Date: October 13th, 2012

Title: Encore: The Fermi Paradox and The Drake Equation

Links:

Interactive Drake Equation Calculator at the PBS/Origins site: http://www.pbs.org/wgbh/nova/origins/drake.html

Astronomy Cast (See episodes 22 and 23): http://www.astronomycast.com/solar-system/episode-23-the-drake-equation/ ; http://www.astronomycast.com/astronomy/episode-24the-fermi-paradox-where-are-all-the-aliens/

Other sources are the entries in Wikipedia for the Fermi Paradox and the Drake Equation : http://en.wikipedia.org/wiki/Drake_equation ; http://en.wikipedia.org/wiki/Fermi_paradox ; http://hubpages.com/hub/Can-there-be-life-on-other-planets

This podcast has been aired on October 31th, 2009
http://365daysofastronomy.org/2009/10/31/october-31st-the-fermi-paradox-and-the-drake-equation/

Description: Among reasonable people (and scientists) there is almost universal agreement that we earthlings cannot be the only intelligent life in the universe. With all the billions of stars in the galaxy and galaxy’s in the universe, it would be arrogant to think that we are the only intelligent
species.

OK, so where are they? We have been searching for decades and sending radio waves out to space for over a century. Why haven’t we found anyone? Why hasn’t anyone found us? In 1950 Enrico Fermi working at the Los Alamos National Labratory in New Mexico was struck by this question which became known as the Fermi Paradox.

In 1960 Frank Drake formulated The Drake Equation as an aid in considering variables that determine the likelihood of intelligent civilization. It has come to be used as a calculator for estimating the number of intelligent civilizations in the universe. The number varies according to the parameters selected, but the result is usually very high, which returns us to the question….”where are they?”

We’re going to talk a bit about the Fermi Paradox and the Drake equation and I’ll show you how to use the equation to work the calculation yourself. Finally, we’ll examine some possible explanations for the absence of any extraterrestrial visitors.

Bio: Al Ashworth manages an engineering team for a Rhode Island based technology company. He is educated in Philosophy, which led to an interest in Astronomy and Cosmology. He is an enthusiastic follower of NASA projects.

Today’s sponsor: This episode of “365 Days of Astronomy” is sponsored by No one. Please consider sponsoring an episode of 365 Days of Astronomy by clicking on the “Donate” button on the lower left.

Transcript:

The Fermi Paradox and the Drake Equation

Hello, I’m Al Ashworth. I’m an amateur Astronomy enthusiast and I live in Warwick, RI in the USA. Thank you for visiting my Podcast.

To me, one of the most intriguing topics in astronomy is the search for extraterrestrial intelligence. It’s a fascinating area of inquiry, and it’s one of the main reasons for my interest in astronomy.

In this Podcast we’ll look at two tools that are essential for speculating about the existence of alien intelligence: The Drake Equation and the Fermi Paradox.

Since Copernicus we have known that earth is not the center of the universe. This and three other widely held modern beliefs make it seem like there must be other intelligent species out there:

First, there is the size of the universe. As our knowledge of the universe has increased and we have become aware of the number of stars in our galaxy and the number of galaxies in the universe it seems that the universe is to big to have only one technological life form.

The second belief is that the origin of life can be explained using the laws of science. It is not necessary to refer to anything outside of nature to explain the origin of life. If life happened within the original environment of Earth according to scientific laws, it is possible that life occurred elsewhere because those same laws apply everywhere.

Finally, there is the Mediocrity Principal, which states that earth is not unique. It may be different from most planets but there is nothing about earth’s size, position in the galaxy, age, or anything else that should be considered one of a kind.

Just how many life forms are out there?

American Physicist Dr. Frank Drake formulated the Drake Equation in 1960 to answer that question. It was part of his preparation for a meeting in Green Bank, West Virginia.

This “Green Bank Meeting” brought together scientists from several disciplines to consider the possibility of extraterrestrial intelligence. It is considered a foundational event in the establishment of the Search for Extraterrestrial Intelligence (SETI) as a scientific discipline.

The Fermi Paradox is a statement of the disconnect between the view that there must be intelligent life somewhere other than earth and the lack of any credible evidence that there is such alien intelligent life.

Remember, we’re concerned with technological civilizations. Not microbes, plants, or wild animals.

The Drake Equation is stated as a mathematical formula where the product is the number of tecnological civilizations in our galaxy. Why does Dr. Drake consider only our galaxy?

Any aliens outside of our galaxy are to far away for us to practicly communicate with. After all, if it takes a thousand years to send and receive a message we can’t have a very meaningful conversation. Second, we can use the number of intelligent civilizations in our galaxy as a baseline for estimating the number that are in other galaxies. Remember the Mediocraty Principal? It also applies to our galaxy- it’s not unique.

The product of the Drake Equation results from seven factors:

! First is the average rate of star formation per year in our galaxy. Dr. Drake estimated a value of ten per year. Currently, NASA estimates that an average of seven stars are formed in the Milky Way Galaxy each year.*

* http://www.physorg.com/news9595.html

! The second consideration is the fraction stars in our galaxy that have planets. Dr. Drake estimated that number at 50%. Current estimates are about 30%.

