COMPUTERS AND MORE

Celestial Sphere and Star AtlasWe will talk more about the celestial sphere and how to tell the positions of the stars in the sky. We will also introduce the constellations and the star atlas.
Celestial SphereWhen we look at the sky, it is difficult to tell how far the stars are. It seems that all the stars lie on a "flat" surface. A similar situation is watching television, the screen of the television represents the three dimensional world.
The sky "surrounds" us from all directions. We placed ourselves at the center of an imaginary sphere, the celestial sphere. Everything on the sky will appear on the celestial sphere.
As mentioned in the last chapter, the celestial sphere does not follow the rotation of the Earth. Thus, stars are fixed on the celestial sphere.
We need a coordinate system to tell the positions of the stars on the celestial sphere. It is very similar to the longitude and latitude on the Earth surface. The projection of the rotational axis of the Earth marks the north celestial pole and the south celestial pole. The celestial equator is just the projection of the Earth's equator.
The declination, similar to the latitude, runs from +90° or 90°N, at the north celestial pole, to -90° or 90°S at the south celestial pole.
The right ascension is different from the longitude. Instead of running from -180° to +180° like the longitude, the right ascension runs from 0 hour to 24 hours from west to east. Each hour has 60 minutes and each minute has 60 seconds, just like the clock. (Note: These minute and second are NOT equal to the arc minute and arc second introduced earlier. Do you know the differences?) The starting point of the right ascension is at the vernal equinox. Recall that vernal equinox is one of the two intersection points of the celestial equator and the ecliptic.
Remarks:
The celestial north does not equal to the magnetic north to which the compass points. (In fact, the difference between the directions of celestial and magnetic north depends on the position of the observer.)
Like a spinning top, the rotational axis of the Earth is not fixed in space. It will move in a circle with a period about 26000 years. We call this the precession. Therefore, the vernal equinox and the pole star will change in time. To be precise, we have to mention the time, for example, year 2000.0, when we talk about the celestial coordinate system. We will not go into the details.
ConstellationsThe ancient people used their imaginations to create patterns and stories of the stars. These patterns become the constellations. Each culture had its own constellations and stories. Before 1930, constellations were regions in the sky with only fuzzy boundaries. In that year, the International Astronomical Union put the scheme of constellations on a definite system. The sky was officially divided into 88 constellations with sharp boundaries, and each star is in one and only one constellation.
Some important constellations are, for example, the zodiac. Zodiac are the constellations that the ecliptic passes through. (Ophiuchus is not one of the zodiac, see Chapter 2.) Note that it is around January when the Sun is in Sagittarius, and in the evening, we will see Taurus and Gemini, etc. They are called the winter constellations. Similarly, we will see other constellations in other seasons.
Star AtlasWhen we use an ordinary map, we do something like this:
But when we use a star map, we have to lie down and look up. Thus, the east and the west are "reversed."
There are many kinds of star atlas. The following is taken from the Hong Kong Space Museum. This shows the whole sky visible at some particular time. Lines connecting the stars are drawn to make the constellations more "visible." A bigger dot does not represent a larger star, it represents a brighter star. We will talk about stellar brightness later.
Courtesy Hong Kong Space Museum.
Just to let you have an idea of what a serious star atlas looks like, the most detailed star atlas on paper nowadays is similar to the atlas below. This figure covers the area bounded by the red circle in the above all sky map.

GLOBAL WARMING

The past 9 years has produced the warmest years due to global warming. In fact, every year from the first to the second warmest years, ranked within the warmest 25 years in the US. In 2006, the annual average temperature was 55 degrees Fahrenheit. Recent warm years point to a climate change being brought on by global warming. There have been more and more frequent droughts in the West in recent years. The last 30 years in particular have seen numerous droughts. These droughts have spawned wildfires that set new records in 2006 for number of fires and of acres burned. Further proof of global warming is seen in these destructive wildfires.The number of times it rains in a year has increased during the last 50 years due to global warming. What is more, global warming is causing storms to intensify. Storms which would have been ordinary thunderstorms in the past are morphing into raging tempests. Hurricanes have been rated higher in recent years as global warming affects their intensity.Difficulty in Predicting the Future of Global WarmingOcean currents can change the temperature of the land on which they strike. The earth's atmosphere is constantly in a cycle of evaporation and precipitation. The nature of this cycle will affect global warming. At the same time, all these variables will be affected by global warming in return.As ice melts in the Polar Regions, the ocean temperatures are affected. This is due to global warming. However, it also can perpetuate global warming by changing the evaporation rates of the sea. The courses and speeds of the oceans currents cannot be predicted with accuracy, but they will have an affect on global warming. While it is nearly impossible to predict the future of global warming with complete accuracy, it is good to explore the subject. It is important to estimate the damage that will be caused by global warming in order to make the concept of global warming more concrete.Reducing Global WarmingHouses give off a high percentage of a country's total carbon dioxide emissions. In the United States, the figure is about 38%. Since carbon dioxide is one of the greenhouse gases, houses contribute strongly to global warming. Buildings are also often built using recycled materials. Wood can be used from an older home that has been torn down. This will prevent the need to cut down other trees. Since the deforestation of the land contributes to global warming, this will help the situation.There are several organizations in the US that aid in the cause of stopping global warming by encouraging green building. One non-profit organization makes it their business to foster green building methods in both houses and commercial buildings. This group of people from the building industry is a part of the Green Building Initiative.Global Warming and Your HealthGlobal warming has caused intense heating up of the environment. In areas where people are not prepared for extreme heat, there have been devastating heat waves recently. There were heat flare-ups in Europe in 2003 which lasted as long as two weeks at a time. Temperatures soared upwards of 104 degrees Fahrenheit. Global warming can also affect the incidence of tropical disease. Mosquitoes have been found in places that were once too cold for them. High elevations, such as mountains were once free of disease-carrying mosquitoes.Often, people take dangerous risks during floods. They drive into water, thinking that they can make it across. When they do not, they can get swept away and drowned. There is no graver consequence of global warming than death, of course. If all people knew how much global warming can affect their health, they might be more prone to working on a solution.
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