Category: History

Mars – From War of the Worlds to The Martian

“No one would have believed in the last years of the nineteenth century that this world was being watched keenly and closely by intellegences greater than man’s…”

So began H.G. Wells’ classic 1898 novel War of the Worlds.  Wells, of course, was describing a vision of Mars occupied by an advanced race.  That stands in stark contrast to the movie The Martian, which focuses on the isolation of an astronaut left stranded on the red planet.  In a sense, that movie completes a transformation of the public’s perception of Mars underway since the Mariner 4 mission transmitted pictures of the Martian surface fifty years ago.  While we can say that astronomy and the space age have played a key role in that transformation, it was also astronomers who provided the previous impression that Mars might be inhabited as well.

Prior to the 1990’s, no planets were known to exist outside our Solar System.  There was a sense that such planets did exist of course, science fiction like Star Trek is proof of that.  Giordano Bruno postulated as far back in the late 1500’s that, “numerable suns exist; innumerable earths revolve around these suns in a manner similar to the way the seven planets revolve around our sun. Living beings inhabit these worlds.”   That, along with a lot of other things, did not endear Bruno to the Catholic Church and he was burned at the stake for his troubles in 1600.  Nonetheless, without concrete observational proof of these planets, Mars seemed the best known candidate for life to exist beyond Earth.

In 1698, Christiaan Huygens published Cosmotheoros, which speculated about not only life on Mars but on the other planets in the Solar System as well.  Of Mars Huygens wrote, “But the inhabitants…our Earth must appear to them almost as Venus doth to us, and by the help of a telescope will be found to have its wane, increase, and full, like the Moon.”  Huygens was the first to discern Saturn has rings and discovered the Saturn moon Titan.  In 2005, ESA landed a probe on Titan named in Huygens’ honor.  It remains the most distant landing attempted in space. While life on Mars was pure speculation on Huygens’ part, he was an accomplished astronomer.  And as we can tell by the rover Curiosity image below, his description of what Earth looked like from Mars is close to the mark.

Credit: NASA/JPL-Caltech/MSSS/TAMU

In 1784, William Herschel published On the Remarkable Appearances at the Polar Regions on the Planet Mars.  Like Huygens, Herschel ranks as one of the great observational astronomers with the discovery of Uranus among his many accomplishments.  And like Huygens, Herschel also speculated on the possibility of life on Mars, stating, ““And the planet (Mars) has a considerable but moderate atmosphere, so that its inhabitants probably enjoy a situation in many respects similar to our own.”  Both Huygens and Herschel set the stage for the boldest claim by an astronomer regarding life on Mars.

Percival Lowell was a contemporary of H.G. Wells.  Born in 1855, Lowell was a successful businessman who had an interest in astronomy.  This interest intensified when Lowell read Giovanni Schiaparelli published maps of Mars with channels across the surface in the 1890’s.  Schiaparelli was Italian, and the English version of his work translated the Italian word for channel -canalis – into canals.  As Mars headed towards opposition (closest approach to Earth) in 1894, Lowell set off to Arizona to make observations.  Perhaps with a strong preconception, or too much desire to make a groundbreaking discovery, Lowell published this drawing of Mars from his telescope.

Credit: Wiki Commons

Lowell speculated that intelligent life on Mars had built a series of canals to draw water from the polar ice caps to the mid-latitudes for irrigation.  Lowell’s work was rejected by other astronomers who also observed Mars during opposition but did not note canals.  Had Lowell been trained as a scientist, the lack of replication may had given him pause.  However, trained as a businessman, Lowell marketed his case directly to the public.  At first, through articles written for magazines such as the Atlantic Monthly, then through a series of books and continued defense of the canal theory until his death in 1916*.  Though rebuffed by astronomers, Lowell’s work on Mars provided a framework for popular culture during the next half century.

Against this backdrop, Wells published War of the Worlds four years after Lowell’s first observation of Mars.  Often lost in the subsequent radio and movie versions was Wells’ original intent to critique British colonialism, in particular, the concept of Social Darwinism.  This concept stated that various nations that are stronger are morally justified in the subjugation of weaker societies in a survival of the fittest competition for resources.  Wells’ point was, if that is the case, how could Britain complain if a stronger race colonized them?  In America, of course, it is the Orson Wells 1938 radio broadcast version of the story that is most well known.

The legendary broadcast was made so with media reports of panic induced by the realistic reporting of a Martian invasion.  However, the extent of the panic, if any existed at all, has been disputed.  From Wells’ work on, Martians became a cottage industry in both print and film.

And that cottage industry was all over the map.  From the classics such as Ray Bradbury’s The Martian Chronicles and Robert Heinlein’s Red Planet to horrendous efforts such as the movie Santa Claus Conquers the Martians, intelligent life from Mars was a staple in popular culture.  Remarkably, astronomers were publishing papers as late as the 1950’s that vegetation might exist on Mars.  Gerard Kuiper published a paper in the Astrophysical Journal during 1956 discussing the possibility of greenish moss (to be fair, Kuiper also postulated inorganic causes as well) on Mars during the spring/summer seasons.  William Sinton published an article in 1958 suggesting spectroscopic evidence of vegetation on Mars.  The concept of life on Mars would take a sobering turn in 1965.

Mariner 4 was launched on November 28, 1964 and begun its seven month journey to flyby Mars.  This mission would be the first to bring close up images of another planet back to Earth.  Prior to Mariner 4, astronomers had to rely on observatories which lacked digital CCD and adaptive optics technology available today.  Below are images of Mars taken from the 100-inch telescope at Mt. Wilson in 1956.

Credit: The Carnegie Institution for Science

What NASA got back from Mariner 4 in July, 1965 were images such as this:

Credit: NASA

The barren, cratered surface of Mars came as a disappointment.  Mariner 4 also measured a very thin atmosphere and lack of magnetic field.  As such, Mars does not have an ozone layer to protect organic compounds on the surface from ultraviolet radiation.  Without a magnetic field, the surface of Mars is also bombarded by a toxic stew of cosmic rays.  Quite simply, Mars is not capable of supporting life on a surface constantly exposed to harmful radiation from space.  However, future missions to Mars made it clear it is an interesting planet in an all together different way.  Much like the planet presented in The Martian.

In 1971, Mariner 9 became the first spacecraft to orbit a planet.  As a result, this mission was able to provide a comprehensive map of the Martian surface.  Imaging was delayed for two months by a massive dust storm, but once the imaging commenced, planetary scientists were delighted.  Among the findings were the largest canyon and volcanic features in the Solar System later named Valles Marineris and Olympic Mons.  Most importantly, Mariner 9 imaged ancient dry riverbeds and channels.  Water did once flow on the surface of Mars, albeit billions of years ago.  The success of Mariner 9 provided the impetus for Vikings 1 & 2, which landed on Mars in 1976 and gave us the first look at the surface.  This is how the landing was covered by ABC including an interview with Carl Sagan.

Viking searched for life on Mars and found none at the landing zones.  There was a 20 year lull in Mars exploration until 1997 when Pathfinder landed on Mars.  Tagging along for the ride was the Sojourner rover, the first of the Mars rovers, named after the 19th century abolitionist Sojourner Truth.  By 1997, the public had more access to NASA missions, specifically the mission website that provided updates and images.  The original website is still online and can be accessed here.

