Monday, July 16, 2018
astro picture for the day/ Isaac Asimov's "Rare Earth Hypothesis"
Image Credit - MeerKat radio telescope - the Event Horizon Telescope guys want to keep people from getting excited; they think the image "may disappoint." I think we can rest any fears of disappointment. Right now, they're keeping the images to themselves till they get the scientific papers out(publish or perish)
- Peter Ward and Donald Brownlee published "Rare Earth" in 2000. At the time, the idea that despite the billions of stars in a galaxy, Earth's and technological civilizations could be rare was new. But, I actually grew up having read Isaac Asimov's "Extraterrestrial Civilizations." Ward and Brownlee don't reference Isaac's book. I wanted to re-read Isaac's book and "Rare Earth" in the light of a recent finding furthering the "Rare Earth Hypothesis."
Appears that Supernova don't all produce the same amount of Phosphorus. Phosphorus is an essential element for life as we know it. I'll link one artilce here --> Phosphorus shortage may make alien life very rare
This finding is just the latest property of our solar system and Earth that Astronomers have found which would indicate that Earth's and Extraterrestrial Civilizations might be rare. As indicated above, Isaac Asimov, and not Ward/Brownlee was the first to think of this Rare Earth hypothesis. Curiously, he doesn't mention Fermi's Paradox. So, I'll start this review of the Rare Earth hypothesis with Fermi's Paradox.
In the 1950's, Fermi was sitting down with a few physicist friends, talking about the recent Big Bang theory of the universe(note, this was over a decade before even cosmologists took the Big Bang seriously), and asked "Where are they?"
What he was getting at is if there was a Big Bang 10 to 20 billion years ago(The Big Bang is well dated in todays' Hubble Space Telescope era - 13.7 billion years), and the Earth is dated to 4.5 billion years old, then shouldn't there be E.T's swarming the galaxy? Shouldn't the galaxy be settled by now?
A further technicality of the Fermi Paradox is that for there to be rocky planets, you need a generation or two of supernova. The Big Bang only produces hydrogen and helium. Elements essential to making stars, but not rocky planets. Supernova go off in about a hundred million years. Factor in the recombination event after the Big Bang, when the universe cooled down enough for light to disentangle from electrons and allow atoms to appear, and you still have billions of years since the Big Bang for E.T's to swarm the universe.
UFO and E.T. enthusiasts have of course had a field day with this one. They've hypothesized everything from they're among us(Einstein was an Alien hypothesis) to making the Egyptian pyramids to there's just getting ready to wipe us out. Getting to Isaac Asimov's "Rare Earth" hypothesis.
Isaac Asimov gets to his Rare Earth hypothesis by means of rational philosophy. He points out the remarkable similarity between the UFO craze and Religions who want there to be a God to save them. Whereas the God believers want a savior god Jesus(or Osirus, or Dionysius, or Mithras . . . see my Gospel of Truth), the UFO guys want E.T.'s to come down to Earth and reveal all their science and technology so we don't have to go through the painful stages of life to acquire all this knowledge. One could further note the analogy with the third world economies being able to go straight to the information age instead of the industrial age - as pointed out by Alvin Toffler.
This proves some interesting ideas of Carnap and other Vienna school of logicians of the 1900s. That often a problem can be proven meaningless. Or, other times a problem is meaningless at one time, and not at another time. This understanding appears to have been lost to humanity since E.T. Bell's "Development of Mathematics" which appears to me heavily influenced by this Vienna logicians scientific humanist philosophy.
The idea of Extraterrestrial Civilizations has no meaning before Astronomers proved the Heliocentric model of the solar system(they'll often say "of the universe" - or Helio cosmology). In a geocentric model of the universe, where the white dots are not suns, there's no way to conceive of Extraterrestrials.
Also, this relates to the nature of all mathematical discovery. A mathematical problem is hard because the viewpoint one is using is not appropriate for the it's solution. Only be re-expression does a hard mathematical problem get solved. In Symbolic logic, one learns that to prove a proposition from the conclusion, one needs to make a re-expression. See perhaps Velleman's "How to Prove It."
Isaac points out that the effort to find Extraterrestrial Intelligence by hypothesizing a god(s) is using unobservables, and since we can't (dis)prove unobservables, we move on to looking for Extraterrestrials like us.
