The significance of the "Copernican Revolution" is that as soon you embrace the Sun as a star, you are immediately faced with the possibility that when you look out into space, someone or something is looking back. Before Copernicus most people thought the Earth was pretty much the whole Universe so the idea of aliens on other planets really creeped them out. The Jesuits had enough trouble deciding whether or not Native Americans had souls, let alone ET. Did each planet have an Adam and Eve, original sin, and passion play with their very own alien savior?
Classroom discussions about extra-terrestrial intelligent life typically begin with an introduction to the Drake Equation. It's the academic thing to do because when you talk about intelligence you don't want the math geeks to feel left out. The equation was developed by Frank Drake in 1961 in order to codify some factors that can then be multiplied to determine how many big-eyed, intelligent, monsters there are in our galaxy trying to get in touch with us right now, or our geeks anyway, by encrypting prime numbers and other obscure nonsense onto radio signals.
The Drake Equation
N = R* fp ne fl fi fc L
The resulting product "N" is the total number of currently communicating civilizations in the galaxy.
R* is the average rate of star birth in the Milky Way Galaxy. For much of my life folks said the galaxy currently has a hundred billion stars. Then at some point they started saying two hundred billion. Then they said "at least" two hundred billion, maybe four hundred billion. Whatever. A "shitload" is safely the lower limit although the rate of birth has slowed greatly since the early days.
fp is the fraction of stars that have planets around them. Again, for much of my life astronomers attempted to rationalize a lower limit to the number. The figure "70%" was loosely thrown around. Now, with modern planet-finder techniques it appears that you can hardly make a star without a bunch of planets swarming to feast on the leftovers. They're like rats. The figure being thrown around with a smug smirk now days is 100%. That's probably not precise but you're free to make up your own argument and outrageous figure to match. That's the beauty of the equation. It's whatever you want it to be. Just throw some numbers in there and spout some gibberish to explain why.
ne is the number of planets per star that are capable of sustaining life. Here in our own humble solar system it appears to be one livable planet out of eight. Or is it one out of nine? Damn you Tyson!
We haven't examined any of the planets very closely except for Earth so there may be some surprises when we get out there poking around. Plus, there are interesting environments on some of the moons of the solar system. We need to send a robot to Europa and teach it to bait a hook.
fl is the fraction of ne suitable planets where life actually evolves. Just because a planet can have life, doesn't mean it actually does. Notice that as we go down the list of variables in the equation, the hypotheticals get more and more dicey. At each stop you need a more eloquent tap dance to justify a real number.
fi is the fraction of fl where intelligent life evolves. Okay here's where we need to define intelligent. For the academic discussion it typically involves beings who use radio transmissions. Astronomers feel very strongly that intelligent beings need radio to communicate with each other across the stars. For one thing it's cheap, it travels at the speed of light, and most of all, it's polite to call first. I wouldn't even drive across town to visit someone without calling first. This seems especially important where a one-way trip of 15,000 years is considered a short jaunt. If they just come whipping over here, they might pass us while we are on our way over to their planet. Wouldn't that be a hoot? By the time they figure it out and go back home, we will have totally trashed the place.
fc is the fraction of fi that try to communicate with us. Just because they have radios doesn't mean they are using them to contact us. They might be listening to Lady Gaga. They're aliens, how do I know what they like to listen to? Anyway, we had radio ourselves for some time before we aimed it at the stars. For a long time we used radios to listen to plays, like War of the Worlds. Even now many folks think searching for life in space is a waste of money, compared to important stuff like campaigning to have our schools lead the kids in a prayer for Obama to not take away our guns.
L is fraction of the planet's life during which the communicating civilizations live and attempt contact. Maybe civilizations only try communicating for a short time, between the invention of radio and nuking themselves into extinction. Maybe self-annihilation is the norm. Maybe at some point we'll realize it's a really bad idea telling all the space-wolves that dinner is ready. The point is, you need to decide how long civilizations usually try to communicate because it has to overlap our time in order for us to notice. They may have tried for a million years, but that was 65 million years ago and the dinosaurs ignored it.
The amazing thing about the Drake Equation is that no matter how conservative you are with the values of the individual factors, it leads to an incredibly large number of beings out there, with radios, attempting to contact one another, during this era of history. That is unless you sabotage the whole effort by slipping a zero in the mix somewhere. But the deal is, we already know the number isn't zero. We are here.
