In previous posts I discussed the Drake Equation (DEq) and the Seager Equation (SEq), and promised to expand those by presenting my own version, the Nastrazzurro Equation (NEq). Let's start with a quick refresher of the DEq and SEq. Both provide estimates regarding extraterrestrial life, but in different ways.
Frank Drake aimed to estimate the number of intelligent civilizations. Actually, the DEq was aimed at just one particular subset of alien intelligences, meaning those that we should be able to detect on Earth because the aliens in question live nearby and obligingly send out electromagnetic signals into space in very much the same way that we do. Quite a bit of effort is spent listening to the stars to find out whether anyone out there is actually doing that. Writing my post on the DEq strongly influenced my opinion on the matter: I do not expect this method to produce any exciting news anytime soon. The numbers seem to be against it: electromagnetic signals decrease with the square of the distance, so they become very weak even over short distances; short in the astronomical sense, that is. To detect such signals with our current equipment the strength of the signal would have to be ludicrously strong, making you wonder why anyone would want to do so. You may also wonder how long a civilization will keep on transmitting, which is an important factor in the DEq. Apart from the question how long civilizations last in the first place, there is added problem that sending out electromagnetic signals into all directions at once, as we do, seems a bit silly. If the message is meant for people on your own planet or in your own solar system, surely an advanced civilization can somehow direct the signal to where it should go.
Sarah Seagers' approach is quite different. Her primary aim is not aim to detect signs of intelligence. Instead, she wishes to study the composition of a planet's atmosphere by seeing how that atmosphere changes the light of the planet's star when it shines through it. If the atmosphere alters the star's light in a way that suggests metabolic processes, than life is the easiest way of explaining their presence. In other words, does the atmosphere host a biosphere? Just as people are trying to obtain factual evidence of alien radio signals, there will be factual efforts to seek for biospheres in this way. The 'Transiting Exoplanet Survey Satellite' (TESS) was launched in 2018, and will probably find lots of potential planets to investigate later. That 'later' means scrutiny by the James Webb space telescope, not yet launched. Here is some more information on that telescope from NASA. By the way, NASA asked artists and the general public to produce art for the occasion; one of the results is the poster above (here is a link to the art section). The James Webb telescope will apparently launch in 2021, so we might have an answer to the question 'Is there life out there?' within 10 years. National Geographic has some nice information on the search for extraterrestrial life and the methods to find out, right here.
|Astronaut Bowman looking at the monolith. "Oh my god, it's full of stars!"|
Anyway, back to the equations: both result in estimates of the number of either civilizations or biospheres that we can detect. And there's the rub: detection! The DEq and SEq aim to obtain factual evidence. And that is precisely the difference with the 'Nastrazzurro Equation' that I propose here. Let me make it clear that I see the NEq as a fanciful thought experiment in science fiction; it is not a competitor of the serious DEq and SEq. If there would be a diminutive of 'Equation', I would use it (it might be 'equationicula', but that sounds as silly as 'equationette').
So what does the somewhat arrogantly named 'Nastrazzurro Equation' actually do? Well, it utterly and completely ignores any wish for actual evidence. That makes it science fiction. Of course, the whole subject of speculative biology is science fiction, even though I like my science 'well done' rather than 'rare'. I like films with alien intelligences in it, especially if these films also betray human intelligence, which is not a given. My main interest in all this is alien biology as a whole, and I can do without the intelligence. I would probably have preferred 'Avatar' to be a documentary rather than a drama. Actually, there is such a documentary, but it is only four minutes long.
The NEq deals with the question 'How many interesting biologies might there be out there?' At present, I will accept anything as 'interesting', such as a planet with microbial life only, although my interest might become less keen quickly. I would accept with unmoving spongy thingies on the sea floor, spending aeon after aeon doing a spot of quiet filtering. I would love things that jump, move and fly, but for now, any life will do. So: how much life could be out there?
|Click to enlarge. Screen shot from this website|
- First, choose an overall setting such as "today's optimistic" and proceed.
- We can leave the first four estimates as they are.
- The fifth box asks for the percentage chance that life develops intelligence. We do not care about intelligence and we do not want that box to reduce the estimate, so we simply put in 100 (If we were to use a proper equation, this term would be left out).
- The next box asks about the percentage chance that life can communicate across space, and we do not want that one either, so we set that to 100% too.
- We then are asked to fill in the length of time that a civilization actually transmits signals. Here, we do have to fill in a number, but it should represent something else: it should be the length of time a planet harbours life. That's a tricky guess, but the number will certainly be much larger than the time a civilization is transmitting. But we can use actual data! Life has already existed on Earth for 3.7 billion years (3.7x10^9 years), and might exist until the conditions for life cease to exist, which might be in 2-3 billion years, according to Wikipedia. So we can put in 6x10^9 years as an estimate. Unfortunately, you will find that the programme does not accept such large numbers, so for now we just leave the setting at 10 million (10^7) instead of 6x10^9 and remember that the result will later have to be multiplied by 600.
- The last box asks for the number of times a civilisation can redevelop. Here, we will assume that life needs to evolve only once, so we set that to '0' instead of '3'.
- Press calculate and get 18,900,000 planets with life in our galaxy, or, say, 1.9x10^7.
|Click to enlarge. From this website|
How about the Seager equation? We can hijack that and turn it into a Nastrazzurro Equation too! Let's go for the "original Seager values".
- The first box asks us about the number of 'observable red dwarfs'. We do not care about 'observable', and we will also allow for other types of stars. Again, we need an estimate for the number of stars in a galaxy, and we can take the 250 billion estimate again (2.5x10^11). The highest settings seems to be 500,000, so let's remember that our calculation will be 500,000 times too low.
- The next box asks for minimal disruptions. Let's leave it at the original 20%.
- The next box concerns the percentage that can be observed. We wish to ignore that, so put it at 100%.
- Let's leave the estimate for 'rocky planets' as it is, at 15%.
- Let's set the percentage with life to a low value of 1% as per the original values.
- The next one is about detectability again, so that becomes 100% for 'omit this box'.
- We press calculate and get 15,000.
So this is the result of the official 'Nastrazzarro Equation' for the number of planets in our galaxy with life on it. It is a bit silly but not idiotic. After all, it is merely a simplified form of the Drake and Seager equations. It only contains one factor not present directly in the DEq and SEq and that is the number of stars in the galaxy. Here's an interesting twist: the NEq reduces the number of parameters in the DEq and SEq, and all these factors have a very large uncertainty. So, and I rather like pointing out this somwewaht cheeky observation, by reducing the number of factors the Nastrazzurro Equation can be said to be more precise than its more serious predecessors. Well, perhaps 'less immensely uncertain' is probably a better term...
|A megarusp; click to enlarge; copyright Gert van Dijk|