He points out animals as intelligences, but since they don't create technologies, they don't count. And, this shows that when we're looking for Extraterrestrial Intelligences, we're looking for Extraterrestrial Civilizations.
Curiously, to me perhaps, he missed pointing out Neanderthals as intelligences other than ourselves. And there were lots of other primates other than Australopithacines and Homo Erectus that we competed with in our evolution. But, getting to the Rare Earth hypothesis . . .
Despite Isaac considering the Moon not that important to the possibility of Extraterrestrial Civilizations(E.C's for short), he starts there.
Isaac points out Torricelli's experiment which found the vacuum for the first time. Astronomers quickly realized that the atmosphere of the Earth does not extend throughout space, and maybe the Moon doesn't have an atmosphere - No atmosphere, no water, not life.
Isaac then goes through all the physics discoveries and history showing there's no life on Venus or Mars(probably not; certainly, we know there's no multi-cellular life on Mars), the Gas giants and their moons.
Just because only one planet in our solar system is covered with life, doesn't mean other star systems are not brimming with life. But, Isaac finds many Astronomy finding's suggesting that Earth's may be rare.
Isaac's first number for habitable stars sytems = 300,000,000,000
Isaac goes through the some rather little known history of the Nebular hypothesis. He shows that Laplaces nebula hypothesis for the origin of a star and planets went through a bit of a scientific process. Laplaces nebula hypothesis had an angular momentum problem. The sun doesn't rotate fast. But, the planets do. It took over a hundred years before Astronomers realized magnetic fields could have transferred the momentum from the Sun to the Planets. I've considerably shortened all the history presented in Isaac's book.
Isaac tries to use this to exclude certain star systems from having planets. Fast rotators must not have planets. He does point out there could be other reasons; but, for the most part, this condition reduces the amount of habitable planets for Isaacs second number - 280,000,000,000
I'm just going to list out for the most part Asimov's numbers for habitable solar systems,
3rd figure = 75, 000,000,000 - this is due to stars being to large(they go supernova), and small stars doing tidal locking, flare stars. These midget stars make up the majority of stars. Sunlike stars are only 25 % of the stars in a galaxy. What happens when binary stars are taken into account?
4th figure = 52,000,000,000 - this figure is arrived at by considerations of binary star systems. The explanation gets a bit complex as he considers every possibility of giant and small stars in a binary system.
5th figure = 5,200,000,000 - the possibility of Extraterrestrial Civilizations takes a big hit with considerations of Population I and II stars. These labelings are a bit backwards for most people(including me). The Galactic core stars are called Population II stars, and the disk stars are Population I stars. The Population II stars are 1) light element stars and probably don't have any heavy element planets. They're also radiated by the central black hole. There's also the consideration of generation 2 stars of the Population I stars. In all, the number of stars with the possibilities of an Earthlike planet takes a big hit.
6th figure = 2,600,000,000 - Isaac's 6th figure is probably the most speculative at the time of his writing. I'm thinking that one article I read about Jupiters spiraling in close to their star and ejecting any inner rocky planets also holds here. I need to re-read that; those close in Jupiters would drastically reduce the number of stars with Earthlike planets.?
7th figure = 1,300,000,000 Isaac arrives at this figure by considering that not all planets in a suitable star system's ecosphere is of the right size.
8th figure = 650,000,000 This figure is come about with the same considerations as the 7th figure. So, these two figures are not precise. I'm thinking this is where "Rare Earth" book comes in to define these parameters more precisely.
figure 9 = 600,000,000 - this figure is a guestimate on the lifetimes that life develops from bacteria to multicellular. It's saying if a star is stable enough and has been around for enough time for life to go from single cell to multicellular. This use the Cambrian explosion as a minimum time when life went multi-cellular. And the 10th figure is related to the this consideration - 433,000,000 . . .also figure 11, which is considering land life - 416,000,000 . . . and the 12th figure is about how many star systems planets could be around with intelligent civilizations = 390,000,000
Isaac's last figure 13 = 530,000
What does Ward/Brownlee show that's new beyond Isaac Asimov's 1980s book? They talk about plate tectonics, and Snowball Earth. The Snowball Earth maybe related to the Moon stabilizing the Earth's tilt. This would be when the Moon wasn't in position to stabilize the Earth's tilt as much. Also, they mention the Moon and Jupiter.
