This article was titled "this Too Shall Pass" by Michael Szpir for the May-June issue of American Scientist, volume 85. It is a a brief sysopsis of a book and a set of theories discussed in a lecture taught at the Unversity of Michigan called, "Death, Extinction, and the Future of Humanity".
The article starts off on a whimsical note retelling a scene for the movie Annie Hall by Wood Allen. A young grade school boy named Alvie Singer who is taken to see a doctor in Brooklyn. The root of the problem is that Alvie has realized the universe is expanding and that one day it shall break apart. Due to this he has become despondent and refuses to do his homework. This brings us around to the lecture that authors Fred Adams and Gregory Laughlin codified into a book they are publishing. These two have decided to write about the future of the universe as so many have turned their talents to the past. However it isn't just a lecture on the end of the universe. It is a study that provides a description, in chronological order, of the stages the universe must pass through as it matures. The remainder of the article discusses briefly the contents of this manuscript.
Starting with the present, the universe is still very young. It is about 10 to the 10th years old, which the authors call the tenth "cosmological decade" (also written as n=10) They call this the steliferous era. This is the period where stellar evolution is the primary form of energy expenditure. It is the time when galaxies, stars, and planets form (though no sooner than n=6) and conventional forms of life are born. It is also the time when Earth will be destroyed by the expansion of our sun, the end of our sun and the destruction of our galaxy.
There are several different ends for these objects. In one scenario, the earth is vaporized by the outer envelope of our sun when it reaches old age. (around n=10.2). If this happens the authors mention the only legacy the Earth will leave is to increase the metallic content of the sun by .01 percent. However the sun will continue until it becomes a white dwarf made mostly of carbon after it blows off the outer half of itself. However there is a small possibility that the Earth will escape destruction if it somehow increases it's orbital radius to be outside of the diameter of the expanded sun. If such a thing happens, and there isn't an explanation on how it would, the Earth would orbit a white dwarf remnant until it is jostled free from the dwarfs gravitational pull and would then wander about the galaxy. If neither object, (the white dwarf and/or the Earth), are absorbed by some other stellar entity, they would continue to exist into the next era in some unrecagnizable form. While this all takes place the Milky Way will collapsing into it's binary partner, the andromeda galaxy M31. These two galaxies would eventually merge into one stellar group and become one stellar system around n=11 or 12.
The end of this era is marked by the end of stellar formation as we know it. This is because the raw materials needed to form stars (mostly gas) will be depleted during n=14. This is also the time that the last main sequence star will die. However this won't happen for a while for we are very near the beginning of the era.
After conventional star formation is over, most of the baryonic mass (normal matter such as protons and neutrons) of the universe is in degenerate stellar objects (white dwarfs, brown dwarfs, and black holes). This is the start of the degenerate era. This spans from n=15 to n=37. There will be comparatively little light as these objects emit very little of it. No longer will there be a universe of stars to light the reaches of interstelar space. There will be occasional bright flashes as stars form out of the collisions of brown dwarfs and supernovae when two white dwarfs collide. Yet there will be a general decline in stelar objects as the collide and in the formation of black holes in the center of the galaxy due to gravitational attraction.
However here is matter still not accounted for. The non baryonic matter also know as dark matter. It is unknown at this time what comprises dark matter. Some or all or none of the dark matter may be in the form of WIMPS (weakly interacting massive particles). Assuming that WIMPS exist, they will eventually be depleted by annihilation by direct collision or capture by white dwarfs. This process should be completed by n=25.
Toward the end of the degenerate era the remaining stellar abjects (except for black holes) will have vanished through proton decay. Assuming there is such a process, proton decay will have the byproducts of particles like photons, neutrinos, and positrons. After all the protons have decayed, the only star like objects left will be black holes. This marks the beginning of the black hole era. In the pervious eras, the black holes have been growing by attracting other objects. It will start on a galactic scale and eventually go on to stellar clusters. However Black holes are doomed to extinction as well as they evaporate through a quantum mechanic tunneling process which will produce electrons, postitrons, and other decay products. A black hole with a mass of a galaxy will decay by n=98.
After all the black holes are gone, only the end products will be left. This will signal the beginning of the dark era. There will be nothing left to produce either energy nor will there be any way for entropy to take place. However, the authors suggest that this era may seem so bleak because it is so far into the future that it is very difficult to predict.
Understand that this is a very basic review of the book that Adams and Laughlin are writing. They go much more in depth into various issues involved in the maturation of our universe and various theories proposed to explain our universe.
The article is an interesting look at the possible future of our universe. While it is still unknown, Adams and Laughlin through Mr Szpir, at least try to take us in a direction little traveled and expose us to new ideas about the end of time.