By this time, it was problematic to present a story with Martians that had serious social commentary a la War of the Worlds.  The notion of an advanced race on Mars could not be taken seriously and was reduced to efforts such as the 1996 comedy Mars Attacks.  During the course of the 20th century, the public perception of Mars went from a planet that might have an advanced race, to a planet that might have vegetation, to a planet that while geologically interesting, was devoid of life.  Conflict is the centerpiece of drama, and without the possibility of life on Mars, the traditional source of conflict had been removed.

Between Pathfinder landing on Mars in 1997 and its use as a plot device in 2015 in The Martian, there have been several orbiter, lander, and rover missions to Mars.  Mars Odyssey has been in orbit since 2001 and rover Opportunity has been exploring the surface since 2004.  NASA’s Mars Exploration website has images and video from all its active Mars missions.  Among the rover images are dust devils which were a feature of the landscape in The Martian.

The results of these missions were used quite effectively to provide a reasonably accurate take on what living on Mars would look like in the movie.  Without an alien race to provide drama, the central conflict is the harshness of space itself.  The challenges of human travel to Mars include limited availability of launch windows (once every 26 months as Mars approaches opposition), protection from cosmic rays, landing significant tonnage on Mars with very little atmosphere to provide braking, physical deterioration caused by Mars low (30% of Earth’s) gravity,  and utilizing recently discovered water resources below the surface.  The last point also underscores the need to determine if microbial life exists in the subsurface of Mars where water still exists.  Can we avoid contaminating Mars with microbial life from Earth and vise-versa?  NASA has an Office of Planetary Protection dedicated to that last issue.  Ironically, it was exposure to Earth’s microbes that did in the invading Martians to conclude H. G. Wells’ The War of the Worlds.

The Martian signifies that Hollywood has caught up with science in terms of presenting dramatic stories of Solar System exploration without intelligent life from Mars.  The other side of the human vs. harshness of space conflict is the fact that while we may send a handful of astronauts to Mars the next few decades, the vast majority of humanity will remain on Earth.  There will not be a mass migration to Mars if we foul things up on our home planet.  If space exploration can help discover a means to solve the challenges we face on Earth during the same time we go to Mars, it may be finding the right combination of international competition vs. international cooperation.  We can only hope that right mix may be found in reality as readily as it can be found in the movies.

*Percival Lowell’s true legacy to astronomy was founding the Lowell Observatory in Arizona where Pluto was discovered.  In 2015, its 4.3 meter telescope became fully operational.  You can check that out on the Lowell Observatory website.

**Image on top of post is Mars Pathfinder landing site in 1997, to be visited by Mark Watney in the future.  Credit:  NASA/JPL

William Herschel, A Man for All Seasons

Located about 100 miles west of London, the city of Bath is known for the ancient Roman Baths that attract 1 million visitors each year.  One half mile west from the baths is the Herschel Museum of Astronomy, the 18th century residence of William Herschel.  As an observational astronomer, William Herschel tends to get overlooked by the great theorists such as Issac Newton.  Nonetheless, the work Herschel did in Bath greatly expanded our knowledge of the universe and remains topical in astronomy research.

In contemporary parlance, Herschel was a career changer.  Originally a musician by trade, Herschel took an interest in astronomy in 1773 at the age of 35.  Herschel was a self-made man.  He had no formal training in astronomy and taught himself the art of telescope making.  What had perked Herschel’s interest in astronomy was a book on musical mathematics called Harmonics by Robert Smith.  Herschel enjoyed the book so much he sought out other books by Smith and found one titled Opticks.  This book, along with Astronomy by James Ferguson, formed the basis of Herschel’s training in the field.  Herschel remained a music teacher during the the day and astronomer at night.  In his endeavors he was joined by his sister, Caroline Herschel, who became his lifelong assistant.

Above:  Herschel’s Symphony No. 8 in C minor by London Mozart Players.  Written in 1761, it is one of 24 symphonies composed by William Herschel.

Herschel was unable to buy a telescope suitable for his ambitions.  As a result, along with his sister Caroline, he took to the task of making his own telescopes.  Astronomers today do not need to do this obviously, but this is similar to the manner many astronomers write their own computer codes for their work.  This type of specialized software is not available at a store in your local shopping mall.  Over his lifetime, Herschel would grind and polish hundreds of mirrors, some of which he sold to help fund his work.

Herschel’s primary goal was quite formidable, to conduct an all-sky survey.  Motorized drives to track objects as they moved in the night sky were not available in the 19th century, so Herschel would observe at a fixed angle on the meridian and logged objects as they crossed the field of view.  The next evening, Herschel would lower or raise the telescope to a different angle for complete coverage of the night sky.   This effort resulted in the publication of the Catalogue of Nebulae and Clusters of Stars (CN) in 1786, the forerunner of the New General Catalouge (NGC).  Along the way, Herschel would make quite a few interesting discoveries.

On the night of March 13, 1781, from his residence in Bath, Herschel observed in his 6-inch telescope what he thought was a comet.  Herschel noted:

“On Tuesday, the 13th of March, 1781, between ten and eleven in the evening, while I was examining the small stars in the neighborhood of H Geminorum, I perceived one that appeared visibly larger than the rest: being struck with its uncommon magnitude, I compared it to H Geminorum and the small star in the quartile between Auriga and Gemini, and finding it so much larger than either of them, suspected it to be a comet.”

Measurements of the orbit of this object revealed it to be not a comet, but a planet, the first planet discovered since the ancient astronomers categorized the five naked eye planets of Mercury, Venus, Mars, Jupiter, and Saturn.  Below is an image of how the night sky appeared in Bath as Herschel made his first observation of this planet.

UranusHerschel wanted to call this planet Georgium Sidus (The Georgian Star) to honor King George III.  Others sought a less English-centric name.  Uranus was proposed as in Greek mythology, Uranus is the father of Saturn.  It was not until 1850 that the planet was officially designated as Uranus.  As Uranus is twice the distance (1,783,939,400 miles or 2,870,972,200 km) to the Sun as Saturn, this discovery doubled the size of the known Solar System.  It takes 84 years for Uranus to orbit the Sun.  Thus, Uranus has only made 2.8 revolutions of the Sun since its discovery.  In 1986, Voyager II would become the only spacecraft to date to pay a visit to Uranus.  A view of Uranus from Voyager II is below:

Uranus on January 1986. Image on right is false color to enhance color differentials. The South Pole (red) is darker than equatorial regions. Credit: NASA/JPL.

Uranus’  South Pole was facing Voyager II as it is inclined 98 degrees compared to Earth’s 23.5 degree axial tilt.  If Earth had the same axial tilt as Uranus, the Northern Hemisphere would face the Sun in June while the entire Southern Hemisphere would be in darkness.  The situation would be reversed in December.  When Voyager II flew past Uranus, the Northern Hemisphere was shrouded in darkness.  If NASA’s plans to send an orbiter around Uranus comes to fruition in the 2030’s, the Northern Hemisphere would then be visible.

This discovery was a game changer for Herschel.  King George III, as the Revolutionary War raged in the American colonies, provided Herschel with a salary to pursue astronomy on a full-time basis.  This would launch Herschel on a decade of discovery.

In 1784, Herschel published On the Remarkable Appearances at the Polar Regions on the Planet Mars.  This paper presented the results of observations taken of Mars from 1777 to 1783.  A few of Herschel’s drawings of Mars is below:

Credit: Royal Astronomical Society
Credit: Royal Astronomical Society

Among the conclusions Herschel came to from these observations are:

The axial tilt of Mars is 280 42′, reasonably close to the now established value of 25 degrees.

The length of the Martian day as 24 hours, 39 minutes, and 21 seconds.  This measurement was off by only 2 minutes.