Astronomer's have found that many solar systems Jovian planets have spiraled close in where the inner rocky planets would be. Because of a resonance between the Star and it's Jovian planets, as the Jovian Planet spiraled in, the resonance would have thrown out any inner rocky planets.
Between the Moon, which Isaac disregards, and the Jovian planets being in close, and the recent Supernova's not making phosphorus equally, that last 13th number is probably considerably lower. Probably less than a hundred thousand. Factor in Nuclear war, and/or Industrial destruction of the environment before they establish themselves out in space, the number of E.T's could be quite low.
But, even if the number is fifty or even less, when we consider billions of years, and what technologies we know are around the corner - A.I, Nanotechnologies, and Quantum Computers, even if one Extraterrestrial Civilization had got as far as the exotic technologies noted above and established themselves out in space, they should have been able to populate the Galaxy.
- I've been refraining talking about the latest Nanotech and Quantum Computing news. Sorry if my readership is innocent; but I've been wondering who my readership is lately. Assuming my readership has been using me for insider news on nanotech and quantum computers, I can only tell you that I am not an insider. I get my news when everyone else. Sure, I peruse the net and I am a longtime watcher of the scene. Other than that, I don't give any kind of secret info. Whether you want to believe this qualification of whether I'm giving secret info or not, I do feel forced to talk about A.I./Nanotech/and Quantum Computers a bit here.
A.I and Nanotech kind of arose together. Once could say chemistry is nanotech. But, what say Richard Feynman and Eric Drexler, the two main founders of nanotech mean is nano-manufacturing. The last term is my own as far as I know. I have, curiously, seen it used from time to time. Anyways, what's meant by nano-manufacturing is making everything from nanoscale to macroscale objects to molecular precision. Molecular is the better term here because to say atomic precision is to suggest subatomic quantum scale. We're talking about getting every atom in a molecule or a macroscopic object in the right place - molecular precision.
NanoManufacturing would be like a computer. Only, instead of juggling bits and getting a picture on a screen, or a printout, we're juggling atoms and getting a product. Two affect could allow this. One, a molecular scale robot. The small size allows rapid movements. The other affect would be massive parallelism.
When/if they get NanoManufacturing to happen, they could recycle the industrial world. We would be in a revolution comparable to the iron age to the Bronze age. We could make things to their scientific limits dictated by natural law. Things could be made anywhere from ten to a thousand times greater in quality. But, it's A.I. that can really drive the NanoWorld.
A.I powered NanoManufacturing could explore those limits of natural law. They can also make the amount of technological development so high, as to be beyond human comprehension. The amount of engineering accomplished in a single day could dwarf all that came for the last so many hundreds of years, much less the thousands and even Millions of years if you count the Austalopithacines stone tools. But, that's nothing or even further augmented by Quantum Computers.
Quantum Computers use quantum entanglement, a state so delicate, you need to work at zero degree temperatures, and get rid of all vibrations to keep the quantum state from withering away. Quantum Computers could make today's supercomputers look like Pascal's adding machine of the 1600s. The Quantum Computers can solve quantum chemistry and differential equations that are unsolvable today.
Quantum entanglement can lead to quantum technologies beyond even computing. They can come up with artificial atoms - and alternative chemistries. Insted of just relying on the periodic table properties, we can come up with alternative periodic tables.
Already, we have cloaking technology. We already have the ability to make refraction free lenses. This allows our Electron Microscopes to see atoms. Where before, the laws of physics prohibited Electron Microscopes from seeing atoms.
I'd like to point out a favorite science/technology that doesn't get mentioned much - chaotic dynamics. Researchers have figured out how to 1) use strange attractors, and/or 2) go from one of the systems strange attractor states to another. They can stabilize one of the possibly infinite behaviors of a chaotic system. They can do this for any medium - mechanical, electromagnetic, chemical.
Point is if an Extraterrestrial Intelligence established itself out in space and/or established even one of the above technologies(establish one, and you could easily establish the others), they should have no problem with interstellar space travel.
So, where are they?
Well, one answer is they've cloaked themselves. Even if this were true. Why do we have supernova? Wouldn't they want to prevent that, and prevent more black holes from forming?
I think the answer lies elsewhere - Religion. Religion doesn't like to be questioned. In such an extremely science future, where science has conquered all; there's no where for Religion to hide. Eventually, they say no.
Subscribe to:
Post Comments (Atom)
Isaac Asimov, once again, doesn't mention "Fermi's Question." But, he does ask "where are they?"
