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Part 8: The solar system and exploration thereof.

These short videos were created in August 2007 by Dr. Christopher D. Impey, Professor of Astronomy at the University of Arizona, for his students. They cover a broad range of terms, concepts, and princples in astronomy and astrobiology. Dr. Impey is a University Distinguished Professor and Deputy Head of the Astonomy Department. All videos are intended solely for educational purposes and are licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License. The full list of collections follows below:

01. Fundamentals of Science and Astronomy
02. Ancient Astronomy and Celestial Phenomena
03. Concepts and History of Astronomy and Physics
04. Chemistry and Physics
05. Quantum Theory and Radiation
06. Optics and Quantum Theory
07. Geology and Physics
08. Solar Neighborhood and Space Exploration
09. Outer Planets and Planetary Atmospheres
10. The Solar System
11. Interplanetary Bodies
12. Formation and Nature of Planetary Systems
13. Particle Physics and the Sun
14. Stars 1
15. Stars 2
16. Stars 3
17. Galactic Mass Distribtuion and Galaxy Structure
18. Galaxies
19. Galaxies 2
20. Galaxy Interaction and Motion
21. Deep Space and High-Energy Phenomena
22. The Big Bang, Inflation, and General Cosmology
23. The Big Bang, Inflation, and General Cosmology 2
24. Chemistry and Context for Life
25. Early Earth and Life Processes
26. Life on Earth
27. Life in the Universe
28. Interstellar Travel, SETI, and the Rarity of Life
29. Prospects of Nonhuman Intelligences

8. Solar Neighborhood and Space Exploration University of Arizona

    • Wetenschap

Part 8: The solar system and exploration thereof.

These short videos were created in August 2007 by Dr. Christopher D. Impey, Professor of Astronomy at the University of Arizona, for his students. They cover a broad range of terms, concepts, and princples in astronomy and astrobiology. Dr. Impey is a University Distinguished Professor and Deputy Head of the Astonomy Department. All videos are intended solely for educational purposes and are licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License. The full list of collections follows below:

01. Fundamentals of Science and Astronomy
02. Ancient Astronomy and Celestial Phenomena
03. Concepts and History of Astronomy and Physics
04. Chemistry and Physics
05. Quantum Theory and Radiation
06. Optics and Quantum Theory
07. Geology and Physics
08. Solar Neighborhood and Space Exploration
09. Outer Planets and Planetary Atmospheres
10. The Solar System
11. Interplanetary Bodies
12. Formation and Nature of Planetary Systems
13. Particle Physics and the Sun
14. Stars 1
15. Stars 2
16. Stars 3
17. Galactic Mass Distribtuion and Galaxy Structure
18. Galaxies
19. Galaxies 2
20. Galaxy Interaction and Motion
21. Deep Space and High-Energy Phenomena
22. The Big Bang, Inflation, and General Cosmology
23. The Big Bang, Inflation, and General Cosmology 2
24. Chemistry and Context for Life
25. Early Earth and Life Processes
26. Life on Earth
27. Life in the Universe
28. Interstellar Travel, SETI, and the Rarity of Life
29. Prospects of Nonhuman Intelligences

    • video
    Cosmic Catastrophies

    Cosmic Catastrophies

    Transcript: The history of life on Earth is not simply a smooth progression governed by natural selection. There have been times when life has been eradicated by cosmic intruders, catastrophes from space in the form of large impactors. These do not occur very often. During the first half billion years of the Earth’s history, the era of heavy bombardment, objects a kilometer or larger hit more than once every million years. Since then the impact rate has been much lower, and an impactor the size that caused the death of the dinosaurs and 75 percent of all planet and animal species on Earth 65 million years ago only occurs once every hundred million years or so. The energy contained in such impacts is huge, roughly equivalent to a hundred million bombs like that that exploded in Hiroshima, an energy deposition instantly into the Earth and its atmosphere of 1026 joules. The last such impact occurred 65 million years ago. But the timing is random, and we cannot predict with any certainty that he next cosmic catastrophe will take place.

    • 1 min.
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    Mass Extinctions

    Mass Extinctions

    Transcript: Fossil record of life on Earth is incomplete, and it only dates back about 500 million years. But there’s evidence at several points in time for mass extinctions in the species record. One of these occurs about 250 million years ago at the end of the Permian period. The other occurs 65 million years ago between the Cretaceous period and Tertiary period. The evidence in the latter case is very good that a cosmic intruder, a giant meteoric impact, caused the extinction of about 75 percent of all plants and animals on Earth. What is the evidence? In the early 1980s, the father/son team of Walter and Luis Alvarez, started to accumulate evidence. First piece of evidence was the presence in a layer of rock, around 65 million years ago, for high concentration of elements that are only found in meteorites. Second piece of evidence was the existence of glassy spheres representing shock heated rock and quartz crystals representing the same thing in that same layer. Also in the layer of rock, soot, possibly and probably caused by widespread forest fires circling the Earth. What was missing in the early 1980s was the smoking gun, the evidence of a crater. That was discovered nearly ten years later, and the crater site has now been identified as being somewhat north of Mexico. This crater corresponded to a 10 kilometer-sized impactor that through off huge amounts of gas and microscopic particles into the Earth’s atmosphere, shielding the Earth from the Sun’s r

    • 1 min.
    • video
    Climate Change

    Climate Change

    Transcript: The Earth's atmosphere has changed its chemical composition systematically over the history of the Earth, but most of these changes occur on very long time scales, hundreds of millions or even billions of years. There's growing evidence for climate change caused by changes in atmospheric composition on times scales of a hundred years or less caused, we think, by human activity on this Earth. This is a profound implication for how we run our affairs because climate change could make the Earth a less habitable place and produce huge costs for most of the world’s richest nations. Climate change involves several components, typically greenhouse gasses, carbon dioxide, water vapor, and methane, but there's also evidence of climate change in the form of ozone holes which grow over the Arctic and Antarctic regions and increase in the amount of pollutants such as sulfuric acid, nitrogen dioxide and sulfur dioxide. In only a few short decades we have been able to change in a measurable way the composition of the global atmosphere of this planet.

    • 1 min.
    • video
    Ozone Layer

    Ozone Layer

    Transcript: The first evidence that human activity could globally affect the Earth’s atmosphere occurred for the situation of the ozone hole. Ozone is trace gas, an isotope of oxygen that occurs 20 to 30 kilometers above the Earth’s surface. It’s a trace gas but an important gas because ozone protects us from ultraviolet radiation. In the 1970s and ‘80s, the ozone hole, a seasonally varying depletion in the ozone layer seen most clearly in Arctic and Antarctic regions, started growing. By the mid to late 1980s the ozone hole was 30 to 50 percent bigger than it had been a decade before. The culprit was chlorofluorocarbons, CFCs, gases such as Freon that are contained in air conditioners and produced in industrial processes. Industrial activity was depleting the ozone layer. Luckily scientists realized what was going on, and governments acted swiftly to outlaw CFCs. Since then we have observed the ozone hole to stabilize and the ozone depletion to have essentially been reversed. This was the first big success in our environmental engineering of the planet.

    • 1 min.
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    Greenhouse Effect

    Greenhouse Effect

    Transcript: The Greenhouse Effect occurs when the Sun’s radiation hits the Earth's surface and is reradiated at longer infrared wavelengths. Those infrared waves are preferentially absorbed by certain gases such as carbon dioxide, water vapor and methane. These greenhouse gases therefore cause a heating effect. In the case of Venus a runaway greenhouse effect raised the temperature of the planet to eight or nine hundred degrees. In the case of the Earth carbon dioxide is a trace gas, but it has increased over the last few hundred years from a concentration of 250 parts per million to 350 parts per million currently with an accelerating increase in the last 50 years. There's good evidence that the increase in carbon dioxide concentration is caused by human activity, the burning of fossil fuels, cutting down of forests, and general industrial activity. Thus, with a 20 percent increase in the CO2 concentration in the Earth's atmosphere, there is a prospect for the Earth to begin to suffer global warming caused by the greenhouse effect.

    • 1 min.
    • video
    Global Warming

    Global Warming

    Transcript: One of the most important scientific issues of the day is global warming. Global warming is subject to a debate, and there is no full consensus yet, but there is growing scientific evidence of greater and greater reliability that human activity is fundamentally altering the atmospheric composition of the entire planet with a possible increase in temperature as a result. The evidence for global warming is growing, but it's not yet totally unambiguous. While it is true that carbon dioxide is growing in concentration in the Earth's atmosphere by about 20 percent in the last 50 years, the causal connection between CO2 increase and temperature rise has not been demonstrated beyond doubt. In fact the engine of the Earth's atmosphere and climate is primarily the oceans which contain 90 percent of the thermal capacity, so until we are carefully measuring the temperature structure of the Earth’s oceans we will not have enough information to make accurate climate models. Another problem is that historically there have been large changes in temperature that have rivaled the current changes that are seen, and we do not understand those changes which take place over hundreds or thousands of years. Nonetheless the evidence is disturbing. In the last hundred years the mean temperature measured across the Earth has increased by about one and a half degrees, with six of the hottest years in the last century occurring in the last fifteen years. Whether this is part of a systemic increase in temperature or not cannot yet be said with absolute certainty, but it would be very dangerous to take a chance. For example, 3 to 5 degrees is the typical amount of climate change associated with an ice age, so the consequences of even a couple of degrees in global warming would be devastating for the world's agriculture and for the world economy.

    • 1 min.

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