Anyone Out Anyone Out There?There?

What are the Chances of What are the Chances of IntelligentIntelligent

Life Existing Beyond Earth? Life Existing Beyond Earth?

Exploring the Drake EquationExploring the Drake Equation

The Big Question: The Big Question: Are We Alone?Are We Alone?

Humans have been asking since the beginning of recorded history.

“In the universe, nothing is the only of its kind. In other regions, surely there must be other Earths, other men, other beasts of burden.” Lucretius, 1st century BC

Frank DrakeFrank Drake

In the 1960’s ET stepped out of science fiction

Drake presented a thought experiment,

not a scientific equation.

It is designed to inspire dialogue

““The Drake EquationThe Drake Equation””• 7 variables that allow us to 7 variables that allow us to

get an estimate of probability get an estimate of probability of intelligent, communicating of intelligent, communicating life in our galaxy (life in our galaxy (NN))

• Important to note, this is just Important to note, this is just a guess!a guess!

N = N* fp ne fℓ fi fc L/Tg

10am Pizza Analogy10am Pizza Analogy

N*N* Number of Stars in the Number of Stars in the Milky Way GalaxyMilky Way Galaxy

• This is the factor we actually have a This is the factor we actually have a decent handle ondecent handle on

• For scientists, that means we are For scientists, that means we are fairly certain that there are between fairly certain that there are between

100-500 billion stars in the 100-500 billion stars in the Milky WayMilky Way

N = N* fp ne fℓ fi fc L/Tg

ffpp What Fraction of Stars Have What Fraction of Stars Have at Least One Planet?at Least One Planet?

• Current estimates: Current estimates:

about 10% to 50% about 10% to 50% of all stars have at least 1 of all stars have at least 1

planet planet

• Scientists are refining this estimate Scientists are refining this estimate all the time with missions like Keplerall the time with missions like Kepler

N = N* fp ne fℓ fi fc L/Tg

nne e How Many of These Worlds How Many of These Worlds Have the Have the ““RightRight””

Environment?Environment?What does What does ““RightRight”” mean? mean?• Small, rocky planetSmall, rocky planet• That has a heat source That has a heat source

– Habitable ZoneHabitable Zone– Tidal heatingTidal heating

• And an atmosphereAnd an atmosphereWhat weWhat we’’re really looking for is…re really looking for is…

N = N* fp ne fℓ fi fc L/Tg

Liquid Water!Liquid Water!

Why water?

• All life that we’ve discovered on Earth requires liquid water to thrive

• Good solvent for organic materials, transporting nutrients, etc.

• It floats, creating an insulating layer for the organisms beneath

Our Solar SystemOur Solar System

• Possibly 6 watery worlds Possibly 6 watery worlds

• We are exploring these with: We are exploring these with: •Orbiters - Cassini around SaturnOrbiters - Cassini around Saturn

•Rovers - Mars evidence of past waterRovers - Mars evidence of past water

•Possible future drilling missions to outer Possible future drilling missions to outer moons? Human exploration of asteroids moons? Human exploration of asteroids and Mars?and Mars?

N = N* fp ne fℓ fi fc L/Tg

ffℓℓ How Many Habitable How Many Habitable Planets Develop Any Life Planets Develop Any Life Forms? Forms? (at any point)(at any point)

Start with what we know: Start with what we know: Our Solar SystemOur Solar System

N = N* fp ne fℓ fi fc L/Tg

Just 1 that we know of - Earth!

ffii How Often Does How Often Does Simple Life Become Simple Life Become Intelligent?Intelligent?

• Billions of species Billions of species have existed on Earth. have existed on Earth. Only one seems to Only one seems to have looked out into have looked out into the galaxy for the galaxy for companycompany

• Does life always Does life always become more complex become more complex over time?over time?

N = N* fp ne fℓ fi fc L/Tg

ffcc How Many Intelligent How Many Intelligent Civilizations Communicate?Civilizations Communicate?

• These civilizations are able and willing to communicate• Is it possible that

they are out there in listen-only mode?

N = N* fp ne fℓ fi fc L/Tg

LL Average Lifetime of a Average Lifetime of a Communicating CivilizationCommunicating Civilization

We have been communicating We have been communicating for for less than a centuryless than a century

How long will we survive?How long will we survive?

N = N* fp ne fℓ fi fc L/Tg

Range of EstimatesRange of Estimates

N* fp

ne

fℓ

fi

fc

L

500 billion Half11 in 101 in 101 in 101 billion

years

100 billion One quarter1 in 10001 in 1000 1 in 10001 in 1001,000 years

Pessimistic FactorsOptimistic

____________ ________________ We are alone Millions of civilizations

In the In the MeantimeMeantime

andand

We watchWe watch

We listenWe listen

Future ExplorationsFuture Explorations

As our tools become more As our tools become more sensitive…sensitive…

As we explore more planets As we explore more planets in our own Solar System…in our own Solar System…

Science Fiction may Science Fiction may someday become Science someday become Science FactFact