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Posts Tagged ‘John O’Keefe’

How likely intelligence?

Carl Sagan, the great scientific pagan of the mid-20th century, estimated that there must be at least 10,000 inhabited planets per galaxy. It would be ridiculous to think we had the universe to ourselves. He was very famous, and the number was repeated again and again.

Still — no sign of anyone else.

In 1965, Penzias & Wilson found the radio signal that Gamov had said would vindicate LeMaitre’s Big Bang and lock physics into a finite universe. The universe was not eternal; it had an age, and in consequence of its age, it had a finite dimension, somewhere between 1024 and 1027th meters. We had a universe size at last. Not perfectly definite, but fairly so. Not infinite. Not even as much as 30 billion light years in diameter. Probably 13 or 14 billion light years radius.

1027 * 1024 * 1021 galaxy size * 1018 * 1015 *

1012 * 109 sun size * 106 * 103 * 100 =1 people size

10-3 * 106 * 10-9 molecules * 10-12 * 10-15

Just at the turn of the century, Robert Jastrow of NASA wrote a book called God and the Astronomers, in which he acknowledged that this discovery had forced him to abandon a lifetime of atheism, and he invited his Catholic subordinate, John O’Keefe, to write an Afterword. O’Keefe had several interesting things to say, including a suggestion on how to approach the relative likelihood of other intelligent life. It could be very simple. If there were, say, 23 independent conditions for the development of intelligent life, and if each one had a 10% chance of turning up near a given star, then the chance of developing life in the universe would be 1/1023rd. That is about the number of stars in the universe. If the conditions were more likely, then we should continue to look around; if less, we’re probably alone.

This was much better than just by saying, “Gee, it’s awful big for just one human race.” Math is always nice; you can get somewhere.

In the 1990’s Ward and Brownlee came along with a book, Rare Earth, which listed all the known conditions for life, including very unexpected conditions such as tectonic plate motions. Many of the conditions were much less than 10% likely and they concluded that, yes, we might be the only ones.

The sense of human specialness was again on the march. It deepened as further consideration of the Big Bang – the explosion at the origin of the universe – showed that it had to have been incredibly specific in order to work – too intense and the universe would have blown to dust without forming stars, planets, or people – too slight and matter would have been recaptured by gravity before it had time to form stars, planets, or people. It was very, very special. The sort of exactitude its numbers required went to 51 decimal places, which is about what it would take to locate your nose within the solar system — the entire system, out to the furthest comets.

It began to look as if the intelligent radio signal had indeed been found, right there in the Big Bang, and it meant that our one intelligent companion was the creator.

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Even those pagans who don’t engage the fantasy of multiple universes are prone to imagine many “earths” at least. Most famously, Carl Sagan quoted an equation (doesn’t that sound objective and irrefutable: an equation!) according to which one should expect to find around 10,000 planets like earth – and therefore harboring intelligent life – in any galaxy such as the Milky Way. Many like him expected to find other intelligent life in short order. This was the 1980’s, and it was based on the Drake equation of the 1960’s.

We have not yet (in 2010) found intelligent life, and the search has been quite sophisticated.

What could be the problem?

In 1978, shortly before Sagan’s utterance, a different expectation was expressed in a small book called God and the Astronomers, by Robert Jastrow. It was part of a 30-page afterword written by John O’Keefe who had worked for Jastrow at NASA, and who was well-known as a believer, as a Catholic in fact. When Jastrow came to write out his new-found perception of the existence of God, he invited O’Keefe to add an essay, and it included a simple suggestion: O’Keefe said that if you thought of as few as 22 independent conditions for human life, and if each of them had about one chance in ten of turning up on a randomly chosen planet, then the chance of all of them turning up at once on a single planet would be 1022nd power, which is about one chance among all the stars of the universe.

The Afterword is a very interesting 30 pages, well worth reading in full, but here, from page 143, is the quotation I refer to:

For my part, I am not so sure that intelligent life exists on other planets. The basic argument for this view is that each star offers life an opportunity, and there are 1022 (ten thousand million, million, million) stars and planets in the observable universe. Even if the chance of life evolving is as small as, say, one in a million, still there must be millions upon millions of inhabited planets in the Universe.

Suppose, however, that twenty-two separate conditions must be met for intelligent life: the star must be single; it must produce visible and ultra-violet light; its planet must have an atmosphere that transmits light but not X-rays or extreme ultraviolet; there must be liquid water; there must be carbon; the star must live a long time; its output of energy must not vary rapidly; the planet must be in a suitable zone of distance from its star; it must have land as well as water; it must not suffer excessive and prolonged bombardment by meteorites; and so on.

