Although little known outside of his native France, Charles Cros (1842-1888) truly was one of the great visionaries of an age of visionaries. He has been described as a figure of transition between the reign of poetry and the patent. A well regarded of poet and writer of humorous stories on one hand and a creative inventor on the other. As an inventor, however, he may also be described as one of the unluckiest.

On the same day in 1869, Charles Cros and Louis Ducos de Hauron, without knowledge of one another sent news of their identical inventions of colour photography to the Société française de photographie. Cros' documentation of proof which had been lodged in a safety deposit box had predated Ducos de Hauron's by nearly a year (although both had been working on the subject for longer than that) but the latter had produced actual samples using this method. The two settled the matter on amicable terms but Ducos de Hauron is now considered to be the inventor of colour photography.

Nearly a decade later, in 1877, Cros presented to the Academy of Sciences a method for the recording and playing back of sounds using his new invention - the phonograph. Later that year, Thomas Alva Edison, demonstrates his own version of the same idea and successfully patented it in early 1878. Despite of Cros' protests, his contribution was once again forgotten.

One area where Cros is still remembered is with regard to his proposal for interplanetary communication. He presented to a conference in 1869, a "Study on the means of communication with the planets" in which he proposed a method of communication with the inhabitants of Mars and Venus. His idea revolved around using an extremely bright light concentrated by an array of parabolic reflectors (these days communication through space is achieved with radio waves but these are, after all, really the same thing). Images could be transmitted by breaking them up into individual pixels, either on or off, and then sending them a line at a time using an encoding that these days we would call run-length encoding.


A few years later he repackaged these ideas into a short story about an interplanetary communication that went horribly wrong. Once again Cros was a pioneer, this time in the field science fiction. Allow me to present for your reading pleasure and edification Un drame interastral by Charles Cros.

(French Speakers: I have a favour to ask of you at the end of the post)

The declaration of Ordinance 97 of the 32nd Grand Master of Terrestrial Astronomy raised a flurry of complaints by the goguenard party. Let me say right away that this party, though it is often furiously defended, calls to mind the wrongheaded beliefs of the free-thinkers that were in favour a few centuries ago. So much so that one fears seeing it going to same negative excesses which consequently would require same repressions.

The goguenards speak with a deep nostalgia for the darkness of the nineteenth and twentieth centuries. They proclaimed that the ordinance was a restoration of the clergies of former times, that it is a superstitious measure which had more to do with fantasy than what is essential to for the march of human progress.

It will be easy for me to reduce to nothing these vain complaints. First of all, it should be noted that this ordinance does not establish anything that has not already been in practice for many long years. It does nothing but summarise what has already existed in the regulations of almost all terrestrial observatories, or what has resulted from numerous decisions made by the Supreme Court.

Indeed, one would have to be unfamiliar with even the most elementary study of administrative law not to know the formalities required by all observatory councils with admission to observatories of correspondence. It is necessary not to have read any astronomical publication from this century to be unaware of the Code of the Observatory of which this much criticised ordinance is all about. The reality is that the Code is already commonly used and has been expressly employed in many official documents, some dating back a great many years.

This is the same set of regulations that applies to all astronomers who aspire to be promoted above the fourth level: obligatory celibacy, the swearing of an oath and the application of penalties, the severity of which vary in direct proportional to the seriousness of the transgression.

For many years applicants for promotion to higher levels have had to establish their condition of celibacy and their moral rectitude with documentary proof. These things have been de rigueur for quite a long time and Ordinance 97 simply serves to regularise practices that had been found necessary from the point of view of morals and policy. And here, the action of this ordinance, instead of tightening these practices, has made them more equitable and broader by preventing the abuse of certain draconian restrictions which had begun to creep into a number of astronomical programmes.

But I know that the goguenards will not be satisfied with these explanations. Such practices, they say, are bad and unjust, an abuse of power, etc.

For the latter question, which, by the way, proves immediately the ignorance and the thoughtlessness of those who raise it, I do not wish to enter into a discussion. I will simply restrict myself to telling the facts from awaken in our most primitive instincts the immediate recognition of the need for vigorous regulation, the same as did naturally prevail and which has just now been defined in Ordinance 97.