This article was titled, "The Lives Of Stars: From Birth to Death and Be- yond(Part 1)" by Icko Iben Jr. And Alexander V. Tutukov. It was published in the December 1997 issue of Sky and Telescope. It talked about the birthplaces, lives, and deaths of stars as we currently understand it.
The beginning talks aboutimportant how stars are formed in spiral areas in space which we call galaxies. The spiral form is important because density waves travel though the galaxy compressing matter along the way. This causes the matter in the galaxy, usually gas and dust, to become highly ionized and hot. These gas ions start to strike each other and the dust grains. The ions that strike the dust grains cool and eventually form hydrogen molecules. These molecules eventually coalesce into giant hydrogen clouds. The clouds become dense enough to split up and then form stars. The article goes into more detail of the exact sequence of the formation and birth of the stars before moving on to the life of a star.
While stars tend to become one of three categories, they all live in roughly the same manner. The primary source of energy for a star is conversion of hydrogen into helium. The duration of this determines the star's life and depends on the temperature and pressure at the core of the star. It turns out that smaller stars live longer because their cores are cooler so they burn the fuel they do have at a much slower rate.
Once the star burns enough hydrogen that the star cools and starts to collapse. The star's core is now primarily helium which helps the contraction. Tis causes the remaining hydrogen to burn faster creating an expansion of the outer shell of the star. This is when the star transforms into a red giant.
Eventually the core temperature will rise again allowing the star so start burning the Helium in it's core. This causes the helium to fuse into both carbon and oxygen. Depending on the size of the star, this may cause a decrease in luminosity. Eventually the helium is also exhausted with a core composed of carbon and oxygen. The star is still powered primarily by the remaining hydrogen and helium burning. However these stars often pulse outward with solar wind. This helps distribute much of the universes carbon and other neutron-rich elements for use in other stellar forms.
Stars die in three distinct manners. After several hundred thousand years of burning helium and the other elements that come next, the star expels the Hydrogen-rich outside. The remaining core contracts quickly emitting large amounts of ultraviolet light and x-rays. This causes the former envelope of hydrogen gas to fluoresce, becoming visible as a nebula. The core compresses until it becomes a white dwarf. The compression is counteracted by the quantum-mechanical force of degenerate electrons, leaving a very cool star.
Other more massive stars become supernovea. The carbon-oxygen core doesn't stop compressing. It continues until neon is produced. At the same time it still contracts until the star can burn the oxygen-neon core.. This keeps compressing and burning until the core is composed of many iron-peak elements are formed. This causes the outer layers to continue burning and transforming into heavier elements. This increases the stars mass and causes it to collapse even further. Eventually the core becomes a neutron star. In the process it rapidly expels all the remaining outer material in a massive explosion. These elements make up the majority of the heavy and light elements found on all stellar bodies including the Earth.
The final type of death, form those stars with the highest masses, continue to col- lapse. They are so massive that the core collapse can't be opposed by the neutron degeneration. The star continues to collapse until gravity becomes so strong that not even life collapses. This is what we know as a black hole.
This article was titled, "The Search For Planets" by Neil de Grasse Tyson. It was published in the October 1997 edition of Natural History.
The beginning of the article is humorous as the author takes a rather pessimistic view of the search for planets as shown by this statement. "A pessimistic estimate for the number of planets in the universe is nine." However he goes into the what is considered to be more realistic estimates and how planets are sought for.
His next point is the difficulties we have had trying to find other planets. He starts with our historic bias that we are special and the center of the universe. He briefly details some of the problems we have had with political and religious systems blocking the exploration of the heavens. Next he talks about the problem of resolution. It is very difficult to see something with the distances involved. In addition there is the problem of the nearby star's light obscuring what little light would be returned from the planet. This is a problem with direct detection though it would be beneficial as we could provide hard evidence in the form of pictures.
There are other methods currently used to detect planets and this is what comes next. First, Mr. De Grasse Tyson, discusses the technique of doppler shift. All bodies in a solar system revolve around the center of mass. This appears to be around the sun because the majority of the mass in a solar system is in the star. However it is far enough away from the center of the star that planetary bodies cause a slight shift in the position of the star. You can use the doppler shift of the light coming from that star to determine the basic motion of the star. If there is a significant jiggle seen in the stars motion, it can be surmised that it has planets. The biggest problem with this technique is Earth sized planets would not make enough of a "jiggle" to be noticed.
A spin off of this technique was developed using pulsars. Due to the regularity of the radiation pulses emitted by pulsars, these can be used to detect doppler shifts and see if there are any planets around pulsar type stars. This has met with some success though the planets orbiting these types of stars would not be very likely to have life as we know it.
