Science - The Pigeon Roost

Science and Authoritarianism

With authoritarianism making headway in both Europe and America, it might be instructive to take a look back at what has historically happened to scientists and their supporting institutions when democracy wanes. Here, I’ll take a look at Nazi Germany. This might tempt some to invoke Godwin’s law as this is the extreme case study. However, the Freedom Party of Austria has its roots in the Nazi party while Greece’s Golden Dawn party employs an altered swastika for its emblem inviting the comparison. In America, the rise of Donald Trump trends more towards the celebrity cult/buffoonery of Gabriele d’Annunzio/Benito Mussolini, but the same can not be said of his most strident Twitter followers. We’ll focus on the three most prominent German scientists of the era, Albert Einstein, Max Planck, and Wernher von Braun.

The Refugee

Over a decade before Hitler rose to power, Albert Einstein became the most famous scientist in the world during 1919 when the Eddington expedition provided experimental confirmation of general relativity. Einstein’s troubles in Germany started only a couple of years later as Philipp Lenard and Johannes Stark, Nobel Prize winners in their own right, began to wage an anti-Semitic campaign against Einstein. Lenard was a fine experimental physicist, but had been left behind in the modern physics revolution. Stark also had difficulty comprehending the mathematics of the new physics. Unable to critique relativity on its merits, both referred to modern theoretical physics as “Jewish science” and eventually espoused what was referred to as Deutsche Physik or Aryan Physics. This politicization of science discarded modern physics and was intended to ride the wave of Nazi power.

Events in Germany came to a head as Hitler became Chancellor in January of 1933. Shortly afterwards, Jews were forbidden to hold university or research positions. Einstein had been in Belgium during early 1933 with the intention of returning to Germany. However, as the situation deteriorated (Einstein’s house had been raided and sailboat confiscated), Einstein appeared at the German consulate and renounced his German citizenship (Einstein was still a Swiss citizen) and resigned his position at the Prussian Academy of Sciences, the same academy where he announced his final general relativity theory in 1916. During the summer of 1933, while still in Belgium, word was put out that a $5,000 bounty had been placed on Einstein’s life.

On October 3rd, four days before he left Europe never to return, Einstein gave a speech at the Royal Albert Hall.

During the speech, Einstein asked, “How can we save mankind and its spiritual acquisitions of which we are the heirs? How can we save Europe from a new disaster?” The eventual answer, of course, was at a cost of millions of lives.

After arriving in America, Einstein took up a job offer at Princeton where he had remained until his death in 1955. Einstein worked to get other unemployed German Jewish physicists jobs in America. In all, over a thousand Jewish scientists relocated to America including several Nobel prize winners. This represented a significant shift in intellectual and innovative resources from Europe to America. In 1939, Einstein wrote a letter to President Roosevelt warning about the potential for Nazi Germany to produce an atomic bomb. Many top refugee scientists worked on the Manhattan Project, whose final result would have been used against Germany had it not surrendered a couple months before the first atomic test.

The essential lesson here is that Einstein’s enormous talent did not spare him from Nazi persecution. Purging or banning an ethnic group, besides the obvious ethical considerations, results in an intellectual drain. Segregating an ethnic group from educational resources presents a loss of potential economic growth, which is why ideologues need to resort to ethnic stereotyping to deflect attention from the negative by-products of their policies. Einstein, to his last days, spoke out for civil rights, lectured at black colleges, and was rewarded for his efforts with an 1,800 page FBI file.

As a pacifist, Einstein deeply regretted the letter that started the Manhattan Project. As a scientist, to this day, his work has held up to every rigorous test experimental physicists have thrown up against it. Relativity theory has provided us with the Big Bang, black holes, time dilation, and gravitational waves. Einstein will be long remembered while those who chose the expedient path of supporting Nazism have had their scientific legacy tarnished greatly. Not everyone in the German scientific establishment jumped aboard the Nazi bandwagon, some tried to mitigate the effects of Nazism by working within the system.

The Statesman

When Hitler ascended to power, Max Planck was president of the Kaiser Wilhelm Society. Planck had revolutionized physics in 1900 by discovering energy was emitted in discrete packages dubbed quanta. This would kick-start the quantum mechanics breakthroughs in the decades to follow. Planck was among the first to recognize the significance of Einstein’s work in 1905 on special relativity, and as editor of the journal Annalen der Physik, published Einstein’s work. It was Planck, as dean of Berlin University, who opened up a professorship for Einstein in 1913. It was here that Einstein finished up his work on general relativity.

Max Planck. Credit: Bain News Service/Library of Congress

Max Planck was born in 1858 and his life arced with Germany’s rise from a patchwork of unorganized states to unification as a single nation in 1871, eventually to rival the British Empire as a European power. Conservative in temperament, Planck was inclined to be apolitical publicly. However, Planck was a firm believer in advancing German science and loyalty to the German state. In May 1933, as Einstein was severing his ties to Germany, Planck announced at the Kaiser Wilhelm Society annual meeting that:

“The Kaiser Wilhelm Society for the Advancement of the Sciences begs leaves to the tender reverential greetings to the Chancellor and its solemn pledge that German science is also ready to cooperate joyously in the reconstruction of the new national state.”

In reality, Planck thought the Nazi party would moderate its views once in power (sound familiar?) and personally endeavored to continue the high standard of German research. That did not happen, of course. Planck met with Hitler personally in 1933 hoping to moderate his policy to stem the exodus of Jewish scientists from Germany. The meeting ended with a Hitler rant that science would have to suffer. Not surprising, as that is how discussions with hopeless ideologues tend to go. At the annual Kaiser Wilhelm Society meeting in 1934, Planck noted while the society was devoted to science in service of the fatherland, pure research was suffering as a result of Nazi policies. By 1935, Planck openly defied Hitler and attended the funeral service for Fritz Haber, who had been in exile from Germany.

It is difficult to maintain a functional operation when the overall organization is dysfunctional. Eventually the dam breaks, and the dysfunctionalty takes control. Planck in 1933 was also playing the role of the extreme centrist, blaming both Nazi and Jewish cultures equally for the situation in Germany. In this one can see the danger in not recognizing an asymmetric authoritarian movement. By 1936, Planck had openly stated that intelligence counts more in science than race. But despite Planck’s efforts, the purging of highly talented Jewish scientists had been complete. In 1937, Planck retired as president of the society, but not without offering the parting shot that scientific work required opposition to prove its merit, something Nazi supported science would not permit.

Planck’s experience offers the cautionary tale that an authoritative movement must be defeated before it obtains the keys to governance. There was no reasoning to be had with Hitler in 1933 and access to power offered no motivation for Nazis to moderate their policies towards Jews. By the end of World War II, Planck’s Berlin house had been destroyed in an Allied air raid, and he lost his son who was put to death for his participation in the plot to kill Hitler. Planck had previously lost another son in World War I during the battle of Verdun.

Eight days after the surrender of Germany in 1945, at the age of 87, Planck resumed his role as president of the Kaiser Wilhelm Society. After Planck had passed away in 1947, the Kaiser Wilhelm Society was renamed the Max Planck Institute. Under a democratic Germany, the institute has produced 18 Nobel prize winners and over 13,000 scientific publications annually. ESA’s Planck mission measured the cosmic microwave background radiation – the remnants of the Big Bang. The spectrum of this radiation is that of a blackbody, the same type Planck studied to determine that energy is emitted in packages. Blackbody spectra are emitted by objects in a hot, dense state, meaning that was the state of the universe when it was 380,000 years old. Planck’s legacy has enabled us to understand the nature of the electron and the origins of the universe.

In 2007, the Max Planck Institute completed a ten-year study on the history of the Kaiser Wilhelm Society during Hitler’s reign. The report acknowledged, especially after Planck’s departure in 1937, unethical scientific research during that period. It was not just party hacks involved in this behavior, some of the most talented scientists engaged in projects that degraded their reputations.

The Opportunist

On July 20, 1969, Neil Armstrong and Buzz Aldrin became the first humans to walk on the lunar surface. It was the culmination of a decade’s worth of work and $150 billion (2016 dollars) to beat the Soviet Union to the Moon. At the head of the Saturn V design team was Wernher von Braun, who was director of the Marshall Space Flight Center in Huntsville, Alabama. During the post World War II era, von Braun was the leading public advocate of space exploration. In many ways, von Braun was the Carl Sagan or Neil deGrasse Tyson of his era. Unlike Sagan or deGrasse Tyson, von Braun’s reputation originated on the backs of slave labor.

In some regards, von Braun was similar to Planck in that he was not a Nazi ideologue. He was loyal to Germany as a nation, but his main focus, obsession really, was space exploration and rocketry. His childhood dream was to go to Mars, but as Hitler rose to power, only military rocket research was permitted. During the early 1930’s, von Braun received a government research grant that permitted him to complete his PhD ahead of schedule. Unlike Planck, he joined the Nazi party in 1937 to advance his career.

Wernher von Braun (in civilian cloths) at the Peenemünde Army Research Center where the V-2 was developed. March 21, 1941. Credit: Wiki Commons/German Federal Archives.

During World War II, von Braun headed up the German V-2 program. While the V-2 killed 9,000 in its attacks, some 12,000 slave laborers were killed in the V-2 Mittelwerk production plant. The facility was adjacent to the Dora-Nordhausen concentration camp which supplied the labor. While von Braun was not stationed near the plant, he did visit it and was aware of the deaths at the plant. The V-2 program was not enough to stave off the eventual defeat of Germany in 1945. Von Braun planned to escape to America as he felt that would provide him the best opportunity to advance his career. Along with about 1,600 other scientists and engineers, von Braun was shepherded to America as valuable assets for the upcoming Cold War against the Soviet Union in a program code named Operation Paperclip.

Von Braun became famous to the American public during the 1950’s. In 1952, von Braun played a key role in a influential series of articles in Collier’s magazine. These articles presented to the public a peek at how future space missions to the Moon and Mars as well as a space station might look like. In 1955, von Braun started work on a series of television programs for Disney promoting space exploration. A sample of which is below:

Von Braun was a true visionary of space exploration. It is difficult to reconcile a man who worked for both Adolf Hitler and Walt Disney. My first lesson on space exploration was an article written by von Braun for the 1969 World Book Encyclopedia. When NASA was founded in 1958, it got to choose the pick of the litter from the existing military rocket programs, and that was von Braun’s army team. The rest is history and cemented von Braun as the face of America’s space program.

