It is one of the most unnerving discoveries in space science - that most of the universe is missing. We live in a material world, so instinctively we know what normal matter is - the world around us, the planets, stars and interstellar dust. But scientists currently estimate that 95 per cent of everything in the universe is actually - one way or another - invisible. Some of this is ordinary matter that we just can't easily see. But there's also stuff that's much more weird. For instance, there's a new kind of matter we think is out there, but whose very existence is still largely hypothetical - dark matter. And most mysteriously of all, scientists think there is an unknown form of energy pervading the universe that we know so little about, all it has so far is a name - dark energy. Embark on a tour of this invisible universe, and shows how its existence - or lack of it - will define the fate of the entire universe.
Category:Science Duration:28:28 Series: The Sky at Night
Dan Snow uncovers the lost Vikings in America with space archaeologist Dr Sarah Parcak. Sarah uses satellites 383 miles above the earth to spot ruins as small as 30cm buried beneath the surface. As Sarah searches for Viking sites from Britain to America, Dan explores how they voyaged thousands of miles when most ships never left the shoreline. He also tracks their expansion west, first as raiders and then as settlers and traders throughout Britain and beyond to Iceland and Greenland. In North America they excavate what could be the most westerly Viking settlement ever discovered.
Professor Marcus du Sautoy explores why we are driven to measure and quantify the world around us and why we have reduced the universe to just a handful of fundamental units of measurement. He tells the story of the metre and the second - how an astonishing journey across revolutionary France gave birth to the metre, and how scientists today are continuing to redefine the measurement of time and length, with extraordinary results.
Alice Roberts explores the latest discoveries in the study of human origins, revealing the transformation that has been brought about in this field by genetics. Traditional Palaeoanthropology, based on fossils, is being transformed by advanced genome sequencing techniques. We now know that there were at least four other distinct species of human on the planet at the same time as us - some of them identified from astonishingly well-preserved DNA extracted from 50,000-year-old bones, others hinted at by archaic sections of DNA hidden in our modern genome. What's more, we now know that our ancestors met and interacted with these other humans, in ways that still have ramifications today. Alice uses these revelations to update our picture of the human family tree.
Electricity is not just something that creates heat and light, it connects the world through networks and broadcasting. After centuries of man's experiments with electricity, the final episode tells the story of how a new age of real understanding dawned - how we discovered electric fields and electromagnetic waves. Today we can hardly imagine life without electricity - it defines our era. As our understanding of it has increased so has our reliance upon it, and today we are on the brink of a new breakthrough, because if we can understand the secret of electrical superconductivity, we could once again transform the world.
Category:Science Duration:58:24 Series: Shock and Awe: The Story of Electricity
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