The newest technique will be using a number of telescopes, mostly space based, to operate like it was on giant telescope. This will give the whole array much greater resolution than is currently possible It is possible and hoped, that when the full array is put into space, the resolution will be great enough to provide pictures of extrasolar planets.
In summation, the article talked about the basis of looking for other planets. Next he described some of the difficulties associated with finding extrasolar planets. In the end he described three different techniques for finding other planets.
This article was titled, "Is This The End?" by Timothy Ferris. It can be found in the Jan 27th, 1997 issue. The article is divided into four parts and is about the possibility of a comet impact on the Earth and the results it would produce.
Part I is titled Death From above. It starts with a fictional portrayal of a comet discovered by an amateur astronomer. The information is forwarded to a man named Brian Marsden (real person). Professor Marsden runs the International Astronomical Union's Central Bureau for Astronomical Telegrams. He spreads news of new comets and asteroids to interested parties all over the world. He is also acknowledged to be a master at determining orbits of these objects from preliminary data like this. So he enters the data given him by the amateur astronomer and types in the command "ORBDET" to determine the orbit of the comet. While the data is very early and the results aren't that accurate, the computer shows a possibility that the new comet may intersect Earth's orbit. He sends the information out to interested parties.
During the next few nights, many observers turn their telescopes to this new object. These people range form professionals to amateurs that have their small telescopes hooked to their laptops. New more accurate information is passed to Marsden. As he enters the updated data, he determines this comet will indeed pass very close to the Earth and will make a spectacular addition to the night sky. He sends the information out via email.Minuets later this data enters the office of Paul Chodas. He works at the Jet Propulsion Laboratory near Pasadena, California. He is responsible for helping to control the spacecraft through the solar system. He decides to enter the data into his systems to compute the orbit of this new comet. The numbers are surprising. He is used to seeing zero chance of an object impacting the Earth. This time there is a chance. While the probability is small, it could happen. While the data still isn't particularly accurate, there is a chance and this information gets sent out. Across the globe, observatories are turning toward this new intruder trying to get more accurate data. The comet will pass closest to Earth on its outbound leg from the sun. It appears the impact percentage is as high as 16%. At this point the newspapers get a hold of the story and it is plastered across the headlines around the world. What happens next?
No one really knows. How will the various societies on Earth react to the possibility that all life on the planet will end? Would people pull all of their money out of the bank and go on one last blowout? Would the collapse of the world economies at this point mean anything? Will survivalists spring up everywhere threatening others who don't give them what they want. Will religious groups suddenly spring up everywhere telling everyone to repent? Either way, the tension level will rise dramatically as there still isn't a way to tell if the comet will hit Earth. When it goes around the sun, venting gasses could cause the orbit to alter enough to hit the Earth or to miss it. When it comes around the Sun , enough data is collected over enough days that it will indeed hit the Earth. Massive amounts of land or water are vaporized instantly. Tidal waves flood all the low lying costal areas around the globe. Enough dust and debris are thrown into the atmosphere to block out the sun. Together with all the ash spewed into the atmosphere from fires Caused by the impact causes the energy and heat of the sun to be reflected away for about a year. Plant life will die leaving the whole food chain with no support all life as we know it will die other than the extreme environment types of bacteria.
Part II is called A Dangerous Place. It tells about the origin of the discovery of comets and other near orbiting planetary items. Jean-Dominique Cassini came up with the idea that comets are interplanetary objects and not missiles hurled by God. In fact some of the comets seen multiple times over the years may be the same ones revisiting this area. Halley confirmed this in 1705 with the comet that bears his name. He computed it would come back in 1785 which it did. From here intellectual thought regarding comets was expanding. How- ever there were many instances where happenings were derided as superstition because there wasn't a way to explain them. An example of this is when there were reports of fire or ice falling from the sky. This was considered superstitious nonsense until proven much later in time.
However that idea started to change in the nineteenth century. Meteorites were found to be higher in nickel than the surrounding rocks upon which they were found., and also because of the rain of more than 2000 stones in L'Aigle Normandy on 23 Apr 1803. The stones were investigated on the evidence stated they must have come from space. Yet the idea of big rocks doing large amounts of damage was still a hard sell.
