Life in the Universe~Part II: The Drake Equation

In Part I of this essay, we looked at how common life might be outside of the Earth. The only type of life considered was microbial life. Most of us, however, are really interested in more advanced life forms – the type of critters we could sit down with, have a cup of coffee and discuss the meaning of life with. Unfortunately, there appears to be a vast chasm between microbe and ET. Single celled creatures appeared very early in the Earth’s history, more than 3.8 billion years ago – not long after the Earth had cooled enough to allow for liquid water. It appears that, given a well-suited environment, life can get started fairly quickly. Those early microbes thrived. After that, however, it took another 2 1/2 billion years before the first multi-cellular life appeared. It was that innovation that really seemed to set us on the evolutionary path toward ever more complex and advanced life forms. That long 2.5 billion year gap between single- and multi-celled life seems to indicates that the jump from simple to more complex life is much more difficult and unlikely than the start of life itself! Even if life is exceedingly common among the stars, complex life might still be a precious rarity.

Even when advanced life does eventually develop, how often does evolution lead to intelligence? While advanced forms like worms and bamboo are very cool, I want more. I want something I can talk to, ask questions of and maybe even learn from. There are innumerable species of plants and animals growing on or roaming this planet but only a handful are thought of as possessing intelligence. Each species develops its own strategy for survival. Some are fast, some big, some stay well hidden and some are just plain mean. Only a handful of animal species appear to have experimented with intelligence. We know that feeding a big hungry brain takes a lot of resources. If it isn’t really advantageous to have one, you’re not going to evolve one. Other survival strategies than intelligence have proven to work very well and don’t require all the resources consumed by that hunk of meat you carry around between your ears. Look at ants, cockroaches or crabgrass; all very successful but far from what we think of as smart. Arguments like these lead me to believe that intelligence is quite uncommon even among complex life forms.

How many intelligent species are then likely to inhabit our galaxy? To try and get a handle on our level of knowledge (or ignorance) concerning this question astronomer Frank Drake (currently with the SETI Institute) developed a simple equation way back in 1961 that details the factors that contribute to the current total number of intelligent civilizations. The equation has come to be famously known as The Drake Equation:
N = R* x f(p) x n(e) x f(l) x f(i) x f(c) x L
The variables in the equation are defined as:

R* – the average rate of star formation in our galaxy (stars per year).

f(p) – the fraction of stars that have planetary systems

n(e) – the average number of planets per planetary system capable of supporting life.

f(l) – the fraction of planets that can support life where life actually begins.

f(i) – the fraction of planets with life were intelligence evolves.

f(c) – the fraction of planets with intelligence that develop long distance communications (such as radio).

L – The average number of years that civilizations continue to communicate (remain radio bright).

Find the value of each variable, multiply then all together and you end up with the number of intelligent civilizations that are currently capable of communicating with us. As simple as that! As you can see, Drake wasn’t as interested in simply the number of intelligent species; he wanted to know how many we could actually contact or at least listen in on. There could be many intelligent species out there that never develop technology for communications or decide for whatever reason that they don’t want to advertise their presence. If we can’t detect them, we can’t chat with them. Here, we will use the working definition of intelligence as a civilization that has the technology capable of interstellar communications.

We currently only know even rough values for the first two variables, R* and f(p).
R* is about 10 stars/year
f(p) is somewhere around 0.3 to 0.6
After these first two variables, anyone’s guess as about as good as any other. Just for fun, let’s have a go at it and see what we come up with:
R* = 10
f(p) = 0.5 (between the current estimates)
n(e) = 1 (Not all stars are likely to have planets that are favorable for life but some could have several. In our own solar system, there are several possible candidates. So, this number is likely fairly large. Let’s just call it one.)
f(l) = 1 (My guess is that given enough time and given a proper environment, life is likely to spring into existence. Again for simplicity, call it one.)
f(i) = 0.01 (Hmmm. I’m not so sure about this one. Just because you have life, doesn’t necessarily mean you get intelligence. Let’s go with a WAG [Wild-Ass Guess] of one in a hundred?)
f(c) = 0.01 (This is another factor that I’m really unsure of. I can imagine many reasons why a civilization comprised of intelligent creatures might never develop the technologies that we have or might make a conscious decision not to let their presence be known. Again, maybe one in a hundred??)

This leaves us with the variable L, the lifetime of a communicating civilization. This is the factor that truly matters. If we take humanity here on Earth to be an average example, we’ve had radio for roughly the last century. In that time, we’ve come perilously close to annihilating ourselves on several fronts; nuclear, environmental, wars and epidemics to name just a few. It seems that a technology that is at a level capable of broadcasting over interstellar distances is also capable of destroying itself! This argues that the lifetime of such a technology is often fleetingly short. On the other hand, perhaps some civilizations are wiser than us and are able to manage the dangers inherent in their technologies. One might imagine that such a civilization could have a vastly long lifetime. So, what’s the average life? I truly wish I knew.

