A Place to Stand

   The very estimable Matt Ridley (of whose articles more later) has this on the improbability of our Moon and its influence on making Earth more suitable for life:

David Waltham, of Royal Holloway, University of London, is the author of the very readable Lucky Planet, which argues that the Earth is probably rare, perhaps even unique, as planets go. He is also a self-confessed “moon bore” who has made important discoveries about how the Moon formed.

Ever since Copernicus, the “mediocrity principle” has been scientific orthodoxy: that our planet is not the centre of the Universe; it’s just one of (as we now estimate) a thousand billion billion spherical objects of similar size orbiting fiery suns just like ours.

But in that case, as the nuclear physicist Enrico Fermi famously asked, where is everybody? Why no faint radio messages from our distant neighbours in space? There should be enormous numbers of planets that have been around for longer than us, long enough surely to get to the point of transmitting some interstellar Muzak. Yet not a peep.

Dr Waltham points out that planets where life fails to survive cannot give rise to sentient life forms, so we are bound to find ourselves on one that has managed to be just right. Precisely because we are afflicted with this severe case of observational bias, the mediocrity principle need not follow. We can be misled by what we can see around us into thinking our case is typical, when actually it might be almost impossibly rare. We might be neither special nor commonplace, just lucky.

And indeed, there does seem to be a long string of coincidences behind our existence. The pressure of anti-gravity in our universe happens to be very, very small — not quite big enough to blow the Universe apart before stars could form. Phew. The relative strength of nuclear and electrical forces is just right to allow carbon to be one of the commonest elements, and carbon’s capacity to form lots of bonds is crucial to life. Cheers. The strength of molecular bonds is just right to allow chemistry to happen at our distance from the Sun. Hooray.

Then there’s the climate. Although there were probably at least four times when the Earth came close to freezing altogether or overheating irreversibly, it somehow recovered each time, unlike on Venus or Mars, and for the last half billion years the weather has been astonishingly benign. Periodic catastrophes, caused by volcanoes or meteorites, have set the evolution of life back, but not often enough to prevent intelligence emerging eventually: another stroke of luck.

Spookily, the slow waxing of our Sun’s strength over four billion years should have produced a ten-degree rise in average temperature, but it has not because it has been almost precisely matched by a slow decline in our greenhouse effect as carbon dioxide became progressively scarcer. This has kept the temperature in a small range for a very long time — long enough once again to allow the emergence of intelligent life. (The recent uptick in carbon dioxide levels as a result of fossil fuel burning is still small in comparison.)

Waltham posits three possible explanations for these great strokes of good fortune: God, Gaia and Goldilocks. God does not show His workings; Gaia says living things themselves somehow unwittingly control the thermostat; and Goldilocks says it’s just an almighty fluke that we’ve managed to keep things neither too hot nor too cold, but just right.

.... the Moon stabilised the rate and angle of our spinning such that we got a fairly long day and regular seasons to keep warming the poles and preventing the irreversible growth of ice. What Waltham has discovered, however, is that this was an even bigger lucky strike than we used to think.

Had the Earth’s day been a few minutes longer just after the collision, or the Moon’s diameter a few miles greater, then the Earth would have had an unstable spin and life would have been repeatedly wiped out by chaotic climate change. If the day had been shorter or the Moon smaller, then we would have had more and longer ice ages, because too little heat would have reached the poles through air currents.

Very few planets indeed could have collided with an object the right size to produce such a moon and even fewer of them would have ended up with a Goldilocks moon that was just the right size. Since life cannot control the Moon’s orbit, Gaia cannot explain this piece of luck. The Moon therefore shows decisively just how hard it will be to find another planet of sufficiently stable climate to spawn life that could last long enough to develop intelligence.

Waltham has persuaded me that we are “perhaps the luckiest planet in the visible universe”, the only one among billions of billions to have thrown six after six whenever the dice were rolled. Whichever planet achieved this would have thinking beings on it who would think they were special, whereas really they were just lucky. And they would be alone, or very nearly so.

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   This is a fascinating subject, and important for anybody who thinks life the universe and everything are important. I have written before on why we appear to be alone in the universe and come up with another explanation other than God, Gaia or Goldilocks - "the Everett-Wheeler Multiverse theory in which every single unpredictable possibility of every quantum movement of each atom in the universe creates a new universe every instant. Even though the overwhelming majority then reunite with the next quantum movement, it does produce a number of possible universes for which the word infinite is inadequate. However it does mean that it is inevitable that there will be a universe where we evolved and obviously that it is going to have the unusual conditions allowing us to evolve. This is what we see.

Indeed for the more mystically inclined one can combine this multiverse with its meta-infinity of uninhabited universes with Schroedinger (and his cat’s) view that a quantum event only achieves actuality when it is observed by assuming that our universe became real (whatever that means) when we evolved to be aware of it and that the uninhabited ones are merely quantum fluctuations.

Either option is possible; it’s the traditional random mechanistic universe that is unbelievable. "
Also on Panspermia - theory that life started elsewhere but only developed beyond the microbes(propagated across the universe by light pressure) on this planet & possibly others, because it is hospitable.

Life first appeared on Earth almost as soon as the surface cooled which suggests either that the actual formation, rather than getting complex, is comparatively easy or that it came from elsewhere.

In 2009 I referred to this as the Craig Paradox (ripping off the term Fermi Paradox).

A much more recent benefit (one which would only have shortened our development by thousands rather than billions of years, so not important except to those primarily concerned about human timescales) is that the regularity of the phases of the Moon brought a mathematical order to early Man's universe which was certainly vital to developing mathematics (see the Antikythera Device) and possibly to the entire concept of a rational universe.

  The Moon looks a pretty good explanation for our uniqueness. Apart from the stabilisation of our orbit, the high and varying tides give a very good mechanism for evolution to put life on land. Tides vary because of the mixture of force from the Sun and Moon which sometimes work together to create high tides and sometimes counteract. This means that there is consistent evolutionary pressure for life to be able to survive on the shore for periods varying up to 2 weeks waiting for the tide to rescue them. Life that can live on land for 2 weeks is close to being able to live there forever.

   Another possibility is that it is lunar tidal pull that has kept the Earth's magma mobile and molten. If so this produces 2 gains - (1) continental drift which means we have many small continents with more equitable weather and with nutrients being replaced (2) volcanic outgassing produces excess CO2. On several occasions the planet has come close to being covered by ice (in one case probably more than close). It is assumed that this was reversed by outgassed CO2 increasing, with no plant life to consume it, till it increased global temperature enough to melt the ice. Without that an iceball Earth would have been stable. If, without a Moon, we would have had no liquid core we have no volcanoes.

   So without this big a Moon no advanced life. Nobody really has a good explanation of how the Moon came about - best is that it was hit by a Mars sized comet and bits knocked into orbit, but that doesn't fit well either. So whatever the explanation for our Moon it must be incredibly unlikely.

  Therefore we are incredibly unlikely. Fortunately we live in an Everett infinite multiverse where everything, no matter how unlikely, has happened. But perhaps only once per Universe.