Geologists of the time considered all craters to be remnants of ancient volcanoes. Finally in 1929, the kilometer wide crater at Winslow Arizona was recognized as the work of a meteorite. This was the first crater found though not the last. More than 150 terrestrial craters have been found to date. Even this seemed benign. Not until the 1970's and 80's did people realize that impacts were a common thing. Pictures of the outer planets from the various space probes show numerous overlapping craters that clearly show the violence and frequent nature of all the planetary impacts. In fact it is determined that planets often owe their existence to these impacts. Whether minor grains of dust or relatively large rocks, all of this material adds up to form a planet. In fact the Earth is slowly increasing in size due to this build up of interstellar material. However there are lots of pieces left over. The majority of these planetesimals are in the Oort cloud. It is estimated that one trillion objects inhabit the Oort cloud and that the comets are members of this congregation that knocked out of place and travel into the solar system. These comets leave a trail of ice and dust as they circle the solar system which is where the earth runs into and accumulates the extra material. Yet there is the possibility that a much larger comet or asteroid could strike the Earth.
If there was ever a doubt of the destructive power of a large comet impacting the Earth, Shoemaker-Levy removed it. The team had been scanning the sky looking for objects that would crash into planets and form craters. Using partially exposed film, they found what became know as the Shoemaker-Levy comet. An amateur astronomer named Syuichi Nakona determined it would impact Jupiter. Sixteen months later, on 161994, the ice fragments impacted Jupiter one after another. Gigantic Fireballs arose from the surface and left large black splotches on the surface for weeks afterwards. No one could dispute the power of cometary impact any longer.
Part III titled, No Island Earth, goes into the probability that a comet will hit Earth. The odds that a large comet impact are quite small. It appears that a thousand years usually pass between one hundred meter objects striking the Earth. This doesn't sound too bad until you realize that a one hundred meter object will destroy an entire city. In November of 96, a meteor hit near San Luis in western Honduras. The impact crater was one hundred and sixty-five feet wide. If the impact orbit had shifted by about ten hours it could have taken out downtown Bangkok or Manila. This is not an isolated event. There are all kinds of reports about people seeing meteor showers or meteorite impacts. For example, 9 Oct 92, a meteorite smashed into the right rear of a 1980 Chevy Malibu in Peeskill, New York. On 8 Nov 82, a couple were watching television when a six pound meteorite smashed into their home causing a hole in the roof. There is the large meteorite that impacted in Siberia in 1908 that leveled trees for fifteen miles in diameter from the impact site. There are even references in historical records. There are possible references in the Book of Revelations. There are instances recorded over Constantinople and a record of an observation of the impacts that struck the moon on 25 Jun 1178. These impacts are estimated to have had the force of 120,000 megatons and created the crater Giordano Bruno.
Not all comets actually impact the Earth. Some are moving fast enough that they skip off the atmosphere and go back into space. This can be fortunate. One such asteroid did this on the afternoon of 10 Aug 72. It was observed by tourists in Utah in the daytime. This object was estimated to be close to 1,000,000 metric tons. If it had been moving as little as one percent slower it would have impacted the Earth with dire consequences.
The frequency of this is even more common than previously though. Small pieces of comets and asteroids hit the upper atmosphere almost once a month. Most detonate in the upper atmosphere with a force of up to one kiloton. These explosions are so high up that it doesn't cause any damage. These are usually monitored by the military's Defence Support Program (DSP) satellites. These satellites watch for enemy activity regarding nuclear weapons. Once the flashes were understood for what they were, the data was ignored. Now that data is being passed onto scientiscts.
Part IV, titled What Is To Be Done, looks at the possible solutions to protecting our planet from these stellar invaders. The first step is to catalogue all of the near Earth object that we can and determine their positions. This will tell us which objects are likely to threaten us. Yet this hasn't been done. This is due to both the lack of studies on the subject and to the limitations of the equipment. The large telescopes we use to observe the skies have a narrow field of view. An object has to bee in this field of view to be seen so it is difficult to scan the sky with them. It is estimated that only a tenth of the earth threatening objects have been catalogued.
Another problem with detecting these objects, is they aren't always easy to see. When a comet starts its way in to the sun it heats up and leaves a long glowing tail which is easy to see. Asteroids don't do that. They are lumps of rock that as similar in color to the background of space which makes them hard to detect. Sometimes there are even surprises. Asteroid 1994XM1 was discovered only a day before it flew past the Earth. It was as large as a house and only missed the Earth by 65,000 miles. While these near misses are probably common, no one really knows because there isn't a large scale survey of the sky.
Then there is another problem. Let's say we find an asteroid hurtling towards the Earth that has the possibility of causing major damage. It will arrive in twenty days. What do we do? Edward Teller, a director emeritus of the Lawrence Livermore Laboratory, is a proponent of large nuclear weapons as a defensive measure. This has proven very unpopular with many astronomers. Even conventional explosives aren't liked. The reasoning is orbital explosives are more dangerous that the threat they are designed to destroy. There is also some worry that a madman may get ahold of these weapons and cause an object to impact the Earth. In addition there are the political aspects of international space treaties and putting weapons into space is prohibited. In the end there really isn't an answer to what to do about an approaching threat. We don't know about them and we can't stop them. At present, the theory ignorance is bliss seems to reign.
