Wednesday, September 12, 2012
What Is Space?
Space. It separates you from me, one galaxy from the next, and atoms from each other. It is everywhere in the universe. But to most of us, space is nothing, an empty void. Well, it turns out space is not what it seems.
Quantum Leap
oin Brian Greene on a wild ride into the weird realm of quantum physics, which governs the universe on the tiniest of scales. Greene brings quantum mechanics to life in a nightclub like no other, where objects pop in and out of existence and things over here can affect others over there, instantaneously—without anything crossing the space between them. A century ago, during the initial shots in the quantum revolution, the best minds of a generation—including Albert Einstein and Niels Bohr—squared off in a battle for the soul of physics. How could the rules of the quantum world, which work so well to describe the behavior of individual atoms and their components, appear so dramatically different from the everyday rules that govern people, planets, and galaxies? Quantum mechanics may be counterintuitive, but it's one of the most successful theories in the history of science, making predictions that have been confirmed to better than one part in a billion, while also launching the technological advances at the heart of modern life, like computers and cell phones. But even today, even with such profound successes, the debate sill rages over what quantum mechanics implies for the true nature of reality.
The Real Eve
Broadcast (2002) Narrated by Danny Glover, "The Real Eve" reveals that our shared genetic heritage links every living person on earth and traces the expansion of modern humans throughout the world. The discovery of the Eve gene stunned the world. It seems we could all be descended from just one female who lived in Africa. In this telling anthropological video, we access the very latest DNA reconstructions, and for the first time, tell conclusively the story of where, when and how the human race came about and then populated the world. The real Eve refers to Mitochondrial Eve, a name used for the most recent common ancestor of all humans in the matrilineal (mother to daughter) line of descent. Scientists have traced the human race to one female in Africa several million years ago and traced the migration pattern of her descendants as they spread across the earth
In the field of human genetics, Mitochondrial Eve refers to the matrilineal "MRCA" (most recent common ancestor). In other words, she was the woman from whom all living humans today descend, on their mother's side, and through the mothers of those mothers and so on, back until all lines converge on one person. Because all mitochondrial DNA (mtDNA) is generally passed from mother to offspring without recombination, all mitochondrial DNA (mtDNA) in every living person is directly descended from hers by definition. Mitochondrial Eve is the female counterpart of Y chromosomal Adam, the patrilineal most recent common ancestor, although they lived thousands of years apart.
Each ancestor (of people now living) in the line back to the matrilineal MRCA had female contemporaries such as sisters, female cousins, etc. but none of these female contemporaries of the "Mitochondrial Eve" has descendants living now in an unbroken female line. Mitochondrial Eve is generally estimated to have lived around 200,000 years ago, most likely in East Africa, when Homo sapiens sapiens ("anatomically modern humans") were developing as a population distinct from other human sub species. Mitochondrial Eve lived much earlier than the out of Africa migration that is thought to have occurred between 95,000 to 45,000 CE. The dating for 'Eve' was a blow to the multiregional hypothesis, and a boost to the hypothesis that modern humans originated relatively recently in Africa and spread from there, replacing more "archaic" human populations such as Neanderthals. As a result, the latter hypothesis is now the dominant one.
One of the misconceptions of mitochondrial Eve is that since all women alive today descended in a direct unbroken female line from her that she was the only woman alive at the time. Nuclear DNA studies indicate that the size of the ancient human population never dropped below tens of thousands. There may be many other women around at Eve's time with descendants alive today, but sometime in the past, those lines of descent included at least one male, who do not pass on their mother's mitochondrial DNA, thereby breaking the line of descent. By contrast, Eve's lines to each person alive today includes precisely one matrilineal line.
In the field of human genetics, Mitochondrial Eve refers to the matrilineal "MRCA" (most recent common ancestor). In other words, she was the woman from whom all living humans today descend, on their mother's side, and through the mothers of those mothers and so on, back until all lines converge on one person. Because all mitochondrial DNA (mtDNA) is generally passed from mother to offspring without recombination, all mitochondrial DNA (mtDNA) in every living person is directly descended from hers by definition. Mitochondrial Eve is the female counterpart of Y chromosomal Adam, the patrilineal most recent common ancestor, although they lived thousands of years apart.
Each ancestor (of people now living) in the line back to the matrilineal MRCA had female contemporaries such as sisters, female cousins, etc. but none of these female contemporaries of the "Mitochondrial Eve" has descendants living now in an unbroken female line. Mitochondrial Eve is generally estimated to have lived around 200,000 years ago, most likely in East Africa, when Homo sapiens sapiens ("anatomically modern humans") were developing as a population distinct from other human sub species. Mitochondrial Eve lived much earlier than the out of Africa migration that is thought to have occurred between 95,000 to 45,000 CE. The dating for 'Eve' was a blow to the multiregional hypothesis, and a boost to the hypothesis that modern humans originated relatively recently in Africa and spread from there, replacing more "archaic" human populations such as Neanderthals. As a result, the latter hypothesis is now the dominant one.
One of the misconceptions of mitochondrial Eve is that since all women alive today descended in a direct unbroken female line from her that she was the only woman alive at the time. Nuclear DNA studies indicate that the size of the ancient human population never dropped below tens of thousands. There may be many other women around at Eve's time with descendants alive today, but sometime in the past, those lines of descent included at least one male, who do not pass on their mother's mitochondrial DNA, thereby breaking the line of descent. By contrast, Eve's lines to each person alive today includes precisely one matrilineal line.
Journey Of Man: Genetic Odyssey
Broadcast (2003) Where did we come from? Spencer Wells, a 33 year old population geneticist, has closed the door on his laboratory and is embarking on the biggest adventure of his life. His mission to retrace the most extraordinary journey of all time, a journey that involves every man, woman and child alive today. He offers his thoughts on this puzzling question, employing the latest in DNA research and technology to track the migration of humanity across the globe.
By collecting blood samples from thousands of men living in isolated tribes around the world and analyzing their DNA, Spencer and his colleagues discovered that all humans alive today can be traced back to a small tribe of hunter-gatherers who lived in Africa 60,000 years ago. Following this genetic trail, Spencer has charted the ancient journey of our ancestors as they populated the planet.
Spencer scours the world for indigenous people with deep roots in one place, asking for samples of DNA to test, in order to piece together our "big family" genetic tree. In Indiana Jones mode, Wells tacks down common ancestors and comes up with some surprising candidates. He shows with DNA results the diverse ways in which people and tribes react to the news of what science says about their arrival and relations. View this as adventure travel or as a painless way to begin your genetic literacy.
By collecting blood samples from thousands of men living in isolated tribes around the world and analyzing their DNA, Spencer and his colleagues discovered that all humans alive today can be traced back to a small tribe of hunter-gatherers who lived in Africa 60,000 years ago. Following this genetic trail, Spencer has charted the ancient journey of our ancestors as they populated the planet.
Spencer scours the world for indigenous people with deep roots in one place, asking for samples of DNA to test, in order to piece together our "big family" genetic tree. In Indiana Jones mode, Wells tacks down common ancestors and comes up with some surprising candidates. He shows with DNA results the diverse ways in which people and tribes react to the news of what science says about their arrival and relations. View this as adventure travel or as a painless way to begin your genetic literacy.
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