Download The Drake Equation

Is there life on other worlds?
If so, how many?
Total number of stars in the Milky Way
galaxy
Based on images from Hubble & other deep space
telescopes
Sample sections the galaxy (count stars in star clusters)
Estimate size of star clusters
Extrapolate to size of our galaxy
There are between 100B-600B stars in the Milky Way
using various estimation techniques
Most scientists believe the number is close to 400B
Percent of stars that are “appropriate”
Most scientists believe that a star has to be like our sun
Main Sequence G-Type star
5% of all stars
10% are closely related F & K type stars
Many stars exist in a binary (or more) system which
some scientists feel make them inappropriate
Estimates for appropriate systems are between 5-45%
Percent of appropriate stars that hve
planetary systems
We have only just begun detecting extra-solar planetary
systems around stars
Kepler space telescope
Some planets we see and some are detected by
measuring the diminishing light/wobble of stars
Conservative estimate – 5%
Optimistic estimate 50%-100%
Average number of habitable planets or
moons
Our only official example is our own solar system
Is Earth the only life-forming body?
How typical is our solar system?
Remember, this is an averaged value across all star
systems
Conservative estimate 0.1 (1 in every 10 systems)
Optimistic estimate 4 (4 in every system)
Percent of habitable worlds that
develop life
No real data are available to help estimate this term
Earth is only known planet to harbor intelligent life
Earth had bacterial life very early after it’s creation
(early as 100MY after cooling!)
This may indicate that development of life is easy
Conservative estimate – 0.00000001 (0.000001%)
Optimistic estimate – 1 (100%)
Percent of planets with life that develop
intelligent life
Somehow, humans gained an evolutionary advantage over
every other species to develop the level of intelligence we have
How do you define intelligence? (Dolphins, whales, octopus?)
Single-cellular life quick (100MY)
Multicellular life 2.5BY on Earth
Conservative estimate – 0.000001 (0.0001%) 1 in a million
worlds
Optimistic estimate – 1 (100%) Every habitable world
Percent of intelligent life that develops
radio technology
 Radio waves travel at the speed of light
 As far as we know, nothing travels faster than light speed
 Radio technology was created on Earth about year 1900 (4.5BY after Earth’s
creation)
 How long does it take for an “intelligent” civilization to produce radio
waves?
 Humans (homo sapien-sapien) 200K-400K YA (4.2BY-4.4BY after Earth
cooled
 Conservative estimate – 0.000001 (1 in a million)
 Optimistic estimate – 1 (100%)
Percent of “current” civilizations having
radio tech trying to contact us
 Signals from ET’s whose civilization died off 100MYA and are 100M light years away took
100MY to get here
 How long do civilizations with radio technology last?
 Did they all destroy themselves with nuclear weapons long ago?
 Worlds smashed by comets or gamma ray bursts?
 Perhaps they survive a long time if they can travel to other habitable worlds
 Can ET’s communicate with us via sub-space transmission, inter-dimensional transmission
or using optical fiber tech? How would we hear those??
 Are we interesting enough to communicate with for an ET?
 Conservative estimate – 0.000001 (1 in a million)
 Optimistic estimate – 0.1 (10% - 1 in 10 civilizations)