The luminous areas at the polar regions were ice caps, which like Earth, would vary in size on a seasonal basis.  Today, we know the northern ice cap has a permanent layer of water ice.  The southern ice cap has a permanent top layer of 8 meters of carbon dioxide ice and a much larger layer of water ice below.  The seasonal variations of the ice caps are due to the freezing and evaporation of carbon dioxide ice.

Herschel concluded his paper by stating, “And the planet has a considerable but moderate atmosphere, so that its inhabitants probably enjoy a situation in many respects similar to our own.” Ok, this one didn’t quite pan out as we know Mars’ mostly carbon dioxide atmosphere is much thinner than Earth’s and life does not exist on the surface.  However, Mars atmosphere in its ancient past must have been warmer and more substantial for water to have been present on the surface, of which the evidence is now pretty conclusive.  The search for life in Mars’ past and microbial life in the Martian sub-surface, which still has water, is a major component in NASA’s Mars Exploration Program.

While several rovers and orbiters have provided thousands of high resolution images of Mars, Earth bound telescopes still acquire key data on Mars past and present:

 

Herschel would also discover two moons of both Saturn and Uranus.

The Uranus moons were discovered on the same day in 1787 and were named Titania and Oberon.  Both moons were imaged by Voyager II on its flyby of Uranus.  Titania featured fault valleys as long as 1,500 km and Oberon has a mountain 4 miles high.

Titania taken by Voyager II 369,000 km (229,000 miles). Credit: NASA/JPL

Two years later, Herschel would discover the Saturn moons Mimas and Enceladus.  Both these moons have been imaged by the Cassini orbiter mission.  Mimas features a large impact crater that has given it the nickname “Death Star”.

Mimas, whose crater gives it a resemblance to the Star Wars Death Star. Credit: NASA/JPL/SSI

The crater has been named in Herschel’s honor.  The crater itself is 140 km (88 miles) wide and the outer walls are 5 km high with a central peak 6 km high.  An impact just a bit larger would have most likely destroyed Mimas.  As interesting as this is, it is Enceladus that has proven to be one of the biggest surprises of the Cassini mission.

Only 500 km wide, Enceladus is very bright as it reflects almost 100% of the sunlight it receives.  Thought to be too small for geologic activity, Enceladus provided an unexpected finding when Cassini imaged geysers spraying ice and water vapor into space.  Further gravity analysis indicates an ocean 10 km deep underneath a ice shell 30-40 km deep.  Recently, it has been determined the geysers are more akin to curtain eruptions seen in volcanic activity in Hawaii and Iceland.  Still, this water is thought to be at least 194 degrees Fahrenheit at the ocean floor, the heat generated by gravitational flexing from Saturn.  Where there is heat and water, there may be life.  Cassini has flown through the geysers but its instrument package was not specifically designed for this task.  As such, Enceladus is a priority for NASA exploration in the next decade.  Unlike the subsurface ocean of Europa, the ocean of Enceladus could be sampled without having to bore down through several kilometers of ice.

Plumes of water ice emanating from the south pole of Enceladus. Credit: NASA/JPL/Space Science Institute.

As impressive as Herschel’s Solar System discoveries were, the task to complete an all-sky survey meant he studied deep space objects moreso than planets and their satellites.  Herschel would discover numerous nebulae and binary stars that prior to his telescope, were not resolvable.  By 1785, with the salary granted by King George III, Herschel had moved from Bath to London and was using a 19-inch aperture telescope to map the Milky Way.  The results were published as On the Construction of the Heavens.  

Credit: Royal Astronomical Society.
Credit: Royal Astronomical Society.

The bright spot in the center is the Sun.  Herschel was operating under the handicap of observing in visible light only, which is extinguished by the interstellar medium.  This gave the illusion the Sun was located in the center of the Milky Way as the interstellar medium dampened optical light in all directions equally.  It is like trying to map trees in a foggy forest.  There may be more trees in one direction than the other, but the fog cuts down on your vision at equal depths in all directions.  In fact, it was not until the 1920’s when Harlow Shapley determined the Sun was located in a spiral arm of the Milky Way  and not in the center was this problem resolved.  For astronomers to obtain a comprehensive view of the universe, the entire electromagnetic spectrum had to be employed.  And it was Herschel who provided the first step in that direction.

In 1800, Herschel was measuring the temperatures of the different colors of sunlight separated by a prism.  As Herschel took temperatures from the violet end of the spectrum to the red he discovered an increase in temperature as the thermometer was moved towards the red.  Finally, the thermometer was placed just beyond the red light, and the temperature increased even more.  It was apparent the Sun was emitting some form of radiation beyond the furthest end of the visible spectrum.  More experiments revealed this invisible radiation had the same properties as visible light, it could be reflected and refracted.  Herschel published this result in the paper titled, Experiments on the Refrangibility of the Invisible Rays of the Sun.  Herschel referred to this radiation as calorific (heat) rays, today we call it infrared light.

Credit: NASA

Optical light is just a small part of the electromagnetic spectrum.  Among the other parts we are unable to detect with our eyes, we can detect radio waves with radio receivers, ultraviolet waves with our skin when we get sunburn, and x-rays with film when we go to the doctor.  Those forms of radiation only differ from light in the size of their respective wavelengths and consequently, their energy.  Infrared is used for remote control and night vision technology. Most of the heat we feel in our day-to-day activities is the result of infrared light and our bodies emit infrared radiation in the form of body heat which is detected in night vision sensors.

Cat in infrared. Eyes appear warmer than body as cat’s fur traps heat, not allowing it to escape into surrounding air to be detected by infrared camera. Credit: NASA/IPAC

Planets radiate mostly in the infrared, as do cool galactic gas clouds.  Certain wavelengths of infrared radiation has the ability to pass through dust clouds.  Thus, infrared observations can peer into dusty regions in space and see what lies behind the shroud of dust.  As a result, infrared astronomy is used for planetary observations, to detect protostars inside of nebulae, and to peer into the galactic center behind the wall of interstellar dust.  In other words, the form of radiation Herschel discovered is now used to better understand the very objects Herschel observed.

The video below is a montage of 2.5 million images of the Milky Way taken by the Spitzer Infrared Space Telescope.  As certain wavelengths of infrared are not absorbed by the interstellar medium as optical light is, the Spitzer images provide us with the true shape of our home galaxy including the central bulge that contains a massive black hole.

The Spitzer GLIMPSE360 website has an interactive where you can explore different regions of the Milky Way or select objects to view.  The Milky Way is not the only region that can be explored in infrared.  In 2014, the Keck Observatory imaged Uranus with infrared.

Images of Uranus, such as the ones taken by Voyager, tend to reveal a featureless planetary disk.  However, the Keck infrared image revealed storm activity to an extent not seen before on Uranus.  This might be indicative of an internal heat source that was not thought to exist previously on the gas giant.  Astronomers will need to revise current theories on the interior of Uranus as a result of this work.

Left-Uranus at 1.6 microns. White spots are storms below upper cloud layer. Right-Uranus as 2.2 microns. White spots are storm activity just below tropopause.  Uranus ring system is visible in this image. Credit: Imke de Pater (UC Berkeley) & W. M. Keck Observatory images.

As one would expect, many honors have been accorded upon the Herschel name.  This would include the 3.5 meter infrared Herschel Space Observatory and the 4.2 meter William Herschel Telescope in the Canary Islands.  However, the highest honor we can bestow upon William Herschel is the continued exploration of the celestial bodies he discovered, using the infrared radiation that he also discovered.