These conditions would not be satisfied on every planet in the Universe. If each were satisfied on only one planet in ten, which is not an unreasonable estimate, then if the requirements are really separate, the chance of finding a planet with all 22 conditions satisfied simultaneously would be one tenth multiplied by itself twenty-two times, or 1/1022. This means only one planet in the Universe is likely to bear intelligent life. We know of one – the earth – but it is not certain that there are many others, and perhaps there are no others.

John O’Keefe, 1978

An interesting challenge…

Ward and Brownlee came along several years later (in 2003) with a fascinating book called Rare Earth, in which they showed that the series of requirements for intelligent life was probably considerably more extensive than Sagan had considered, and we might very well be the only intelligent life in the Milky Way, or even in the universe, just considering the problem statistically – how many stars, how likely that one would have planets the right size, the right distance, with water, with plate tectonics, without supernova interference during the development of life, and so forth. It was a direct response to Sagan and to the Drake equation. Brownlee was a friend of John O’Keefe and may well have been aware of his suggestion. In any case, Rare Earth is a very interesting read, and spells out some of the things O’Keefe mentioned as well as others that are quite unexpected. (Who thinks plate tectonics is essential to life?) I never counted exactly how many conditions are listed but several of them required planetary conditions that are much rarer than 10% of what’s out there. Here are some excerpts.

The following year, yet another book appeared: The Privileged Planet, by Guillermo Gonzalez (as well as a companion DVD by John Rhys-Davies) in which the theme of Earth’s uniqueness was taken still further. Gonzales stated that Earth was not only uniquely placed for the emergence of human life, but also uniquely placed for the study of the universe. For example, it is so placed that our moon perfectly eclipses our sun, enabling certain observations (in the corona) that would not be possible from any other vantage point in our solar system and would be rare in any case. This takes the concept of design one step farther – the universe was designed to give us life – and our universe home was designed to serve our curiosity!

Awesome!

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Of course thousands of things happened in geology in the 20th century, but two stand out as changing the whole approach to geology not just one particular detail. These two are plate tectonics and space geodesy. The first is a new and more comprehensive view of the Earth and its changes, based on the idea that whole continents move about on an underlying sea of convecting rock. The second is the vision and then the use of a new set of tools, specifically satellites that would look at the earth from above and, using camera and radio, send whole new images of everything we have ever seen or known or tried to map.

Plate tectonics

What makes mountains? The effort to answer this question had gone through a lot of changes by the twentieth century. Obviously some mountains are volcanic – but equally obviously to the thoughtful observer, others are not. Mount Monadnock – and all other monadnocks – are just fragments of high land, leftover after the erosion of everything else. They are not and never were volcanic.

Why didn’t they erode with everything else? Maybe there was an especially resistant stone formation at the top of a monadnock, such as the vast slab of pure quartz on top of South Pack Monadnock. But that’s not a common form. Other questions persist.

Why do mountains march in lines?

So many of our mountains are in lines and chains. Why is that? A line of mountains demands that the geologist look for the reason for the line, not just the reason for the mountain. That’s much more demanding. Even if it’s volcanic, why would a bunch of volcanoes be lined up? On the Moon and on Mars, they’re just random pock-marks. Why is Earth so different?

Kudos if you know the answer, but then ask yourself at what point in history might you have guessed it?

Could continents drift?

The concept that whole continents might be on the move, the concept of continental drift, is generally thought of as a 20th century idea, but it was first proposed in 1596 by Abraham Ortelius. Isn’t that a surprise! He was a Flemish cartographer, just 100 years after Columbus, and so he was basically one of the first men to compare the coastlines of the Americas with the matching coastlines of Europe and Africa. The match leaps to the eye, and he suggested that volcanism and floods had separated these vast lands. At a certain simple level, this is not far from the truth: continental rifting involves volcanism and can open interior lands to the nearby ocean; but notice that now we are talking about an extraordinarily extended line of volcanism – the mid-Atlantic rift. Look at it! Thousands of miles long! How does that happen?

MId-Atlantic Ridge/Rift

Here is the center of the Atlantic Ocean, assumed to be a plain until discovered to be quite otherwise!