Von Braun passed away in 1977, about a decade before Operation Paperclip was investigated by the Justice Department. While von Braun’s work on the V-2 project was common knowledge, his membership in the SS was not well known to the public until 1985. Arthur Rudolph, whose contributions were crucial to the development of the Saturn V, was also the operations manager at Mittelwerk. Rudolph was deported in 1984. Kurt Debus, the first director of the Kennedy Space Center and an ideological Nazi during the war, avoided the investigation by passing away in 1983. How would have von Braun fared if probed by the Justice Department?

Wherner von Braun and Kurt Debus, roll out of Saturn V, May 26, 1966. Credit: NASA

Von Braun’s supporters point out that he would have been executed had he opposed the working conditions at Mittelwerk. No doubt, that is the case. In fact, von Braun was arrested by the SS in 1944 for carelessly opining that the war was a lost cause and the future of rocketry would be space exploration. However, this is a variation of the I was following orders routine, and von Braun was too high up in the food chain to use that as a passable defense. Clearly, von Braun had charted his own course in the Nazi apparatus. It is difficult to imagine a rigorous investigation ending well for von Braun.

What can we take from all this? Under an oppressive authoritarian regime, you can leave the country, try to maintain institutional integrity within the system, or advance your career regardless of personal debasement. If you want to leave, you’ll have more difficulty than Einstein securing a visa and a job. If Max Planck could not preserve the integrity of the Kaiser Wilhelm Society, what are the chances you’ll be able to where you are situated? As for careerism, if landing a man on the Moon is not enough to cleanse questionable past associations, do you really think you could pull that off?

The easiest solution is simply to reject authoritarianism before it takes power. Democracy is far easier to sustain by pushing for needed reforms than it is to re-institute it after it falls. Authoritarianism typically ends in chaos, war in the case of Germany and Japan in 1945 and Syria today, economic in the case of the Soviet Union in the 1990’s or Venezuela today. Regardless how you navigate your path through it, don’t think you will get out unscathed one way or another.

*Photo at top of post: Nazi Germany’s loss is America’s gain. Albert Einstein receives from Judge Phillip Forman his certificate of American citizenship. October 1, 1940. Credit: Al Aumuller/Library of Congress.

The American Eclipse of 2017

On November 18, 1805, the Lewis and Clark expedition explored Cape Disappointment off the Pacific coast in what is now Oregon. This concluded an 18 month journey to reach the Pacific Northwest. Today, the Cape is home to a state park which includes the Lewis and Clark Interpretive Center. On August 21, 2017, some 150 miles south, a solar eclipse will begin its race across the United States eastward until it exits into the Atlantic at Charleston, South Carolina. If you intend to travel to view the eclipse, several spots along the path of totality offer short day trips to some interesting historical spots. With proper planning, you can combine science and history in your trip.

Google and NASA has put together a neat interactive map for the eclipse that allows you to determine the time of totality for any given location. Below is how the eclipse enters the United States in Oregon starting at 10:15 A.M. PDT in the morning.

“men appear much Satisfied with their trip beholding with estonishment the high waves dashing against the rocks & this emence ocian.” – Lewis and Clark Journal, November 18, 1805.

If you are not from the Northwest, you might think this was a poor spot to view the eclipse as the climate is notorious for rain. However, most of the rain falls from October to March and the eclipse occurs during the driest month of the year for this region. Salem averages less than half an inch of rain for the entire month of August compared to over six inches in December. Salem will experience 1:53 of totality compared to 2:00 in the center of the shadow. This site has the added benefit of a major airport in Portland 45 miles north. And north of Portland, you can trace the trail of Lewis and Clark as they reached the Pacific along the Columbia River in the Lewis and Clark National Historical Park. From there, you can move on to Cape Disappointment to the Lewis and Clark Interpretive Center to take in the Pacific at the North Head Lighthouse.

North Head Lighthouse at Cape Disappointment. Credit: Wiki Commons

After Oregon, the path of totality enters Wyoming just south of Yellowstone National Park then eastward. The city of Casper is near the center of the path and will experience totality for 2:25. Casper is also very dry in August, averaging less than an inch a rain during the month. The airport in Casper is serviced by Delta and United Airlines with the major connections at Denver and Las Vegas. While in Casper, you can visit the National Historic Trails Interpretive Center which has exhibits on the Oregon, California, Mormon, and Pony Express Trails. If you are feeling adventurous, there are several spots in Wyoming where the ruts of the wagon trains are still embedded in the ground. One such spot is the “Parting of the Ways”

Parting of the Ways, Credit: National Park Service.

“If any young man is about to commence the world, we say to him, publicly and privately, Go to the West” – Horace Greeley in the New Yorker, August 25, 1838.

There is a bit of a historical dispute on this spot. Some claim this is where the Oregon and California trails branched off. The more accepted version is the right fork was the Sublette Cutoff which was a shortcut, but presented 50 miles of waterless trails. The left fork led to Fort Bridger and was a longer, but less riskier passage. Either way, it is an awesome piece of natural preservation. This is pretty rugged territory and a four wheel drive is recommended along with stocking up on supplies as there won’t be a 7-11 around the corner. Directions and background on this site can be found here. The Parting of the Ways is a four hour drive from Casper.

History always has two sides, and the other side of the westward expansion can be found 200 miles north of Casper at Little Bighorn Battlefield National Monument. Here is where Cheyenne and Lakota forces defeated General Custer’s 7th Calvary Regiment. The site houses memorials to both sides of the conflict. Millions of Native Americans were eventually killed as a result of war, disease, and forced relocation over the course of several centuries as European descendants made their way westward into the Americas.

After Wyoming, the path of totality barrels through Nebraska including the town of North Platte, also part of the Oregon Trail. Then through Missouri, the eclipse travels over the northern part of the Metro Kansas City area including the Harry S.Truman Library and Museum in Independence ten miles east of the city. Totality lasts about a minute over the museum, to experience over two minutes of totality, you’ll want to head towards the center line in the map below. St. Joseph will enjoy 2:38 of total darkness. As you move east, the climate gets wetter, meaning cloud cover becomes more of a possibility. Kansas City averages almost four inches of rain in August.

“We must build a new world, a far better world — one in which the eternal dignity of man is respected.” – Harry S. Truman address to the United Nations Conference, April 25, 1945.

The Truman Library has exhibits on the end of World War II, including the decision to drop the atomic bomb, the start of the Cold War, and the upset win in the 1948 election as well as his formative years serving in World War I. To learn more about Truman’s early life, there is the Harry S. Truman National Historic Site which was his home. This site preserves over 50,000 objects related to Truman.

Harry S Truman National Historic Site, Credit: National Park Service.

Independence was also the starting point for the Oregon, California, and Santa Fe Trails. This is commemorated in the National Frontier Trails Museum. The museum contains pioneer narratives, a public research library, as well as a Lewis and Clark exhibit as the expedition stopped there early in their journey.

From Kansas City, the path of totality heads towards St. Louis and the Gateway Arch. If you like country music, Nashville will experience totality, then the eclipse moves directly towards the Great Smokey Mountains National Park. The best way to reach this region is to fly into Knoxville which is less than an hour away. One caveat here, there’s a reason they are called the Great Smokey Mountains and that is because…they are smokey. The region receives 50-80 inches of rainfall per year. And this, of course, can reduce the visibility of the eclipse.

Great Smokey Mountains, Credit: Gregory Pijanowski

Still, if you decide to go this route, you will not be disappointed by the scenery. This is the most visited national park with over ten million taking in the vistas annually. There is also no charge to enter the park.

“We knew the world would not be the same. A few people laughed, a few people cried, most people were silent. I remembered the line from the Hindu scripture, the Bhagavad-Gita. Vishnu is trying to persuade the Prince that he should do his duty and to impress him takes on his multi-armed form and says, “Now, I am become Death, the destroyer of worlds.” I suppose we all thought that one way or another.” – J. Robert Oppenheimer on the first atomic explosion, quote televised in 1965.

Less than a half hour from Knoxville is the formally secret town of Oak Ridge. Secret in that this was where uranium was enriched during the Manhattan Project for the atomic bomb. The K-25 gaseous diffusion plant was a U-shaped building a half a mile long with some 2,000,000 square feet of floor space. Eventually, 12,000 people were employed at the plant and was so designed that they were not aware what they were producing due to the secretive nature of the project. The plant was demolished in 2014, but the American Museum of Science and Energy offers exhibits on the history of the Manhattan Project and nuclear energy. The museum offers bus tours of the historic Oak Ridge facilities which are now part of the Oak Ridge National Laboratory.

Finally, the path of totality moves into South Carolina, over Charleston, and out into the Atlantic Ocean at 2:49 P.M. EDT, ninety-three minuets after touching down in Oregon. Charleston will experience a minute and half of totality, situating yourself towards the center of the path of totality will stretch out total darkness for two and a half minutes.

“The last ray of hope for preserving the Union peaceably expired at the assault upon Fort Sumter.” – Abraham Lincoln, First Annual Message, December 3, 1861.

As anyone who has lived down South can tell you, Summer is the rainy season and Charleston is no exception averaging over six inches of rain in August. Still, if you make Charleston your destination, there is an excellent historical district downtown and in the harbor, Fort Sumter National Monument where the Civil War started on April 12, 1865 when Confederate forces attacked the fort.

As the eclipse moves from Oregon, across the Great Plains, and through the South, its path crosses over or near some of the history that helped define the United States as a nation from our westward expansion, the Civil War, to the emerging superpower at the end of World War II. Not all of the history has been pretty, the push west resulted in the deaths of millions of Native Americans. Over 700,000 died in the Civil War that abolished slavery, but did not give African-Americans total equality, the atomic bomb ended World War II, but gave humanity the ability to terminate its existence. Those events also gave us the great cities on the West Coast, our current African American president, and a peaceful relationship with a democratic Japan that has lasted since 1945. With history, you take the successes alongside the failures.

*Image atop of post is solar eclipse on March 20, 2015. Credit: Damien Deltenre/Wiki Commons.

Planets and Dwarf Planets – What’s in a Name?

The term dwarf planet was introduced in 2006, the same year I started teaching astronomy. It has been a source of confusion for students ever since. The confusion lies not only with the re-designation of Pluto, but also that an asteroid is considered a dwarf planet while the other four objects so designated lie in the Kuiper Belt outside the orbit of Neptune. The term dwarf planet was something of a compromise for those reluctant to modify Pluto’s status as a planet. As the living memory of Pluto as a planet fades, I suspect the term dwarf planet will fade as well. So how should we categorize the objects that lie in our Solar System?