! Next, we consider the average number of planets that can potentially support life per star that has planets.

Dr. Drake estimated there are two per star. Current estimates range from 0.005 per star (that is one potential life supporting planet per 200 stars) up to 2 planets per star that can host life. That is a very wide range, partially because we are now getting into conjecture. The elements of the equation prior to this allowed for some fact based estimate. From here on in, it’s almost pure guesswork.

! Fourth, we consider what fraction of those planets that could support life actually do develop life at some point. Dr. Drake estimated 100%. Current estimates range from 13% to 25%. Some estimates have been based on the length of time it took to develop life on earth. There is very little else available to base this estimate on. Supporters of higher estimates point out that life seems to have developed just about everywhere on earth, even in the harshest environments.

! The fifth factor to consider is the fraction of life bearing planets that go on to develop intelligent life. Dr. Drake estimated that number at 1%. There is no evidence for this number and there is no consensus of current estimates.

! The sixth factor is the fraction of those of intelligent species that that are willing or able to communicate with us. It’s conceivable that a technological civilization may not want to communicate outside of their world. It’s also possible that an intelligent species may not develop the technology. Dr. Drake estimated that 100% of planets that have intelligent life will have at least one species that are willing and able to communicate using technology.

! The final variable is the length of time that technological civilizations survive. Dr. Drake estimated 10,000 years.

So there are the variables that are used. When multiplied, Dr. Drake’s values provide an estimate that there should be ten technological civilizations in the Milkey way Galaxy.
(N = 10 × 0.5 × 2 × 1 × 0.01 × 0.01 × 10,000 = 10)
Current estimates run somewhat lower- about two to three. (see the Wikipedia entry on the Drake Equation).

Now, on to the Fermi Paradox which asks:
Where are these aliens?

The Fermi Paradox was formulated by Italian born physicist Enrico Fermi in 1950 while working at Los Alamos National Lab in New Mexico, USA. Dr. Fermi and some of his colleagues were engaged in a discussion about alien life. Dr. Fermi made a quick estimate of the likelihood of extraterrestrial civilizations and came to the conclusion that earth should have been visited many times.

The paradox is: why haven’t we seen them?

Your first reaction to this may be “Why is this Paradox?” Why can’t we just say that we believe that there is intelligent life out there, but we just haven’t run into anyone yet?

Well, the universe is 13.5 billion years old. Earth has existed for 4.5 billion years. So, the universe was around for 9 billion years before the earth even existed. That’s 9 Billion years that could have produced other civilizations. It seems reasonable to think that some civilizations should have been around longer than us and should have advanced farther than we have. Imagine what we would be capable of if we continued developing for another five thousand years. Even if no civilizations was able to surpass the speed of light, over the eons some civilization should have left signs of its existence.

What’s the answer? There are many possible explanations for the Fermi Paridox. Let’s look at a six popular views:

First, there is the Rare Earth hypothesis. There may be very specific requirements for life to develope. Other technological civilizations either don’t exist, or they are so few and far between that it isn’t likely that we’ll meet.

The Doomsday theory posits that a civilization will destroy itself through warfare or accident before or shortly after developing technology.

Another explanation for the Fermi Paradox is Creationism. Some (but not all) Creationists believe that human beings were created alone and that the universe was created solely for us.

Some believe that extraterrestrial civilizations do exist, but we can’t communicate because they are to different for us to recognize.

Perhaps we have not been searching for long enough. On a cosmic scale our civilization has only existed for a blink of an eye.

Finally, is it possible that many people have seen extra terrestrial life and we just choose to ignore them, or our leaders keep it a secret?

What do you think?

There are several Interactive Drake Equation Calculators available on the web that you can use to develop your own estimate of the number of technological civilizations that are in our galaxy.

My favorite tool is on the PBS Origins web site. The address is included in the show notes.

http://www.pbs.org/wgbh/nova/origins/drake.html

I used the tool and came up with an estimate of three technological civilizations in our Milky Way Galaxy.

Whatever number you or I arrive at, I don’t think that the Drake Equation is as much of an attempt to determine the number of alien civilizations in our galaxy as it is a proposed framework for thinking about it.

The fact that we have not found alien intelligence is not a failure. Discovery of alien intelligence or finding that we seem to be alone are equally profound discoveries and both have dramatic implications.

Either way, it’s a fascinating topic.

If you’re interested in learning more I recommend that you start with the excellent Astronomy Cast Podcasts. Episodes #23 and 24 deal specifically with the Drake Equation and the Fermi Paradox. You can access these Podcasts through iTunes, but if you go to the Astronomy Cast web site you’ll find a lot of other useful information. I have included a link to Astronomy Cast in the show notes.

Other good sources are the PBS Origins web site and the Wikipedia entries for the Drake Equation and The Fermi Paradox.

Well, thanks for joining me and please make sure to check the show notes.

Thank you!

End of podcast:

365 Days of Astronomy
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