*Image on top of post, Sir William Herschel, by Lemuel Francis Abbott, oil on canvas, 1785, © National Portrait Gallery, London, Creative Commons License.

Mount Wilson – the Birthplace of Solar Physics

Perched 5,710 feet above the Los Angeles Basin in the San Gabriel Mountains, Mt. Wilson Observatory is noted for the ground breaking work of Edwin Hubble during the 1920’s.  In that decade, Hubble would discover galaxies beyond the Milky Way and the expansion of the universe at the observatory’s 100-inch telescope, then the world’s largest.  Located a few hundred feet from the famous telescope lies three solar telescopes whose observations provided the groundwork for our current understanding of the Sun.  This story did not begin in the warm climes of Southern California, but in the Upper Midwest at Yerkes Observatory, 90 miles northwest of Chicago.

The first director of Yerkes Observatory was George Ellery Hale.  The observatory, established in the 1890’s, is dubbed the birthplace of modern astrophysics.  Hale was the guiding force behind the building of the observatory and wanted to move astronomy from the study of the positions of celestial bodies in the night sky to the physics behind those objects.  Hale had an intense interest in the study of the Sun and set out to build a solar telescope on the grounds at Yerkes.  The result was the Snow Solar Telescope built in 1903.  The name of the telescope is not derived from Wisconsin winters, but from Helen Snow of Chicago who anted up $10,000 ($258,000 in 2014 dollars) to build it.  However, poor optical quality necessitated a move of the Snow from Wisconsin to California.

Driving down a highway on a hot summer day, you have probably seen heat waves rising from the ground and distorting your vision.  This effect is magnified if you attempt to take a picture through a telephoto lens.  The Snow Solar Telescope design had a movable mirror (coelostat) reflect the Sun’s image to a 30-inch mirror which in turn reflected the light 60 feet to 24-inch mirror that projected the final 6-inch image of the Sun.  Heats waves from the ground interfered with the image quality as the light traveled its 60 foot path horizontally to its final destination.  Hale thought relocating the Snow to an area with thinner air would reduce the heat interference problem.

As a result, the Snow was dismantled and transported to Mt. Wilson in California in 1904.  One does not normally associate the Los Angeles basin with good optics, but the summit of Mt. Wilson lies above the atmospheric inversion layer that traps the infamous Los Angeles smog like a lid on a pot.  This, combined with the thinner air of the higher altitude, improved the image quality of the Snow.  Hale set out to study sunspots, which would provide the first significant scientific finding from Mt. Wilson.

The Sun on July 28, 1906. Earth superimposed for scale. Credit: Mt. Wilson Observatory.

The oldest known observations of sunspots dates back to 800 B.C. both from ancient Chinese and Korean astronomers.  Historical recordings of sunspot numbers dates back to the 1600’s and constitute one of the longest ongoing scientific programs of observation.  At the dawn of the 1900’s, the nature of these spots on the Sun’s surface were not known.  Among the competing theories at the time were sunspots as debris clouds from solar tornadoes, areas hotter than the surrounding surface, and one of the most colorful ideas, sunspots as holes in a shroud of the Sun that hid a solid surface underneath.  The Snow Solar Telescope would begin the process to clarify the nature of sunspots.

The Snow was equipped with a high resolution spectrograph.  With this, Hale was able to record and compare spectra lines from regions of the Sun’s surface with and without sunspots.  These spectra lines were in turn compared to spectra produced in a laboratory under different temperature regimes.  In the cooler regime, many spectra lines were strengthened, and a few were weakened.  The spectra obtained from sunspots correlated with the spectra obtained in the laboratory in the cooler regime.  Hence, sunspots were regions on the solar surface that are cooler and thus, darker than the surrounding area.  The question remained, why were these regions cooler?  To answer this would require better solar images than the Snow could provide.

As George Ellery Hale was wont to do, he built a bigger and better telescope.  Despite the thinner air at Mt. Wilson, heat interference still proved to be an issue with the Snow.  To solve this, Hale built a telescope with a vertical, rather than horizontal design.  At 60-feet, the new solar tower was completed in 1908.  In his observations of sunspots, Hale was reminded how their structures were similar to the classic iron filings magnetic field experiments.  Based on this hunch, Hale set off to detect the presence of Zeeman lines in sunspot spectra.

60-foot Solar Tower (left) next to Snow Solar Telescope (right). Credit: Gregory Pijanowski
60-foot Solar Tower (left) next to Snow Solar Telescope (right). Credit: Gregory Pijanowski

The black lines seen in spectra are absorption lines.  Different elements absorb light at different wavelengths and this is how astronomers can figure out what stars, including the Sun, are made of.  If an atom absorbs light of the same energy as the difference between two electron orbital levels, the light energy is converted to energy that moves an electron to a higher orbit.  The result is the absorbed light creates a black line on a spectra.  The presence of a magnetic field creates more potential electron orbital levels.  As a consequence, a single absorption line can split into several absorption lines as can be seen below:

Credit: Astrophysics and Space Research Group, The University of Birmingham.

Using the new 60-foot solar tower, Hale was able to detect the presence of Zeeman lines in the spectra of sunspots.  In fact, the magnetic field in sunspots are several thousands times stronger than Earth’s magnetic field.  The intense magnetic fields in these areas of the Sun push plasma convection to areas outside of sunspot regions.  As it is this convection that transports heat to the solar surface, the magnetic blockage of this convection causes sunspots to be cooler by about 2,000 Celsius than the surrounding region.

Hale published this result in 1908,  six years after Zeeman won the Nobel Prize for his discovery of this effect.  This was the first time a magnetic field was discovered beyond Earth.  Hale would be nominated for a Nobel as a result of this discovery, but ultimately was not awarded.  Health issues eventually forced Hale away from Mt. Wilson, but not before building what would be the largest solar observatory from 1912 to 1962.

Mt. Wilson 150-foot Solar Tower. Photo: Gregory Pijanowski
Mt. Wilson 150-foot Solar Tower. Photo: Gregory Pijanowski

The 150-foot solar tower would be Hale’s last major contribution to solar astronomy.  The 150 foot vertical focal length produces a 17-inch image of the Sun at its base.  It was with this facility that Hale was able to determine the magnetic polarity of sunspots and the 22-year solar cycle.  The 11-year solar cycle had been long known and pertains to sunspot numbers only.  It usually takes 11 years (sometimes longer, sometimes shorter) for the solar cycle to reach one maximum to the next.

Magnetic fields are dipoles.  That is, a magnetic field will have a north and south pole.  Sunspots occur in pairs with one being the north pole and the other being the south pole, albeit at times a single spot in a pair will break up into several spots with the same polarity.  Hale discovered that sunspot pairs exhibit the opposite order of polarity in each solar hemisphere.  The polarities then reverse at the end of each 11-year cycle.  Consequently, a Hale 22-year solar cycle would look like this:

     Cycle (11-years)    Northern Hemisphere   Southern Hemisphere
                   1                        N-S                    S-N
                   2                        S-N                    N-S

The most recent occurrence of polarity reversal happened on January 4, 2008.  This event heralded the arrival of the current solar cycle.

By the mid-1920’s, Hale spent most of his time at his private solar observatory located in his residence in Pasadena.  He passed away in 1938 as work was ongoing for the 200-inch Mt. Palomar Observatory.  A new generation of solar astronomers would carry on his legacy at Mt. Wilson.

