Dark Matter, Dark Energy: The Dark Side of the Universe [TTC Video]
01 December 2016, 20:28
Course No 1272 | AVI, XviD, 512x384 | MP3, 128 kbps, 2 Ch | 24x30 mins | 4.3GB
There's more to the universe than meets the eye—a lot more. In recent years, scientists have discovered that 95% of the contents of the cosmos are invisible to our current methods of direct detection. Yet something is holding galaxies and galaxy clusters together, and something else is causing space to fly apart.
Scientists call these invisible components dark matter and dark energy; "dark" because these phenomena do not emit light, not because we are not learning more and more about them. In fact, dark matter and dark energy are the most eagerly studied subjects in astronomy and particle physics today.
If and when we discover this matter, it will further validate the "standard model" of physics which, so far, is the best description of how our universe works; if we cannot find this matter, or if it does not exist, then we will completely need to rethink the current "standard model" theory.
Join the exciting search for these mysterious phenomena in Dark Matter, Dark Energy: The Dark Side of the Universe, a mind-expanding, 24-lecture course taught by Dr. Sean Carroll, a theoretical physicist with a profound knowledge of the field. Starting with the early 20th-century work of Albert Einstein in theoretical physics and Edwin Hubble in observational astronomy, Dr. Carroll takes you through the key concepts of this revolutionary view of an expanding universe, concepts which have brought us—for the first time in history—to the brink of knowing what the universe is made of.
Welcome to the Dark Side
Everything you see with your eyes and with powerful instruments—stars, planets, galaxies, dust, and gas—and everything that you think of as atom-based matter is only 5% of what we now know exists. The rest is what Dr. Carroll calls the "dark sector," which consists of the following:
- Dark matter: First proposed in the 1930s, the idea that there is missing mass influencing the behavior of galaxies began to look more and more likely from the 1970s on. We know that it is matter because we can detect its gravitational influence on visible matter, but we cannot see it. An inventory of the distribution of dark matter throughout space shows that it constitutes 25% of the energy density of the universe.
- Dark energy: The greatest discoveries are the unexpected ones, which was the case in the late 1990s when two teams of astronomers competing to measure the rate at which the expansion of the universe is slowing down (as virtually everyone thought it must be) discovered that it is speeding up instead. A previously unknown, all-pervasive dark energy must be at work, representing 70% of the energy density of the universe.
Together, dark matter and dark energy account for all but a tiny fraction of everything there is; the ordinary matter that is left over is like the seasoning on the main dish. The story of how we arrived at this startling cosmic recipe is an absorbing drama that takes you through the breakthrough discoveries in astronomy and physics since the turn of the 20th century.
Concept by concept, Dark Matter, Dark Energy gives you the tools to appreciate this subject in depth. Dr. Carroll explains why scientists believe we live in a smooth, expanding universe that originated in a hot, dense state called the big bang.
You investigate the features of the infant universe that led to the large-scale structure we observe today, explore the standard model of particle physics and see how it provides the framework for understanding the interaction of all matter and radiation, and come to understand why dark matter and dark energy are logical consequences of a range of scientific theories and observations and how together they complete a grand picture of the universe.
Deduce the Existence of the Dark Sector
Several significant clues disclose the existence of dark matter and dark energy. In the case of dark matter, we have the evidence of:
- Galaxy dynamics: The motions of the stars in galaxies and galaxies within clusters indicate that there is far more matter than is implied by visible stars and gas.
- Echoes of the big bang: Variations in the leftover radiation from the big bang demonstrate that there must be dark matter pulling the ordinary matter we see.
Dark matter is clear to see compared to dark energy, which reveals itself subtly but unmistakably through:
- Exploding stars: Type Ia supernovae provide a standard candle to measure the distances to faraway galaxies. By combining this information with redshift (which measures how fast a galaxy recedes), astronomers conclude that something is causing galaxies to recede at a faster and faster velocity.
- Geometry of space: Observations that space is "flat" (with neither positive nor negative curvature) imply a total energy density for the universe that is stunningly consistent with the dark energy hypothesis.
Each of these techniques deduces the existence of dark matter or dark energy from the gravitational fields they cause. But what if our theory of gravity is faulty? Could adjustments to Einstein's general theory of relativity, which forms our modern understanding of gravity, do away with the need for the dark sector?
You explore a theory called Modified Newtonian Dynamics, which successfully dispenses with dark matter in individual galaxies. This theory fails, however, when applied to clusters and has nothing to say about the expansion of the universe.
