The Drake Equation

Drake's Equation is an often quoted formula that is used to guesstimate the number of extraterrestrial civilizations that might be in existence at any one time. It combines eight (often arbitrary) elements from star formation to stages in life development. From this is derived a supposed number that represents how many advanced civilizations might exist in our galaxy right now.

These elements are:

• Average rate of star formation in our galaxy (R*)


• Fraction of those stars that have planets (f_p)


• Average number of planets that potentially support life per star that has planets (n_e)


• Fraction of those planets that actually develop life at some point (f_l)


• Fraction of those planets that then develops intelligent life (f_i)


• Fraction of those civilizations that develop technology that can and does send detectable signals of their existence into space (f_c)


• And, the length of time such civilizations remain detectable via their transmissions (L)

The formula this looks something like N = R* x f_p x n_e x f_l x f_i x f_c x L.

Here's an example of how to use the formula based on estimates of values for its variables.

• R* = 10/year (10 stars formed per year, on the average over the life of the galaxy)


• f_p = 0.5 (half of all stars formed will have planets)


• n_e = 2 (stars with planets will have 2 planets capable of supporting life)


• f_l = 1 (100% of these planets will develop life)


• f_i = 0.01 (1% of which will be intelligent life)


• f_c = 0.01 (1% of which will be able to communicate)


• L = 10,000 years (which will last 10,000 years)

Drake's values give N= 10 × 0.5 × 2 × 1 × 0.01 × 0.01 × 10,000 = 10 civilizations with which there is possibility for us to currently communicate. This can be useful to provide rough guests as to the chances of how successful we can expect to be in our hunt for E.T.'s with programs like SETI.  SETI has a lot of equipment pointed into space looking for signals.

However, the formula is so full of guests, it may not have any value at all. In fact, even the elements of the formula are themselves guests. For example, one might question why star formation rate has any impact on how many planets may form with life. Also, given more modern understandings of our galaxy, such as the Rare Earth Hypothesis, many other factors may be more important that those used the Drake Equation. Additionally, there is a problem that many stars have been discovered to have Hot Jupiters, which would destroy any terrestrial worlds, thus preventing the opportunity for life to develop in that star system. Even worse, the question is raised about our own arrogance in the assumption that all life would resemble us enough to communicate in the same forms as we do.

It appears now that the Drake Equation is actually pseudo-science. It is not based on any hypothesis. It is nothing more than a series of guests. It does not produce anything that is testable. In fact, it's author, Dr. Frank Drake, didn't originally intend for this formula to be used in the way that is has been. It was meant to be an organizational tool for the discussion about intelligent life in the Universe specifically for a gathering called The Green Bank Meeting in 1960, so named for its location at the Green Bank Telescope.

Right now, it seems the best way to know how common life is in our galaxy is to explore it. The Drake Equation is more of a mathematical toy than an actual useful formula.

California Nature (minor tweak)

Your journey roads herald adventure,
Impelling me to climb your cloven heights,
And romp carelessly,
as aureate poppy fields beckon.

Sun-kissed waters bounce along your shoreline.
They entice me to surf the crashing calm waves.

Canopy-enveloped valleys thrive with floral scents
That draw my ingression, but I forestall.

Instead I caper like Racetrack Playa’s sailing stones,
Which tickle your basin by some unseen will.

I endeavor to hike your proud hills,
And find places to gaze lostly into lakes full with sky.

Vineyard nectar overflows like sweet sweat,
To spur my soul’s arousal as I partake.
Your boundless attributes gratify my wanderlust,
And allure me to appease your nature.

"In the Hopper"

As far as I can remember, the very first (and only) time I've ever heard the phrase "in the hopper" occurred this week.  It was such a strange phrase; I had to look it up.  It turns out that the person who introduced me to this phrase used it completely incorrectly.  The statement from that person made to me was similar to "let's keep this in the hopper for awhile."  The inference is that something is being put on hold for a particular time frame.  However, "in the hopper" actually has a meaning that is quite the opposite.  When I looked it up on http://www.dictionary.com, I found that it refers to something being introduced or something about to happen or be realized.  Now that I've learned a new phrase, I just might start using it (correctly, of course).  One might say that my use of "in the hopper" is now in the hopper.

Possible type of Alien Lifeforms (Part 2: Exotic Amino Acids)

For the most part, life on Earth uses the same set of nucleotides (amino acids) to form the basis of their DNA. In all, almost all known life uses 20 particular amino acids. These are often classified by their bases as A (adenine), C (cytosine), G (guanine) and T (thymine). These are the basic building blocks of DNA. They are also used to build proteins. Of course, from a certain point of view, DNA is just a really long protein.