Perhaps one remembers about thirty years ago the sudden and unexplained retirement of a certain director at the Observatory of the South Andes and the noise that followed this retirement. One heard talk of criminal negligence and the violation of the Code of the Observatory, the word "code", incidentally, being precisely the one used in the newspapers of the time. The government wisely suppressed the story and the director, regretfully because of his very remarkable work on the flora of equatorial Venus, was allowed an early retirement, ostensibly for health reasons.

He's been dead now for many years, as are the majority of the interested parties, so let me relate the facts as they had occurred. I will not, however, be naming anyone.

This director, exceptionally even for the time, had married. To tell you the truth, he was a widower during his term but there remained to him a son of twenty two or twenty three years of age.

The young man who was endowed with a sharp mind, although almost undisciplined, had no taste for astronomical studies and much preferred painting and writing verse. He has left behind some well regarded verses of love poetry although they have a strangeness which is not very agreeable for those who, like me, do not much admire what are normally considered masterpieces inthe twenty fifth century. But let us return to our history.


The studies made by the observatory about Venusian flora were done by exchange with the inhabitants of Venus, i.e. it was necessary to transmit as many of Earth's flora types to Venus as one received in return. To achieve this transmission an enormous array consisting of three thousand reflectors, each one 50 centimetres in diameter, was used. It is known that this array, which resembled an immense eye of an insect, took 29 years to build and was said to be the most beautiful of its kind on the Earth. Viewed from the surface of Venus, the figures displayed on th array appeared at about a four-hundredth of their original size so that it was enough for the Venusian astronomers to enlarge the image themselves by four hundred times for them receive it at the correct size on their receiving devices.

One thus carried out the exchange of the Venusian and terrestrial botanical specimens, and the array was constantly pointed at the peak of a particular Venus mountain (the location of which is useless for me to indicate). The director, absorbed by the powerful interest of his research, had the idea, a rather unfortunate one we may say in retrospect, of using the assistance of his son for the fixing and classification of the photographs that were being transmitted to him.

He continued in this fashion for a while until eventually entrusting the young man with the task of direct observation with the eyepiece. This can be explained only by some kind of senile madness because later, at the time of the investigation, to justify such a serious lapse of memory with regard to the interplanetary conventions, our unhappy director's only excuse was the tiredness of his eyes at that time. But let us continue.

This grand botanical research occupied only half of the time of the transmission; other half was devoted to the current correspondence. The young man was thus placed in charge of all the processes of this correspondence and this was without studies, discipline, rank or oath!

The subordinate astronomers, perhaps more anxious about their own treatment than any concern for the social interest, or perhaps it was because of their practice, commendable in itself, of absolute respect and obedience to their director, these agronomists allowed this practice to go on with a word of protest. Later, as they told it in the investigation, the service of the correspondence was done under these irregular conditions in a very active and quite productive way.

To facilitate this account, I shall call the young man in question by the banal and common name of Glaux.

Glaux all of a sudden seemed to have taken to heart his ocular functions and he investigated every possible improvement that he could bring to the transmissions. It was he who was the first to put into practice many advanced techniques that had been previously been neglected or were thought to be purely theoretical or impractical. It was at this time that techniques were developed to enable the sending and receiving of audible phenomena, something with an arguable utility. It was said that we didn't understand anything about Venusian music and that, as for the spoken words, we would only be able to pronounce them using a mechanical articulator. We could learn to speak Venusian, added another, but it would be a waste of our time except perhaps in the obviously absurd case of space travel.

These were, in my opinion, objections born of acrimony. But let me continue.

Where did this sudden astronomical zeal come from? The cause should have been easy enough to see if only normal habits these astronomers hadn't caused them to regard as strange or impossible one of the most natural things in the world. In truth, science progressed faster than sense or reason.

Here is what had happened.

One day Glaux, having finished the day's transmission, was about to take his leave when he saw, walking out upon the terrace of the Venusian observatory, a being which he did not recognise as one of the personnel up there.Taking account of the distinctions and the restrictions in our scientific understanding, I will say, to keep it simple, that this being was a woman.

Here my task of narrator becomes difficult (it would have been impossible had not Ordinance 97 defined the restrictions of the press laws precisely). Thus for legal reasons, and I will relate only the essential facts and be temperate with the details.