Rather than looking at the shape and size of these objects, I prefer to examine how they were created in the solar nebula that formed the Solar System. When we divide the solar nebula into concentric circles, each section formed a distinct type of object. The solar nebula concept was first hypothesized by Immanuel Kant in The Universal Natural History and Theories of the Heavens published in 1755. As often is the case in astronomy, it took awhile for the ability to verify the theory to emerge. In this case, the process spanned some three centuries.

Part of the holdup was determining if the Sun, planets, and asteroids are all the same age as they must be if formed together in the solar nebula. A model of stellar evolution had to be created and that required Einstein’s relativity theory to explain nuclear fusion. This model puts the Sun’s age at 4.6 billion years. The age of the Earth also had to be determined and given the amount of erosion that takes place on the surface, finding rocks from Earth’s early days is difficult. Nonetheless, radiocarbon dating has put the age of zircon found in Australia at 4.4 billion years. This result also matches up with the age of the oldest Moon rocks brought back from the Apollo program. Also during the 1970’s, Russian physicist Victor Safronov formulated a modern solar nebular theory to compare the evidence against.

The Solar System began when a rotating interstellar cloud containing gas and dust grains began to collapse under its gravity. The rotation of the cloud caused this collapse to create a disk. The bulk of the matter was still in the center of the solar nebula and this is where the Sun materialized. Today, the Sun contains 99.8% of the Solar System’s mass. There is no difficulty categorizing the Sun as a star as nuclear fusion occurs in its core. The difficulty comes in the layers of the solar nebula outside the Sun.

The first concentric ring around the Sun is where the inner, rocky planets are located. These would include Mercury, Venus, Earth, and Mars. In this zone, as the Solar System was forming, the Sun kept temperatures warm enough to keep hydrogen and helium from condensing. As these two elements comprised 98% of the solar nebula, only trace amounts of heavier elements were left to construct planets. This explains the smaller size of the rocky planets. However, they were still large enough to become spherical in shape. The gravity of the planets pulled equally inward from all sides, overcoming the internal mechanical strength of its constituent material forming a sphere.

At the outer edge of this zone beyond the orbit of Mars lies the asteroid belt. During the epoch of the solar nebula, there was enough material here to form a planet. However, the presence of Jupiter’s gravitational influence caused enough disruption to keep this material from coalescing into a single planet. Today, there is not enough matter here to form a body the mass of the Moon. Nonetheless, one asteroid, Ceres, was large enough to become spherical in shape. As such, it was designated as a dwarf planet in 2006. When discovered in 1801, is was classified as a planet and remained so until the mid-1800’s. Here you can see the ephemeral nature of this categorizing. Ceres was in fact the first object discovered in a belt consisting of over 1 million asteroids. Once it was understood Ceres was simply the most visible of a large number of asteroids, its classification was changed. In this, Ceres is very similar to Pluto but their point or origin makes their physical makeup very different.

Between the orbits of Mars and Jupiter lies what is called the frost line. Beyond the frost line, both heavy elements and hydrogen compounds such as water, methane, and ammonia condensate (convert directly from gas to solid). As the hydrogen compound ice particles and rocky material began to stick against each other, they eventually grew large enough to gravitationally attract the surrounding hydrogen and helium gas. In this region, the hydrogen and helium gases’ temperature was colder than inside the frost line. Colder gases move with slower velocity than hot gases and this enabled planets outside the frost line to trap huge amounts of hydrogen and helium. Consequently, being outside the frost line allowed the outer planets to grow significantly larger than the inner planets. Thus, the gas giant planets Jupiter, Saturn, Uranus, and Neptune bear little resemblance to Mercury, Venus, Earth, and Mars as you can see below.

Terrestrial planets have small rocky bodies with thin atmospheres while gas giants have small icy/rocky cores surrounded by large amounts of hydrogen and helium gas. Distance between planets not to scale. Credit: Wiki Commons.

The third concentric ring in the Solar System beyond the orbit of Neptune is the Kuiper Belt, of which Pluto is a member. Also, short period comets such as Halley’s are thought to originate from the Kuiper Belt. These objects differ from the asteroid belt in that they are more icy than rocky in nature. This makes sense as the Kuiper Belt lies beyond the frost line where hydrogen compounds can condensate. Pluto was the first Kuiper Belt object to be discovered in 1930. It stood alone until 1992 when the second Kuiper Belt object was found. While Pluto is highly reflective, most Kuiper Belt objects are dark, in fact, darker than coal. That, along with their small size makes them difficult to detect. To date, more that 1,000 Kuiper Belt objects have been discovered giving the Solar System a third zone of objects orbiting the Sun.

Kuiper Belt objects in orange, outer planetary orbits in green. Credit: The Johns Hopkins University Applied Physics Laboratory

Looking at the above image, it is tempting to think that the Kuiper Belt objects were formed beyond the orbit of Neptune. However, the origins of the Kuiper Belt are still a matter of debate among astronomers. As these are icy bodies, they originated beyond the frost line, but precisely where is uncertain. One theory, called the Nice model, postulates these objects are left over remnants from where the gas giant planets formed and pushed outward by the migration of Neptune’s orbit beyond Uranus. This model explains Kuiper Belt objects that have highly elliptical orbits but not those with circular orbits. As it is estimated some 200,000 objects exist in the Kuiper Belt, there is quite a bit of discovery and mapping to perform to pin down the origins of these objects.

Beyond the Kuiper Belt is the Oort Cloud where long period (orbits that last thousands of years) comets are thought to originate. The Oort Cloud consists of trillions of icy bodies ranging from 1-20 km and extends about 1 light year from the Sun. To date, astronomers have not directly detected the Oort Cloud but we have observed long period comets traveling through the Solar System at different angles indicating an origination point from a spherical cloud. Like the Kuiper Belt, models have determined these icy objects formed beyond the frost line near the gas giant planets and were ejected by the gravity of these planets to their current location.

Oort cloud relative to the planets. Credit: ESO

If the solar nebula existed 4.6 billion years ago, how can we prove this theory is correct? We cannot observe the formation of our own Solar System, but we can observe, thanks to the Hubble and the next generation ALMA radio telescope, stellar and planetary systems forming around other stars. Below is perhaps the most iconic image taken by the Hubble, the Pillars of Creation in the Eagle Nebula located 7,000 light years from Earth. This is a large (the column on the left is four light years long) interstellar gas cloud acting as a nursery for new stars. In fact, ultraviolet radiation from newly born stars eats away at the dust cloud which gives it its shape.

Credit: NASA, ESA, STScI, J. Hester and P. Scowen (Arizona State University)

Below is an image of a spinning protoplanetary disk in the Orion Nebula 1,500 light years from Earth. The spinning motion has flattened the dust cloud to a disk shape. The disk contains dust grains that will clump together to form planets, asteroids, and small icy bodies such as Kuiper Belt objects.

A Protoplanetary Disk Silhouetted Against the Orion Nebula — Credit: NASA, J. Bally (University of Colorado) and H. Throop (SWRI)

The next image is planet creation in process around HL Tauri 450 light years from Earth. Taken by the ALMA radio array in Chile, you can see the gaps in a protoplanetary disk cleared of dust by planets forming in the rings. This is direct evidence of stars and planets creation matching up with the solar nebula theory of how our Solar System formed.

Getting back to the first point, when thinking how to categorize Solar System objects, it is best to consider how these objects formed. The term dwarf planet covers objects that originated inside and outside the frost line in the solar nebula and is of little use here. And as I mentioned before, most likely will be discarded as the collective memory of Pluto as a planet fades. It is a transition term much like Ceres was referred to as a minor planet between its time as a planet and asteroid. As such, I do not consider it a good point of emphasis when learning about the Solar System. Instead, I would summarize as follows:

Objects formed inside the frost line: Rocky planets with thin atmospheres, rocky asteroids, some of these asteroids are large enough to become spherical in shape, but most are not such as Eros below.

Objects formed outside the frost line: Gas giant planets with small icy-rocky cores and large atmospheres, small icy bodies such as the Kuiper Belt and Oort Cloud objects. Some, like Pluto, are large enough to form a spherical shape but most are not.

The Solar System is not static: After these objects are created and the solar nebula was dissipated by the young Sun’s solar wind, gravitational perturbations caused migration of these objects. In our Solar System, the orbital resonance of Jupiter and Saturn caused Neptune to migrate outward and took the Kuiper Belt objects with it. However, around other stars, Jupiter sized gas giants have migrated inwards to occupy orbits closer to their host star than Mercury is to the Sun. Over the course of 4.6 billion years, the Solar System has been a dynamic place.

Our lifetimes are very small compared to the cosmic time scale and thus, we tend the think of the Solar System as a static system. Nonetheless, we do see migrations of objects whenever a comet pays us a visit from the outer reaches of the Solar System. By classifying objects in the Solar System by their composition, it allows you to understand how the Solar System formed and what path those objects took to reach their final destination. And that is more important than worrying if a celestial body is a planet or a dwarf planet.

*Image atop of post is sunset over the mountains of Pluto taken 15 minutes after New Horizons closest approach. Credits: NASA/JHUAPL/SwRI.

The Two Sides of the Sombrero Galaxy

While in grade school, the classic image (above) of the Sombrero Galaxy was one that perked my interest in astronomy. The disk with the bright central core gave it a mysterious look, something I wanted to learn more about. Located 30 million light years from Earth, it is not bright enough to see with the naked eye, but easily captured by amateur astronomers armed with small telescopes. Although reasonably close as far as galaxies go, it still is an enigma for astronomers.

The Sombrero Galaxy was discovered on May 11, 1781 by Pierre Mechain, who was working with Charles Messier to build a catalog of nebulous objects so astronomers would not mistake for comets. The Sombrero Galaxy was not included in the original catalog, although Messier hand wrote a description of it in his personal copy. Mechain announced the discovery in a letter to the Berlin Royal Academy of Sciences and Arts on May 6, 1783. Eventually, in 1921, the Sombrero Galaxy was entered into the Messier catalog and given the designation M104.

