Presentation: are we alone?

Adam Godley (Dr. Nogrady): "Today really marks the first stage of an unprecedented technological advancement. We have begun to identify a so-called 'Goldilocks planet.'"

Peter Berg (Director): "'Goldilocks planets' are planets that have a similar sun, a sun that burns about as bright as ours..."

Adam Godley (Dr. Nogrady): "...If a planet is too far away from its sun, it's too cold; if it's too close to its sun, it's too hot, but for an Earth-like planet, the distance is just right--potentially perfect--for sustaining life."

Hamish Linklater (Cal): "What we're doing is sending out radio signals into deep space..."

Peter Berg (Director): "...high-frequency signals, which are beacons saying, 'Hey, if you can hear this, we're out here, we're Earth, hello.'"

Adam Godley (Dr. Nogrady): "Ladies and Gentlemen, prepare to bear witness to the making of history."

(Video link: "Goldilocks Planet.")

Wait--isn't this from a movie or something?

Yeah, thought so.

This presentation will take a more serious look at the possibility of life elsewhere in the Milky Way, and discuss efforts in communicating with any advanced technological civilizations that may be out there.

First, estimating the number of advanced technological civilizations in the Milky Way.

This can be done using the Drake equation, which multiplies a number of factors that reflect more and more restrictive conditions for an advanced technological civilization to arise to calculate N_C, the number of these civilizations just in our galaxy, the Milky Way. For the purposes of this discussion you do not have to memorize all of these different factors, but understand how they place constraints on the possibility of life, and the general trend from less to more restrictive conditions.

The first factor in the Drake equation is N_*, the number of stars in the Milky Way. Recall that we can only see the stars in our immediate vicinity, but by estimating the overall size of the Milky Way, we can derive a relatively certain value for the number of Milky Way stars. This is the most certain of all the factors in the Drake equation, and we these values will progressively get less and less certain as we go through the rest of the equation.

The next factor f_P is the fraction of stars in the Milky Way that have planets. More specifically, terrestrial planets, or rocky moons around gas giants, both of which must have formed after the Milky Way sufficiently increased in metallicity over time. This is actively being measured by NASA's Kepler Space Telescope, as well as other Earth-based telescopes.

And of the stars in the Milky Way that have terrestrial planets, the next factor n_HZ is the number of planets that would be in their stars' habitable zone--making them "Goldilocks planets"--not too close and not too far from their stars, such that liquid water (or some other liquid that can readily dissolve and hold nutrients) can exist. Although not very water-bearing planets have been verifiably discovered, many candidates have been recently found.

The next factor f_L is the fraction of these potentially habitable water-bearing planets that life actually arises from chemical evolution. There is currently no way to even estimate this factor other than giving pessimistic values (even with the right conditions it is not likely life will ever arise) to more optimistic values (with the right conditions, life is likely to eventually arise). At least some constraints can be placed on the stars that may potentially harbor life on water-bearing planets, taking into account that life on Earth took approximately a billion years to arise, which would eliminate short-lived massive stars. However it is possible to attempt to make some estimates of this value by investigating other places within our solar system where liquid water exists, or has existed in the past (which locations might these be?). If life or some remnants of life are found, then perhaps it is likely that life can arise with the right conditions, or if no sign of life in our solar system is every found, this may suggest a more pessimistic value for f_L.

The remaining factors in the Drake equation begin to be classified as "SWAG" ("Scientific Wild-A__ Guesses"). Such as f_I, which is the fraction of life, once it starts, that will eventually evolve and become intelligent enough to develop technology that we can communicate with. There is currently no way to scientifically determine this factor.

And the last factor in the Drake equation is even less answerable: F_S, the fraction of a star's main-sequence lifetime that an advanced technological civilization will survive, whether a short time (due to destroying itself through nuclear war, biohazards, climate change, etc.), or being able to survive a long time by avoiding such calamities. Again, there is no way to even begin to scientifically determine this factor.

So the Drake equation starts out with well-established values, and multiplies progressively less reliable factors to estimate the number of advanced technological civilizations in the Milky Way. The last few factors can be filled in with pessimistic values--perhaps it is not likely that life will arise, even with the right conditions; life probably would have a tendency to remain boring; and an advanced technological civilization would probably extinguish itself in a short time anyway. With such pessimistic values, the Drake equation results in only one advanced technological civilization in the Milky Way, which has to be us, and we are alone.

But what if more optimistic values are placed into the last few factors in the Drake equation--perhaps life is very likely to arise given the right conditions; life has a tendency to evolve more intelligence; and an advanced technological civilization would probably work things out to ensure its survival in the long run. With such optimistic values, the Drake equation results in a large number--possibly 10 million--of advanced technological civilizations in the Milky Way, of which we are one, and we are not alone.

These two estimates wildly vary because the last few factors in the Drake equation are filled with "SWAG." There is no way to solve the Drake equation to determine whether the number of advanced technological civilizations in the Milky Way are one, or 10 million, or somewhere (anywhere?) in-between these values.

Second, instead of trying to solve the Drake equation, how about searching directly for other advanced technological civilizations in the Milky Way? SETI is the "Search for Extra-Terrestrial Intelligence," while BETI is "Broadcasts to Extra-Terrestrial Intelligence." (This is getting back to the clip from Battleship (Hasbro, 2012).)

The Arecibo Observatory is a large radio telescope in Puerto Rico that has been used to listen for signals from other advanced technological civilizations. This is still being done at other radio observatories as well.

But in 1974, Frank Drake (of the Drake equation) decided to use a broadcast test from the Arecibo Observatory to send a message, anticoded using pulses for pixels to build up a simple, but information-packed message to whatever advanced technological civilizations that are out there...

...and we actually received a reply to this message in 2001, at the Chilbolton Observatory in Hampshire, England. However, this "reply" was not sent to us as an anti-coded radio signal...

...but appeared as a crop circle in the field adjacent to the Chilbolton Observatory. With tongue planted firmly in cheek, let's consider the following: (a) this crop circle appeared overnight, next to a radio telescope manned by technicians working overnight; (b) unemployment is very high in this rural part of England; (c) many tourists come to rural England to look at the new season of crop circles; (d) many of these tourists eventually eat, drink, and board at the local pubs and inns. Draw your own conclusions.

In the subsequent in-class activity, you will decipher a simple anti-coded message, and try to decipher the purported Chilbolton "reply" by comparing it to the original Arecibo message.