How DNA uses these amino acids is described by Paul Davies in his article Are Aliens among Us? published in Scientific American, Dec 2007. He states, "The genetic code is based on triplets of nucleotides, with different triplets spelling out the names of different amino acids. The sequence of triples in a gene dictates the sequence of amino acids that must be strung together to build a particular protein."

Alien lifeforms may use exotic amino acids that are far different than the ones used by life on Earth. It is possible that the set of amino acids we use may not even appear on other worlds. Evidence by scientific study suggests that there are many other forms of amino acids that may be useful (or at least available) for other types of life. Evidence of exotic amino acids on other worlds has come from meteorites. Also, others have been synthesized in the lab.

Other lifeforms from other worlds may be completely different from us while still using the same basic DNA structure we use. A question remains, would life formed by exotic amino acids be all that much different than Terran life in appearance? Would the exotic amino acids lead life to evolve along completely different paths that we as yet have not conceived?

Reference: “Are Aliens Among Us?” by Paul Davies, Scientific American December 2007

Related articles

• Video: What Would Trees Look Like On Other Planets?
• Predictions of Evolution of Alien Life
• Communicaion with Alien Civilizations
• Odds of Humaniods Evolving again
• Part 5: Blue Plants
• Part 4: Silicon Life
• Part 3: Arsenic Life
• Part 2: Exotic Amino Acids
• Part 1: Mirror Life

What are the odds of Humaniods evolving again?

Humans take human-level intelligence for granted.  So much so, that our humanoid form seems to prevail any of our notions of intelligent life on other worlds.  Images of Greys, EBENs and other aliens have the same general plane symmetry body plan as us, with two arms, legs, a torso, a head, symmetric features, two eyes, mouth, nose holes, brain, etc.  But what are the chances of life evolving in this way again, either on another world or evolving again here on Earth after humans are gone?

The major problem with this is that life goes through a great number of changes as it evolves over time. At each point, a very specific set of criteria sets the stage for what is eventual deemed successful adaption and what comes to the end of the line. Given what little we know right now, it seems unlikely that changes at each step will follow the same path twice in different ecosystems and different worlds.

Sure, we do have convergent evolution, where multiple species evolve the same abilities in separate epochs and ecosystems.  But is human-level intelligence something that will happen naturally again?  Is having two legs, two arm, a face, etc, something that happens naturally as a matter functionality?  Could there be intelligence as advanced as ours, but in a completely different form?

We don't know anything concrete regarding evolution of life on the cosmic scale.   For years it was assumed that the form of our Solar System was common, and that is what makes life elsewhere likely.  We exist; there's nothing special about us; therefore life like us exists elsewhere.  This is a bit silly since we have no data to support that.   In fact, when we started finding planets in other star systems, the Solar System model proved to be quite unusual.

Maybe our understanding of evolution is still incomplete at the cosmic scale.  Maybe traits we see in Terran life are common on other worlds simply because these adaptions are the most successful in general, regardless of specific ecosystems that may exist.  Before people start declaring this or that is unlikely, let's collect data and find out.

Start sending probes to other star systems and poke about.  The probes will take a long time to get where they're going, but so what.   Unless we humans kill ourselves off (or nature does it for us), our posterity should be around to receive the results of our efforts, so that they can figure this out with actual evidence, instead of relying on unscientific guesses (see Drake's Equation).

Related articles

• Video: What Would Trees Look Like On Other Planets?
• Predictions of Evolution of Alien Life
• Communicaion with Alien Civilizations
• Odds of Humaniods Evolving again
• Part 5: Blue Plants
• Part 4: Silicon Life
• Part 3: Arsenic Life
• Part 2: Exotic Amino Acids
• Part 1: Mirror Life

Possible types of Alien Lifeforms (Part 1: Mirror Life)

On Earth, life uses what is called right-handed DNA. Right-handed DNA uses left-handed amino acids, sometimes described as homochiral. The fact that all lifeforms on Earth use Right-handed DNA suggests that all life here is descendant from a common group of ancestors.

Why does the difference matter? If single cell members of mirror life (with left-handed DNA) are placed in a nutrient broth consisting of only left-handed amino acids, the lifeforms will not be able to thrive. The same is true of the reverse.

Mirror life is a type of lifeform that uses the same type of DNA structure, but where the DNA is left-handed. This type of life, in turn, used right-handed amino acids.

The possibly that life on other worlds may be mirror life is very exciting. If found, it would lend tremendous evidence that life is possible in other forms as well.

----

Reference: "Are Aliens Among Us?" by Paul Davies, Scientific American December 2007

Related articles

• Video: What Would Trees Look Like On Other Planets?
• Predictions of Evolution of Alien Life
• Communicaion with Alien Civilizations
• Odds of Humaniods Evolving again
• Part 5: Blue Plants
• Part 4: Silicon Life
• Part 3: Arsenic Life
• Part 2: Exotic Amino Acids
• Part 1: Mirror Life