News traveled slow in the 1780’s, and the Sombrero Galaxy was discovered independently by William Herschel on May 9, 1784. Herschel’s superior optics allowed him to view the dark dust lane in the disk that provided the Sombrero Galaxy with its moniker. In 1800, Herschel would discover infrared light. Two centuries later, infrared imaging would allow astronomers to make an important discovery about the Sombrero Galaxy.

During the 1800’s, spiral galaxies were referred to as spiral nebulae. At the time, it was thought the Milky Way was the sole galaxy to exist and the spiral nebulae were located within. Telescopes did not have the ability to resolve individual stars in galaxies outside the Milky Way. During the early 1900’s, astronomers began to challenge this view of the universe and a discovery from the Sombrero Galaxy played a crucial role in this debate.

In 1912, Vesto Slipher of the Lowell Observatory measured the red shift of the Sombrero Galaxy. If an object is moving away from us, its light waves become elongated, that is, the light shifts towards the red part of the spectrum. The red shift of the Sombrero Galaxy indicated it was moving away from us at a velocity of 1,000 km/s. Moving at such a fast rate suggested M104 resided outside the Milky Way, as this is almost twice the escape velocity of our galaxy. From an observational standpoint, this was among the first clues that the universe was expanding and not static, as was the prevailing wisdom at the time.

On April 26, 1920, what became known in astronomy circles as The Great Debate, took place in the Smithsonian Museum of Natural History between Harlow Shapley and Heber Curtis. Shapley proposed there was only one galaxy in the universe and that the Solar System was located far from the center of that galaxy. Curtis countered that we were located near the center of the Milky Way, but the spiral nebulae were galaxies residing outside the Milky Way. As is often the case with debates such as this, both were right…and both were wrong.

The observations of Edwin Hubble at Mt. Wilson Observatory throughout the 1920’s proved Curtis right in that the spiral nebulae were not gas clouds in the Milky Way, but other galaxies outside the Milky Way. However, Shapley turned out to be right on the location of Earth residing outside the center of the Milky Way. We tend to want to confer the status of a winner and loser with debates such as these, but remember, it is the evidence, not the person, that determines if a scientific proposal is correct or not. You’ll want to keep this in mind with similar debates today on string theory and parallel universes. The Sombrero Galaxy, like other spiral nebulae, was reclassified as a spiral galaxy outside the Milky Way.

The Sombrero Galaxy lies about 30 million light years from Earth. If you happen to catch it in a telescope, the light entering your eye started its journey from the galaxy when India began to slam into the Asia continent to form the Himalayan mountains. North America looked like this 30 million years ago.

Credit: Ancient Earth Globe/Ian Webster and C.R. Scotese

To put a light year in perspective, even though the Sombrero Galaxy is moving away from us at a rate equal to the distance from Paris to Copenhagen every second, it has only receded 1/3 of a light year since its red shift was first measured in 1912. The nearest star from us is Proxima Centauri at 4.2 light years. Even traveling at 1,000 km/s, it would take some 1,200 years to reach. That demonstrates the challenges facing those working on methods of interstellar propulsion.

Over the past two decades, space telescopes have afforded astronomers a better understanding of the internal structure of the Sombrero Galaxy. The Hubble, of course, is the most famous of these observatories and took this iconic image in 2003.

Credit: NASA and the Space Telescope Science Institute (STScI)

Seen here is the notable bright core of the Sombrero Galaxy, with its signature dust lane across the disk titled only 6 degrees from our vantage point on Earth. At 50,000 light years, the Sombrero Galaxy is only half as wide as the Milky Way but has more than 10 times the globular clusters with 2,000. In 1996, Hubble picked up a high rate of rotation near the core of the galaxy, confirming the 1988 ground observations by John Kormendy at the Canada-France-Hawaii Telescope. This rotation is accelerated by the presence of a black hole with a mass one billion times that of the Sun. It is one of the largest black holes detected in a nearby galaxy.

By and large, this is the way astronomers have seen the Sombrero Galaxy until recently viewed by other parts of the electromagnetic (EM) spectrum.

Just after the above image was taken by the Hubble, NASA launched the Spitzer Space Telescope. Named after Lyman Spitzer, Jr., who first proposed an orbiting telescope in 1946, the Sptizer observes in infrared. Cooler objects such as planets and dust radiate most strongly in infrared. Certain wavelengths of infrared have the ability to pass through dusty regions without being absorbed. This gives astronomers the ability to peer behind the curtain of opaque, dusty areas to see what lies behind. When the Spitzer took a look at the Sombrero Galaxy, this is what it saw.

Credit: NASA/JPL-Caltech/University of Arizona/STSc

The red represents a dust ring in the spiral disk. This is the area of a spiral galaxy where stars are born. That was expected, what was unexpected was the blue starlight in the galactic halo. Prior to this image, it was thought the bright halo was tenuous and small. Instead, it is an elliptical galaxy with a spiral galaxy embedded within. The Spitzer enabled astronomers to see stars behind the dust in the halo. This also explained why the Sombrero has far more globular clusters than spirals normally have. Elliptical galaxies typically have a couple thousand of these clusters.

Besides the Spitzer, the Chandra X-Ray Observatory has imaged the Sombrero Galaxy. Objects that are very hot will radiate high energy x-rays. Galactic dust and gas does not generally fall into this category unless it is heated up by a nearby source. What the Chandra imaged when pointed at M104 was this.

With the x-ray image, the spiral disk disappears as it consists of cool dust. The point sources in this image are high energy stars and background quasars. The Chandra also picked up halo of hot gas that extends 10,000 light years beyond the spiral disk. It is thought this gas is disbursed via a galactic wind originating with supernova activity throughout the galaxy.

If you want to look at M104 yourself, May is the optimal month to do so. Best to seek a dark sky location far from city lights, and while it is too dim to be seen with the naked eye, a pair of binoculars or a small telescope is sufficient to bring it into view. An 8-10 inch telescope will start to resolve features such as the dust lane. Below is an image of where M104 will be located on May 14th from my hometown Buffalo, NY. At 10:30 PM, it will be directly due south in the constellation Virgo.

It is always a challenge to target a deep space object such as M104, but like anything else, you’ll get better and better with more experience. Do not get discouraged if unable catch it on the first try and good hunting!

*Image on top of post is the Sombrero Galaxy taken at Mt. Palomar’s 200-inch Hale Telescope. Credit: Mt. Palomar/Caltech.

Beware of Outliers

As we currently digest the run-up to the 2016 presidential election, it can be expected that the candidates will present exaggerated claims to promote their agenda. Often, these claims are abetted by less than objective press outlets. Now, that’s not supposed to be the press corps job obviously, but it is what it is. How do we discern fact from exaggeration? One way to do that is to be on the lookout for the use of outliers to promote falsities. So what exactly is an outlier? Merriam-Webster defines it as follows:

A statistical observation that is markedly different in value from the others of the sample.

The Wolfram MathWorld website adds:

Usually, the presence of an outlier indicates some sort of problem. This can be a case which does not fit the model under study, or an error in measurement.

The most simple case of an outlier is a single data point that strays greatly from an overall trend. An example of this is the United States jobs report from September 1983.

bls — Credit: Bureau of Labor Statistics

In September 1983, the Bureau of Labor Statistics announced a net gain of 1.1 million new jobs. As you can tell from the graph above, it is the only month since 1980 that has gained 1 million jobs. And why would we care about a jobs report from three decades ago? It is often used to promote the stimulus of the Reagan tax cuts. When you see an outlier such as this being used to support an argument, you should be wary. As it turned out, there is a simpler explanation for this that has nothing to do, pro or con, with Reagan’s economic policy. See the job loss immediately preceding September 1983? In August 1983, there was a net loss of 308,000 jobs. This was caused by the strike of 650,000 AT&T workers who returned to work the following month.

If you eliminate the statistical noise of the striking workers from both months, you have a gain of over 300,000 jobs in August 1983, and 400,000 jobs in September 1983. Those are still impressive numbers and require no need for the use of an outlier to exaggerate. However, it has to be noted, it was the monetary policy of the Fed Chair Paul Volcker, rather than the fiscal policy of the Reagan administration that was the main driver of the economy then. Volcker pushed the Fed Funds rate as high as 19% in 1981 to choke off inflation causing the recession. When the Fed eased up on interest rates, the economy rebounded quickly as is the normal response as predicted by standard economic models. So we really can’t credit Reagan for the recovery, or blame him for the 1981-82 recession, either. It’s highly suspect to use an outlier to support an argument, it’s even more suspect to assume a correlation.

To present a proper argument, your data has to fit a model consistently. In this case, the argument is tax cuts alone are the dominant driver determining job creation in the economy. That argument is clearly falsified in the data above as the 1993 tax increases were followed by a sustained period of job creation in the mid-late 1990’s. And that is precisely why supporters of the tax cuts equals job creation argument have to rely on an outlier to make their case. It’s a false argument intended to rely on the fact that, unless one is a trained economist, you are not likely to be aware of what occurred in a monthly jobs report over three decades ago. Clearly, a more sophisticated model with multiple inputs are required to predict an economy’s ability to create jobs.

When dealing with an outlier, you have to explore whether it is a measurement error, and if not, can it be accounted for with existing models. If it cannot, you’ll need to determine what type of modification is required to make your model explain it. In science, the classic case is the orbit of Mercury. Newton’s Laws do not accurately predict this orbit. Mercury’s perihelion precesses at a rate of 43 arc seconds per century greater than predicted by Newton’s Laws. Precession of planetary orbits are caused by the gravitational influence of the other planets. The orbital precession of the planets besides Mercury are correctly predicted by Newton’s laws. Explaining this outlier was a key problem for astronomers in the late 1800’s.

At first, astronomers attempted to analyze this outlier within the confines of the Newtonian model. The most prominent of these solutions was the proposal that a planet, whose orbit resided inside of Mercury’s, perturbed the orbit of Mercury in a manner that explained the extra precession. This proposed planet was dubbed Vulcan, after the Roman god of fire. Several attempts were made to observe this planet during solar eclipses and predicted transits of the Sun with no success. In 1909, William W. Campbell of the Lick Observatory stated no such planet existed and declared the matter closed. At the same time, Albert Einstein was working on a new model of gravity that would accurately predict the orbit of Mercury.

Vulcan’s Forge by Diego Velázquez, 1630. Apollo pays Vulcan a visit. Instead of having a real planet named after him, Vulcan settled for one of the most famous planets in science fiction. Credit: Museo del Prado, Madrid.