In our example solution to the Drake Equation, so far we have:

N = 10 x 1 x 1 x 0.5 x 0.001 x 0.001 x L

N = 0.0005 x L

To get N, the number of communicating civilizations in our galaxy, up to just one, the average lifetime of such civilizations needs to be at least 2000 years! If it’s less than that, there aren’t likely to be many, if anybody, out there to talk to. Keep in mind that we’ve been at it for only about 100 years. On the other hand, if some civilizations can find ways to survive long-term, say millions of years, there could be hundreds to thousands of civilizations out there right now. So, what is the answer? We simply don’t know. Only through doing the searches to fill in the variables in Drake’s seminal equation can we hope to get to the answer.

Claude Plymate
Engineering Physicist
National Solar Observatory


Scherzo Tutti: Symmetry Violation

Our resident physicist & occasional guest columnist Claude Plymate offers something for our lazy summer brains to consider.

Symmetry Violation

There is something very strange about the universe we live in and the evidence is quite literally all around us. Go ahead, look around. What do you see? Stuff. Everywhere, stuff. Now that might not seem all that profound at first until you think about the conditions in the very early universe. In the smallest fraction of a second after the Big Bang, the entire Universe was compacted into a tiny volume. All the energy in the Universe was contained it this minuscule space. The temperature was so extreme that matter couldn’t yet even exist! The immense energy density would cause material to spontaneously pop in and out of existence. As the Universe expanded, energy was spread over a greater volume and the temperature dropped. Matter & antimatter began to condense out but would pair up and annihilate almost immediately.

Now we were taught that matter & antimatter are exactly symmetric differing only in the sign of some of their parameters, such as charge and spin. It would seem, therefore, that they should have been produced in equal quantities. But obviously this was not the case. After all the matter & antimatter paired up and converted back to energy, there was a small residual amount of matter left over – all the stuff you see around you! All matter we see today is a result of this minor excess in production of matter over antimatter. Apparently, our Universe has a slight proclivity for stuff versus anti-stuff. The fact that more matter was originally produced is what is known as a symmetry violation. (Specifically CP-violation. “C” for charge conjugate and “P” for parity meaning the particles are mirror images of each other.)

Why there is a preference for stuff over anti-stuff isn’t really understood. As a physicist, it would be more satisfying to have a nice simple symmetric universe but without this complication, the Universe would be a very bland place without any matter to look at, or for that matter, no “you” to look at it. It seems quite profound how perfectly CP-violation is tuned to allow a universe so well suited for things like us to exist. Many might see this as an example of intelligent design by some omnipotent deity. It is all too easy to come to such a conclusion. But, must such remarkable-seeming coincidences require invoking the supernatural? Some might argue “what else could it be?” Not at all if you assume ours is not the only Universe, only one amongst an unimaginably huge and diverse multiverse. It doesn’t matter how unlikely the combination of parameters are, if you try enough examples, you’ll eventually hit upon the ideal magical seeming mix. And of course, we find ourselves in one of the extraordinarily rare universes that is ideally fine-tuned to allow us to exist. If it weren’t, there wouldn’t be any stuff and wouldn’t be any you to look at it.


Claude Plymate, Engineering Physicist

National Solar Observatory

Strani eventi: Physics of Precognition or Just Fuzzy Logic?

(At left, the Carina Nebula. Photo courtesy of

A few days ago, I had a metaphysical discussion with an old friend, Claude Plymate. Claude is an astronomer. A real astronomer who has spent his life massaging a very special observatory, the McMath-Pierce Solar Telescope atop Kitt Peak outside of Tucson. Claude has cred. His wife, Teresa Bippert is also an amazing astrophysicist who does crazy things with optics at the University of Arizona- things I can’t begin to understand. Both attended undergraduate school with me. Just so you know:

“The McMath-Pierce solar telescope is the world’s largest solar telescope, and the world’s largest unobstructed-aperture optical telescope with a diameter of 1.6 meters. Permanent instruments include a dual grating spectrograph capable of extended wavelength coverage (0.3-12 microns), a 1-meter Fourier Transform Spectrometer for both solar and laboratory analysis, and a high-dispersion stellar spectrometer.

Important discoveries include: detection of water and isotopic helium on the Sun; solar emission lines at 12 microns; first measurement of Kilogauss magnetic fields outside sunspots and the very weak intra-network fields; first high resolution images at 1.6 and 10 microns; detection of a natural maser in the Martian atmosphere.” (  Smart folks, these friends of mine.