"It is impossible, in principle, to think of a theory in this day and age that will completely do away with dark matter," says Dr. Carroll, pointing in particular to a convincing piece of evidence from the aftermath of the collision of two galaxies.
Known as the Bullet Cluster, it shows a central region of ordinary matter (evident through telltale x-ray emissions), on either side of which are far more extensive clouds of what can only be dark matter, disclosed by gravitational lensing.
Explaining away dark energy is similarly difficult, because it requires revising the fundamental equation of general relativity. "The problem is that this equation of Einstein's is actually quite remarkable," says Dr. Carroll. "If you try to mess with it just a little bit, you break it."The overriding question remains: What are dark matter and dark energy? We do not yet know for certain, but physicists have come up with an array of creative ideas and ways to test them. Dark Matter, Dark Energy covers the most promising proposals and looks ahead to experiments that will dramatically improve our understanding of the dark sector.
Take a Voyage of Scientific Discovery
Dr. Carroll has a knack for explaining the latest complex picture of the universe in easy-to-follow terms—a skill honed by his more than 250 scientific seminars, colloquia, educational discussions, and popular talks. Relaxed, eloquent, wryly funny, and brimming with ideas, he has received the Graduate Student Council Teaching Award from MIT for his course on general relativity, as well as research grants from NASA, the U.S. Department of Energy, and the National Science Foundation.
With his expert guidance, your previously held ideas about the fate (and possibly the origin) of the universe will be altered permanently. A rich voyage of scientific discovery, Dark Matter, Dark Energy provides you with a comprehensive look at these two mysterious phenomena—and their startling implications for our understanding of the universe.
The Rise of Humans: Great Scientific Debates [TTC Video]
01 December 2016, 20:08
Course No 1612 | AVI, XviD, 640x480 | MP3, 128 kbps, 2 Ch | 24x30 | + PDF Guidebook | 8.27GB
Trying to understand our human origins has always been a fundamental part of who we are. One of the core things we want to know is how we came to be. Thousands of years ago, human civilizations developed elaborate stories to explain the origins of humans. But today, with the help of dramatic archaeological discoveries and groundbreaking advancements in technology and scientific understanding, we are closer than ever before to learning the true story. In recent decades, paleoanthropology has exploded, bringing us closer than ever before to making sense of this controversial subject and providing us with a richer understanding of our origins. It's also sparked continued debate among the greatest minds in the field and prompted anthropologists to revise, update, and even, in some cases, overturn ideas and theories about key issues in human evolution.
- Was Australopithecus afarensis really our earliest ancestor?
- Did early humans evolve in Africa alone, or in regions throughout the world?
- Do Neandertals play an important role in our genetic heritage and, if so, how?
- Why did prehistoric humans form cooperative communities and create art?
Complete your understanding of the most up-to-date science behind our origins with The Rise of Humans: Great Scientific Debates. Delivered by expert paleoanthropologist and professor John Hawks of the University of Wisconsin–Madison, these 24 lectures bring you to the forefront of scientific arguments and questions that will become more important in the coming years. Surveying both the questions that continue to rile the world's greatest minds in anthropology and the cutting-edge science responsible for them, this course is an expert guide to the wide-ranging debates over the most essential questions we can ask. Meticulously crafted and packed with insights, this rewarding and sometimes even provocative course is a fascinating investigation of the branches, trunk, and roots of the greatest family tree there is.
Profound Answers to Questions about Your Origins
Each lecture of The Rise of Humans focuses on a single profound question about human origins and the sometimes surprising, sometimes fierce, and always illuminating debates surrounding them. You'll learn how paleoanthropologists have used everything from the tiniest fossil remains (such as teeth and fragments of jawbones) and stone tools to DNA sequencing and genetic mapping in an effort to definitively determine how we got to be the way we are today.
Here are just four of the many exciting debates Professor Hawks describes in this masterful course.
- Was Africa or Asia more central to human origins? Charles Darwin believed that Africa was the most likely place for humans to have originated because of our relationship to African apes. Other scientists, such as Ernst Haeckel, argued that Southeast Asia was the most likely site of human origins because geography would have differentiated us from African apes. While it's now clear that early hominins were all found in Africa, debate continues over whether our genus Homo might have involved a time of evolution in Asia.
- What did prehistoric cultural groups look like? Early archaeologists systematized the stone tool traditions in prehistory by recognizing types of artifacts that might be found in one tradition and not others. The debate over two different perspectives on differences in stone tools—that they reflect different traditions or that they reflect the tasks a single group of prehistoric people performed—has deepened our understanding of rich archaeological sites.