The general theory of relativity describes the motion of matter in two areas that Newton could not. That is, when located near a large gravity well such as the Sun or moving at a velocity close to the speed of light. In all other cases, the solutions of Newton and Einstein match. Einstein understood that if his new theory could predict the orbit of Mercury, this would pass a key test for his work. On November 18, 1915, Einstein presented his successful calculation of Mercury’s orbit to the Prussian Academy of Sciences. This outlier was finally understood and a new theory of gravity was required to do it. Nearly 100 years later, another outlier was discovered that could have challenged Einstein’s theory.

Relativity puts a velocity limit in the universe at the speed of light. A measurement of a particle traveling faster than this would, as the orbit of Mercury did to Newton, require a modification to Einstein’s work. In 2011, a team of physicists announced they had recorded a neutrino with a velocity faster than the speed of light. The OPERA (Oscillation Project with Emulsion-tRacking Apparatus) team could not find any evidence for a measurement error. Understanding the ramifications of this conclusion, OPERA asked for outside help in verifying this result. As it turned out, a loose fiber optic cable caused a delay in firing the neutrinos. This delay resulted in the measurement error. Once the cable was repaired, OPERA measured the neutrinos at its proper velocity in accordance with Einstein’s theory.

While the OPERA situation was concluding, another outlier was beginning to gain headlines. This being the increase in the annual sea ice in Antarctica, seemingly contradicting the claim by climate scientists that global temperatures are on the rise. Is it possible to reconcile this observation within the confines of a model of global warming? What has to understood is this measurement is an outlier that cannot be extrapolated globally. It only pertains to sea ice surrounding the Antarctica continent.

Glaciers on the land mass of Antarctica continue to recede, along with mountain ranges across the globe and in the Arctic as well. Clearly something interesting is happening in Antarctica, but it is regional in nature and does not overturn current climate change models. At least, none of the arguments I’ve seen using this phenomenon to rebut global warming models have provided an alternative model that also explains why glaciers are receding on a global scale.

Outliers are found in business as well. Most notably, carelessly taking an outlier and incorporating it as a statistical average in a forecasting model is dangerous. Lets take a look at the history of housing prices.

In the period from 2004-06, housing prices climbed over 25% per year. This was clearly a historic outlier and yet, many assumed this was the new normal and underwrote mortgages and derivative products as such. An example of this would be balloon mortgages, where it was assumed the homeowner could refinance the large balloon payment at the end of the note with newly acquired equity in the property as a result of rapid appreciation. Instead, the crash in property values left these homeowners owing more than the property was worth causing high rates of defaults. Often, the use of outliers for business purposes are justified with slogans such as this is a new era, or the new prosperity. It turns out to be just another bubble. Slogans are never enough to justify using an outlier as an average in a model and never be swayed by any outside noise demanding you accept an outlier as the new normal. Intimidation in the workplace played no small role in the real estate bubble, and if you are a business major, you’ll need to prepare yourself against such a scenario.

If you are a student and have an outlier in your data set, what should you do? Ask your teachers to start with. Often outliers have a very simple explanation, such as the 1983 jobs report, that will not interfere with the overall data set. Look at the long range history of your data. In the case of economic bubbles, you will note a similar pattern, the “this time is different” syndrome. Only to eventually find out this time was not different. More often than not, an outlier can be explained as an anomaly within a current working model. And if that is not the case, you’ll need to build a new model to explain the data in a manner that predicts the outlier, but also replicates the accurate predictions of the previous model. It’s a tall order, but that is how science progresses.

*Image on top of post is record Antarctic sea ice from 2014. This is an outlier as ice levels around the globe recede as temperatures warm. Credit: NASA’s Scientific Visualization Studio/Cindy Starr.

Science’s First Rough Draft

It has often been said that newspapers are “history’s first rough draft.” The same is true of science. One could argue that journals fill the role, but historically, the vast majority of the public reads of scientific discoveries and/or events in the newspaper. It is quite interesting to see how these events were interpreted at the time without the benefit of hindsight. The New York Times online archive dates back to the paper’s origins in the 1850’s and represent a rich source of historical material that can be used in the class or for personal research. Here are some historical articles pertaining to astronomy and physics.

Auroral Phenomena – September 5, 1851. This article describes the aftermath of the Carrington Event, the most powerful magnetic storm in recorded history. The aurora was seen across America and telegraph operators could still send messages even after disconnecting the batteries. Below, NASA presents a computer model of the 1859 magnetic storm.

Glowing After – Sunset Skies – December 1, 1883. Three months after the Krakatoa eruption, the skies around the world appeared deep red after sunset as a result of aerosols ejected into the atmosphere. The cause of these sunsets were not known at the time – the article never refers to the Krakatoa eruption.

A Comet Visible by Daylight – September 20, 1882. The Great Comet of 1882, considered the brightest comet of the past 1,000 years, is visible during the day. The image atop this post is this comet. In 2015, the Rosetta mission became the first to attempt a landing on a comet.

The Roentgen Discovery – February 7, 1896. The discovery of x-rays and possible applications in the medical field. A century later, astronomers would use the orbiting Chandra X-Ray Observatory to discover the universe to be a violent place.

Wireless Signals Across the Ocean – December 15, 1901. Guglielmo Marconi receives radio signals in Newfoundland from London to open the era of mass communication. Decades later, astronomers use radio telescopes to discover pulsars and peer into the center of the galaxy.

The Greatest Telescope in the World – January 27, 1907. Plans to build a 100-inch telescope on the summit of Mt. Wilson in California. Opened in 1917, this telescope is where Edwin Hubble discovered the universe was expanding.

Mt. Wilson 100-inch telescope. Credit: Gregory Pijanowski

Comet Gazers See Flashes – May 19, 1910. Report on Earth passing through tail of Halley’s Comet. The comet tail was 100 degrees long and 10 degrees wide in the sky. Whatever was seen that night, comet tails are much too tenuous to cause flashes in the atmosphere.

Lights All Askew in the Heavens – November 10, 1919. Eddington Expedition proves Einstein’s General Relativity theory correct by measuring the bending of starlight during a total solar eclipse. Relativity has passed every test since, including the recent observation of gravity waves.

Ninth Planet Discovered on Edge of Solar System – March 14, 1930. Pluto is discovered. Since reclassified as a dwarf planet, the New Horizons mission gave us the first close up images of Pluto in 2015.

Nebula Velocities Support Einstein – June 12, 1931. Edwin Hubble discovers the expansion of the universe as predicted by Einstein’s relativity theory. Actually, Einstein was originally skeptical the universe could expand. It was Fr. Georges Lemaitre, Catholic priest and physicist, who proposed what was later called the Big Bang theory. The word nebula in the title refers to what we now call galaxies.

Lemaitre Follows Two Paths to Truth – February 19, 1933. Fr. Georges Lemaitre does not find a conflict between science and religion. Einstein and Lemaitre, “Have a profound respect and admiration for each other”. Article quotes Einstein as stating, “This is the most beautiful and satisfactory explanation of creation to which I have ever listened” regarding Lemaitre’s Big Bang theory.

Fr. Georges Lemaitre (center) and Albert Einstein, January 10, 1933. To the left is Robert Millikan who was the first to measure the charge of an electron. Credit: California Institute of Technology.

Bohr and Einstein at Odds – July 28, 1935. The conflict between relativity and quantum mechanics. The quest to unify the theory of relativity, which governs large objects, and quantum mechanics, which explains physics on an atomic scale, continues to this day.

Science and the Bomb – August 7, 1945. One day after Hiroshima, nuclear fission as a weapon and the implications for humanity are explained.

Palomar Observers Dazzled in First Use of 200-inch Lens – June 5, 1948. Delayed by World War II for five years, Mt. Palomar Observatory finally opens for business.

Radio Telescope to Expose Space – June 19, 1959. Navy to build largest radio telescope in West Virginia. The current radio observatory in Green Bank, WV is surrounded by a 13,000 square mile (slightly larger than the state of Maryland) radio quiet zone, meaning no cell phones, radio, or microwave ovens.

New Clues to the Size of the Universe – March 26, 1963. The brightest objects in the universe, dubbed quasars, are discovered. Located over 10 billion light years away, these objects are so bright some astronomers thought they must reside within the Milky Way. However, further research would prove quasars to be the most distant objects observed by humans.

Signals Imply a Big Bang Universe – May 21, 1965. The discovery of the cosmic microwave background radiation (CMB) proves the universe was born in a hot, dense state aka the Big Bang. The CMB was most recently mapped by the ESA Planck mission. The map shows the state of the universe when it was 380,000 years old.

*Image on top of post is the Great Comet of 1882 from the Cape of Good Hope. Credit: David Gill.

Vollmond, High Tides and Lunacy

When teaching astronomy to non-science majors, I try to make connections with the student’s field of study or personal interests. Sometimes this is not difficult. For example, I can discuss NASA budgets and cost estimating with business majors. For art majors, the deep red sunsets that followed the Krakatoa eruption of 1883 found their way into many paintings of the era. The most notable example of this was The Scream painted by Edvar Munch in 1893.

The Scream by Edvard Munch. National Gallery, Olso, Norway. Aerosols injected into the atmosphere by powerful volcanic eruptions can cause very deep red skies at sunset.

A while back, I talked with someone whose career was in the performing arts, specifically dance. I was stumped at the time to think of a possible tie in between astronomy and dance. The closest analogy I could come up with was the classic case of a figure skater demonstrating the concept of angular momentum during a spin such as below.

Angular momentum is conserved, that is, it is not created or destroyed (it can be converted to heat via friction). Angular momentum (L) is defined as:

L = mrv

m = mass, r = radius, v = velocity

As angular momentum is conserved, the value L is constant. In the case of the figure skater in the video, she reduces r by drawing in her arms and legs closer to herself. As the skater’s radius decreases, velocity must increase. Hence, the rate of spin increases as radius decreases. You can try this at home even if you do not know how to skate. Just find a swivel chair and have a friend spin you around with your arms extended, then draw in your arms close to your body. You’ll feel your spin velocity accelerate. Not as much as the skater, but enough to notice.

The conservation of angular momentum has several applications in astronomy, in particular, pulsars. Pulsars are the remnants of stars that went supernova. As the outer layers of the star are dispersed in the aftermath of a supernova, its inner core compresses forming the pulsar. In a pulsar, the gravitational force is so great that electrons merge with protons to form neutrons. Consequently, pulsars are a sub-class of what are known as neutron stars. As the radius of a pulsar is reduced, its spin rate greatly accelerates.

