by Dr Henry RichterThis is a continuation of my discussion on the requirements for life to exist on a planet elsewhere in the universe. Facing Reality #1 listed 20 features and characteristics, all of which are required for life to exist and flourish. It also addressed the importance of our location in the galaxy. Facing Reality #2 addressed our location in the solar system and characteristics of our orbit. Now we will move in closer to our planet earth, and look at what our moon does for us, examine a little about the earth itself, and then discuss our atmosphere.The MoonApollo astronaut Jim Irwin standing on the moon in “Moon Rovers” by Alan Bean. Used by permission.Earth has a satellite moon, about a quarter of a million miles away. It is about one-fourth the size of the earth, and in a nearly circular orbit around the earth. Each orbit takes just under thirty days – a month (from “moon-th”). This moon does a number of things for us, some of which are important to the support of higher forms of life.First, the gravitational pull of the moon helps stabilize the tilt of the earth as it spins once a day. This tilt is important because it creates the seasons. As the earth progresses around the sun, making a complete trip in a year, direct sunlight varies throughout the year. For the summer solstice the northern hemisphere get more straight-on sunshine, for the two equinoxes the sunshine illuminates our sphere equally, then for the winter solstice the southern hemisphere gets more sun. Having these seasons fosters plant growth and re-growth in a cyclic pattern, giving us more productivity of plants—not to mention a more interesting environment to live in.Second, the gravitational pull of the moon creates tides in the ocean and in the earth’s crust. Tides in the oceans are important since this is what stirs the water up, allowing it to absorb oxygen from the atmosphere (essential to marine life) and moves nutrients around. The movement of water from the ocean’s depths causes constant mixing; without it, the oceans would be stale water, not healthful to life forms (both plant and animal). The tidal action is minimal at the equator, and substantial at high latitudes, being as much as fifty feet of vertical movement in parts of Alaska. There the tides are such that one does not want to be trapped on one of the mud flats in the ocean inlets, as this much tidal action means the water rushes in and out faster than one can run.The pull on the earth’s crust is not so noticeable, but does cause some movement on a geographical scale. This flexes the earth’s surface, and does facilitate tectonic movement under the crust. It helps the earth’s dynamics, freshening the surface and sub-surface mantle. Let me digress a moment with something that really impresses me.There are a large number of features that do not relate to allowing life, but make life interesting. I have commented from time to time about features that allow scientific exploration related to an understanding of the universe and its principles. I note that the moon is of an exact size and location to exactly blot out the sun in a very precise way. The fact that we have solar eclipses that allow a special examination of the sun is remarkable. When the moon juxtaposes itself in front of the sun, often there is an exact fit to blot out just the sun, but not its atmosphere. When a total solar eclipse occurs, the sun’s atmosphere (the chromosphere), and its spectra can be recorded. Because of this tight fit, much was learned about the sun – one example being the discovery of the element helium. If the moon were 1% larger, the chromosphere would be hidden. If the moon were 1% smaller, there would be too much light to see the chromosphere (as occurs in annular eclipses) Fascinating!Great American Eclipse of Aug 21, 2017, by Dave WeberThe AtmosphereMoving in even closer we come to the earth’s atmosphere. The atmosphere is very thin and is held in by gravity. The amount of atmosphere results in a gas pressure that is low enough to not crush delicate life and chemical structures. Some planets have an atmosphere that is destructively dense with correspondingly high pressures. Venus, for example, has a dense atmosphere of carbon dioxide with such pressure that it crushes spacecraft that have landed on the planet. That particular notorious ‘global warming’ gas also creates a greenhouse effect, making the atmosphere unsurvivably hot. Earth’s atmospheric pressure is high enough to supply oxygen to tissues in a quantity sufficient to facilitate metabolism.Again, we see other factors that are just right, such as the composition of the earth’s atmosphere. Three main components comprise our atmosphere: 21% oxygen, 78% nitrogen and 1% carbon dioxide. The oxygen is necessary for metabolism. Too much oxygen would overwhelm the metabolic chemical reactions; i.e., they would in essence burn up. Too little oxygen would not support metabolic reactions. The nitrogen, although somewhat inert, provides enough substance to the atmosphere to maintain its thickness. Nitrogen is used by plants to build molecules such as amino acids, and thus is also a vital element for life. As