It was thus a woman. Glaux, his curiosity piqued, observed her movements. She moved with an idle gracefulness and this is to say nothing of her extraterrestrial beauty. Her attractiveness was such that even the vision of one of our most sumptuous flowers would give only a dull and pale idea... Only astronomers inducted into the eleventh level are informed precisely of these matters and by means other than a mere description of words.

But so it was that she appeared on the terrestrial apparatus of correspondence and stood there.

Glaux transmitted a greeting as one does at the beginning of a correspondence and she answered it directly by repressing, what one could call under the terms of a legitimate analogy, a burst of laughter. These details are known to us from a journal of prose and verse that Glaux left.

After exchanging some symbols, Glaux saw with surprise that she was perhaps more fluent than he with the interstellar language and the dialogue continued.

But the Earth and Venus turned and the refractions of their atmospheres began to scramble the images and allow nothing more than the symbol repeated several times: Tomorrow!


It was from this day that one saw Glaux putting such zeal and ingenious activity into his functions as correspondent. Did he conceive of by himself these marvelous innovations which we now take for granted and still use to this day? Or did he learn of them through communication with her? Were they perhaps indiscretions, most advantageous for us, of the young Venusian not terribly concerned, as so often is the case with women, to carefully guard the scientific secrets of her planet.

One may assume thus that by now the two young people had fallen in love with one another. What madness! What a deplorable consequence of the non-observance of the regulations!

They believed they were able to overcome the distance which separated them by exchanging the most complete outlines of their persons. They exchanged a stream of photographs of themselves sufficiently large as to allow the recreation of their shapes in three dimensions and their movements.

Glaux, during the hours when the observatory was closed, locked himself up in a room and reproduced onto a medium of smoke or fine particles the moving image of his beloved made of nothing but the impalpable substance of light itself. He also sculpted her motionless form in clay.

At this point in time it is imagined that they began to send the sound of their voices, their words and their songs. These oscillations were recorded as mathematical curves and reproduced by an electrical device that employed tuning forks...

All that I have said with due brevity continued for three years.

The third year was terrible, a turbulent storm of rapture and despair... Could one have saved the foolish pair at this time by drastic measures? It is doubtful, the damage by now had already been done.

One evening when our own twilight corresponded to the twilight of that Venusian country, the two lovers resolved to bring it to a end. Glaux and the girl exchanged a final kiss through the relentlessness of space and then they took their own lives.

The tragedy failed to compromise the good relations that existed between the two planets because the Venusian young lady that we have been discussing was the daughter of one of the most powerful astronomers up there. It was then that the precise conventions governing interplanetary relations were concluded. Ordinance 97 ratified these conventions on the Earth so that misfortunes such as these would never be repeated. All of the papers, photographs, photosculptures and phonographies of Glaux were deposited in the central archives were it is necessary, as I have mentioned before, to be of the have an eleventh level clearance in to obtain access to them.

In spite of what I have just told you, with official authorisation, it doesn't concern me that the goguenards continue to deny the benefits of Ordinance 97.

This animation is based on photographic plates taken of the Transit of Venus in 1882 by David Peck Todd at Lick Observatory in California [more]

Staying with the Venusian theme, the planet will transit across the face of the sun tomorrow.

While the earth, sun and Venus line up quite regularly (every eight years in fact) Venus only travels across the sun's disc (i.e. transits) twice every 121.5 years. Normally it passes either above it or below it. While this event will be completely invisible over the Americas it will observable over the entire African and Eurasian landmasses where the vast majority of humanity resides. If it's a sunny day tomorrow, I'll be outside after 3pm (eastern Australian time) trying out the pinhole lens approach. If not I'll be checking out one of the many webcams: from Iran (1); from Iran (2); from Iran (3); from the Canary Islands; from the Netherlands; from Denmark; from Turkey; from Greece; from Hong Kong; from Norway; from Australia; from Sweden; from Macao (near Hong Kong); from India; from Brazil; from Earth orbit; from GONG.

Obligatory warning: Don't look directly at sun, kids. It's really, really bad for your eyes.