- How long ago did humans reach the New World? Scrutiny over archaeological discoveries in the United States led to the "Clovis first" hypothesis, which held that the first humans to enter the New World came over ice sheets that once covered northern North America about 12,000 years ago. Yet during the 1990s, geneticists began to contribute to the debate, tracing the origins of today's American Indians to a small population that left Asia sometime closer to 15,000 years ago.
- How important was symbolic representation to modern humans? Prehistoric art found in caves throughout France and Spain show a growing interest among our ancestors for artistically representing the world. Anthropologists still debate the importance of this kind of representation to our evolution; some argue that prehistoric art is fundamental to our cultural abilities, while others posit that it's merely a side effect of human intelligence.
Reunite with Some of Your Earliest Ancestors
With these lectures, you'll travel across time and around the world, from Ethiopia and Tanzania to Pakistan and Java to Sumatra and North America. You'll peer over the shoulders of archaeologists as they unearth fossils, tools, and other artifacts from the earth and reconstruct the bodies and lives of our earliest ancestors. You'll follow geneticists as they use mitochondrial DNA to draw startling connections between prehistoric human populations from around the world. And you'll encounter some of our most intriguing distant relatives.
- Australopithecus afarensis: In the 1970s, paleoanthropologist Mary Leakey uncovered evidence for the earliest known hominin in Tanzania, at a site that preserved not only the jaws and teeth of this prehistoric species but also fossil footprints showing its adaptation to upright walking. Paleoanthropologists still argue over whether better evidence for the ancestry of Homo will come from A. afarensis or some earlier, as-yet-unknown species.
- Homo habilis: A series of skulls dating back to around 2 million years, with larger brains than other species, was described by paleoanthropologist Philip Tobias as the earliest members of our genus Homo. With a body like Australopithecus and a meat-based diet, H. habilis could be part of our genus; although with some evidence of Homo erectus dating back to the same age as these fossils, it could be a totally different kind of hominin.
- Homo floresiensis: A recent burning debate in paleoanthropology is over the identity of Homo floresiensis. A fossil skull found on the island of Flores suggests an extremely small-bodied population with individuals about three to four feet tall. Found together with indigenous animals such as pygmy mastodons and giant storks, these "hobbits" could represent a unique population of humans isolated from the rest of humanity.
- Neandertals: Neandertals were the earliest fossil humans to have been found and, at the time of their discovery, there was debate over whether they were our ancestors or part of a much less specialized population. We now understand that humans and Neandertals trace a common ancestry to sometime before 250,000 years ago and that the early population of Europe may reflect the emerging Neandertal population. In fact, people of European descent can have up to 4% of Neandertal genes in their DNA.
Your Guide to Human Evolutionary History
What makes The Rise of Humans so unique is the approach Professor Hawks brings toward explaining the field's hottest debates. One of the first paleoanthropologists to study fossil evidence and genetic information together in order to test hypotheses about human prehistory, Professor Hawks is adept at looking at human origins not just with one lens, but with two.
He has traveled around the world to examine delicate skeletal remains and pore over the complex results of genetic testing. His research and scholarship on human evolutionary history has been featured in a variety of publications, including Science, American Journal of Physical Anthropology, Slate, and Journal of Human Evolution.
But more than that, Professor Hawks has crafted a course that demonstrates the passion and excitement involved in the field of paleoanthropology. With his engaging lecturing style and his use of fossil finds taken from his personal collection, Professor Hawks will capture your attention and show you all the drama and excitement to be found in eavesdropping on the latest debates about human evolutionary history.
So join him for this engrossing and eye-opening learning experience—one that will bring you to the cusp of our 21st-century knowledge about the origin of humans, that will fill in critical gaps in your understanding of where we come from, and that will better prepare you for the great discoveries and fresh debates of tomorrow.
Masterworks of American Art [TTC Video]
01 December 2016, 19:39
Course No 7158 | AVI, XviD, 640x480 | MP3, 128 kbps, 2 Ch | 24x30 mins | + PDF Guidebook | 4.63GB
A nation's identity is expressed through its art. Great painters capture the essence of a culture's brightest hopes, deepest anxieties, and most profound aspirations. They provide an aesthetic road map to a nation's history, recording the lives of its citizens and reflecting the personality of an entire people.
But all too often, Americans themselves are unfamiliar with the great artistic legacy of their own country. Many of us study the great artists of Europe—Leonardo and Rubens, Degas and Monet—but neglect the remarkable painters of our own national tradition.