We can measure the spin rates of pulsars as they emit radio waves in the same fashion a lighthouse emits a light beam. The most famous pulsar is located in the Crab Nebula, which is a remnant of a supernova observed by Chinese astronomers in 1054. This pulsar spins at a rate of 30 times per second. To put that in perspective, the skater in the video above is spinning 5 times per second.

The pulsar in the Crab Nebula emits high energy x-rays. Red is lowest energy and blue highest energy x-rays. Credit: NASA/CXC/SAO

Is there any sort of analogy in the world of dance? Ballet dancers use the same method as figure skaters to increase their spin. However, as there is more friction from a wood floor than there is from ice, the effect is not as pronounced. Looking around I found a different approach when it came to this and found a connection, albeit allegorical, to the dance performance Vollmond.

Translated from German, Vollmond means Full Moon. Choreographed by Pina Bausch, the performance centers on two themes addressed in my class. One is scientific, how the full Moon increases tides, the other not so scientific, how a full Moon affects human behavior.

During a full (and new) Moon, the difference between high and low tides are at their greatest. During these two phases, the Earth, Moon, and Sun are aligned with each other. At this time, the effect of the Sun and Moon’s gravity is greatest on the oceans as can be seen below.

The gravity from the Sun amplifies the lunar tides. During a full Moon, high and low tides occur twice a day. Tides during the full and new phases are referred to as spring tides. This has nothing to do with the season of Spring. In a way, it is during this time when the tides spring to life. When the Moon and Sun are at a right angle relative to Earth, the Sun’s gravity partially offsets the Moon’s gravity and modulates the tides so low and high tidal differences are not as great as the spring tide. These are referred to as neap tides. Local conditions can also amplify the tides. The most dramatic example of this is the Bay of Fundy where high and low tide can differ by 56 feet.

Spring tides at the Bay of Fundy Credit: Samuel Wantman/Wiki Commons.

So, if you live by the ocean, you’ll associate high tides with a full (and new) Moon. How about the Great Lakes? Not so much. The lakes greatest tide is only 5 cm, not enough to be noticed with the naked eye. The earth you stand on also feels the tidal pull from the Moon. Like the lakes, it is not noticeable at 25 cm. As the landmarks rise up and down with the ground, your eye cannot detect ground tides. We can say, quite confidentially, that the full Moon affects tidal motions. Can we say the same regarding human behavior?

The words lunar and lunatic have their roots in the Latin word luna. In ancient Rome, Luna was the goddess of the Moon. Lunatic means to be moon struck. We are all familiar with the phrase, “It must be a full Moon.” Meaning that the full Moon provides an explanation for an increase in bizarre/criminal behavior. Does the empirical evidence support this? The short answer is no. Studies have indicated no change in criminal behavior during a full Moon, or even a scientific model to explain why that would happen. This highlights the key difference between science and mythology.

Statue of the Roman Goddess Luna. Credit: Wiki Commons

Whenever a student writes the phrase, “I believe” in a science paper, I advise them to take pause and ask yourself why do you believe that? Science is not about beliefs, but about investigation of the nature and causes of phenomena we observe around us. If you want to assert something as being true in science, you need a model to explain why it happens, empirical evidence it actually does happen, and independent verification of the original results. Sometimes you might have a model you think is reasonable, but the empirical evidence does not back it up. One such case is in economics, where demand and supply curves indicate a minimum wage set above the market rate creates unemployment. The evidence does not support that meaning a newer, more sophisticated model is required to explain what is happening.

The purpose of this exercise was to find ways to connect a student’s personal interest to a scientific topic. If that can be accomplished, the chances of building the student’s interest and motivation in the class increases. In this case, we can use two situations to discern between what passes for science and what does not. For the teacher, it provides the opportunity to explore areas that were previously unknown. I would have never learned of the Vollmond dance performance without attempting to match my specialty with the student’s. It’s a good experience to reach out of your comfort zone to find common ground with your students. Often, in the classroom, who is the teacher and who is the learner can be a fluid situation. You have to permit yourself enter your current student’s world of interests. I have found that as a teacher, that prevents my lessons from going stale over the years.

*Image on top of post is the full Moon, or Vollmond in German. Credit: Katsiaryna Naliuka/Wiki Commons.

Gravitational Waves – A New Window to the Universe

Some 1.3 billion years ago, as plant life was making its first appearance on Earth, two black holes 29 and 36 times the mass of our Sun, collided. The result of this collision was a single black hole 62 times the mass of the Sun. The remaining mass, equal to three Suns, was expelled as energy. This energy created a ripple in the space-time fabric referred to as gravitational waves. These waves, which emanated from the colliding black holes like pond waves formed by a rock tossed into it, were detected by the LIGO team on September 14, 2015. The announcement made today, culminates a 100 year effort by physicists to confirm Albert Einstein’s prediction of gravitational waves.

What are gravitational waves?

Issac Newton’s theory postulates that gravity acts as an instantaneous force throughout the universe. That is, the gravitational force from the Sun, Earth, even your body, is felt immediately on every other body everywhere. As Einstein worked up his theory of relativity, he knew there was a problem with this. According to relativity, there is a firm speed limit in the universe, this limit being the speed of light. As nothing, whether it is matter or energy, could travel faster than this, it would not be possible for the effect of gravity to travel faster than light as well. Clearly, a new way of explaining gravity was required.

Einstein found this explanation in the form of gravitational waves. If there was to be some sort of perturbation in the Sun’s gravitational field, we would not sense it right away on Earth. Instead, the disturbance would radiate from the Sun at the speed of light in the form of gravitational waves. It takes light eight minutes to reach Earth. Thus, a time lag of eight minutes would occur before we would feel the gravitational disturbance on Earth. In the same manner, there was a 1.3 billion year lag to detect the gravitational waves from colliding black holes located 1.3 billion light years away. Had Newton’s theory of gravity been correct, the gravitational effect of the colliding black holes, however faint, would have reached Earth instantly 1.3 billion years ago rather than last September.

I want to emphasize that Newton’s theory of gravity works in most situations. Newton’s predictions deviate from Einstein’s predictions in two key situations. One is when a body is located very close to a large mass, such as Mercury is to the Sun. The other is when a body is traveling near the speed of light. In other situations, Newton’s and Einstein’s equations yield the same result. In fact, NASA engineers will use Newton’s version of gravity when they can as it is easier to work with than relativity. The Apollo program, for example, sent humans to the Moon using Newton as a guide. Replicating Newton’s results where they are accurate was a key stepping stone for Einstein when devising relativity theory.

Another key stepping stone for relativity was making successful predictions where Newton could not. One such example is the orbit of Mercury. The perihelion (spot closest the Sun) of Mercury’s orbit advances 43 seconds of arc per century (43/3600th of a degree) more than predicted by Newton. This advance is visualized in exaggerated form below.

Credit: Wikipedia/Rainer Zenz

When Einstein found out that his theory’s solutions predicted Mercury’s orbit perfectly, he was so excited he experienced heart palpitations. As opposed to being a force, general relativity views gravity as a bending of space-time.

As an object bends the space around it, another object will travel along the path of that curvature. Also, electromagnetic radiation such as light will follow the curvature as well. If an object accelerates, as when happens when black holes are colliding, it will generate ripples in space time. And it is these ripples that LIGO detected.

A 3-D visualization of gravitational waves generated by colliding black holes. Credit: Henze, NASA

The universe is not very pliable and it took a tremendous amount of energy to create these waves which are very small, only 1/1000th the size of a atomic nucleus. How much energy? Matter in the amount of 3 solar masses was converted into energy in the collision. Using Einstein’s famous equation:

E = mc²

E = 3(1.99 x 10³⁰ kg)(3.0 x 10⁸ m/s)²

E = 1.79 x 10³⁹ J where J = Joules

The Hiroshima atomic bomb released about 10¹⁴ J of energy. This means the black hole collision detected by LIGO released 1.79 x 10²⁵times the amount of energy as the 1945 atomic bomb. When you see the amount of energy involved, and how small the gravitational waves detected were, its easy to understand how difficult it is to observe these waves. In fact, Einstein was doubtful gravitational waves could ever be detected as they are so faint. The announcement today is a result of an effort started in the 1980’s to build the LIGO facility.

LIGO’s two gravitational wave detectors. Credit : LIGO

In 1992, the NSF granted funding for the LIGO project to commence. It consists of two facilities, one in Livingston, LA, and the other in Hanford, WA. As a sidenote, Hanford was the site of a key plutonium production plant during the Manhattan project. Each facility has two 4 km tubes where a laser is sent through. The mirrors in the interferometer are calibrated so when the two light beams reach their final destination, they cancel each other out so no light is recorded at the photodetector. This is known as destructive interference and is pictured below.

If a gravity wave passes through LIGO, the ripple in space-time moves the mirrors just enough to cause the laser to captured by the photodetector. This movement is much too slight to be felt by humans and thus the need for sophisticated equipment to catch it.

LIGO has been operational since 2002. During its first run, no gravitational waves were detected. LIGO underwent a recent $220 million overhaul to increase its sensitivity. As mentioned in the press conference today, LIGO is only at a third of its final expected resolution capability. This bodes very well for more discoveries at LIGO over the next decade. In all, LIGO has cost $650 million since its inception in 1992. That is 1/10th the cost to rebuild the San Francisco-Oakland Bay Bridge. This discovery has the potential to open a new window of observation for astronomers.

To the general public, astronomy for the most part means the classic image of an astronomer peering through an optical telescope or the famous imagery from the Hubble Space Telescope. What is not as well known are telescopes that observe other forms of radiation. This includes Earth-bound radio telescopes and space telescopes such as the infrared Spitzer Space Telescope and the Chandra X-ray Observatory. Why bother with these other forms of radiation? Think of it this way, imagine a tower located a mile away on a foggy day. The tower has both a light beacon and radio transmitter. The fog blocks out the light, making it invisible. However, if you have a radio receiver, you’ll be able to pick up the radio transmission as fog is transparent to radio waves. In this manner, astronomers use different types of radiation to detect objects not visible in the optical range.