ReplyDeleteHe talks about interstellar distances and twentieth century ideas of how to travel at light speed. His answer is "impractical." He essentially says traveling at light speed, no matter what method means running into many meteoroids, and the smallest meteorite turns into nuclear blasts.
I think this is almost certainly the pre-Nanotechnology/Quantum Computer era answer. But, this problem running into even the smallest thing is too energetic is still a problem in the ultra high tech world of nanotechnology and quantum computers. Certainly, we don't see light speed ships zipping around through the cosmos. We should be able to see them.
There's an idea of folding space. I forget the authors name; but, it was noted that if one turns on this spacedrive and aims for a stellar system, well, you're fry the star system you just spacedrove to. You'd have to turn it off pretty far from the star system. So far out, you'd probably have to take a few years going the rest of the way at much slower non-Relativistic speeds.
Isaac Asimov's answer is, whatever Extraterrestrial Intelligences are out there, haven't been able to get much further than a couple of light years.
A couple of light years beyond their home-world.
DeleteOne more proof that our Solar System is an odd-ball
ReplyDeletehttps://blogs.scientificamerican.com/observations/a-trillion-worlds/
"The planets within a particular system tend to have very similar sizes (and masses) and tend to adhere to a geometric uniformity of spacing, much like the arrangement of peas in a pod."
Meaning, if the planets are say larger than the Earth, most other star systems planets are all of that same size. If they have seven planets, they all have the same size. Likewise for smaller star systems whose planets are smaller.
Certainly most star systems planets are either larger or smaller.
Our sun is an odd ball - https://www.sciencenews.org/article/sun-peculiar-makeup-compared-solar-twins
ReplyDeleteAppears our Sun is an oddball amongh sunlike stars. Our sun doesn't have all the heavy elements other sunlike stars do. For some reason the other sunlike stars absorb those heavier elements, while element differentiation occurred in our solar system.
yet another factor in support of Isaac Asimov's Rar Earth hypothesis - https://phys.org/news/2018-10-protoplanetary-disk-material-sparse-planet.html
ReplyDeleteHere, we see that a proto-planetary disk of sufficient density to make any planets is rare.
The Earth/Moon oddball theory strengthens - turns out that the essential life elements of the Earth . . . the abundance of them can only come from a moon forming impact.
ReplyDeleteStuart Kauffman's complexity theory says a diversity of elements is needed for life to self-organize as a complex whole. The following article shows that the abundance we see on Earth can only come from a Moon forming impact.
https://phys.org/news/2019-01-planetary-collision-moon-life-earth.html
And, as Isaac Asimov and Rare Earth hypothesis guys point out, a Earth/Moon system is improbable.
https://www.space.com/28901-wandering-jupiter-oddball-solar-system.html
ReplyDelete"Jupiter-like planets are uncommon — "only about 10 percent of sunlike stars host them," Batygin said."
What Konstantin means here, is only 10% of sunlike stars have Jovian planets much further out than the inner rocky planets. In other words, 90% of sunlike stars have "Hot Jupiters" - Jovian planets close in to the solar system where rocky planets should be. But, since a Jovian planet would throw out these rocky planets(or absorb them, or throw them into the parent star), those sun-like stars would not have Earths.
Factor in the need for a Moon, and that's like a very small percentage of sunlike stars that would even have life much less technological civilizations.
In yet more "Rare Earth" hypothesis findings -
ReplyDeleteA Limited Habitable Zone for Complex Life
Edward W. Schwieterman1,2,3,4,5, Christopher T. Reinhard3,4,6, Stephanie L. Olson3,7, Chester E. Harman4,8,9, and Timothy W. Lyons
https://phys.org/news/2019-06-narrows-advanced-life-universe.html - and, https://iopscience.iop.org/article/10.3847/1538-4357/ab1d52
"The habitable zone (HZ) is commonly defined as the range of distances from a host star within which liquid water, a key requirement for life, may exist on a planet's surface. Substantially more CO2 than present in Earth's modern atmosphere is required to maintain clement temperatures for most of the HZ, with several bars required at the outer edge. However, most complex aerobic life on Earth is limited by CO2 concentrations of just fractions of a bar. At the same time, most exoplanets in the traditional HZ reside in proximity to M dwarfs, which are more numerous than Sun-like G dwarfs but are predicted to promote greater abundances of gases that can be toxic in the atmospheres of orbiting planets, such as carbon monoxide (CO). Here we show that the HZ for complex aerobic life is likely limited relative to that for microbial life. We use a 1D radiative-convective climate and photochemical models to circumscribe a Habitable Zone for Complex Life (HZCL) based on known toxicity limits for a range of organisms as a proof of concept. We find that for CO2 tolerances of 0.01, 0.1, and 1 bar, the HZCL is only 21%, 32%, and 50% as wide as the conventional HZ for a Sun-like star, and that CO concentrations may limit some complex life throughout the entire HZ of the coolest M dwarfs. These results cast new light on the likely distribution of complex life in the universe and have important ramifications for the search for exoplanet biosignatures and technosignatures."
"New study darkens hope for Earth-like planets -
ReplyDeleteA new study examines if exoplanets get enough stellar radiation to support photosynthesis.
Many planets within the habitable zones of stars do not receive enough energy to support plant life.
Earth-like planets are probably very rare.
Since 1961, astrobiologists and others interested in finding extraterrestrial life have used the Drake equation to speculate on the possible number of technologically advanced alien civilizations in the Milky Way. By multiplying factors like the number of new stars in the galaxy per year, how many planets those stars have, the number of planets suited to life, and how long intelligent civilizations emit radio waves, one can get an estimate of how many other intelligent species are out there right now.
The problem is that the equation is almost entirely speculative because many of the factors have unknown values. But every once in a while, new information helps to narrow down the range of reasonable values to plug in.
Bad news for E.T. enthusiasts: a new study published in Monthly Notices of the Royal Astronomical Society offers a further narrowing of those values. By examining the conditions needed for photosynthesis, the authors propose that biospheres suitable for life might be rarer than we thought.
Let there be (a little more) light
The study's authors looked at what conditions are needed for the biochemical process that makes most life on Earth possible, oxygenic photosynthesis. By combining carbon dioxide with water and light, species capable of oxygenic photosynthesis produce sugar and oxygen. The latter is released as a waste product.
"The authors, like many before them, conjecture that photosynthesis is common throughout the galaxy on account of how much stellar radiation there is to collect, the (comparative) simplicity of the process, and the abundance of the other input elements.
DeleteUnlike others before them, they set out to see if any known exoplanets in the habitable zones of their stars actually got enough photosynthetically active radiation (PAR) — a term for solar radiation in the wavelength range between about 400 and 700 nm that most plants can use — to support life. By analyzing how much PAR known exoplanets are getting from their stars, the researchers were able to estimate which of them are getting enough stellar energy to have an Earth-like biosphere filled with photosynthesizing plants.
As it turns out, good real estate is hard to come by in the Milky Way.
Stars that burn at half the heat of the sun do not provide enough energy for a rich biosphere to ever arise. Red dwarf stars, which are small, numerous, and burn at about a third of the sun's temperature, were even worse. They couldn't provide the energy needed for much photosynthesis at all.
This is a particular issue for the search for alien life. As lead author Prof. Giovanni Covone of the University of Naples explained:
"Since red dwarfs are by far the most common type of star in our galaxy, this result indicates that Earth-like conditions on other planets may be much less common than we might hope. This study puts strong constraints on the parameter space for complex life, so unfortunately it appears that the 'sweet spot' for hosting a rich Earth-like biosphere is not so wide."
On the other end of the scale, very large and bright stars do produce enough light to drive photosynthesis. However, these stars also run out of fuel and either burn out or explode before advanced life would have a chance to evolve.
DeleteThe Rare Earth hypothesis
This doesn't mean that we are alone in the universe. While the study does suggest that the number of planets suitable for life is lower than we thought, the number is not impossibly small. The authors mention the existence of some planets, such as Kepler-442b, which do get enough solar radiation to sustain an Earth-like biosphere.
The study supports the argument known as the "Rare Earth hypothesis." It is, as the name suggests, the idea that planets like Earth — that is, planets that have the right combination of factors for complex life to evolve — are comparatively rare in the cosmos. (Those who object claim that life could evolve in ways unknown on Earth.)
The hunt will continue for alien life. Just don't get your hopes up."
I copy and paste this article in full, because the website I found it will probably go away, and it just keeps adding more and more material as you scroll; it's not the only article you find there
Delete