40 BILLION EARTHS? Yes & NO.

Abstract: Habitable does not mean inhabited. And habitable does not even mean inhabited by bacteria. Earth’s advanced life barely survived many disasters. Advanced life on Earth may well be a miracle, as so many dangers lurk in the galaxy. So a profusion of water bearing planets and satellites ripe for colonization by humanity does not imply a zoo of little green persons out there. The evidence points in the opposite direction. 

Up to twenty years ago, a reasonable opinion among scientists was that there might be just one solar system. Ours. Scientists like to project gravitas; advocating the potential existence of a profusion of planets with little green men all over didn’t look serious. Cardinals held the same opinion, five centuries earlier, and burned Giordano Bruno for suggesting that stars had planets with intelligent life on it, as the shocking concept seemed to compromise the special relationship between humanity and divinity.

However, studying delicately the lights of stars, how they vary in intensity, how they doppler-shift, thousands of planets have been found… most of them very strange (maybe because of our present observational methods). Solar systems seem ubiquitous… But NONE of them like ours… And our own Sun is gloriously alone, not in a cluster. Astronomers reported in 2013 that there could be as many as 40 billion habitable Earth-size planets in the galaxy. Suddenly wisdom had gone to the far side. However, as I said, our solar system is special, in more ways then one, as far as we can see, so far… And consider this frightening sight:

A really big bang deleterious to life: Centaurus A: Lobes Of Tremendous Black Hole Explosion Are Fully Visible

Yes, that’s the center of a galaxy, and it has experienced a galactic size explosion from its central black hole. Giant  black holes at the core of giant galaxies regularly suffer giant explosions, making probably the central zone of giant galaxies unsuitable for animal life.

One out of every five sun-like stars in our galaxy has a planet the size of Earth circling it in the Goldilocks zone, it seems — not too hot, not too cold — with surface temperatures compatible with liquid water. Yet, we have a monster black hole at the center of our giant galaxy,  just like the one exploding above.

The Milky way’s black hole is called Sagittarius A*. It exploded last two million years ago. Early Homo Erectus, down south, saw it. The furious lobes of the explosion are still spreading out, hundreds of thousands of light years away.

We are talking here about explosions potentially stronger than the strongest supernova by many orders of magnitude (depending upon the size of what’s falling into Sagittarius. By the way, a large interstellar cloud is just heading that way, and astronomers hope to see fireworks soon, just like an avalanche makes sparks, but on an immensely greaters scale).

Such galactic drama has a potential impact on the presence of advanced life. The richer the galaxy gets in various features with potentially catastrophic developments, the lower the probability of advanced life to flourish. Reciprocally, the metallic content of stars has to be enough to develop life. Metals are found closer to the center of galaxies. Hence the galaxy itself is endowed with a potentially inhabited-with-indigenous life zone (generally labelled by the misleading “habitable” adjective; the main point of this present essay is the distinction between planets that humanity could colonize, and planets harboring advanced indigenous life; anything with a brain is advanced).

The profusion of potentially habitable planets is all the more remarkable, as the primitive methods used so far require the planet to pass between us and its star.

(The research, started on the ground in Europe, expanded with dedicated satellites, the French Corot and NASA’s Kepler spacecraft.) Sun-like stars are “yellow dwarves”. They live ten billion years. Red Dwarves live much longer (giving more time for life to evolve)

From that, overlooking the distinction between “habitable” and “inhabited“, the New York Times deduced: “The known odds of something — or someone — living far, far away from Earth improved beyond astronomers’ boldest dreams on Monday. “

However, it’s not that simple.

Primitive bacterial life is probably frequent. However advanced life (animals) is probably very rare, as many are the potential catastrophes which would set life backwards. The case of Earth shows that one needs billions of years to go from primitive life to the creation of animals.

After life forms making oxygen on Earth appeared, the atmosphere went from reducing (full of strong greenhouse methane) to oxidizing (full of oxygen). As methane mostly disappeared, so did the greenhouse. Earth froze, all the way down to the equator:

When Snowball Earth Nearly Killed Life

Yet volcanoes kept on belching CO2 through the ice. That CO2 built up above the ice, caused a strong greenhouse, and the ice melted. Life had survived. Mighty volcanism has saved the Earth, just in time.

That “snowball Earth” catastrophe repeated a few times before the Earth oxygen based system became stable. Catastrophe had been engaged, several times, but the disappearance of oxygen creating life forms had been avoided, just barely.

Many are the other catastrophes we have become aware of, that could wipe out advanced life: proximal supernovas or gamma ray explosions.

Cataclysmic eruption of the central galactic black hole happen frequently. The lobes from the last one are still visible, perpendicularly high off the galactic plane.  The radiation is still making the Magellanic Stream simmer, 200,000 light years away. Such explosions have got to have sterilized a good part of the galaxy.

In 2014 when part of the huge gas cloud known as G2 falls into Sagittarius A*, we will learn better how inhospitable the central galaxy is for advanced life.

Many of the star systems revealed out there have surprising feature: heavy planets (“super Jupiters“) grazing their own stars. It’s unlikely those giants were formed where they are. They probably swept their entire systems, destroying all the rocky planets in their giant way. We don’t understand these cataclysmic dynamics, but they seem frequent.

Solar energy received on Earth fluctuated and changed a lot, as the Sun itself changed. Maybe the energy received from the Sun doubled over the last five billion years. But, as it turned out, just so, that Earthly life could survive. Also the inner nuclear reactor with its convective magma and tectonic plates was able to keep the carbon dioxide up in the air, just so.