In years past this event held considerable interest for astronomers because Edmund Halley (the one for which the comet is named) produced a paper demonstrating that the transit was a particularly useful event because it could be used to determine the precise distance between the earth and the sun. By measuring the times that this event occurred at two distantly placed points on the earth, the distance to the sun could be calculated geometrically using a process of triangulation. Students of Australian history will no doubt recall (unless they were home sick that day) that observing the transit of Venus from Tahiti was James Cook's primary mission for his voyage across the Pacific (his secondary and top-secret mission was to chart the hitherto unknown east coast of the Australian mainland).

Why was important? It was needed in order to calibrate Kepler's Third Law, i.e. the period of a planet's orbit is equal to the cube of its radius from the sun (actually this was its average radius because Kepler also knew that planetary orbits are elliptical rather than purely circular). By knowing, as we now do, that the average radius of the earth's orbit is about 150 million kilometres and that its period is 365.25 days, we can easily calculate the size of the solar system and the distances between all of the planets solely from the periods of their orbits.

Unfortunately for Cook and others, the exact timing of the start and end of the transits was obscured by an optical effect know as the black-drop effect caused by refraction in our atmosphere. This experimental uncertainty greatly reduced the usefulness of the transit of Venus and the correct distance was eventually found by a different route, by calculating the speed of the planet earth in its orbit from an anomaly known as the aberration of starlight.

More recently this figure has been refined to a very accurate degree through the use of radar.

(tip o' the hat to Pete)

Update:

Well the pinhole approach was a complete failure in Melbourne's feeble winter sunlight but Peter did a remarkably good job with a pair of binoculars (following the method outlined here). This image was taken from Melbourne at 6:40 am UTC
while this quite similar picture wasn't taken until 9:16 am UTC at the Nehru Planetarium in Mumbai.

While studying the ripple patterns laid down when the universe was just 380,000 years old, Astronomer Mark Whittle of the University of Virginia realised they could be interpreted as sound waves. He condensed the patterns the first million years, compressed to 5 seconds down to five seconds, and boosted them up 50 octaves to fall within the range of human hearing.

One of the most impressive developments in modern cosmology has been the measurement and analysis of the tiny fluctuations seen in the cosmic microwave background (CMB) radiation -- the omni-directional wall of hot glowing gas which dates from when the universe was only 400,000 years old. When discussing these fluctuations, cosmologists frequently refer to their acoustic nature -- sound waves move through the hot gas and are seen as peaks and troughs when they cross the glowing wall. As is now well known, the most recent observations (culminating with the February 2003 WMAP results) quantify the amplitudes of these waves, revealing both a fundamental tone and several harmonics, whose relative strengths have played a key role in determining a number of fundamental cosmological parameters. Not surprisingly, these recent results have wonderful pedagogical value in educating and inspiring both students and the wider public, and indeed many excellent non-specialist articles have already been written about the CMB. To further enhance this opportunity to communicate the field, I have attempted what might seem rather obvious: to reproduce the CMB power spectrum as an audible sound, preserving both volume and sound quality while shifting the frequency up by the necessary 50 or so octaves to bring it into the human range. By choosing the fundamental to fall at 200 Hz (matching its harmonic "l" value), the resulting sound is a rather loud hissing roar, of about 90 decibels volume.

Matching the progress in observational results has been an equally impressive development of the theoretical treatment of CMB fluctuations, culminating in highly sophisticated computer simulations which can accurately reproduce the observations, once the various fundamental parameters are set. Using these simulations it is possible to recreate the sound generated by various types of universe with, for example, different curvature (yielding sounds of different pitch) or different baryon content (yielding different higher harmonics). Pushing further, one can generate the "true" sound, characterized by P(k), rather than the "observed" sound, characterized by C(l). From P(k), we learn that the fundamental is offset from the higher harmonics, yielding a chord somewhere between a major and minor third. Finally, tracking P(k) forward in time one can listen to the development of cosmic sound from the Big Bang, through recombination, and beyond. This sound sequence can be loosely described as a descending scream, changing into a deepening roar, with subsequent growing hiss, nicely matching the increase in wavelengths caused by universal expansion, followed by the post recombination flow of baryons into the small scale potential wells created by dark matter. This final sound, of course, sets the stage for all subsequent growth of cosmic structure, from stars (hiss) through galaxies (mid-range tones) to large scale structure (bass notes).