In 1957, Horace Babcock would install the first magnetograph in the 150-foot tower.  Rather than just study the strong magnetic fields of sunspots, the magnetograph was sensitive enough to map the magnetic field across the entire solar surface.  Essentially, the magnetograph maps the Zeeman effect across the entire solar disk.  Astronomers would take the work at the 150-foot tower a step further in the 1960’s by using it to study the Sun’s interior with a field called helioseismology.

In 1962, Robert Leighton discovered oscillations all across the solar surface which occurred in 5 minute cycles.  The theoretical modeling of these oscillations were refined by Roger Ulrich, who also kept the 150-foot Solar Tower in operation after the Carnegie Institution pulled their financial support in 1984.  These oscillations are caused by acoustic waves trapped inside the Sun.  Measurements of these waves allowed for modelling the solar interior.  One of the findings is the amount of hydrogen converted to helium in the solar core via fusion reactions.  This finding verified current models of solar evolution.  In other words, we know the Sun will be around for another 5 billion years or so.

The mapping of the solar magnetic field and helioseismology forms a key part of NASA’s current Solar Dynamics Observatory’s mission, as explained in the video below:

During the late 1990’s, I had the opportunity to go inside all three of the Mt. Wilson solar telescopes as a student in the observatory’s CUREA program.  The Snow was used primarily and I’ll never forget cleaning off the direct current switches, seemingly straight out of Frankenstein’s laboratory.  Also had encounters with both tarantulas and rattlesnakes.  In between those adventures, got to study the Sun’s spectrum (just as Hale did 90 years earlier), imaged the Moon at night, and gaze out over the cliff into Pasadena and the Rose Bowl.  The  60-foot solar tower had AC/DC blasting in the observation room, while the 150-foot tower had a visitor’s book signed by both Albert Einstein and Stephen Hawking.

Looking down the ladder on the 150-foot Solar Tower. Credit: Gregory Pijanowski
Looking down the ladder on the 150-foot Solar Tower. Credit: Gregory Pijanowski

Since then, there has been two recessions and a major financial crash.  The result has been cutbacks in funding and a need for the solar towers to reduce staff like many businesses have.  The Snow is still used by CUREA students every summer.  The 60-foot solar tower is run by USC.  The 150-foot tower had its funding shut down and is run on a volunteer basis.  The historic magnetograph made its last observation in 2013.  It could be much worse, in 2009, a forest fire came within a few hundred yards of the observatory which was saved by the efforts of several hundred firefighters.

Below is a video on the current effort to keep the 150-foot solar tower’s record of observations unbroken:

The observatory continues to reinvent itself.  The Pavilion, closed in the 1990’s, is now home to the popular Cosmic Cafe.  The grounds, once open to the public only on weekends is now open daily.  Public viewing is now offered on both the 60 and 100-inch telescopes.  The CHARA interferometer, which had started construction when I was there, is producing scientific results.  How do the solar towers fit in?  The 150-foot tower has been an important link in the continuous observations of sunspots since the early 1600’s.  In fact, those records compose 25% of that history.  And so far, it has been able to continue to do so.  I truly hope that chain is not broken.

*Image on top of post is the 60 and 150-foot towers keeping their vigil on the Sun.  Photo:  Gregory Pijanowski

Teaching About the Confederate Flag

The recent controversy concerning the display of the Confederate flag presents an excellent opportunity for teachers to employ constructivist learning techniques for students to understand the flag’s original intent.  Also, this can provide a good lesson in the value of examining original historical documents rather than relying on interpretations of those documents.  When I took American history in high school, back in the early 80’s, these documents were not readily available for inspection.  The internet now allows students to access these documents with little difficulty.

Four states, South Carolina, Georgia, Mississippi, and Texas, wrote formal declarations as to the cause of succeeding from the Union.  Students can access these documents here.  The students can read the documents as a homework assignment in preparation for a discussion segment follow-up in class.

Themes the teacher can present in the discussion are these:

What was the major cause for Southern states to leave the Union?

Did the assigned documents list any secondary causes?

Did the documents conflict with the student’s pre-existing notions as to why the South succeeded from the Union?

Explain what the word seminal means.  Ask your students if the lesson helped them to understand why it is important to review and cite seminal sources, rather than solely rely on secondary sources, for academic work.

The National Archives has several photographs from the Civil War.  A picture of the Confederate flag (seen at the top of the post) flying over Fort Sumter can be accessed here.

Students should be asked, how does this flag differ from the one normally associated as the Confederate flag?  Why does this flag only have 7 stars?  What is the significance of the date, April 14, 1861, and what happened at Fort Sumter that caused this event?  Why did Confederate battle flags evolve to look differently than the one that flew over Fort Sumter?

Finally, the class can discuss how the flag is displayed today.  Does it match the original intent of the flag?  Discuss the difference between a hate group displaying the flag and a historical exhibit of the flag.  Ask your students if they think the individuals who display the flag as a personal statement have inspected the historical documents as the class just did.  If those individuals did read those documents, would it alter their perspective on displaying the Confederate flag?

Going into this exercise, students may have been taught versions of what caused the Civil War that conflict with the historical record.  And they may have learned these alternative versions from the people they trust the most in their lives – family and friends.  If that is the case, it will often take some time for a student to resolve this internal conflict.  In fact, it could be after the student has completed the course before this conflict is resolved.  A teacher should be prepared for that.

And that might be the most difficult academic lesson to learn in life, always do your due diligence, no matter how much you trust a person.

Hubble’s Successor and the Man it’s Named After

In 2018, NASA is scheduled the launch the James Webb Space Telescope (JWST). The JWST is the successor to the Hubble Space Telescope. The Hubble, upgraded in 2009, is still producing high quality science. However, it has been in operation for 25 years, and like an old car, will begin to break down sooner or (hopefully) later. It is projected that Hubble will fall back to Earth sometime around 2024.

The JWST will be fundamentally different from the Hubble in three ways, its mirror type, location, and the part of the electromagnetic spectrum observed.

The Hubble’s primary mirror is a single piece 2.4 meters (8 feet) in diameter. The mirror is made of ultra low expansion glass that weights 2,400 lbs. This is pretty lightweight; a regular glass mirror the same size would weigh five times as much. The JWST primary mirror will consist of 18 segments with a total weight of 1375 pounds. The total mirror size will be 6.5 meters (21 feet) in diameter.

Why are the JWST mirrors so light?

The mirrors for the JWST, rather than composed of glass, are made of beryllium. This substance (mined in Utah) has a long history of use in the space program, as it is very durable and heat resistant. In fact, the original Mercury program heat shields were made of beryllium. In space, weight is money. Currently, it cost $10,000 to put a pound of payload into orbit. Since the JWST mirror has 7 times the area of the Hubble mirror, a lighter material had to be found.

Beryllium itself is a dull gray color. The mirrors will be coated with gold to reflect the incoming light back to the secondary mirror to be focused into the JWST instrument package.  The choice of gold was not for aesthetic purposes, but rather gold is a good reflector of infrared light and that is key to the JWST mission.  The total amount of gold used is a little over 1 1/2 ounces, worth roughly $2,000, which is a minute fraction of the JWST $8.5 billion budget (about the same price tag for an aircraft carrier).

The final assembly of the primary mirror will take place at the Goddard Space Flight Center in Maryland. The contractor for the assembly is ITT Exelis, which was formally a part of Kodak and is still based in Rochester, NY.

