[ad_1]
ATo think that extraterrestrial life should be like life on Earth is the surest way to scientifically search for evidence. A recent article on arXiv by an Oxford research team is likely to cause headaches for SETI. In short, this should not be the case since the Oxford team made a fundamental mistake in the middle of a masterful application of statistical analysis. When you are looking for the truly unknown, you must take the least possible. In theoretical physics, the mark of a good theory is one in which the most testable implications arise from the smallest number of assumptions and adjustable parameters. This is the case in most fields of science. The same goes for astrobiology and researches intelligent life.
In an article titled "Dissolving the Fermi Paradox" (arXiv: 1806.02404v1), Anders Sandberg, Eric Drexler and Toby Ord of the Oxford University Futures of Humanity Institute demonstrate the danger of assuming too much of things and of do it implicitly. Their mathematical techniques intrigue and seem solid at first reading. I have not done a full review where I am trying to recreate their results for the moment. The purpose of this blog is to get the rest of the media to hold their horses in reporting on it. Their analysis implicitly relies on the work done in search of an extraterrestrial intelligence that believes it or not tends towards the conservative.
[ad_2]
In an article titled "Dissolving the Fermi Paradox" (arXiv: 1806.02404v1), Anders Sandberg, Eric Drexler and Toby Ord of the Oxford University Futures of Humanity Institute demonstrate the danger of assuming too much of things and of do it implicitly. Their mathematical techniques intrigue and seem solid at first reading. I have not done a full review where I am trying to recreate their results for the moment. The purpose of this blog is to get the rest of the media to hold their horses in reporting on it. Their analysis implicitly relies on the work done in search of an extraterrestrial intelligence that believes it or not tends towards the conservative.
In particular, they dispute the way the Drake equation is applied.
From left to right, the number of intelligent civilizations is equal to the rate of star formation, multiplied by the fraction of stars with planets, multiplied by the number of planets that are similar to the earth, multiplied by the fraction that develops intelligent life, once the fraction that develops technological civilization times the lifespan of these civilizations.
The Oxford team challenges how the fraction that develops life and the fraction that develops intelligent life are valued. The problem is that the conservative estimates of these fractions assume that life and intelligent life must be much like humans. May be in reptilian or avian form but following the same pattern of being bipedal tetrapods that live for about 100 years or more. that they would take most of the living life of their planet to develop this intelligence. In short, they would be like most extraterrestrials of the week on Star Trek.
The hypothesis that must be questioned in the present case is the notion that extraterrestrial life must be very similar to life on Earth. Even though this life is based on carbon and water, breathes a nitrogen atmosphere and that their planet has about 65% of the surface covered with liquid water, it could be VERY DIFFERENT.
The failure to find extraterrestrial life may be due to the look where there is the effect of light. We can only look for life on the only example we have, let alone with extraterrestrial intelligence. Just like a person looking for their car keys at night. They can only watch where the street turns light up the ground.
Masterful Mathematics
let me be clear, their application of statistics to this question is masterful. Essentially, they looked at the published literature for the data supporting their calculation of the fractions of planets that will develop life and the fraction where life will become intelligent. It's a healthy thing to do.
Again, I did not do a thorough peer review of their work. At first reading, it seems very likely that they simply chose the most conservative and unimaginative documents on which to base their examination. It's a healthy approach for most things. Just not looking for extraterrestrial life.
Consider the colorful story of life on Earth. For about 100 million years, we had feathered giants and colorful things like Therazinosarus and their parents walking on Earth.
At this moment we have enormous and rather intelligent creatures living in the sea, cetacean whales that are known to be intelligent and that seem to possess a form of language. They are creatures that share a large part of our DNA. Creatures that have a brain largely similar to ours. Creatures with whom we share hundreds of millions of years of common ancestry. Still, we can not even be sure if they talk to each other and try to talk to us or just make noise because it seems like it's a mewing of cats. Last but not least, we have discovered in my life that life can exist without sun. Science books now write as if it was always a known fact that life could exist through deep sea vents and not rely on photosynthesis for energy.
Variables are the only true answer.
Given our level of ignorance of life on Earth and our own solar system, let alone in other solar systems, all we can do now is to leave the fractions f sub l and f sub i as variables. We do not know enough to do anything but solve them according to the other known quantities. f sub c the number of intelligence that develop a technological civilization should also be left as a variable. Moreover, if N. makes the basic algebra to put the quantities we know on one side of the Drake equation and the quantities we do not know about it. on the other hand, we can at least solve the relationship between these values.
Then flip the equation over
Looking at the equation from another point of view **, we see that we can say a little without assuming anything. For simplicity, we can assume that each star will have some planet orbiting around it. A planetary disk seems to accompany the formation of most, if not all, stars at a given moment. Even in the case of very large mass stars, if they form via a disk-output model, as suggested by my MS thesis (which was made in a published article arXiv: 1311.3983 10.4236 / ijaa.2014.44053) then clearly their could be planets even around these stars. Probably not life since the most massive stars are, as I say to the students, the John Belushi from the space. They are tall and bright and never stay long enough. Fortunately, according to the Harvard Astrophysics Center, at least one sixth of the stars will have at least one planet similar to Earth. There is no need for speculation on my part anymore. Note, by "Earth like", they refer to the mass and distance of their parent star being located in the habitable zone. As for L, we can estimate that. On the basis of ourselves, we had radio technology that could broadcast and receive an additional terrestrial signal over the last 100 years. Taking the star training rate to be a star a year. Which is WAY too low. It leaves we with the following inequality a lower bound of the number of extraterrestrial intelligences.
If the actual number of intelligence is equal to 17 then why not see them or hear them in our receivers?
The main reason is that the Milky Way is huge. 100,000 light-years or about 30 kiloparsecs in diameter. If we assume that a circular disk is close enough to the shape of it, this gives each of these 17 species a huge 462 million square light-years Given that this area of the galaxy, we could have everything for us, it is unlikely that we would ever manage to live on extraterrestrial intelligent beings.
Using NASA's findings on star formation and the number of pieces of information, there are at least 119. Each of them would have 66 million square light-years to itself.
Given the distances, it does not seem reasonable to pretend that we are the ONLY intelligence that is likely to exist. Once we have had time for the signals to reach us from this whole area, which would have a radius of about 4500 light years and hear nothing then we can say that we can be the alone. Until then, we really do not know and at best we can talk in terms of limit values and probabilities (even then being more optimistic, we might be able to know with only a little bit better than the trust in the draw one way or the other).
In short, I would advise you not to put too much stock in such a definite and certain conclusion on this question. The paper that stimulated this blog is well done, but the conclusion we reached is a big step on the basis of our limited information.
__________________________________
** In things that seem to have nothing to do with theoretical physics in the purest sense of the world, I find that it helps to fall back on the disciplined thinking that it needs. To be ready to question everything to death, even oneself.
__________________________________
** In things that seem to have nothing to do with theoretical physics in the purest sense of the world, I find that it helps to fall back on the disciplined thinking that it needs. To be ready to question everything to death, even oneself.
Source link
