water: underground oceans on Europa

Energy: geothermal from tidal stresses on Europa

Materials: organic materials spotted in plumes from

Enceladus

Current Best Bets: Titan

Water: no, but surface oceans & lakes of methane/ethane

Materials: covered in organic

materials, including tholins

Atmosphere: only moon to have a dense atmosphere

https://public.nrao.edu/news/organic-molecules-titan

Habitable Environments Beyond Our Solar System

• Focused on the Habitable Zone: where liquid water is possible on a planet’s surface (Goldilocks zone)

Habitable Zone

• May change throughout a star’s lifetime

• Atmosphere may affect it (too much or too little)

• Doesn’t help if planet has no water (like Venus)

• Habitable Exoplanet Catalog:• Watch/Show: http://phl.upr.edu/projects/habitable-exoplanets-catalog

Habitable Zone: Weird Possibilities

• Tidally locked planets close to a star might be habitable (clouds bounce light off the top of the atmosphere and strong winds move heat around)

• Pulsar planets might survive with thick atmospheres. Radiation from pulsar could keep them warm.

• Exomoons?? Just starting to find moons outside our solar system

Looking Closer: Biomarkers*• *Water – naturally occurring but good sign• *Oxygen – produced by life on Earth, but can be made without life• *Oxygen + methane – good sign & hard to do without life• *Green – Earth is noticeably green in visible light thanks to plants

Earth’s spectrum

Infrared is a great place to look!

• Bad news: exoplanets are far away and hard to observe

Looking Closer: Biomarkers

• Good news: big molecules like H2O, CO2, CH4 make big signals

• Good news: we’re getting better at observing!

James Webb Space Telescope will look for

these signals in exoplanet atmospheres!

Have aliens visited us? No evidence.How would they travel?• Fast (impossible)

• Faster than light travel is impossible as far as we know

• Almost-fast-as-light travel makes your ship infinitely heavy (Einstein)

• We don’t know how wormholes work

• Slow (very slow) Humans are pretty smart – and bad at keeping secrets

Have aliens visited us? No evidence.

Science can’t prove a negative.

BUT

Science does start with the simplest answer: No aliens have made contact

• Too costly in terms of energy

• Most UFO sightings are not UFOs

• Ancient monuments do not point to aliens

But could aliens be out there?

If we’re the only ones, that means there’s less than 1 in 10 billion trillion chance of intelligent life forming.

Watch/Show: http://www.rochester.edu/news/are-we-alone-in-the-universe/

The Drake Equation: The equation is used to estimate the number of likely civilizations in the universe

Frank Drake: How likely is it that we are alone?

The Drake Equation: Estimating the Number of Civilizations

R∗ = 1.5–3 yr−1, fp · ne · fl = 10−5, fi = 10−9, fc = 0.2 and L = 304 years

= 10−11

Not good

Conservative numbers:

R∗= 1.5–3 yr−1, fp · ne · fl = 0.026, fi = 1, fc = 0.2 and L = 109 years

= 15,600,000 A lot better!

Optimistic numbers:X

The Fermi Paradox*• Contradiction of the missing evidence of life

outside Earth & how common life should be*

• If life and intelligence are common, why haven’t we heard from aliens?

• In Fermi’s words: “Where is everybody?”

• An alien civilization could conquer a galaxy in a few tens of millions of years. The universe is billions of years old.

Enrico Fermi

Watch (6:21): Where are all the aliens?https://www.youtube.com/watch?v=sNhhvQGsMEc

The Fermi Paradox & many solutions*

The Fermi Paradox & many solutions*

The Fermi Paradox

https://xkcd.com/638/

Communications with Other CivilizationsSETI: Search for Extraterrestrial Intelligence

The Allen Telescope Array (only SETI), California

- Listening for radio waves

To explore, understand and explain the origin and nature of life in the universe and the evolution of intelligence• Listening for radio waves is one of

many areas of research*

• Optical SETI – looking for visible light*

• Possibly send out laser signals?

https://www.seti.org/

Should humans be sending out signals?• NASA’s Pioneer 10 & 11

• NASA’s Voyager 1 & 2: Golden Record

• Messaging Extraterrestrial Intelligence (METI) sent a radio transmission from Tromsø, Norway

• Unintentional transmissions to the universe• Laser pulses• General radio noise

Show/Watch: Spacecraft Locations

Scientists Leading the Way

Sara Seager at

MIT is looking for

another EarthJill Tarter led SETI for decades,

making the Allen Array possible

Slido.com Class Poll

• Enter code: #K261

• Answer this:

• Do you think life exists outside of Earth now?