This looks like a double miracle, and maybe, it’s all what it is. If it’s really a double miracle (that is the square of two very low probabilities), advanced life could be very rare, indeed.

The Goldilocks zones, the habitable zones, that astronomers presently consider seem to be all too large to allow life to evolve over billions of years. They have to be much narrower and not just for those around red dwarves.

Red Dwarves are (by far) the most frequent and long living stars. But they seem prone to X Ray flaring, inimical to life as we can imagine it, and possibly eroding planetary atmospheres.

One of our Goldilocks, Mars, started well, but lost its CO2 and became too cold. The other Goldilocks, Venus, suffered the opposite major technical malfunction: a runaway CO2 greenhouse.

Mars’ axis of rotation tilts on the solar system’s plane enormously: by 60 degrees, over millions of years. So Mars experiences considerable climatic variations over the eons, as it goes through slow super winters and super summers (it’s imaginable that, as the poles melt, Mars is much more habitable during super summers; thus life underground, hibernating is also imaginable there).

Earth’s Moon prevents this sort of crazy hyper seasons. While, differently from Venus, Earth rotates at reasonable clip, homogenizing the temperatures. Venus takes 243 days to rotate.

It is startling that, of the four inner and only rocky planets, just one, Earth has a rotation compatible with the long term evolution of advanced life.

Earth has also two striking characteristics: it has a very large moon that store much of the angular momentum of the Earth-Moon system. Without Moon, the Earth would rotate on itself once every 8 hours (after 5 billion years of braking by Solar tides; the braking by Moon tides is much stronger).

The Moon used to hover at least ten times closer than now, when Earth’s days were at most 6 hours long.

The tidal force is the difference between gravitational attraction in two closely separated places, so it’s the differential of said attraction (which is proportional to 1/dd; d being the distance). Hence the tidal force is inversely proportional to the cube of the distance.

Thus on early Earth tides a kilometer high were common, washing back and forth every three hours. a hyper super tsunami every three hours, going deep inside the continents. Not exactly conditions you expect all over the universe.

Hence biological material fabricated on the continental margins in shallow pools  would get mixed with the oceans readily. That would guarantee an accelerated launch of life (and indeed we know life started on Earth very fast).

Acceleration may imply existence, though: life, once started for real, is very adaptable. So the tremendous mixing of the kilometer tides may be a necessary condition for life!

If such is the case, it goes without saying life is exceedingly rare. (I’m exaggerating the point a bit here; yet, it’s entirely possible that the tides made the difference between bacterial life in a few dozens of million years, and having it in a few billions. Incubators where life starting processes are engaged work better with mixing.)

The theory of formation of the Moon is wobbly (recent detailed computations of the simplest impact theory do not work). All we know for sure, thanks to the Moon rocks from Apollo, is that the Moon is made of Earth mantle materials.

Somehow the two planets split in two. (Fission. Get it? It maybe a hint.)

Another thing we know for sure is that Earth has, at its core, a giant nuclear fission reactor, keeping Earth’s  core hotter than the surface of the sun. An unimaginable liquid ocean of liquid iron deep down inside below our feet undergoes iron weather. Hell itself, the old fashion way, pales in comparison.

Could the Moon and the giant nuclear reactor have the same origin? This is my provocative question of the day. The Moon, our life giver, could well have formed from giant nuclear explosions, of another of our life givers, what became the nuke at the core. I can already hear herds of ecologists yelp in the distance. I present the facts, you pseudo-ecologists don’t decide upon them. It’s clear that nuclear fission is not in Drake equation: if nothing else, it’s too politically incorrect.

All the preceding makes this clear:

Many are the inhabitable planets, yet few will be inhabitated by serious denizens.

This means that the cosmos is all for our taking. The only question is how to get there. The closest stars in the Proxima, Beta and Alpha Centauri system are not attainable, for a human crew, with existing technology.

However, if we mastered clean colossal energy production, of the order of the entire present energy production of humanity, we could get a colony there (only presently imaginable technology would be fusion).

Giordano Bruno, professor, astronomer, and priest suggested that there were many other inhabitated systems around the stars. That insult against Islam Christianity was punished the hard way: the Vatican, the famous terrorist organization of god crazies, put a device in Giordano’s mouth that pierced his palate, and having made sure that way that he could not tell the truth, the terrorists then burned him alive. After seven years of torture.

The horror of truth was unbearable to theo-plutocrats.

Now we face something even worse: everywhere out there is very primitive life. It is likely gracing 40 billion worlds. But, if one has to duplicate the succession of miracles and improbabilities that made Earth, to earn advanced life, it may be just here that civilization ever rose to contemplate them.

Congratulations to India for launching yesterday a mission to Mars ostensibly to find out if there is life there (by finding CH4; while life is presently unlikely, Mars has much to teach, including whether it started there). That’s the spirit!

The spirit is to have minds go where even imagination itself did not go before.

If we sit back, and look at the universe we have now, from Dark Matter, to Dark Energy, to Sagittarius, to the nuclear reactor below, to billions of Earths, to a strange Higgs, to Non Aristotelian logic, we see a wealth, an opulence of possibilities inconceivable twenty years ago.

Progress is not just about doing better what was done yesterday. It’s also about previously inconceivable blossoms of entirely new mental universes.

***

Patrice Ayme

Tags: 40 Billion Earths, Habitable Zone, Kilometer Tides, Mars Tilt, Planets, Sagittarius A*, Snow Ball Earth