The Fermi ParadoxFermi’s ParadoxAnalogous StoryOrigins from Behind the FridgeIs this typical?TimescalesFirst come, first servedThe PremiseDoes our Galaxy Meet the Basic Premise?Are we first in the galaxy?Interstellar ColonizationThe Galaxy is HumungousTake it SlowlyThe 1% SolutionHow would it work?Robots or HumansBudgetThe 3% Growth ApproachRealistic?MotivationConvicts or PilgrimsThe New WorldThe Australian ExampleContinuing the analogyExponential GrowthSpeed of LightBlink of an Eye?Lower limitSo - why haven’t aliens visited Earth?MavericksDifferent NumbersPrime DirectiveSelf DestructionTwo Alternatives?Conclusion1The Fermi ParadoxSo is there life in space? In addition to the issues we have already discussed, there is a rather amusing argument.2Fermi’s Paradox•This paradox was proposed by Enrico Fermi, he helped design the first nuclear reactors.•Consider the question–Did life only start once on Earth?3Analogous Story•Life got started on Earth relatively quickly –Perhaps life forms easily• whenever conditions are right.•DNA evidence suggests all living creatures on Earth are descended from the same microbial ancestors–Why?4Origins from Behind the Fridge•Let’s say the first self-reproducing chemical (whatever it was) appeared in a pool of slime in Africa. Why couldn’t a second self-reproducing chemical have appeared in say North America, and a third in the pool of slime behind your fridge, for example.•Then there might be three completely unrelated families of life-forms on Earth.5Is this typical?•Will most inhabited planets have only a single family of life-forms? What do you think?–A Yes–B No•Consider this–life forms take hundreds of millions of years to evolve–But how long would it take one to spread?6Timescales•Even the most primitive organism can be carried around the world in only a few thousand years–by the wind–by ocean currents•Thus, the time needed to spread throughout the world is far less than the time needed to evolve.7First come, first served•So any new life that forms, unless it is first, probably has to compete with previously existing life.•The new life will probably lose, the old life has had time to evolve and is probably far more capable than something newly created by chance.•Thus it makes sense that we are all descended from the first life form to evolve. Other subsequent life will have been wiped out by our competing ancestors.8The Premise•So - here is the premise for there to be more than one family of life in some region:The average time needed to spread throughout the region is much greater than the average time to evolve.•This premise is not met on Earth. If a planet were much bigger than Earth, it might be met, and you would get different families of life in different regions.9Does our Galaxy Meet the Basic Premise?•Does our galaxy meet this premise, specifically for intelligence? What do you think?–A Yes B No•Let’s examine this more closely•Once intelligence evolves on some planet, how long would it take to spread throughout the Milky Way?•Is this greater or less than the time it takes to evolve intelligence?10Are we first in the galaxy?•If an intelligent species can spread through the galaxy fast enough, then you would expect whichever species evolved first to completely colonize the galaxy before the second species even gets started.•So what are the two timescales?•Evolution (if Earth is typical) seems to take billions of years.11Interstellar Colonization•How does the time needed for evolution compare with the time needed for a typical alien species to colonize the galaxy?–A Evolution >> Colonization–B Colonization >> Evolution–C Roughly the same timescales for both•The galaxy is BIG! – Consider this:–If we scaled the Earth down to the size of a pea, the Sun would be 300 meters away, while Pluto would be orbiting 12 kilometers away.12The Galaxy is Humungous•On this scale, the nearest other star (Proxima Centauri) would be twice around the world.•Consider that humanity’s fastest spacecraft, Voyager, has taken 34 years to get where it is now.•The gaps between the stars seem very intimidating. Could we ever cross them?13Take it Slowly•We do have lots of time.–Distances that seem impossible to humans, used to dealing with weeks and months, seem pretty easy when you have thousands of years at your disposal.•Consider what we could do even with current technology.14The 1% Solution•With nothing much more than current technology, we could accelerate a spacecraft up to 1% of the speed of light.•At this speed, we would take about 1000 years to reach the nearest likely locations of habitable planets.•The only drawback - it would cost trillions of dollars and maybe bankruptcy.15How would it work?•A thousand years sounds like forever. But this may not be a barrier.•Consider a trip in something like suspended animation.–Frozen fertilized eggs could be sent out, implanted in artificial wombs and raised by robots.•The spacecraft could be really big and inhabited for generations.16Robots or Humans•Consider just sending robots, and downloading something of our own personalities into them.•100 years from now, medical technology may slow aging. Do you believe this?–A Yes B No•A 1000 year trip may not sound so bad if you live to be 10,000 years old.17Budget•Thus, length of time for travel may not be an issue–we may well figure out faster methods of travel•How about that colossal budget?•A few trillion dollars may sound like a lot today. But if the world’s economy continues to grow, does this become affordable. What do you think?–A Yes B No18The 3% Growth Approach•If we assume 3% per year economic growth, then by the year 3000, the world economy will be 6,000,000,000,000 times bigger than it is now.•A few trillion dollars may be “small change.”19Realistic?•Is this realistic? It’s not as silly as it seems. Imagine that the medieval world had wanted to build a modern oil tanker. In principle they could - they knew how to smelt iron and shape it.•But doing something like an oil tanker using medieval blacksmiths would have bankrupt the world back then. 500 years later it is easy.•Even 100 years from now, building an interstellar spacecraft may seem routine.20Motivation•So - 1000 years from now, we may be able to travel to other stars quite easily.•It would be rash to speculate on what will motivate our descendents