The JWST will launch in 2018 on an Ariane 5 rocket at the ESA launch facility in French Guiana. This is near Devil’s Island, the site of the former penal colony featured in the film Papillon. Its location near the equator provides a competitive advantage over the American launch site at Cape Canaveral. The closer to the equator, the greater the eastward push a rocket receives from the Earth’s rotation. In Florida, the Earth’s rotational speed is 915 mph. At French Guiana, it is 1,030 mph.  That extra 1,000 mph boost allows a launch vehicle to lift more payload into orbit.

Even if the shuttle program were still active, unlike the Hubble, it would not have been used to lift the JWST into space. The Hubble is situated in orbit 350 miles above the Earth. This was the upper end of the shuttle’s range. The JWST will be placed 1,000,000 miles away from Earth at a spot known as the L2 Lagrange point.  What is the L2 point?  Think of the launch of the JWST as a golfer’s drive shot.  The interplay between the Earth and Sun produce gravitational contours as seen below:

Credit: NASA / WMAP Science Team

The gravitational contours are like the greens on a golf course.  The arrows are the direction gravity will pull an object.  The blue areas will cause the satellite to “roll away” from a Lagrange point.  Red arrows will cause the satellite to “roll towards” the desired destination.  Kind of like this shot from the 2012 Masters:

The L2 spot is not entirely stable.  If the JWST moves towards or away from the Earth, its operators will need to make slight adjustments to move it back towards the L2 spot.  Due to this placement, the JWST will not have the servicing missions the Hubble enjoyed. The specifications of the JWST must be made correctly here on Earth before launch.

Why does the JWST need to be so far away from Earth?

The answer lies in the part of the electromagnetic (EM) spectrum the telescope will observe in. Don’t get turned off by the term electromagnetic, as we’ll see below, you will already be familiar with most parts of the EM spectrum.

Credit: NASA

The word radiation tends to be associated with something harmful, and in some cases, it is.  However, radio and light waves are also forms of EM radiation.  What differentiates one form of radiation from another is its wavelength.  Cool objects emit mostly long wavelength, low energy radiation.  Hot objects emit short wavelength, high energy radiation.  The JWST will observe in the infrared.  And this is a result of the objects the JWST is designed to detect.

The JWST will search the most distant regions of the universe.  Due to the expansion of the universe, these objects are receding from us at such a rapid rate, their light is red-shifted all the way into the infrared.  Planets also emit mostly in the infrared as a consequence of their cool (relative to stars) temperatures.    The infrared detectors on the JWST will enable it to study objects in a manner that the Hubble could not.

The L2 location allows the JWST to be shielded from the Earth, Moon, and Sun all at the same time.  This prevents those bright sources of EM radiation from blotting out the faint sources of infrared that the telescope is attempting to collect.

The video below from National Geographic provides a good synopsis of the JWST.

So, who was James Webb? And why did NASA name Hubble’s successor after him?

The short answer is that James Webb was NASA Administrator during the Apollo era. Given that Apollo may very well be NASA’s greatest accomplishment, that alone might be enough to warrant the honor. However, Webb’s guidance during NASA’s formative years was also instrumental in commencing the space agency’s planetary exploration program. To understand this, lets take a look at John Kennedy’s famous “we choose to go to the Moon” speech at Rice University on September 12, 1962.

During that speech, President Kennedy not only provided the rational for the Apollo program, but stated the following:

“Within these last 19 months at least 45 satellites have circled the earth. Some 40 of them were made in the United States of America and they were far more sophisticated and supplied far more knowledge to the people of the world than those of the Soviet Union.

The Mariner spacecraft now on its way to Venus is the most intricate instrument in the history of space science. The accuracy of that shot is comparable to firing a missile from Cape Canaveral and dropping it in this stadium between the 40-yard lines.

Transit satellites are helping our ships at sea to steer a safer course. Tiros satellites have given us unprecedented warnings of hurricanes and storms, and will do the same for forest fires and icebergs.”

It has to be noted here that soaring rhetoric notwithstanding, Kennedy was not exactly a fan of spending money on space exploration. At least not to the extent the Apollo program demanded. Kennedy felt the political goal of beating the Soviet Union to the Moon trumped space sciences.  Nonetheless, you can see the origins of NASA’s planetary & Earth sciences programs along with applications such as GPS in Kennedy’s speech. So how does James Webb fit into all this?

When tapped for the job as NASA administrator, Webb was reluctant to take the position. Part of it was his background as Webb was a lawyer. He was also Director for the Bureau of the Budget and Under Secretary of State during the Truman Administration. Webb initially felt the job of NASA Administrator should go to someone with a science background. However, Vice President Lyndon Johnson, who was also head of the National Space Council, impressed upon Webb during his interview that policy and budgetary expertise was a greater requirement for the job.

That background paid off well when dealing with both Presidents Kennedy and Johnson. As NASA funding increased rapidly during the early 1960’s, there was great pressure to cut space sciences in favor of the Apollo program. Webb’s philosophy on that topic was this; “It’s too important. And so far as I’m concerned, I’m not going to run a program that’s just a one-shot program. If you want me to be the administrator, it’s going to be a balanced program that does the job for the country that I think has got to be done under the policies of the 1958 Act.”

The 1958 Act refers to the law the founded NASA and stipulated a broad range of space activities to be pursued by NASA.  The law can be found here.

During the 1960’s, NASA’s percentage of total federal spending is below:

Credit: Center for Lunar Science and Exploration

NASA has never obtained that level of funding since. Most of it was earmarked to develop and test the expensive Saturn V launch vehicle. And pressure was often applied from the President to Webb to scale back or delay NASA’s science program to meet Apollo’s goal of landing on the Moon before 1970. The video below is a recording of one such meeting between Kennedy and Webb.

Webb’s law background served him well in making the case for a balanced NASA agenda.  Despite pressure of the highest order, Webb was able to guide both Apollo to a successful conclusion and build NASA’s science programs as well.  The latter would include the Mariner program that conducted flybys of Mercury, Venus, and Mars.  Mariner 9 mapped 70% of Mars’ surface and Mariners 11 & 12 eventually became Voyager’s 1 & 2, humanity’s first venture beyond the Solar System.

Quite a legacy for a non-science guy.

This also demonstrates you do not necessarily have to have a science/engineering background to work in the space program.  Take a gander at NASA’s or SpaceX’s career pages and you will find many jobs posted for backgrounds other than science.  As James Webb proved, it takes more than science to study the universe.

*Image at top of post is JWST mirror segment undergoing cryo testing.  Credit:  NASA.

Corning, Kodak, and Hubble

This being the 25th anniversary of the launch of the Hubble Space Telescope, it is an opportune time to take a look at the connections between Upstate New York and the Hubble. I will focus on two companies. Corning, whose technological innovations made the Hubble possible, and Kodak, whose efforts could have spared the NASA the grief of Hubble’s original design flaw.  The story begins in the 1930’s, as the proposed 200-inch Mt. Palomar Observatory mirror required a low expansion material to make the large mirror possible.

During the 1920’s, the largest telescope in the world was the 100-inch reflector at Mt. Wilson Observatory. It was in this decade that Edwin Hubble would make his historic observations at Mt. Wilson, which included the discovery of galaxies outside the Milky Way and the expansion of the universe. At the time, George Ellery Hale was in the planning stages of building the 200-inch telescope at Mt. Palomar. To understand the engineering problem at hand, the surface area of the Mt. Wilson mirror is:

A = πr2

Which is (3.14)(502 inches) = 7850 square inches or 54.5 square feet.

The surface size of the Mt. Palomar mirror would be:

(3.14)(1002 inches) = 31,400 square inches or 218 square feet.