This article is titled, "The Great Climate Flip Flop" by William H Calvin. It was published in the January 1998 edition of The Atlantic Monthly.
This was a very interesting article. It starts with the realization that Global Warming may not cause the planet to heat up but may plunge the Earth into the next ice age. This is know as climate flip.
The article discusses the basics of how the planet goes from warm period to cold period and back again. The next ice age would at best, reduce the popultion massively and at worst destroy all human life.
Next the author talks about how Europe is an anomoly on this planet. While Europe is very north compared to the other regions of the world, the climate is similar to that of lower North America. The wind blowing across the North Atlantic is being warmed by the wate in the North Atlantic. There is a major flow of warm surface water in the Atlantic Ocean which provides the heat resevoir for the winds to pick up. This warmth in turn is delivered to Europe in the form of nice weather. At the same time the author is providing proof for the existence of climate flip-flops throughout history. He shows some of the damage it did to the eccosystems of the time and the effect of life on Earth.
The flushing of all the warm water in the current flows is discussed next. The pathways the water takes are discussed as well as the probably pathways of the ocean currents as extrapolated during the previous cold phases. It is also noticed how the Pacific Ocean does not experience similar effects. Also discussed are the effects of the disruption of the currents and what would happen. He includes the link to global warming at this point
The author next writes about how to possibly prevent these climate flip-flops. The difficulty would be detecting the lack of the flow and then correcting it. We don't have enough data on what happens. Nor do we have a good idea on what it would take to fix it and how quickly it would work.
The final portion of the article talks about three different scenarios if we went into a cold spell. The destruction of food sources could lead to anything from tribal conglomerations to World War III. It also outlays some possible solutions to any shift and a reccomendation to seriosly prevent greenhouse gas emissions to prevent the acceleration of the next ice age.
This artilcle was titled, "Life: A Cosmic Imperative?" by Yvonne J Pendleton and Jack D Farmer. It deals with the possibility of life forming on other planets and the cycle of life that we know about here on Earth.
To start with, life on Earth is talked about. Early history about formation of the planet is the start and the consequnces this would have had for life beginning on Earth. The formation of the planet including the collision that formed the moon show early bombardment and tectonic activity. This was both good and bad for life. On the positive side it provided a lot of elements necessary for the formation of life including water. It may even have provided early organic compounds needed to form life. Estimates are as much as 10,000 tons of organic matter a year were accrued by the early bombardment. This isn't so hard to believe when, currently, we collect around 300 tons a year at the present time. While the period that life could have been present was between 4.4 and 4.2 billion years ago, it was definitely established by 3.5 billion years ago.
Two other important factors regarding life on Earth were the presence of stable water and the Sun's output. Water was added by the impact of comets which eventually formed the bulk of the water on the planet. This water accreted slowly as the temperature of Earth cooled. A stable supply of water less than 100 degrees Celsius was necessary for organic molecules to form. It is also believed that the sun didn't put out as much energy during it's younger years. The energy would have been trapped by the Earth's atmosphere, then rich in carbon dioxide, allowing a rise in temperature necessary for life.
However this greenhouse effect hurt the probability of life forming on Venus. It does appear that Venus once had water. It is possible that there was some form of life on Venus in its distant past. However the increase in the sun's energy output would have cause problems. As the composition of Venus's atmosphere was different, the increase in energy split a lot of hydrogen from the water and that hydrogen dissipated into Space. In addition, volcanic activity was causing a lot of carbon dioxide to form in the atmosphere of Venus. This caused a runaway greenhouse effect until the surface reached it's present temperature of 475 degrees Celsius. More than likely this is too extreme for life to still exist today.
Mars had a different problem. It's atmosphere wasn't stable to begin with. The atmospheric pressure on Mars was far too low for water to exist and therefore there would be no protective ozone layer. It is possible that there was life on Mars earlier when the atmosphere was thicker and water was present. This possibility has been given credence by the Viking landers and the meteorite ALH 84001. The probable explanation for past life would have been hydrothermal venting. This has been found deep in the Earth's oceans where sulfur eating microbes sythesize their own food without need for sunlight. Mars shows evidence of previous tectonic activity that would have had volcanos in it's earlier periods. Currently the only possibility for life on Mars is that water has retreated underground and that the core of Mars is active enough to keep this water liquid. The only way to find wether this is true or not is by deep drilling and a human presence is likely required for this.