Besides the continuing upgrade at LIGO, there are future gravitational wave observatories anticipated in India, Japan, and it is hoped, in space. Today’s result overcomes the most important hurdle. When LIGO was funded, many scientists were skeptical it could actually detect gravitational waves. Now that we know it can be done, that clears a major obstacle for funding. The opening of the radio window allowed the discoveries of pulsars and the cosmic microwave background radiation. The x-ray window allowed us to view accretion disks around black holes. The next decade should provide us with additional surprises about the universe as the gravitational wave window opens up.

Above is the LIGO gravitational wave detection result announced today. The strain is the distance space-time was stretched during the event. At 10^-21 m this is, as mentioned before, about 1/1000th the size of an atomic nucleus. What gives the LIGO team confidence this is not a false detection as the one produced by the BICEP team two years ago is the gravitational wave was detected by both the Livingston and Hanford observatories. You’ll also note how closely the observed wave matches with the predicted wave. The hallmark of progress in science is when theoretical prediction matches observation. If Einstein were around to see this, I suspect he may have had heart palpitations just as when he found a match between relativity and the orbit of Mercury 100 years ago.

*Image on top of post displays how the colliding black holes produced the gravitational waves discovered by LIGO. Credit: Credit: LIGO, NSF, Aurore Simonnet (Sonoma State U.)

The End of the World as We Know It

Centuries ago, Polynesian explorers settled on dozens of Pacific islands spanning from New Guinea to Hawaii to Easter Island. Living on several islands provided the Polynesian culture a better chance for survival. If disaster struck one island, the culture could still thrive on the other islands. This is often, as recently expressed by Stephen Hawking, used as a rationalization for space colonization. Is this a realistic model for human survival? The best way to answer that is to understand how Earth protects life, what could endanger life on Earth, and how difficult it would be to migrate into space.

The Sun resides in a relatively quiet area of the galaxy referred to as the Local Bubble. This bubble was created by a series of nearby supernovae events some 10-20 million years ago. Even so, the Solar System is bathed with galactic cosmic rays and ionized solar winds which are harmful to life. The Earth offers protective layers that insulates life from the harsh realities of space. The magnetic field guides ionized particles towards the polar regions. The harmful kinetic energies of these particles are absorbed by oxygen and nitrogen atoms in the upper atmosphere and converted to harmless light radiation in the form of the aurora. The ozone layer blocks harmful ultraviolet (UV) rays from reaching the surface. In fact, the upper atmosphere heats up at the ozone layer where the high energy UV radiation is absorbed.

Stratospheric heating (red) caused by ozone layer absorbing UV rays. Credit: ESA

The Earth’s atmosphere also absorbs high energy x-rays and gamma rays. This is a key point as our first attempt to colonize space will most likely be on Mars. And Mars does not offer the protective layers that Earth does from the harmful radiation of space. Any attempt to colonize the red planet will need to invent technologies to provide protection from space radiation. Also, Mars has only 1/3 the gravity of Earth which can deteriorate body muscle throughout a long duration stay. We cannot change Mars’ gravity and for this reason, some propose to make future Mars missions a one way colonization effort* as returning to Earth’s gravity may be problematic.

How feasible is it to colonize Mars? To put it in perspective, it is much easier to colonize Antarctica. Currently, there are a few dozen scientists who occupy the South Pole station in any given year. Going to Mars is possible, but during the next few decades only a handful, at best, will occupy our nearest neighbor. When evaluating possible disaster scenarios on Earth, what type of timeline are we looking at?

For now, I want to focus on natural, rather than human induced, disasters. First on deck are supervolcanoes. A supervolcano is an eruption that releases at least 500 cubic km of magma. By comparison, this is 500 times larger than the Mt. St. Helen’s eruption in 1980. These events are pretty rare, about once every 100,000 years. To put that in perspective, the Pyramids of Ancient Egypt were built 5,000 years ago. The last supervolcano eruption was Lake Toba 74,000 years ago in Indonesia. These events can lower global temperatures 10 degrees Celsius over a period of ten years. Once believed to have reduced the human population to 11,000, new evidence suggests that Lake Toba was not as catastrophic to humanity as originally thought.

While that is good news, a supervolcano would certainly be disruptive to human civilization. And while the chances are such an eruption in the near future are remote, at some point in time there will be one. One such mantle hotspot resides in Yellowstone. Recently, the Yellowstone magma chamber was mapped.

Credit: Hsin-Hua Huang, University of Utah.

The newly found lower chamber contains about 11,000 cubic km of magma. The last Yellowstone eruption occurred 640,000 years. The chances of an eruption in the near future is very slim. As destructive as these events can be, it appears that the next such event could be 10,000 or more years in the future. At this point, there seems little that could be done to thwart the threat of a supervolcano. That is not the case with the danger of an asteroid/comet strike.

Impact events are not uncommon. Small meteors collide with Earth everyday, usually burning up in the atmosphere. When they are large enough to survive the frictional forces of the atmosphere, they strike the ground and are then called meteorites. These objects are collector items but also valuable for scientific research. Unlike the Moon, erosion typically wipes away evidence of past large impact events. One exception is in Arizona where the dry climate has kept intact a 1,300 meter wide crater for 50,000 years from a 30-meter meteor impact event.

Arizona Meteor Crater and Visitor Center. Credit: Shane Torgerson/Wiki Commons

If a impact is large enough, sizable amounts of material can be ejected into the atmosphere causing global cooling and potential danger to life. Most famously, an impact near the Yucatan Peninsula 65.5 million years ago killed off the dinosaurs. This was one of the largest impacts in the inner Solar System since the heavy bombardment formation stage some four billion years ago. The cause of this was an object 10 km wide. How often does such an event take place?

Fortunately, extinction type impacts are very rare. In fact, the impact causing the dinosaur extinction is the last known event of this magnitude. More common are smaller, but still damaging impacts such as the 1908 Tunguska event in Siberia. In this case, a 120 foot object vaporized some 5 miles above the ground and the concussion was felt dozens of miles away. While potentially devastating on a local scale, these impacts would not present a threat to humanity on a global basis. Impacts of this scale occur around once every 300 years.

Trees knocked over by Tunguska impact. Credit: Leonid Kulik

Unlike supervolcanoes, it is feasible to mount a defense against a possible asteroid or comet impact. NASA now has Planetary Defense Coordination Office whose mission is to locate, track, and devise efforts to defend against collisions with Near Earth Objects (NEO). NASA has discovered over 13,000 NEO’s and detects an additional 1,500 NEO’s per year. The program’s budget is $50 million annually. That is 25% the cost to make the most recent Star Wars movie. NASA’s goal is to have a test mission to redirect an asteroid during the 2020’s. While we can plan to defend against impact events, the stellar evolution of the Sun is much more problematic.

The Sun is an average sized main sequence star halfway through its expected lifespan of 10 billion years. Main sequence stars like the Sun fuse hydrogen into helium in their cores. Over the next billion years, the Sun will become hotter and more luminous. As a star ages, the rate of fusion in its core rises. Some 3.5 billion years from now, the Sun will emit enough energy to vaporize the oceans and propel Earth’s remaining water vapor into space. And it doesn’t stop there. About 5 billion years from now, the Sun’s core will run out of hydrogen and begin fusing helium into carbon. The core will become hotter causing the Sun to expand into a red giant. At this point, the Sun will consume the inner planets including Earth. Here, humankind will need to develop interstellar travel or cease to exist.

Would interstellar travel guarantee our survival as a species? Not quite. The universe itself is evolving and has a life span. Currently, the universe is expanding at an accelerating rate. If this trend were to continue, 22 billion years from now some models predict the Big Rip will occur. In this state, all matter down to sub-atomic particles will have been shredded apart, making life in our universe impossible. Unlike stellar evolution, the eventual outcome of the universe is not completely known. While we can observe other sun-like stars to see how they live and die, we do not have the ability to observe other universes to do the same. And in fact, we do not even know what 95% of our own universe is made of. Nonetheless, physicists, such as Michio Kaku, have floated proposals for life to escape to a parallel universe when ours becomes uninhabitable.

So, how should we plan for the future of humanity and where do we place our priorities? Lets take a look at a potential timeline of possible threats.

Climate change: 0-100 years

Nuclear proliferation: 0-100 years

Supervolcanoes: 0-30,000 years

Impact: 0-tens of millions of years

Sun: 3.5 billion years

Universe: Tens of billions of years

The most imminent threats are human made, rather than natural. It is technically feasible to defend against meteor/comet strikes while not the case with supervolcanoes. More than likely, that leaves us with a few thousand years to figure out how to establish a permanent human presence on Mars. Certainly, going to Mars is doable if the incentive is there to devote resources and funding. It will not be possible to defend Earth against the Sun’s stellar evolution. If interstellar travel is possible, and that’s a big if, we have on the order of a billion years to find a way to do that. Like a lot of space enthusiasts, I’d like to see that happen in the 23rd century just as in Star Trek. However, unlike exploring the Solar System, the distances involved with interstellar travel will require a far-reaching advancement of physics and engineering that is not guaranteed to happen. So what do we do now?

Hollywood blockbusters notwithstanding, the major priority should be getting a handle on human induced dangers such as climate change and nuclear proliferation. Concurrently, we can continue our efforts to begin human exploration of Mars. All this can take place in the next century but it must be stressed a human settlement on Mars is not a substitute for cleaning up our act on our home planet. During this time, we will begin to discover Earth-like planets, and possibly, life beyond our Solar System.

Efforts to begin interstellar exploration are in a very, very prototype stage. Relativity places a limit on velocity at the speed of light. Concepts to bypass this limit are speculative at best and are why, as mentioned earlier, will require a deeper understanding of physics to accomplish. This advancement will have to be on the order of what Issac Newton achieved in the late 1600’s and modern (both Einstein and the quantum physicists) physics in the 20th century. When and if this happens, we can plan for humanity’s migration to the stars to escape the Sun’s vaporization of Earth. If we are fortunate enough to accomplish that, we can owe it to the same spirit that carried the Polynesians in their wooden canoes across the vast expanse of the Pacific.

*To be clear on this point, the Mars One initiative is not realistic in its timeline or funding. However, other proposals, such as offered by Buzz Aldrin, may be more realistic.

**Image on top of post is the famous Earthrise photograph from Apollo 8, the first space mission to carry humans to another celestial object. Taken on Christmas Eve, 1968. Credit: NASA.