Although popular presentations of CMB studies already make use of many visual and conceptual aids, introducing sound into the pedagogical mix can significantly enhance both the intellectual and the emotional impact of the subject on its audience, without sacrificing scientific honesty.

Water exists in abundance on the planet Mars but all of it is locked up in the polar ice caps or is buried deep below the surface. In 2000, photographs coming back from the Mars Global Surveyor spacecraft, which has been orbiting the planet since 1997, caused a sensation because they provided the first evidence that water may also exist in a liquid form close to the Martian surface and might at times actually erupt from the ground and run in torrents down its mountain slopes. These Martian rivers would be short lived because water in its fluid state cannot exist for long on the Martian surface without either freezing in the incredible cold or rapidly boiling off into the thin atmosphere. However evidence of the possibility of liquid water excited many scientists because of what this could mean for the likelihood of life in or around these underground bodies of water. The idea of water bubbling to the surface, somewhat like geysers, has been described as the soda fountain view of Mars.

There are some problems with this theory, however. Chief amongst them is the fact that these ice thaws have not been observed in the equatorial regions but only towards the southern pole with latitudes of around thirty degrees of more. This is a region where the surface temperature rarely rises above -50 degrees centigrade (and is oftentimes much colder than even that) which raises the question of how this thawing could even occur. Volcanic activity as a heat source seems unlikely, it is thought to ceased at least a hundred million of years ago however there is still the possibility that remnant pockets of vulcanism do still exist on the planet.

An alternative suggestion is that these river-like erosion features are not caused by liquid flows at all but are instead caused by landslides of dry sand. This theory has been rejected in the past because, it is argued, grains of dust simply do not flow like a liquid. Troy Shinbrot of Rutgers University challenges this view and has been conducting experiments that demonstrate that if you take into account Mars' much weaker gravitational field and its much thinner atmosphere, things can behave very differently. In fact, in a low gravity environment sand does indeed flow like a liquid and can do so over long distances. In experiments using synthetic grains made from hollow spheres he claims been able to simulate most of the visible features of these Martian flows.

Over the past decade or more, contradictory evidence of Martian climate, indicating that surface temperatures seldom if ever approach the melting point of water at midlatitudes, and geomorphic features, consistent with liquid flows at these same latitudes, have proven difficult to reconcile. In this article, we demonstrate that several features of liquid-erosional flows can be produced by dry granular materials when individual particle settling is slower than characteristic debris flow speeds. Since the gravitational acceleration on Mars is about one-third that on Earth, and since particle settling speeds scale with gravity, we propose that some (although perhaps not all) Martian geomorphological features attributed to liquid flows may in fact be associated with dry granular flows in the presence of reduced gravity.

A number of recent studies have investigated evidence for liquid water on Mars. Much of the available evidence has concerned recent, or even contemporary, geomorphological features, such as eroded channels and gullies that are common signatures of terrestrial water flow. This evidence is difficult to reconcile with surface temperatures on Mars, which seldom exceed 50°C at latitudes and locations where these features are often found. This paradox persists despite recent Mars Rover data supporting the case for ancient surface water. Several authors have proposed possible resolutions to this contradiction, notably a recent analysis suggesting that some liquid-like flow features in Martian gullies may instead be associated with dry granular flow. In this article, we observe that gravity on Mars is 38% that on Earth, and behaviors of dry grains at reduced gravitational acceleration have never, to our knowledge, been catalogued. As we will show, reduced gravity has the effect of prolonging fluidization of particle flows by decreasing particle settling speeds as compared with debris flow speeds. We present data demonstrating that many features that have been attributed to liquid flow in Martian gullies can indeed be reproduced in terrestrial laboratory experiments designed to mimic reduced gravity...

Unfortunately the paper is password protected at the Proceedings of the National Academy of Sciences site but it is possible to see a text-only version of it via this Google cache.

Just a reminder that we could all be paying more attention to the Cassini-Huygens space probe right now.

Busy again. No futher updates until the 1st of October. Thanks for reading.

Le château des Pyrénées (1959), René Magritte

Some very nice and interesting images of the Transit of Venus may be found here.