And yet the tradition of American art is filled with spectacular masterpieces that raise intriguing questions:
- How did the founding of this new nation find expression in art?
- Have our democratic ideals influenced the growth and development of American art?
- Did artists in this nascent culture follow time-honored aesthetic models, or did they pioneer new styles to communicate their burgeoning sense of national pride?
- Is there something uniquely "American" about American art?
These are the kinds of questions you explore in Masterworks of American Art. In this sweeping survey, you encounter the brilliant paintings of the homegrown masters who documented the birth of our nation from its colonial roots up to the brink of World War I and the birth of Modernism. As you examine this vital artistic tradition in its historical, cultural, and political contexts, you discover how appreciating the legacy of American art is crucial to fully understanding the story of our great nation.
A New Art for a New Nation
Your guide is Professor William Kloss. A noted scholar and art historian, Professor Kloss has taught more than 100 courses as an independent lecturer for the Smithsonian Institution's seminar and travel program. Through 24 engaging and informative lectures, he shares his deep passion for the art of this nation while offering remarkable insights into the relationship between America's history and its art.
What you discover is a revolution in art. Sometimes borrowing from European models, just as often departing from them, American artists pioneered new attitudes and styles to express the aspirations of a new nation.
Professor Kloss highlights this uniquely American approach to art, examining some of the greatest paintings of the tradition within the larger context of our country's history and culture. The result is a grand survey of the American experience, in which some of the most critical eras of this nation's history are viewed through the lens of great art:
- The American Revolution: Great artists captured a new spirit of liberty through scenes of war and government. You examine key examples of their revolutionary approach to art, including The Death of General Wolfe, in which Benjamin West pioneered a new vision of democratic leadership by rendering the British general in contemporary dress.
- The Civil War: You see how this tumultuous period of American history found expression on memorable canvases, such as James Hamilton's symbolic representation of the battered ship of state in Old Ironsides and Winslow Homer's vivid reenactment of skirmishes on the front, Inviting a Shot before Petersburg.
- The Reconstruction: After the war, painters sought to create an image of the nation reunited, as in George P. A. Healy's portrait of The Peacemakers, while others reflected the readjustments of postwar life, as in Homer's A Visit from the Old Mistress.
- The Westward Expansion: Great masters such as Albert Bierstadt, in his monumental canvas Valley of the Yosemite, recorded the natural splendors of a nation pushing westward, while Emanuel Gottlieb Leutze's allegorical mural Westward the Course of Empire Takes Its Way embodied the idea of Manifest Destiny.
At the same time, you witness the rise of the great artistic institutions that fostered the development of the nation's arts, such as New York's Metropolitan Museum of Art, Boston's Museum of Fine Arts, and the Philadelphia Museum of Art.
Along the way, you sample some of the finest works in the American tradition—memorable masterpieces that rival the great paintings of Europe. These masterworks represent a wide rich array of styles and subjects—from sweeping landscapes to intimate portraits to scenes of everyday life.
With Professor Kloss as your guide, you will appreciate the hallmark innovations and breathtaking artistry of American painting:
- An emphasis on linearity and weightlessness in the earliest works of the American tradition—qualities that sprang from generations of self-trained artists who cultivated a unique, homegrown aesthetic
- The remarkably lifelike trompe l'oeil paintings of William Hartnett and Charles Willson Peale, who created painstaking, dazzling reproductions of objects in real life
- James McNeill Whistler's simple but striking use of shape, line, and a muted color palette, as seen in his famous portrait of his mother
- The vivid portrayal of physical movement in art, as exemplified in remarkable compositions such as Thomas Eakins's The Biglin Brothers Racing.
With each example, you not only gain a sense of the larger trajectory of the American tradition in painting, but you also develop your appreciation of the artistry represented in each work. With his insightful comments on style, composition, and color, Professor Kloss offers an enlightening guide to appreciating virtually any great work of art.
The American Experience—on the Canvas
With Masterworks of American Art, you view these great works as part of an ever-developing story, in which master artists capture the portrait of a nation as it grows and changes. As you savor Professor Kloss's enlightening commentary, you also enjoy a feast for the eyes, as each painting is shown in rich, full-color reproductions worthy of these great masterpieces.
If you've already studied the great art of Europe, Masterworks of American Art is an essential complement to your studies, and if you're new to the world of painting, this course offers an enlivening introduction to this remarkable body of work.
Join Professor Kloss as he reveals the vital and vibrant tradition of American art, and witness the birth, growth, and development of our great nation as it was painted by some of the greatest artists the world has known.