Finally there is the discussion of life in the outer solar system. Out here the heat generated by the sun is insufficient for the formation of life. This would have to be supplemented by radioactive decay and tidal forces. The most likely places are the Jovian moons of Europa, Io, and Ganymede. Io has clear evidence of tidal effects by all of the volcanic activity present on it's surface. Europa and Ganymede have large crusts of ice. The exteriors have patterns that suggests the ice cracks and plates of it move around the surface. The most exciting possibility is that tectonic activity creates enough heat that water is warmed and rises toward the surface where it melts some of the ice and causes the cracks we have seen.
There is the possibility of life on other outer planets. Saturn's moon Titan, is of particular interest. It has an atmosphere 1.5 times as dense as the Earth's and has a strong magnetic field. Bombardment by the solar wind could cause chain reactions in it's atmosphere that would lead to complex organic molecules. However the surface temperature is too cold to support life as we know it which makes it improbable. However all three moons may sprout life when Sol goes red giant and expands through the orbits of the terrestrial planets. Enough energy may then be given to these moons to heat them up sufficiently for life to form.
To review, the article talks about the formation of our solar system and particularly Earth. This gives us the basic idea how the Earth became habitable. Next, the other terrestrial planets were discussed showing what the problems are for life existing at this time. Finally we looked at the outer planets and some of the more likely places for life to exist currently and in the future.
This article was titled, "Welcome to Mars" by Carolyn Collins Petersen. It was very sparse in text though it does have some beautiful pictures of the Martian landscape.
the article primarily talks about the Mars Pathfinder mission. It landed on the sur- face of Mars on 4 July 1997 after a seven month journey. The target zone was a spot in Ares Vallis, a windswept plain of Mars. The Mars Pathfinder is one of Nasa's new breed of probes. Designed and built with a budget of $200 million dollars, it has proven very successful. In contrast, the previous Viking landers cost around a billion dollars for the program.
Mars Pathfinder consisted of two parts. The lander, renamed the Carl Sagan Memorial Station, was the transport and base for a tiny rove named Sojourner. The base station had a 360 degree camera, pressure sensing equipment, and a thermometer system, and was the radio platform as well as being a base for Sojourner. Sojourner had a tiny camera for controlling the rover and a Alpha Proton X-ray Spectrometer which helped it determine the composition of nearby rocks.
The combination also blazed trails in new techniques and technologies for the . The lander used the concept of aerobraking upon entering the atmosphere. It entered the atmosphere without first orbiting the planet as well. In addition the lander was cocconed in a tetrahedron shaped ballon which absorbed a lot of the impact force upon touchdown. While the spacecraft did bounce a bit on the surface of Mars, it managed to land right side up which dispensed with a planned maneuver to right the lander after touchdown. In all it validated all of these previously unproven and untried technologies.
Finally, the Mars Pathfinder mission proved to be a public relations success for NASA. It proved that NASA could do things "smaller, faster, better, cheaper." It also aroused public interest in space and NASA's mission as the landing was all over the worldwide news services. It also showed individual interest. On the NASA website, the Mars Lander page registered 40 million hits by 4 July.
In all it was a wildly succesfull program. It tested new technologies. It completed the mission for much less than previous programs. Finally it reawakened the public's interest in space.
HR>This article was titled "Structure and function of the vertebrate magnetic sense" by Michael M Walker, Carol e Diebel, Cordula V. Haugh, Patricia M Pankhurst, John C Montegomery, and Colin R Green. I found this article somewhat difficult to read as it was written for other scientists and the article read like a lab report.
The beginning of the article was about the background of animals using the Earth's magnetic field for navigation during migration and other homing procedures. There has been a lot of hypotheses regarding this ability. The most promising is magnetoreception using magnetite particles. The problem is, magnetite particles have yet to be found in an animal. In fact all theories have failed on some level. This is not particularly surprising. Identifying and describing the components of such a system has proven challenging. Magnetic fields are relatively simple stimuli with only two dimensions, direction and intensity. Reception of these fields would not need complex systems. However it appears that animals only respond to these magnetic fields if they are moving. This es it difficult to prove a theory because space is limited in a lab setting and there isn't room to see any strong behavioral responses. Another challenge is living tissue is transparent to these fields so special structures to focus the fields are unnecessary. Finally you have the problem that the size of the required magnetite particle is so small that detection is next to impossible with current technology.
To try and prove the magnetite receptor theory, an experiment using three juvenile Rainbow Trout. They were taught to strike a target near a magnetic field. Some of the experiments used food as a reinforcement while other experiments did not get food. By the third session, the fish were consistently responding at a higher rate to the reinforced stimulus. The individual responses seemed to depend on the fish themselves with some fish discriminating the change in the magnetic field more readily than others. However the results were consistent with the idea that animals learn to discriminate between magnetic fields when there is reinforcement and the response requires movement.
In an attempt to study this more thoroughly, nerves and areas where magnetite was previously found were tested. The only area that responded positively was the ros V nerve. A series of experiments was run using various magnetic waves that differed in both intensity and direction. They were produced by subtracting, adding, and switching between the two, 50 microTesla to the background magnetic fields. The first stimulus (search stimulus or SS), SS!, subtracted 50 MicroTesla which reversed the magnetic field in the tank. The second, SS2, added fifty microTesla which trebled the intensity but didn't change the direction. The final stimulus, SS3, combined these two. This simulated a place where the magnetic field was reversed in direction but of the same intensity to one of the same direction but triple the intensity. This led to the finding of two neurons in the ros V nerve which were active. In addition there were fast units and slow units. None of the fast units showed any response to magnetic field changes but the slow units did.. Regular firing patterns were shown except during the SS1 signals. These results are consistent with the behavioral responses of the trout.
The scientists decided to try and find a magnetite based detection mechanism. As mentioned before, finding the crystals themselves is extremely difficult due to the small size of the crystals and the low concentration of them in the tissues.. To get around that they used a confocal laser scanning microscope (CLSM) in reflection mode. This would render the magnetite crystals visible by reflection at the microscopic level. This was proven to work in scanning magnetotactic bacteria so it should work on the trout.. After embedding some trout heads in various resins, the CLSM did find reflections in certain olfactory tissues. It was seen that the tissues with the crystals were quite rare, never more than two or three in a given area scanned. While other areas of the trout head did reflect light, they were other explanations for this. Fro example the bones of the skull were reflective but they were obviously bone structure and not tissues with magnetite crystals.To determine wether these cells could indeed be part of a magnetoreceptor system, the nerves were dyed to try and find out where they went. The dye went both ways down the nerve showing on one hand, that the nerves do indeed enter into the cranial cavity and into the anterior ganglion and the medula oblongata. There nerves also went down the snout of the trout and surrounded nerves in the olfactory region. In this region was a fine web of nerves and sensory cells that required a computer model to see how they all interconnected. In the end it is feasible to make a case that this is a magneto receptor system as this system would reach from the olfactory system, where the majority of the magnetite crystals were found, to the brain which would then process the signals. While the function of this system is still unknown, it does fit the theory.
The current theory is that vertebrates do indeed detect magnetic fields using a similar system of olfactory systems with magnetic crystals and linked to the brain via a series of specialized nerves. This idea is reinforced by both behavioral and biological responses observed in the experiments. This system suggests that a magnetic sensing system is important for long distance navigation in various animals It is also important to note that the location in the snout of the trout near the olfactory system raises the question of olfactory impairment creating magnetic impairment. This will lead to new research to determine these effects and to get a better analysis of what exactly animals due use to detect magnetic fields.
This article is titled "SETI Searches Today" by Andrew J LePage. It can be found in the December 1998 edition of Sky and Telescope magazine. It is about the current searches for Extraterrestrial Intelligence and the various organizations that run them.
The Difficulty in finding a signal from another civilization is immense. Yet there is a plan in place and operating. Most hunt for an extremely narrowband signal in the microwave radio spectrum originating from beyond out solar system. This is considered to be the best place to find a signal as the entire band, from 1 to 50 gigahertz, has the least natural background noise. We figure this is the same range an alien civilization would also use for transmission. We have an additional difficulty because our atmosphere limits us from approximately 1 to 12 gigahertz. Perhaps another civilization would use this low range as well but perhaps not. On top of this, the only type of signal we would have a chance of discovering would be some sort of beacon. A signal delib- erately set up to say "we are here". Internal traffic inside the civilization wouldn't have the power to cross interstellar distances.
Project Phoenix is run by the SETI Institute of Mountain View, California. Their plan is to search 1000 mostly older stars within 200 light years. They have a truck trailer filed with equipment and computers. They travel to radio telescopes around the world to monitor the target stars. Their equipment can listen to more that two billion channels between 1.2 and 3.0 gigahertz with a resolution of 0.7 hertz per channel. Any signal detected that is this narrow would be artificial as the narrowest natural source is 300 hertz wide.
Project Phoenix started from the end of NASA's High Resolution Microwave Survey. That project was cancelled in 1993. The SETI Institute was able to secure the equipment used in the previous project to start their own using private funds with supplementary public donations actively sought after. In 1995, the 64 meter radio Telescope at the Parkes Observatory, Australia was used between February and June. The advantage here was to see stars that weren't visible in the Norther Hemisphere. In 1996 they went to National Radio Astronomy Observatory in West Virginia. Here they shared time on the 43 meter radio telescope to observe a different set of targets. This year they were able to get time on the 305 meter radio telescope at Arecibo, Puerto Rico. These observations began in September and will continue for the next five years. The hope is to be able to build their own radio telescope of 100 meters at Hat Creek, California. This would serve as a prototype for a proposed 1 kilometer telescope which would be a set of many small antennas linked into a single array.