For me, our chat was a flashback to the days when a group of about eight to twelve of us undergrads sat around a large round table, drinking coffee and arguing and speculating over the Big Questions late into the night. We studied different disciplines, but among the many other things we had in common was one biggie: we were night owls. Students of astronomy & related sciences, writers and musicians. And there was the campus radio station in which we criss-crossed at various times.  People who were up awaiting  a celestial event, or the quiet in which to think, or the need to burn off energy from a rehearsal or performance. These were the people I loved most, and after all these years, know that I still do.

I got into the subject of precognition with Claude. Just like the old days. I told a story of an experience I had some years ago. I was on our sailboat, pre-kid era. We had dropped anchor and slept in Clipper Cove between Treasure Island and Yerba Buena Island, near where we berthed. In the early morning, I looked up at the Bay Bridge nearby, and pondered aloud to my spouse, “Do you see the ramp on the lower deck (eastbound) of the bridge by the bottom of the cantilever? It looks like one of those ramps kids use to launch their skateboards. Wouldn’t it be weird if a car drove up it and flipped into the Bay?”  The guy looked at me cock-eyed. He had learned by then that sometimes I say weird things that come true.

We had a lovely sail, tied up the boat and headed to the clubhouse to use the facilities. Walking up the dock, we heard sirens. Lots of sirens, and a Coast Guard helicopter zoomed over us to the south side of the bridge. We noticed traffic stopped on the lower deck.  We thought, “Oh shit. Bridge accident. Might as well go fix a drink and hang out until the thing is cleared.”  True, we were going back home into the City on the upper, western deck, but a serious accident will occasionally slow the whole structure.

In the clubhouse, actually “shack” was a more fitting description of the Treasure Island Yacht Club back then,  nobody was around. We turned on the television to see if there was information available.

Yes, there was.  A car had driven off  the little ramp, gone over the side of the bridge and into the Bay. There were fatalities. Spouse performed a double cock-eye at me. Meanwhile, I was trying to wrap my head around the big picture. Someone later asked me if I felt responsible. That never entered my mind.  Just absurd. I may practice certain spiritual rituals,  but overall I embrace empiricism. I have no explanation for this experience, or any of  the others. No way to prove or disprove. So I just let it be.

But Claude, being grounded in empiricism and the scientific method wrestles with these questions every day. Claude and I talked about my story and a few related matters, and this is what he wrote. It is used by Claude’s permission.

“I’d like to apologize from the start for the new-agey, pseudoscientific tone of this. Recently, I’ve been hearing about some experiments that appear to show test subjects responding stimuli a fraction of a second BEFORE receiving the stimulus! It is easy to ignore or discard such anomalous results as bad experimental technique or analysis. But what if the results are revealing a real effect? What if there is reproducible laboratory results showing people have some precognitive abilities? Is there any way we might concoct a reasonably conceivable physical explanation for such phenomena? Perhaps what some refer to as the “quantum foam” might provide some insight.

On the smallest scales, the so-called Planck length of around 10^-36 m (trust me, that’s REALLY small), space is expected to deviate from the smooth continuum we’re used to. The contour of space becomes rough or bumpy, changing randomly at each instant. This is where it gets its name quantum foam. In other words, our concept of position becomes fuzzy and even completely breaks down at the very smallest spatial scales. Presumably, time is equally distorted and fuzzy near its smallest divisions. The sizes of these deviations are randomly distributed but heavily weighted toward the smallest scale distortions. However, larger distortions in space/time must also occasionally occur. In this way, it is just conceivable that every once in a while some bit of information will pass from a moment in the future, into the present or even into the past! (Likewise, information from the past could find itself thrust into the future. This, however, would be of less interest and indistinguishable from the normal flow of time and causality.)

Such time/space distortions are happening continuously at every point in the Universe. Larger, even discernibly large, variations in time and/or space are statistically extraordinarily improbable but must occasionally happen. Now consider the brain – it’s made of a whole lot of neurons that are made of lots and lots of quanta. Every once in a while, some of these improbably events must happen in our brains. Could a brain neuron occasionally be triggered by an event that has yet to occur? If so, it would be expected that such occurrences would happen much more frequently for events from the very near future (small fractions of seconds) as apposed to from farther into the future. The ability to reacting to future events would clearly represent a strong survival advantage and would be very strongly selected for. Even if developing precognitive abilities were biologically expensive and/or quite difficult but just possible, evolution would demand that we developed the capability! Might it even be that evolution could have fine-tuned emotions to play the role of filtering out random noise while amplifying important signals? Perhaps this is why precognition tends to be associated with emotionally charged events”

(c) GoshGusMusic (ascap) 2010

For a better, very cool view of the Carina Nebula, check this link from Kitt Peak ‘s website: