Thursday, October 3, 2019

c. 1600 - An Interesting Confluence


c. 1600 – An interesting confluence
I have been a casual collector of rare and scarce books and other items from the early days of science. Among my most treasured acquisitions is a facsimile copy of Tycho Brahe’s 1573 publication “Novae Stella,” (New Star), published in 1901 and dedicated to the King of Belgium. Brahe did not subscribe to the new Copernican ideas of the sun-centered solar system but he was the last of the great naked eye astronomers and a superb observer of the skies. His observational data were impeccable and accurate for the time. Poor Kepler, his impecunious assistant, was forced to steal this observational data in order to have grist for his brilliant work in developing the laws governing the motions of the planets around the sun.

Below are two pages from this 1901 facsimile.

 
 


Remarks that Kevin Brown wrote in his encyclopedic work, “Reflections on Relativity,” involving Brahe are worth repeating. Much of what follows is centered on Tycho Brahe and his, one might say, unconscious role in the history of England and the dawn of modern science. What follows is tangled but is indeed a confluence of events.

John Craig, an advisor to King James VI of Scotland, later King James I of England, once made a remark to John Napier that turned Napier’s attention back to the task that resulted in his momentous discovery of logarithms. Maestlin, Kepler’s math tutor at Tubingen, once jokingly cautioned him not to use logarithms for his calculations – it would be cheating for a scientist to take a short cut in doing multiplications and divisions of large numbers.

The story as Brown tells it finally centers on James and his journey in 1590 to Denmark to escort his bride, Anne of Denmark, back to England. A fierce storm forced them to take shelter in Brahe’s Uraniborg observatory on the island of Hven. It is conjectured that William Shakespeare used the news of this occasion as inspiration for his play "The Tempest” (c, 1611), one of the only two of his productions having an original plot. Suggestive are the presence of Rosencrantz and Guildenstern as two minor characters in his earlier play “Hamlet” (c. 1600), the play that suggests the connection to the above interpretation. These same names, family antecedents, occur in Brahe’s head dress band in one of his portraits. Brahe was related to a great many of the titled figures in Danish history. Some scholars have conjectured that Shakespeare had an island in the Mediterranean or perhaps Bermuda itself in mind. Surely, given the strong public awareness of the events of King James’ adventures encountered in bringing his bride home, the marooning of the King and his bride on Hven would have been well known and would have been a touchstone for playgoers of the time.

This brief time in English History, The Jacobean period, was host to some remarkable individuals related perhaps by circumstance: Tycho Brahe, King James I, John Napier, Johannes Kepler, William Shakespeare, and, of course, Rosencrantz and Guildenstern.


Friday, September 13, 2019

Black



It seems like ‘black’ was an important topic of much of my early technical career. It all began with a story told us by Dr. Seibert Quimby Duntley during my second job out of college as a research engineer at the Scripps Institute of Oceanography, Visibility Lab, in San Diego. Doc Duntley, the director of the lab, had been a research scientist at MIT during WWII doing military camouflage studies. This work continued after the war in California at what came to be known as “The Vis Lab.”

Duntley described the development of the “Black Widow” paint used on night fighter aircraft during the forties. Before the days of radar antiaircraft defense by the Germans consisted of sonic detection with big horns and search lights to spot the overhead aircraft. When pinned by the lights the planes, as Duntley described them, appeared as easily seen bright grey silhouettes – even though painted black. It turned out that the best black paints diffusely reflect at least 5 or 6 percent of the light that illuminates them. That’s enough to make them easily seen and identified. Take the moon for example. We are used to seeing it as a brilliant white object in the night sky. It’s not at all white. The Moon’s average albedo (reflectance) is only 12% and the mare, flat areas, are probably closer to 5 or 6% - like black paint.

To achieve a reflectance of less than one percent a priority wartime project was undertaken. A pharmaceutical firm came up with the solution to the problem – a paint that consisted of tiny exploded carbon particles similar to popcorn suspended in a glossy transparent durable binder. This top secret material was sent to England in a container locked to a courier’s wrist for trials as a coating on the North American P-61 night fighter, the Black Widow. It was highly successful. Even though the glossy binder gave a substantial specular reflectance there was practically no diffuse reflectance. As seen from the ground. Only a few sparkles might appear and identification as an aircraft was exceedingly difficult.

Cmdr. Dayton R. E. Brown, a mentor of mine and the Navy’s camouflage expert during the war, tells the story of designing the paint for aircraft in the pacific. The Navy had already rejected the idea of black – to much like a coffin – and had opted for a deep blue. Admiral John Sidney McCain, ComNavAirPac, was paying a quick visit to an island base in the Pacific during a period that coincided with Brown’s presence at the base. Brown wanted to sell his idea for painting Navy planes more effectively and tried to get the Admiral to give him some time. The Admiral was in a hurry so Dayton volunteered to paint a plane at the side of the runway with a fire hose while the Admiral’s plane was waiting to depart. McCain agreed and Dayton Brown succeeded in selling his paint scheme to the Navy. It wasn’t black but it was a good camouflage story.

Eliminating stray light inside of optical instruments is always a prime concern in the design process. Various techniques have been used in cameras, telescopes and the like. Usually it’s just black paint which in most cases serves well. One technique for absorbing light that is little used but is very effective is a stack of razor blades seen edge on. If they are brand new and have never been handled the edges are very sharp and the incident light vanishes down the interstitial cavities between the individual blades. It's an interesting technique but hardly suitable for coating the entire inside of an instrument. One needs a hundred or more to make a small black trap.  Over the years we came to use a 3M product called Velvet Black. It may no longer be available but it had a diffuse reflectance of about 2 or 3 percent. It produced a very matte surface and was fairly delicate so it would not weather well if used on the exterior surfaces. 

Our major efforts at instrument design were directed to the measurement of "meteorological range." Roughly, this is defined as the maximum distance at which one could detect a small  dark object seen against the horizon sky. There are exact mathematical formulas for this distance and any reader who wishes to pursue it can look up the article referenced at the end of this blog.

In particular it found a good home inside the Meteorological Range Meter we installed on the aircraft pictured below which required a phototube to measure the scattering of light by particles and air molecules of a one meter column of air at an altitude of 35,000 feet. The photo below shows the MR Meter installed on the upper fuselage of the B-29 that the Air Force assigned to the Vis Lab for research purposes.

The most interesting and “colorful” use of black surfaces, however, was the employment of a very large amount of heavy black velvet cloth in our research station at Point Barrow, Alaska. The station consisted of a well-insulated cubicle facility containing all the electronic and mechanical machinery along with a stool, a desk, and a coffee pot for the attending scientist. This facility was located on a low platform well out on the tundra away from the base and village itself. The MR Meter machinery, optics, and recording devices were safely enclosed in the cubical. Out on the distant tundra were two black cavities – the more distant a ten foot cube –and the nearer one a three foot cube. They were arranged so that they both appeared the same size to the meter’s optics. During recording the telescope was electrically driven to view one after the other of these cavities and then the horizon just above them. If the reader is interested in the details of these experiments and the theory behind the measurements see the reference below.

The scale of the distant black cavity is evident in this shot of the construction process.




The large cavity, complete, and braced for bad weather.

This view below is similar to what the MR Meter saw except for alignment and actual distances.

 

Many Inuit helped with this project, all under the direction of Chester, the village chief. When all was complete Chester instituted the penultimate use of our wonderful black fabric by asking if he could have some of the scraps to decorate his best parka. We, of course, gave him all he wanted. One of my prized possessions is a photo of him leading his people in some of their ceremonial dancing at the village hall.


 



John M.  Hood Jr., "A Two Cavity Long-Base Mode Meteorological Range Meter”,  Applied Optics, Vol. 3, P. 603-8, May 1964.



Tuesday, August 27, 2019

Global Warming



One would think after all this time, with the subject being discussed or mentioned daily in the papers and on TV, that everyone would understand what it’s all about. Surprisingly, not true. The whole subject, existentially catastrophic as it clearly is, has been politicized. I am no recognized authority, but it only takes a person moderately informed and schooled in simple science to lay out what are the settled facts.

Science agrees life probably appears on any star’s planets that happen to be circling in the ‘Goldilocks’ zone, that region where water is liquid. There are three such planets in our system; Venus, Earth, and Mars. We live on the lucky one. Evidence shows that in the early days Venus, Earth’s twin, probably had oceans. The same with Mars. Runaway Greenhouse effect occurred on Venus and now it has no water, the surface temperature is equal to that of molten lead, and the surface atmospheric pressure is 50 times that of Earth. Mars could have fared better but it was a bit too small and had insufficient gravity to hold an atmosphere (currently about 1% of Earth’s pressure). In addition the lack of a moderately strong magnetic field such as that of the Earth’s allowed solar winds of high energy particles to sweep way the top layers of the atmosphere. If it were bigger and had a layer of Greenhouse gas it might have maintained the oceans it once had and could have been a pretty nice place.

Science estimates there may be as many as one trillion galaxies in the universe, each with from 100 to 400 billion stars and each star home to a number of planets. Not all planets would be in the liquid water zone but at least a few trillion would be. There is sadly a fateful story that goes with these possible habitations. Stars get old, increase their radiative output, and eventually swell up and actually devour all these cozy inner planets. Not to worry though. Our sun has a few billion years to go before we are burned to a crisp.

Part of our difficulty in dealing with the problem has to do with our sense of time and number. Most of us are just beginning to get a grasp of a million. Say a moderately successful person makes $100,000 a year. One million dollars is ten years wages. That person would need to work at that salary for 10,000 years to earn one billion dollars. The Great Lakes came into being about 12,000 years ago, a minuscule flash of time in the geological scale. Arctic and Antarctic ice is currently melting at a blindingly rapid rate.
We know what causes greenhouse warming, primarily excesses of CO2 and methane. Methane is approximately 200 times more effective at trapping heat on the Earth’s surface than CO2 but it is CO2 that has pulled the trigger. Methane is the principal ingredient of natural gas. We have all seen flames of burning methane spouting from stacks associated with oil wells. It is generally uneconomic to capture and market it and as is obvious from its greenhouse effect it cannot be released into the air. Better to convert its ingredients to CO2. The topic of methane’s role in global warming is under study. There are a small number of scientists who disagree on methane’s hazardous effect. The worry is that the vast quantities of methane that are frozen into the arctic tundra and exist at the bottom of the colder oceans as ‘methrates,’ a solid icy form of methane, could be released into the atmosphere with the warming of the oceans and the thawing of the tundra.

These dire facts remind me of a remark I heard at a cocktail gathering at the US Grant Hotel in San Diego several decades ago. Roger Revelle, eminent oceanographer, author of much of the global warming data, and founder of UCSD, and the President of SDSU,  Tom Day, were chatting. Revelle remarked that we were doing this gigantic experiment involving the whole Earth and alarmingly we had only this one planet and no idea how this experiment would turn out.

Effects of very small increases in average temperature planet wide include rises in sea level caused by swelling of the water. There are however drastic differences in yearly temperatures in the polar regions compared to the lower latitudes. Polar ice is melting at six times the rate earlier estimated. Warmer oceans result in a reduction of food supply at the bottom of the food chain. I guess I needn’t mention typhoons, hurricanes, tornadoes, floods, and wildfires in the dry areas. 

What are the simple physics explanations of global warming? This is a topic seldom dealt with in the popular press even though the basic ideas are accessible to any normal person. The sun radiates its energy across the spectrum from the ultraviolet to the infrared but most of the sun’s energy is heaped up in the region from the near ultraviolet through the visible to the near infrared. Its distribution is very much like that of a black body heated to about 6000 degrees Kelvin. The largest share of the energy is in what we normally think of as the optical region. It passes from the sun through our atmosphere with little impedance and is absorbed by the water, the land, and whatever else is illuminated. Most of these surfaces have a lower reflectivity than 100% so much of the radiation is absorbed and converted to heat – the temperature of the surface rises. There has to be a balance – what comes in has to be radiated out at some point so the surface gets hotter and hotter till its own blackbody radiation equals what it its receiving. This radiation however is not in the optical region. It is in the far infrared.

Greenhouse gasses in the atmosphere have a molecular structure that makes them prone to absorb the heat rays from the surface instead of passing them through to outer space. These gasses do emit their absorbed radiation but they emit it in all directions including back down to the surface. The incoming radiation came straight through and any reflected radiation in the optical region goes straight out.  But about half of the absorbed radiation never gets out. In some instances this might be a desirable effect. It would mean that somewhat cold planets could be warmed up through the presence of a limited amount of greenhouse gasses. In other instances, such as with our own planet, there is a runaway effect – increased temperatures will affect the uptake of CO2 sequestering mechanisms. This is especially true of the polar regions and the vast forested areas that may be denuded by the warming trend and wildfires such as are occurring in Brazil. It is crucial to understand that trees are the key. Grass and crops do not replace the beneficial effects of trees.

The argument is made that water and other gasses in the atmosphere also have a greenhouse effect. That is true but it's a matter of balance. An excess of any of these agents can tip the balance.  Currently the human population of the Earth, about 7.6 billion, contributes 24 billion tons of CO2 to the air through industrial and other fossil fuel expenditures.. To maintain a balance it is estimated that normal human activity might be managed at a much lower amount. There is a normal carbon cycle in the natural Earth's processes. The amounts of carbon in this cycle may seem quite large in comparison to the quantities cited above but the crucial factor is balance. It apparently takes only a very small fraction to upset this cycle.

Keep in mind that without life there is no oxygen. There was a time when the Earth’s atmosphere did not have oxygen in it. Plants, in the ocean primarily, put it there. Carbon was sequestered hundreds of millions of years ago in vast amounts as oil and coal. Now we are digging it all up and putting it back into the air and water. There is enough oil and coal in the ground – easily accessible – to kill the planet dead many times over. Sequestration is the ultimate answer. CO2 can be sequestered in the oceans to a certain degree. Beyond that the oceans become more acidic. Coral dies. Other vital life forms disappear.

People often cite volcanoes as a  major source of CO2. An article in Scientific American points out that volcanic activity (200 million tons) contributes less than 1% of that contributed by human activity - 24 Billion tons per year.

What can we do about all this? Here are a few things that are being done or have been proposed. It’s all pretty small peanuts so far.
1)     *   Quit using so much fossil fuel.
2)     *   Develop safe nuclear energy.
3)      * Put the CO2 back in the ground.
4)      * Sprinkle iron on the oceans to promote formation of plankton with carbonate shells.
5)      * Put a cloud of reflectors in space.
6)       *   Convert the CO2 to useful solid carbon industrial products.
7)      * Reforest several billion hectares of forest (Yes, the land is available


IIn response to the many global warming deniers around, and there are plenty of them, have them take a look at the latest map of Greenland that shows all the new coastal topography and islands that have been revealed by the melting of that icecap in the last few years.