The Dark Universe

During the 1930’s, Mt. Wilson Observatory was famous for the revolutionary work of Edwin Hubble. Galaxies were discovered to exist outside the Milky Way and the universe was found to be expanding. In 1931, Einstein would visit the observatory and at Caltech, listen to a seminar by Fr. Georges Lemaitre on the theory of the origins of the universe, later dubbed the Big Bang. The founder of observatory, George Ellery Hale, was busy working on the successor to the 100-inch Mt. Wilson telescope. In 1934, the 200-inch mirror was cast, with a great amount of public fanfare for the future observatory at Mt. Palomar. Meanwhile, at the same facility, under the radar of the media, Fritz Zwicky was unearthing one of the great mysteries of astronomy today.

Fritz Zwicky. Credit: California Institute of Technology.

The Coma Cluster consists of some 1,000 galaxies at a distance of 320 million light years from Earth. The cluster itself is about 20 million light years wide. In 1933, Zwicky published a study of the cluster which indicated its mass was much greater than its visible content could account for. Had the optical mass of the cluster was all that existed, the velocities of the galaxies would have exceeded the escape velocity of the cluster, meaning there would not have been a cluster at all. Zwicky realized there must have been mass in the cluster that could not be seen. It was this extra mass that increased the escape velocity of the cluster keeping it intact. The results were originally published in a Swiss journal Helvetica Physica Atca (Zwicky was originally from Switzerland). Zwicky dubbed the invisible mass dunkle materie, or dark matter.

The Coma Cluster. Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA).
Acknowledgment: D. Carter (Liverpool John Moores University) and the Coma HST ACS Treasury Team.

It would take a few decades for the concept of dark matter to gain traction in astronomy. Part of it was new technology needed to be developed before it could be researched further. Part of it was Zwicky was ahead of his time. Besides dark matter, Zwicky developed the groundwork for ideas such as supernovae, neutron stars, and galactic gravitational lenses. Familiar to astronomers today, these were radically advanced concepts during the 1930’s. Zwicky also had, even by the standards of academia, a contentious personality towards other astronomers. Most famously, Zwicky referred to his fellow astronomers as “spherical bastards”. Why? They were, according to Zwicky, bastards any way you looked at them. Needless to say, this did not endear Zwicky to other astronomers, who were reluctant to promote Zwicky’s ideas.

Those issues aside, one by one, Zwicky’s theories received observational confirmation. Zwicky would discover 120 supernovae, the most by any astronomer. The first neutron star was discovered in 1967 with the radio detection of a pulsar in the Crab Nebula. The first image of gravitational lensing of a quasar occurred in 1979. As for dark matter, it would take the efforts of Vera Rubin, who faced bias against her work, to provide verification of its existence.

Unlike Zwicky, Vera Rubin did not give cause for astronomers to disdain her work. Astronomy has been traditionally a male dominated field. Many top graduate astronomy departments did not admit women until the 1970’s, and it was Vera Rubin who became the first women to observe at Mt. Palomar in 1967, nearly two decades after it had seen first light. The overall bias against women caused astronomers to greet Rubin’s early work with skepticism, and in some cases, downright hostility. In the end, the high quality of Rubin’s work would break through these barriers.

During the 1970’s, Rubin and her colleague Kent Ford, embarked on a study of galactic rotation curves. Kent Ford was responsible for building spectrographs sensitive enough to detect the Doppler shifts of stars as they orbited around a galactic core. Rubin decided upon this program for among other things, it would not require as much telescope time to complete as she had to balance her career with her family life. The expected result was that the farther out a star was from the center of mass in a galaxy, the slower its velocity would be. When it came time to bump the data against the model, the results came out like this.

This mirrored Zwicky’s study of the Coma cluster four decades earlier. If the optical mass was all there was to the galaxy, the stars at the outer edge were going so fast they would escape the gravity of the galaxy. However, that was not the case and there was much more dark matter holding these galaxies together than luminous matter. In fact, Rubin’s measurements indicated that only 10% of galactic mass was of the visible variety, and 90% was dark matter. Thus, 90% of galaxies were made of stuff that astronomers had no idea what it was. This was a staggering revelation.

When a discovery such as this that runs so counter-intuitive to the expected result, it will typically come under very critical review. That’s a good thing and a necessary part of the scientific process as long as it is the data being scrutinized and it does not become a personal matter. The best way to rebut criticism of a discovery is to provide replication. In 1970, Rubin and Ford published the flat galactic rotation curve for the Andromeda Galaxy. Throughout the decade, astronomers sought out a solution for the rotational curve without dark matter. However, by 1978, dozens of rotational curves reproduced the original result and hundreds more would follow the next decade. The dam had broke and by the time I was an undergrad student in the early 1980’s, dark matter had become standard material in galactic astronomy courses.

I distinctly remember the shock of learning 90% of the universe was made of dark matter whose nature was not known, but whose gravitational effects were clearly observed. In 1998, astronomy was rocked again by the discovery that matter, both luminous and dark, itself comprised only 20-25% of the universe. And this discovery would again trace its roots to Fritz Zwicky.

In 1937, Zwicky discovered a supernova that was distinctly different from what he had observed before. This supernova was brighter, and faded at a slower rate. Unlike the other supernovae, this was not the death throes of a high mass star. This was an explosion of a white dwarf that was siphoning mass from a companion star. Six years earlier, Subrahmanyan Chandrasekhar determined the maximum mass a white dwarf can obtain is 1.4 Suns. Once a white dwarf tops this amount of mass, its dense (a teaspoon of a white dwarf weighs 15 tons) carbon rich core ignites and creates a supernova. Since white dwarfs are the same mass when they explode, the brightness of these events are roughly identical. This gives astronomers a “standard candle” to calibrate distance. These events were eventually referred to as a Type 1a supernova.

Subrahmanyan Chandrasekhar won the Nobel in 1983 for his work on stellar interiors. The Chandra X-Ray Observatory was named in his honor. Credit: University of Chicago.

During the late 1990’s, two teams of astronomers were competing to measure how gravity slowed the expansion of the universe since the Big Bang. The expectation was over time, gravity would rein in the rate of expansion. The way to determine this is to measure the red shift of Type 1a supernovae. As an object races away from Earth, its spectrum is shifted towards the red. The faster it is moving away, the greater the red shift. As these supernovae serve as a standard candle, their distance could be determined. The farther away these events were, the older they occurred as it would take longer for their light to reach Earth. Thus, the goal was to utilize Type 1a supernovae to measure the expansion of the universe throughout its history.

In 1998, the High-Z Supernova Search Team and the Supernova Cosmology Project independently released their results. What they found was not only did gravity fail to slow the expansion of the universe, but the expansion was accelerating. Gravity, obviously, was still around, but there was a mysterious force in the universe that not only counteracted gravity, but was of increasing presence as the universe expands. This force was referred to as dark energy and makes up some 70% of the universe.

What was discovered as well is the universe, like stars and galaxies, has evolved over time. Up to 5 billion years ago, gravity did slow down the expansion of the universe. After that epoch, dark energy became a stronger force and the expansion began to speed up. To put that time into perspective, the Earth and the Solar System is 4.5 billion years old. The timeline of the expansion is shown below.

As the expansion accelerates, some hypothesize that the universe will end in what is called the Big Rip. This refers to a state where the universe expands to the point where stars, planets, and even atomic particles are shredded apart. To be sure, life could not exist in such a universe. However, there is no need to worry, the latest estimate is a Big Rip would take place 22 billion years from now. And at any rate, we’ll need to learn more about what exactly dark energy is before we arrive at a definitive theory on the ultimate fate of the universe.

Currently, the South Pole Telescope is dedicated to researching dark energy. Built by the University of Chicago, the 10-meter telescope is dedicated to locating galaxy clusters for the purpose of mapping cluster formation throughout the life of the universe. It is hoped this effort will provide further answers on how both gravity and dark energy has shaped the expansion of the universe. The future of dark energy research remains in the Southern Hemisphere but in Chile.

The Vera Rubin Observatory is currently under construction in Northern Chile and is expected to be operational by 2024. The cost of the Rubin Observatory is estimated at $465 million, about half the cost of a new NFL stadium. Funded by a combination of public and private sources, this 8.4 meter wide angle telescope is designed to have the ability to survey the entire sky in three nights. The wide field of view will enable the Rubin Observatory to map large scale galactic structures and survey Type 1a supernovae over a ten year period. This will provide a more comprehensive map of how dark energy and dark matter have influenced the overall structure of the universe throughout time.

Rubin Observatory under construction with Milky Way overhead. Credit: Bruno C. Quint/Rubin Observatory CC 4.0.

Given the dramatic nature of the discovery of dark energy, dark matter has been a bit overlooked since 1998. However, there have been some key advancements in the study of dark matter during that time. The Hubble Space Telescope was able to map dark matter by measuring gravitational lensing. Gravity bends light rays and as a result, distorts galactic images. While dark matter cannot be seen its gravitational effects can be observed. What was found is that dark matter had a smoother distribution during the early universe but is more clumpy now. This clumpiness creates a scaffolding for which galactic clusters form upon.

In 2015, dark matter was detected interacting with itself. In a galactic collision in the cluster Abell 3827, dark matter was detected to lag behind normal matter. This could provide a key clue as to what dark matter is as previously it was only detected to interact gravitationally. If “dark forces” among dark matter exist causing this interaction, then this discovery may help physicists model dark matter in a more complex and accurate manner. Ideally, this will help determine what exactly dark matter is.

So where does our knowledge of the universe stand now? The recent ESA Planck mission mapped out the cosmic microwave background (CMB). The CMB is the remnant of the Big Bang and shows us the state of the universe when it was 380,000 years old. By measuring the fluctuations in the CMB, astronomers were able to breakdown the universe as follows:

Dark Energy: 68.3%

Dark Matter: 26.8%

Ordinary Matter: 4.9%

So the matter we see around us, the Earth, Sun, stars and galaxies, only comprise slightly less than five percent of the universe. The remaining 95% is made of stuff that is unknown to us. That, along with the question of life beyond Earth, represents the most important mystery for astronomers to solve in the upcoming decade.

*Image on top of post is the galactic cluster Abell 2218. Where there is a galactic cluster, there is dark matter. The gravity of both ordinary and dark matter deflects light just like a lens does. The result is galaxies behind the cluster are magnified and distorted. The magnification effect allows astronomers to image galaxies far away behind the cluster that ordinarily would not visible. Credits: NASA, Andrew Fruchter and the ERO Team [Sylvia Baggett (STScI), Richard Hook (ST-ECF), Zoltan Levay (STScI)] (STScI).

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