we breathe, nitrogen helps sweep out our lungs, clearing out carbon dioxide, a waste product from our body metabolism. The low concentration of carbon dioxide provides enough carbon for plant growth. It also helps regulate the temperature of the atmosphere. There is much public concern about the amount of carbon dioxide in the atmosphere and the possibility of climate change. Just a small change in the carbon dioxide percentage can cause global changes in temperature. Some of the oxygen exists in the form of ozone in the high atmosphere which absorbs harmful ultraviolet light from the sun.Lightning storms from Earth orbit (NASA)Another important role of the atmosphere is to transport water. As planets go, Earth’s atmosphere is generally pretty mild wind-wise. Some of the planets have violent windstorms with velocities of many hundreds of miles per hour. We have an occasional hurricane or typhoon, but, in general, winds are gentle. Water evaporates from the ocean and lakes and is carried around by our atmosphere. Clouds form and the water drops to earth as rain or snow, thus watering most of the continents. Although probably not a key requisite for life, the transport of water to wet the land is sure a good thing.The inner planets have atmospheres of carbon dioxide, methane, oxygen, and nitrogen. The outer planets – the gas giants – are mainly hydrogen, helium, and traces of methane and ammonia. All the planets (except earth, of course) have atmospheres that would not support life. They also have temperatures that will not support life.Earth’s MassThe mass of the earth is just right to create gravitational attraction sufficient to hold things to the surface, and to maintain our atmosphere. Too much gravity would make living structures (at least as we know them) have a difficult time growing and moving. Too little gravity would mean no atmosphere, so the mass of a planet needs to be within a certain range. The mass of the earth is distributed from the iron-nickel core, to the mantle, and to the subsurface material and the rocky surface.In the next segment of this series, we will examine additional realities that must be faced to have a habitable planet, finding once again that the earth is right in the ‘Goldilocks Zone’ of being just right.Is the earth a product of design or chance? Photo by David CoppedgeDr Henry Richter, a contributing science writer to Creation-Evolution Headlines, was a key player at NASA/JPL in the early days of the American space program. With a PhD in Chemistry, Physics and Electrical Engineering from Caltech), Dr Richter brings a perspective about science with the wisdom of years of personal involvement. His book America’s Leap Into Space: My Time at JPL and the First Explorer Satellites (2015), chronicles the beginnings of the space program based on his own records and careful research into rare NASA documents, providing unequaled glimpses into events and personnel in the early days of rocketry that only an insider can give. His next book, Spacecraft Earth: A Guide for Passengers, is due out later in 2017. For more about Dr Richter, see his Author Profile.(Visited 420 times, 1 visits today)FacebookTwitterPinterestSave分享0
The City of Joburg has retrofitted five buildings with energy efficient lights. It plans to do the same with 104 more council buildings. (Image: Media Club South Africa) • Christa Venter Project Assistant C40 Climate Change Summit +27 82 492 2424 • Megacities to talk climate change in Johannesburg • Cities combat climate change • Climate Reality Project counts carbon costs • Green buildings sprouting in South AfricaLucille DavieMitigation and adaptation are universally accepted approaches to tackling climate change. Johannesburg, the host city of the fifth biennial C40 Cities Mayors Summit in February, has a climate change strategy that is in line with these imperatives.The C40 is a network of 63 of the world’s megacities that are taking action to reduce greenhouse gas emissions, in an effort to reduce climate risks locally and globally. The summit will bring together mayors for three days, from 4 to 6 February, to consider urban solutions to global climate change “through individual efforts as well as international engagement and collaboration”.“A principle of working together to create and build partnerships is crucial to the success of achieving the city’s strategic agenda, including matters relating to resource sustainability,” says Joburg Executive Mayor Parks Tau. He will host the summit, together with C40 chair Michael Bloomberg, who is the mayor of New York City.City delegates, business people, environmentalists, activists and community representatives are expected to attend. They will deliberate on the progress being made by cities around the world, and suggest interventions that can be jointly undertaken to address environmental issues. The theme for the summit is “Towards resilient and liveable megacities: demonstrating action, impact and opportunity”.