Project BETA (Billion-channel Extra-Terrestrial Assay) uses a different strategy. It is run by Paul Horowitz of Harvard University. It is supported by the Planetary Society and others. His plan, along with a team of graduate students, is to systematically scan the entire sky form declination -30 to +60 degrees during the year. They use an old 26 meter radio telescope in Harvard, Massachusetts. They started in October of 1995 and they scan the 1.40 to 1.72 frequency band. They chose this frequency because it is surrounded by the emissions of hydrogen and hydroxl components of the water molecule. They figure another society will also use this well marked band. However, as they sweep the entire sky in a year, each frequency band gets observed for approximately eight seconds.
BETA replace a limited project called Project META (Million-channel Extra-Terrestrial Assay) built by Horowitz. The hardware was duplicated by the Argentine Institute of Radioastronomy (IAR). They get funding from the Planetary Society for use in the Southern Hemisphere. Now called META II, this group uses the 30 meter IAR antenna #2 near Buenos Aires since 1990 to survey the sky. It monitors 8 million .05 hertz channels near the hydrogen line frequency between the -90 and -10 degree declination. They also look near the hydrogen line's second harmonic frequency as well.
The biggest problem of these groups is they have to schedule time on radio telescopes which are often scheduled to look at other things as well. Project SERENDIP (Search for Extraterrestrial Radio Emissions from Nearby Developed Intelligent Populations) gets around this. It looks for narrowband signals whenever a radio telescope happens to be pointed somewhere for other purposes. This is a piggyback arrangement and while it may not allow SERENDIP choose where it looks, it doesn't interfere with ordinary radio astronomy either. This lets the program run continuously. The project has been run by a team from the University of California, Berkeley since 1978. In may of 1997 , SERENDIP IV replaced its predecessor at the Arecibo Observatory to search 168 million channels around the hydrogen emission line. Over time it manages to scan most of the sky between the declination of +38 to -3 degrees. SERENDIP III now resides at Australia's Parkes Observatory. Run by the SETI Australia Centre, it piggybacks other astronomy to search 4.2 million channels near the hydrogen line. In addition two 4 million channel versions of SERENDIP IV are being built for the University of Western Sydney and the Institute of Radioastronomy in Bologna, Italy. This shows how widespread and accepted the program is.
All of these program shave been funded and/ run by professionals. However this is an area where amateurs can play a large part. Using as little as a home satellite dish and a narrowband signal analyzer, amateurs can scan larger areas of the sky because these dishes have a much wider field of view. An example is BAMBI (Bob and Mikes Big Investment). A pair of 3.1 million channel radio telescopes that observe from Colorado and California. The distance help then remove local interference. These two scan higher than most, up near the 4 gigahertz range.
Project Argus is a SETI league based in Little Ferry, New York. They coordinate a number of amateur efforts. Their goal is to have 5000 small amateur radio telescopes monitoring the entire sky. While far from it's goal, they did just acquire a decommissioned 18 meter radio telescope in Australia to help out.
Another project that will allow anyone to participate is called SETI@home. It is difficult to get the computing power necessary to find a narrowband signal in all the background noise. To fix this problem, an idea to distribute some of the data to personal computer users and take advantage of all the free time these computers have. A 250 Kilobyte data file goes to registered participant along with a processing program. This will run whenever your computer idles in screensaver mode. When it is done processing the data, typically in a week, your computer sends the results back to SERENDIP and will get another data file. This may allow SERENDIP to increase it's sensitivity by a facto of ten. The public response has been incredible. Approximately 120,000 people have expressed interest in this program.
The last group discussed is COSETI. Stuart Kingley's COSETI (Columbus Optical SETI) Observatory in Ohio targets stars using optical telescopes. They search for narrowband laser signals which would be ideal for interstellar communcation and can be visible by a 10 inch amateur telescope. A beacon sent using a laser similar to today's, would be visible by optical telescopes and be obviously artificial in origin. Anyone can help with a modest investment.
For more information regarding any of the groups discussed, turn to the following
websites.
Project Phoenix www.seti-inst.edu/Welcome.html
Project BETA http://seti.planetary.org
SERENDIP http://seti.ssl.berkeley.edu/serendip/html
BAMBI www.bambi.net
Project Argus http://seti1.setileague.org/homepg.html
SETI@home www.SetiAtHome.ssl.berkeley.edu/
COSETI www.coseti.org