Human attempts to connect with a galactic community are only fledgling. The most famous and organized effort is called SETI (Search for Extraterrestrial Life) which was founded by Frank Drake in 1961. Anyone with an Internet connection can now join the effort by lending their computer's idle time to analyzing radio signals from space in the hopes of finding unnatural patterns. The computer sharing program is administrated by SETIatHOME at University of California Berkeley. http://setiathome.ssl.berkeley.edu/
Carl Sagan Center for the Study of Life in the Universe
Named for the famous popularizer of astronomy, SETI has created this team of diverse researchers in a interdisciplinary field called "astrobiology." Supporting institutions included NASA, the National Science Foundation, and major universities. Research includes such related areas as astronomy, chemical evolution, origin of life, biological evolution, cultural evolution, and active search for extraterrestrial intelligence.
Carl Sagan conceived the idea of attaching pornography to a spacecraft destined to leave the solar system for the entertainment of extraterrestrials that find it. He succeeded in delivering that message to interstellar space in the form of gold-plated plaques attached to the space probes Pioneer 10 launched in 1972 and Pioneer 11 launched in 1973.
The message was designed to encode the most information possible in minimal space, to maximize the difficulty in decoding it. At the top is a diagram representing the hyperfine transition of neutral hydrogen, something alien kids learn in kindergarten. This is meant to convey the standard galactic unit of length (21 cm) which is used to indicate measurements elsewhere in the message, not bragging.
The radial lines emanating from a point show the relative distances to 14 pulsars from our Sun, and the distance to the galactic core. This could conceivably be used by a clever creature to identify our Sun's location within the Milky Way Galaxy, assuming that creature's last name is Sagan and first name is Carl. A tick mark at the end of each line gives the Z coordinate perpendicular to the galactic plane. The pulse rate of the pulsars is included, and since pulsars slow their pulsing at a predictable rate, a successful decoding of the plaque would also indicate precisely "when" the spacecraft was launched, which is a nice touch.
The image also includes a diagram of our solar system and the spacecraft's route out of the solar system. Finally, there is a silhouette of the craft itself in relation to our bodies, so the aliens will know how big of a cooking pot they need to bring.
In addition to the message on the Voyager space probes, NASA included phonograph albums with cuts of everything from Beethoven to Chuck Berry. This was a brilliant move. If we ever get a message back from aliens as a result, and the message is "Send more Chuck Berry" then we will know they are truly intelligent.
There is a game I invented for instruction and amusement for my students. I have the class pretend that we are the crew of a starship. All the nations of Earth have cooperated their efforts to build it, so this is obviously a fantasy game.
We travel with full diplomatic authority to represent all of humanity, and eventually we find a planet with life. Looking down from orbit, we see beings which remind us of our own 14th century. They have castles and bows and arrows, but it's clear they do not know we are up here watching. As captain, I've ordered that our findings be radioed to Earth but that will take years to arrive. So I've also called together the crew to decide what we should do next. A discussion ensues.
I've played this game dozens of times with all different age students, so I kind of know how the discussions go. I've even named the common threads. First there is the "Take me to your leader" idea. As one astute youngster once pointed out, they might have lots of leaders. What if we are taken to their Hitler? How would we know? An evil leader might use his association with us to intimidate his enemies. One time a student suggested that we sneak into one of their libraries and photocopy lots of books. Then we could decipher their language at our leisure and study their history, biology, and religion and so forth, before making formal screw-ups.
Another line of reasoning is the "Techno-spy" approach. We sneak down and plant microphones and cameras everywhere. Eventually someone in the discussion points out that if we ever try to be friendly, and they find out we have been spying on them, it might not go well for us. No one likes to be spied on. It's creepy. The old "Would you like to go out with me? I've been stalking you for months and I think we're compatible" never really works, at least not for me.
Then there is the "Prime Directive" discussion. This comes from the famous Star Trek protocol of non-interference, as in "This was an awesome planet until they Kirked it." The idea is that until they become space-faring themselves, we leave them alone. So we put a small satellite in orbit and if they send something up near it, we get a notification, on our phone or something. A text maybe.
One thing I find very instructive in all the times I've led this discussion, and played the game over the last 20 years or so, maybe a total of 500 students, maybe more. In all that time, never, ever, ever, has anyone suggested we make circles in their crops. It just never comes up.