“The universe is a pretty big place. If it's just us, seems

like an awful waste of space.”

― Carl Sagan

Look up

Keep learning

Be you

Dream big

“The Universe… is an unsettlingly big place, a fact which for the sake of a quiet life most people tend to ignore.”

• Douglas Adams, author of The Restaurant at the End of the Universe, Hitchhiker's Guide to the Galaxy

• Look Up: There is a big universe out there.

• Be You:• Recognize your place in the universe.• There is no one else like you.

Big numbers,only 1 you!

• 2 trillion galaxies

• Each with at least 100 billion stars

• Each star with at least 1 planet

• There is only 1 planet that we know of which holds life

• Over 7 billion people on Earth and only 1 you!

• Be You

• Look up: Shift your perspective

• Be you: Share your skills, gifts & talents

“The more clearly we can focus our attention on the wonders and realities of the universe about us, the less taste we shall have for destruction.”

- Rachel Carson, scientist, nature lover & conservationist

• Keep Learning: Focus on understanding

https://commons.wikimedia.org/wiki/File:ISS-35_Parts_of_Mexico,_California_and_Nevada_(2).jpg

“The purpose of education is to stretch your mind so that it never returns to its original shape.” – Horace Mann, educator

• Keep learning: Stay curious

Charles H. Townes

• Nobel Prize in Physics in 1964 for inventing the laser, physicist and astronomer

“Science and religion are both efforts to understand the universe.

Science seeks to understand how the universe works and how humans work,

while religion is an attempt to understand

the meaning and purpose of the universe and of humankind,

which requires an understanding of their workings.”

• Keep Learning: Investigate faith

• Dream a crazy, big dream!

https://nypost.com/2017/02/21/uae-wants-to-put-600000-people-on-mars-within-100-years/

Look up

Keep learning

Be you

Dream big

Want more astronomy?

• Join the Minnesota Astronomical Society:http://www.mnastro.org/

• Space news websites:• www.space.com

• www.astronomy.com

• www.skyandtelescope.com

Class Feedback for Raquel

• Notecard

• One side: What did you like about astronomy class?

• Turn over, Other side: What would you change or improve about astronomy class?

• Name is optional

• When finished, place in big envelope

Optional – watch:• Life in the Universe: Crash Course Astronomy #46

• Ted Talk: Where are all the Aliens? By Stephen Webb

Homework & Updates• Keep up with Study Points• D2L Quiz 9-13 available; Quizzes 9-13 for Test 3• Optional – watch:

• Life in the Universe: Crash Course Astronomy #46• Ted Talk: Where are all the Aliens? By Stephen Webb

• Try out Grade Calculator on class website• Tutor Oskar available in T bldg. room 3200• Observations:

• Astronomy News Evalution Due TODAY Dec. 10 (20 pts) Evaluate astro. news• Sunset – Part 2 Due TODAY Dec. 10 (10 points) Take 2nd picture of sunset in

same place• Take picture about 4pm; sunsets about 4:30pm

• Stargazing Due Dec. 17 (20 pts) Go stargazing & write report• Telescope Due Dec. 17 (20 pts) Look through a telescope

• Look at calendar options & weather• Moon Craters Due Dec. 17 (10 pts) Look at magnified moon craters

• Borrow binoculars from Lab room

• Optional Lab Test 2 today, Dec. 10 or Thursday, Dec. 12

Calendar Summary• Tuesday, 12/10: Life in the Universe (optional Lab Test 2)• Thursday, 12/12: Test 3 (60 multiple choice questions)

• Based on last 8 lectures & 5 D2L quizzes 9-13• Some questions from D2L quizzes• Bring pencil, no calculator needed• Optional Lab Test 2 during lab time

• Tuesday, 12/17: Final Test today & handback Test 3• Based on all 23 lectures & 13 D2L quizzes (the whole semester)• Many questions from D2L quizzes• Bring pencil & calculator if you have one (some in classroom for you)• Remember lowest of 4 tests is dropped (Test 1, 2, 3, & Final). • If you took 3 previous tests and are happy with your grade, then you

don’t have to take the Final Test. If you missed a previous test, you must take the Final Test. If you are trying to increase your grade, take the final to hopefully drop a different test. No Astronomy on 12/19.