Despite the fact the diameter of the mirror at Palomar would be only double that at Mt. Wilson, the surface area would be 4 times larger. The mirror at Mt. Wilson was made at the French Glass Works and weighed 9,000 pounds (the mirror at Mt. Wilson is green just like a wine bottle). The greater surface area of the Mt. Palomar mirror demanded a material that did not expand or contract as much to temperature changes. Unless an alternative material could be found, this expansion and contraction would distort the optics to the point of making the primary mirror useless.

Enter Pyrex

The invention of Pyrex at the Corning Glass Works was the result of an effort to make lantern glass suitable for railroad watchmen. Traditional glass lanterns would shatter when the heat of the flame combined with cold winter weather. By 1915, Pyrex was being produced for its most well known application-kitchenware. The low heat expansion quality of Pyrex made it an excellent material for cooking.

Image: Wiki Commons.

In 1932, George Hale was looking for a material to cast the 200-inch Palomar mirror. His first choice was fused quartz, but the efforts at General Electric to cast the mirror this way proved unsuccessful. After spending $600,000 ($10 million in 2015 dollars) on the failed quartz effort, Hale turned to the Corning Glass Works and its Pyrex product to give it a try for the Palomar mirror.

Besides kitchenware, you may be familiar with Pyrex from your high school chemistry lab. Pyrex is regular glass with borax oxide added to it. The combination produces borosilicate glass, which experiences low expansion when exposed to heat. This is what keeps Pyrex kitchenware and lab equipment from breaking when it is heated up rapidly. So, why is this important for a telescope mirror that does not experience the same type of heating when Pyrex is put in an oven or over a Bunsen burner?

The optical precision required for the Palomar mirror meant that the mirror could not deviate more than two-millionths of an inch from its prescribed shape. Needless to say, the slightest amount of thermal expansion would have grievous effects on the optical quality of the images produced by the mirror. With this in mind, the Corning went to work on producing the Palomar mirror blank with its Pyrex material.

It would take two tries for Corning to build the mirror to be used at Palomar. During the first attempt, pieces of the mold in the mirror broke off due to the heat used in the casting process. This flawed mirror is now on display at the Corning Museum of Glass (see video below). The second mirror was shipped via a highly publicized train ride cross-country to California in 1936. There, over 10,000 pounds of the glass was shaved off in an extensive grinding process to polish the mirror to its required shape to produce the high-quality images for the telescope. World War II delayed this work a few years, but eventually the mirror was installed in the telescope in 1948.

Mt. Palomar would remain the world’s largest telescope until 1993 when the Keck Observatory in Hawaii surpassed it. During its run as the world’s largest telescope, astronomers at Palomar would refine the measurement of the expansion of the universe and discover quasars among its many other discoveries.  At the same time, Corning’s experience with producing observatory mirror blanks would be called upon again to make another groundbreaking instrument of astronomy.

In 1946, Lyman Spitzer proposed an observatory be placed in orbit above the distorting effects of the Earth’s atmosphere. In 1962, at the dawn of the space age, the National Academy of Sciences recommended that Spitzer’s concept be adopted by NASA as a long-term goal of the space agency. In 1977, Congress approved funding for an orbiting space telescope. In 1978, Corning went to work to produce two mirror blanks for the Hubble.

The Hubble mirrors were not made from Pyrex. By the 1970’s, Corning developed Ultra Low Expansion (ULE) fused titanium glass. Rather than use borax oxide as Pyrex does, ULE is made with a blend of titanium and silica to give it a nearly zero expansion coefficient. Besides being used for telescope mirrors, ULE was also utilized for space shuttle windows, as it could resist expansion when frictional heat built up during re-entry into Earth’s atmosphere.  This ability to maintain its shape made ULE an excellent candidate for the space telescope mirror.

Even though the Hubble mirror is kept at constant 700 F, the mirror shape only deviates 1/800,000 of an inch. If the Hubble mirror were the diameter of the Earth, its highest “mountain” would only be six inches. The nearly expansionless ULE maintains this optical precision.  ULE is also very lightweight.  Despite being the same size as the 100-inch Mt. Wilson mirror, the Hubble mirror is only 20% the weight.

After the production of the two mirror blanks, one was shipped to the Perkin-Elmer Corporation, the other to Kodak-Eastman for polishing. The blank sent to Perkin-Elmer eventually was used for the Hubble.  It was at this stage the fateful flaw would be made in the Hubble mirror.

A Kodak Moment NASA Regrets Passing Up

NASA received two bids to polish the mirror blanks from Corning. The Kodak bid was for $105 million while Perkin-Elmer bid was for $70 million ($300 million and $200 million in 2015 dollars respectively). Naturally, the Perkin-Elmer bid was viewed as the most competitive but it contained some troubling aspects. The Kodak bid was to polish two mirrors with different testing techniques. The testing mechanism on each mirror would then be used on the other to determine which was the better mirror and as a quality control measure. Perkin-Elmer relied on a single method to polish the mirror. It then sub-contracted Kodak to polish the back-up mirror, albeit at NASA’s request.

Further complicating matters (wonderfully described in Robert Capers and Eric Lipton’s report) was the budgetary and time constraints the Perkin-Elmer employees were working under. Perkin-Elmer had deliberately low-balled their bid to win the contract with the expectation Congress would approve more funding as the project progressed. However, the early 1980’s experienced the greatest recession since World War II as unemployment climbed towards 10% and Congress was in no mood to allocate more funding to polish the mirror.

washers
Wiki Commons

In the proverbial cruel twist of fate, the famous flaw in the Hubble mirror was a result of the use of three washers (yes, the very same kind used in your kitchen faucet) by Perkin-Elmer technicians to shim the optical testing device referred to as a null corrector. A piece of worn paint caused a misalignment of a laser that calibrated the distance from the null corrector to the mirror.  The overworked and rushed Perkin-Elmer technicians failed to report the calibration error to meet the deadline to produce the mirror.  This was combined with overconfidence in the null corrector device as signs of a design flaw in the mirror were ignored by the Perkin-Elmer project management. In the end, the mirror was polished perfectly to the wrong prescription, as the null corrector was 1.3 mm closer to the mirror than it should have been. The flaw in the mirror itself was 2 micrometers or about 1/50th the width of a piece of paper.

Consequently, the $1.5 billion Hubble was launched into orbit 25 years ago today with spherical aberration in its mirror causing blurry images due to three washers worth about twenty cents.

And what happened to the Kodak mirror? It stayed here on Earth. Kodak was not able to use its cross testing method as it only made one mirror rather than two. However, Kodak had used more traditional, time-tested methods to grind its mirror and finished its work in 1980, well before the Perkin-Elmer mirror. When the Hubble mirror flaw was discovered shortly after launch, the Kodak mirror played a key role in the ensuing investigation. The final determination was that the Kodak mirror was ground to the right specifications and the corrective measures would not have been required had it been placed in the Hubble. Since Kodak was subcontracted by Perkin-Elmer, it was the latter who had the final say which mirror to use and quite naturally, Perkin-Elmer decided to use its own mirror. The flaw was corrected in 1993 by the STS-61 mission.  The shuttle mission replaced the original Wide Field and Planetary Camera (WFPC1) with another* (WFPC2) that contained optics to counteract the spherical aberration in the Hubble mirror images.  The difference before and after are below:

M100 before and after Hubble repair mission. Credit: NASA

For the other instruments on the Hubble, the Corrective Optics Space Telescope Axial Replacement (COSTAR) was installed.  This was a set of mirrors used to act as “glasses” to correct the spherical aberration for the Faint Object Camera & Spectrograph, along with the High Resolution Spectrograph.