The failure to find an explanation for such massive rifting prevented the acceptance and development of Vesalius’ idea for the next 300 years. Not for lack of effort! It was proposed that the interior of the earth was more dense than the outer crust (which is true) and that periodically the interior simply burst through original super-continent, breaking it up into the continents as we now know them.

Wrong.

Alternatively, it was proposed that the Earth gradually enlarged by consuming the ether, and this enlargement stretched the original continent and then pushed its pieces apart.

Wrong; almost funny. Note that such growth would change the gravity of the Earth and its relationship with the Moon.

The idea of a broken super-continent would have been dropped completely except that new evidences for a past closeness between the continents kept surfacing in things like similar fossils or similar stone and soil chemistry in precisely the locations that would once have been close if the matching coastlines were attached in ancient times.

From continental drift to plate tectonics

In 1912, Alfred Wegener marshaled all the evidence for continental drift and argued forcefully for it. The idea never went away again, but there was still no credible mechanism to drive the motion of entire continents. He even pointed to the Mid-Atlantic Ridge zone as a spreading zone, but there seemed to be no way for the continents to ride over the wide oceans, so he dropped it. He wasn’t seeing the continual generation of new ocean floor as part of the picture.

In 1928, Arthur Holmes suggested that convective motions in the mantle might drive the motions of the continents.

If you go to make oatmeal, jelly, or soup from soup bones – any cooking that involves an episode in which scum rises to the surface, — you have a chance to see how convection cells from the bottom of the pan drive little mats of surface material from side to side, occasionally joining them, occasionally breaking up a large mat. In the case of cooking, the scum is soon driven to the sides of the pan, but on the Earth, the bottom of the pan is the inside of the planet, and there are no sides. The mats of scum, the islands and continents, go from side to side and are occasionally driven all together, and later driven all apart.

So at least Holmes had a mechanism, but it seemed too far-fetched. The pressures on the mantle are very powerful and it is very rigid. And if ever the continents were driven together, why not stay that way?

Well, for one thing, there would be a build-up of heat below such a large continent, and that might soften it and start volcanism… Maybe.

But even aside from heat buildup, the convection cells which are carrying the continents change in size and orientation – convection cells are more or less random things – and when two cells are pressed together such that their upwelling centers draw near, the stress on the overlying land is such as to pull it apart. This is happening right now in Nevada, and is the cause of its extensive hot springs.

Still, continental drift was not accepted until the 1960’s. It was hard to imagine the convection of solid rock, no matter how hot. It was only when all the ocean floors were surveyed in detail in the 1950’s that deep-ocean ridges were found in every ocean and a new piece of evidence needed a home. Now the question changed from: could the Mid-Atlantic ridge be a spreading zone? to the question: why does every ocean have these ridges?

It was in answer to that question that Arthur Holmes’ suggestion finally took its proper place in geology and the slow, slow convection of the mantle, solid as it seems, was accepted.

We know, then, why mountains often form in lines and ranges. Mountain ranges are formed by the subduction of one tectonic plate below another and the resulting turmoil (long story for another day) along the line of contact.

Mars and the Moon don’t convect, and thereby hangs a tale.

Space geodesy

The second great shift in 20th century geological understanding was a matter of new tools, and was as fundamental as the invention of the telescope.

The basic difficulty about mapping the whole Earth so that you can really see these mountain ranges and their rivers, lakes, and other geology, is that it is so hard to measure great distances. You can walk across your garden with a tape measure; fine. You can, with a good watch and a good companion and good weather, time the difference between the moment that stars disappear behind the Moon in different locations. That can be translated into miles. And, once you have the instruments, you can even send mirror blinks from mountaintop to mountaintop and time them for distances, presuming that the mountaintops are not too full of vegetation to see or too glacial to climb or too full of wild animals or volcanic smokes to prevent access. No mountain will help you measure the Pacific, of course. Airplanes help, but you have to know your speed and direction, and so many things confuse that, jet streams for one.

So it’s difficult, you see.

But if you could go to the Moon and just calmly look down…?

No, the Moon is too far away to be much use.

But… If you had an artificial moon, a satellite that was just high enough to stay in orbit but just low enough to stay in good communication and take good pictures, that would really help. When John O’Keefe proposed this to the Army Map service after World War II, they thought it was ridiculous. But then they changed their minds and it happened. Satellites are totally a part of our world now, and what they have told us about everything from inaccessible mountain ranges, to magnetic anomalies is a crucial part of our comprehensive geological knowledge. Life without satellites seems like life in the stone age.

Ah, if  Mungo Park could have had just one such picture of the river he was surveying!

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