The Drake Equation and history

The Hubble eXtreme Deep Field.

If you've ever spent time sifting through Wikipedia or watched a documentary about the likelihood of life existing elsewhere in the cosmos, then you have undoubtedly ran into the Drake Equation. This string of variables was thought up by the astronomer Frank Drake in 1961 as a means of generating discourse about the likelihood of mankind communicating with an alien civilization. Despite Dr. Drake not thinking it should be used for such, it is frequently deployed by believers and skeptics of aliens alike to "nail down" how many such civilizations exist in our Milky Way. The equation has the following form:

As the equation indicates, the variables which are thought to be relevant quantify the likelihood that intelligent life exists at the current moment and is capable of communicating back with us. Some of the variables, such as fP, are vastly better understood now than when the equation was first proposed (keep in mind that Dr. Drake proposed this equation eight years before Apollo 11 and decades before we had confirmation of exoplanets). This is thanks to observational research done by projects like NASA's Kepler satellite. Alas, however, I am not an astronomer and the astronomical variables are not what this post is about. If this is the part of the equation that interests you, then I highly recommend Ethan Siegel's excellent blog, Starts With a Bang. My interest is with the last two variables, fC and L. As an amateur historian of science with some engineering training, I think I can provide some insight into these two terms.

One thing that needs to be taken into account for fc is that, even if a human-like civilization emerged on a far away planet, there is still no guarantee that it would undergo the prerequisite Scientific Revolution for the development of radio. This is attested to by our own historical record. History shows that rich and powerful civilizations with developed mathematics, empirical philosophy, and careful observational techniques don't necessarily undergo scientific revolutions. In my opinion, some of the thinkers that consider the Drake Equation do not take this point seriously enough. They seem to assume that science simply pops up when you have natural philosophy planted in the soil of stable societies that appreciate and support learning. Not so. 

In fact, many historians of science like H. Floris Cohen have spent their careers explaining the rarity of science in this historical record. To many thinkers that ponder the Drake Equation, science seems to be something like underpants and profit are for the underpants gnomes on South Park. In the image below, simply replace "collect underpants" with "have a rich society" and "profit" with "scientific revolution."

How science is born. 

This is apparent when one examines the case of ancient China. Two and a half thousand years ago, seven kingdoms were in a state of all out war with one another for control of the territory that is now China. This state is disunity was ended when all of the kingdoms were annexed and consolidated under Qin Shi Huangdi (259-210 BC), the first emperor of a unified China. The era that led up to this consolidation, known as the "Warring States period," featured a historically unmatched flourishing of philosophical systems. When the Warring States period ended and China became a unified state, various parts of the preexisting philosophies were synthesized into a single, coherent natural philosophy.

The interactions of the five Chinese Elements. 

Like the later European synthesis of Ptolemy, Aristotle, and Galen, this Chinese system was deeply interwoven. The elements, which are shown above, each also represented a planet. This tied them into Chinese astrology and, by extension, medicine (astrology was considered a part of medicine in both Europe and Asia). When the elements were combined with careful observation and other ideas like yin and yang, the Chinese natural philosophers gained access to a systematic theory of the world capable of explaining quite a lot. However, despite its incredible explanatory power, Chinese nature knowledge never transformed into experimental science. The relevance of this for fc is that it shows it is possible to have a wealthy and powerful civilization that takes learning very seriously without it ever undergoing a scientific revolution. 

Science seldom emerges even on Earth.  

If we consider that something very similar happened in the Islamic Caliphate of the Middle Ages and classical Greece, then we must conclude that scientific revolutions are rare on Earth even among advanced civilizations. Our own planet's success rate of experimental science emerging from nature knowledge, as the chart above shows, is a mere 25% among the four civilizations which were the best candidates. This makes it seem plausible that, on the planets lucky enough to have intelligent life, there may be far more civilizations like ancient China than there are like our own. This may make fc a much stronger filter than many astronomers anticipate. 

L, which is arguably the hardest term in the entire equation to gauge, is the length of time that civilizations, once they get the means to communicate across space, exist. Skeptic and historian Michael Shermer states in his article, Why E.T. Hasn't Called, that he is perplexed by the massive range of L "because it is the one component in the Drake equation for which we have copious empirical data from the history of civilization on Earth [1]." Shermer came to his own value by compiling the length of 60 civilizations. The mean of their live left him with L = 420.6 years. "For more modern and technological societies," he explains, "L became shorter, with the 28 civilizations since the fall of Rome averaging only 304.5 years [1]." 

I, however, have one major reservation with Dr. Shermer's estimate. While I applaud his desire to use the historic record, his number crunch is merely estimating the fall of states (i.e., the Soviet Union). Not of civilization itself  (e.g., the fall of all states) after the attainment of the ability to communicate across space. While we may have records of the time that the Roman or the Ottoman Empires lasted, we have absolutely no numbers for the collapse civilization itself.

Civilizations may inevitably gain the ability to extinguish themselves around the same time they gain the ability to communicate with other planets. 

While we certainly cannot know for sure, the timeline for this could be far worse than Shermer estimates. One reason to think this is that our civilization figured out petroleum-based transportation, radio, and nuclear weapons in relatively quick succession. Karl Benz was awarded the patent for the first practical automobile in 1886 and Guglielmo Marconi invented radio in the 1890's. The USA dropped the first atomic weapon half a century later on August 6, 1945. I am certainly not a believer in strong technological determinism (e.g., the idea that technology determines the course of history), but it may be the case that the two inventions which ultimately doom civilizations via catastrophic global warming or nuclear holocaust tend to pop up around the invention of radio.

"Well," you might think, "we have had both the combustion engine and nuclear weapons for a long time and we are still here." That's certainly true. This point is merely hypothetical. However, given that Dr. Drake didn't intent this equation to "nail down" anything, pointing out the inventions that may end up hastening the panoramic collapse of civilization pop up around the same time as the invention which allows to to communicate across space may be enough to dampen L.

If I am right about either one of these variables, then life in the Milky Way that can talk back to us might be very rare indeed.