The Kodak mirror (below) now resides at the Smithsonian Air & Space Museum.

Courtesy National Air and Space Museum

* Both the WFPC2 and COSTAR that corrected the mirror flaw in the Hubble were removed in 2009 by the final Hubble shuttle servicing mission. The WFPC2 and COSTAR were also donated to the Smithsonian Air and Space Museum.

Image on top of post is the Hubble mirror.  Photo:  NASA/ESA

Apollo 11

Each semester during the Earth & Moon segment of my astronomy course, I like to show this video for the class of the Apollo 11 liftoff. It gives the students, most too young to have witnessed this, an opportunity to see how the event was covered at the time. Also, it ties in well with the concepts learned in the prior module involving Newton’s Laws of Force. Many of the concepts apply to launches today and this is a good opportunity to break down NASA jargon into comprehensible English.

Working the broadcast that day for CBS was Walter Cronkite and Wally Schirra, who was an astronaut on three space missions including Apollo 7.  The description of the video is as follows with the time being for the video rather than launch itself.

0:12 These are the 5 stage one F-1 engines each capable of producing 1.5 million pounds of thrust for a total of 7.5 million pounds of thrust. The Saturn V weight was 5 million pounds at launch. Newton’s third law states for every action, there is an equal and opposite reaction. The excess 2.5 million pounds of thrust is what lifted the Saturn V at launch. The engines were produced by Rocketdyne (dyne is Greek for power) which is now part of GenCorp Inc.  Now known as Aerojet Rocketdyne, the company has had some difficult times recently. The center engine is referred to as the inboard engine and the four outer engines as the outboard engines. The outer four gimbal and guide the rocket.

0:21 The voice you hear is Jack King, then the Kennedy Space Center Chief of Public Information.  King passed away in June of 2015.

0:30 The steam you see from the Saturn V is boil off from the cryogenically cooled liquid hydrogen and oxygen.  Hydrogen boils at – 4230 F.  That is only 360 F warmer than absolute zero.  Oxygen boils at -2970 F.  Venting the boiling liquid hydrogen and oxygen prevents the fuel tanks from being deformed.  The black markings on the Saturn V are quarter marks and are used to study the roll of the rocket during launch.

0:43 The fuel tanks are continually pressurized until right before launch as discussed above, liquid hydrogen and oxygen boil at very low temperatures and the boiled off fuel needs to be replenished.

1:53 Walter Cronkite mentions the water deluge on the launch pad. This system could release 45,000 gallons per minute as a sound suppression device to avoid acoustical damage to the Saturn V.  A nuclear weapon is the only human made device louder than a Saturn V.

2:21 Ignition of the F-1 engines starts 8.9 seconds before launch. This is the amount of time it takes to build up the required thrust for lift-off.

2:32 Lift-off! The Saturn V is angled 1.25 degrees away from the launch pad to avoid contact.  Close up videos of the launch (below) will reveal large chucks of ice vibrating off the rocket.  The Saturn V would have 1,200 pounds of ice on its sides created by the very cold liquid hydrogen and oxygen in the fuel tanks.

2:41 Jack King announces the tower is cleared. At this point, control of the flight is transferred from the Kennedy Space Center in Florida to the Johnson Space Center in Houston.

2:43 Neil Armstrong announces the beginning of the roll and pitch program to send the Saturn V over the Atlantic. This is the same direction the Earth rotates.  At the Cape, the Earth rotates at 914 mph (1471 km/hr).  That is the amount of velocity boost Apollo 11 receives from Earth’s rotation to help attain orbit and that is why all launches are eastward.  The closer to the equator, the faster the Earth’s rotational movement is. Launch facilities located near the equator such as ESA’s Guiana Space Center have a competitive advantage of being able to life more payload per amount of thrust.

2:48 Walter Cronkite mentions the building is shaking, a common occurrence during Apollo launches.  The press was stationed three miles from the launch pad. One (of many) reason the recent movie Apollo 18 was not realistic, lift-off would have set the entire Cape shaking. It would not be possible to launch a Saturn V there in secret.

3:31 As Apollo 11 approaches the speed of sound, the pressure differences from the shock waves lift water vapor away from the vehicle.

4:06 The region of maximum dynamic pressure, or Max Q, is when the combination of velocity and air pressure is greatest on the Saturn V. Although the velocity will continue to increase, the atmospheric density begins to drop off rapidly after this point. This can be seen by the widening thrust field from the rocket due to the rapid decline in atmospheric pressure.

5:12 Staging, the first stage is released and dropped into the Atlantic Ocean and the second stage ignites.  Apollo 11 is now in the stratosphere at an altitude of 42 miles.

5:16 The second stage has 5 J-2 engines. Like the F-1, these are also made by Rocketdyne. At this point in the flight, thrust is less important as the rocket is lighter and burn time takes precedent. The thrust of the J-2 is 230,000 pounds each but the burn time is about 7 minutes.

5:43 Skirt sep refers to the skirt between the first and second stage being separated.

5:58 Mike Collins reports visual is a go. He is referring to the command module launch shield being removed along with the escape vehicle. At this point, the astronauts now have a view out the window.

7:50 Here, many of my younger students express shock at the animation used in the coverage. A common device during the early years of the Space Age as there was not the miniaturization of cameras as there is today which allowed for on-board cameras famously seen on the shuttle launches.

8:45 Fitted between the third stage and the service module was the IBM computer for Saturn V. The computer ring was 3 feet high, 22 feet in diameter, and had 32 kb of memory-about half the size of a blank Word page.

IBM Saturn V Computer Ring – Courtesy: NASA

9:20 The water deluge on launch pad 39 to mitigate damage from the lift-off burn. After the Apollo program was complete, this launch pad was converted for use during the Shuttle program.  Today, launch pad 39 is leased out to SpaceX for its future space operations.

10:38 This was a very troubled time for American passenger railroads as alluded to by Walter Cronkite. Penn Central would file for bankruptcy less than a year later prompting Congress to form Amtrak in 1971.

Two hours and fifty minutes after launch, Apollo 11 began trans-lunar injection and was on its way to the Moon.

*Top image launch of Apollo 11, July 16, 1969.  Photo:  NASA.

Remagen

March 7th was the 70th anniversary of the capture of the Ludendorff Bridge crossing the Rhine River at Remagen. Hitler had ordered all the bridges across the Rhine to be demolished to stop the American advance into Germany. The U.S. Army 9th Infantry Division managed to capture the bridge while the German Army was attempting to blow it up.

Remagen
Ludendorff Bridge, 1945. Photo: National Archives.

General Omar Bradley said the bridge was worth its weight in gold as the American Army poured personal and equipment across the Rhine. In fact, so much tonnage crossed the bridge the overuse caused its collapse ten days later.  Twenty-eight were killed during the collapse which is described by Army Engineer John Morgado below.

The Third Reich would end exactly two months after the capture of the bridge.

Remagen Bridge Today
Ludendorff Bridge, 2011. Photo: Gregory Pijanowski

The bridge itself was never rebuilt.  However, the remaining bridge towers are now home to the Remagen Peace Museum. I highly recommend a visit if you find yourself in that region of Germany. Remagen is now a peaceful river town and it is difficult to image all the violence that took place there seventy years ago. However, sitting on a bench on the riverside by the bridge allows one to quietly reflect on the events there that helped end one of the most hideous chapters in human history.