“Even if emissions are stabilised relatively soon, climate change and its effects will last many years, and adaptation will be necessary. Climate change adaptation is especially important in developing cities since those cities are predicted to bear the brunt of the effects of climate change.”The city of Johannesburg, the country’s commercial heart – which contributes 16% to the country’s gross domestic product – is among the biggest emitters of greenhouse gases in South Africa, largely from industrial, transport and residential activities. Its long-term growth and development strategy, Joburg 2040, has a strong focus on climate change and depletion of natural resources.Climate change mitigationRegarding climate change mitigation, Joburg’s Rea Vaya Bus Rapid Transit system, introduced in 2009, has resulted in 233 buses taking to the roads, driving in dedicated lanes. It has led to the removal of 500 taxis and minibuses from Joburg’s streets. Some 44 new buses will be introduced to the roads in mid-February, taking the total to 277. Rea Vaya transports more than 50 000 commuters daily.“With the full implementation of Bus Rapid Transit it is estimated that the city will save 1.6 million tons of carbon dioxide equivalent emissions by 2020,” explains Matshidiso Mfikoe, the mayoral committee member for environment and infrastructure services.The Rea Vaya buses will eventually transport passengers along 330km through the suburbs and city, with modern fleet buses. This will give more than 80% of Joburg’s residents the choice of catching a bus, placing residents within 500m of a trunk route or feeder corridor. Running on low-sulphur diesel with the most advanced pollution reduction equipment, the Rea Vaya buses are the cleanest on the continent. They reduce nitrous oxides, the most dangerous health risk from vehicular emissions, by thousands of tons a year, and particulate matter, such as soot, by hundreds of tons annually.Joburg aims to replace more than one third of its Metrobus fleet with modern dual fuel green buses in the future. It is also developing a Metrobus gas refuelling station, and has retrofitted five municipal buildings with energy efficient lighting with a total saving of 100 tons of carbon dioxide.“One hundred and four municipal buildings have been identified to be retrofitted under a larger energy efficiency building retrofit programme. This building retrofit programme will include lighting, cooling, and heating systems,” says Mfikoe.Efforts are being made to convert waste to energy. The city is now flaring methane gas at one of its five landfill sites, producing 5MW of renewable electricity, which is sufficient to supply power to 4 500 houses. This reduces the carbon emissions from the landfill by about 149 000 tons of carbon dioxide a year. The other four sites will be operational in the near future, and will generate 19MW of electricity to supply 12 500 households over the next 20 years and beyond.Sections of the city are also being greened, such as the townships of Soweto in south-western Johannesburg. Since 2006, 200 000 trees have been planted in the region. Joburg is already one of the most forested cities in the world, with over 10 million trees, making it an urban forest. This has led to an improvement in the air quality. “Furthermore, there has been rehabilitation of the southern catchments, park developments in disadvantaged areas, and the provision of green servitudes and ecological assessments of the city’s catchments,” adds Mfikoe.Joburg has also installed over a thousand low pressure solar water geysers to households in Cosmo City, a housing development in the north. Installing energy efficient lights and planting fruit trees has also been undertaken. In 2012, it launched the Solar Water Geyser Programme, under which it aims to roll out 110 000 geysers to poor and low income households over three years.Climate change adaptationA Johannesburg Climate Change Adaptation Plan or CCAP was completed in 2009. Adaptation initiatives coming out of this plan include a Vulnerability Assessment and Risk Management Plan, flood modelling for flood prone areas, and disaster response. Johannesburg has several rivers running through its suburbs, which flood readily during the city’s summer heavy rains.The CCAP was recently one of only 29 projects globally nominated for the C40 and Siemens Climate Leadership Award.Guided by the CCAP, Joburg is mapping flood prone areas, developing early warning systems, and raising awareness in vulnerable communities, particularly through Alexandra township. CCAP recommendations have been integrated into long-term city strategy and day-to-day operations.Some 30 organic food gardens were planted in schools and communities between 2010 and 2011, a project that is “a vehicle to grow green minds and hearts”. The project supplements the schools’ feeding programmes, at the same time giving communities an additional source of income through the sale of produce. “Organic food gardens produce fewer greenhouse gases and are better for the environment and our health,” notes Mfikoe.Johannesburg is one of four C40 cities in Africa, along with Addis Ababa in Ethiopia, Cairo in Egypt and Lagos in Nigeria. Climate change affects not only the industrialised but also those living in rural areas, where changes in weather patterns threaten crops and livestock.