Star Points for December, 1999; by Curtis Roelle The End of the World As We Know It. With any luck, it will all be over soon. The daily dose of "millennium madness" and Y2K "doomsday cult" scenarios in the news media that is. Numerous mythologies and religions both ancient and contemporary have grappled with the question of how the world meets its end. Science has also considered this issue and constructed theories that are amazing and humbling at the same time. One might say they inspire a sense of awe and wonder not unlike traditional mythologies that have marveled people in ages past. In the current widely accepted theory the sun is about 4.5 billion years old. In his book "The Sun Our Star" Robert W. Noyes writes about the future of the sun. The sun continues increasing in brightness and 1.5 billion years from now its temperature will have increased by 15%. The age of ice on Earth comes to an end. The ice caps will melt and sea levels will have risen several hundred feet. At an age of 10 billion years the sun's supply of hydrogen will be nearing exhaustion. As the supply runs out the sun swells turning noticeably red. In the daytime sky the red sun is about three times larger than the full moon. On Earth the oceans have boiled away and the surface has become uninhabitable. To maintain human life mankind will have to leave this world and recede from the expanding sun. The sun continues enlarging until it engulfs the orbit of Mercury incinerating that planet. The surface of the earth is turned into a molten sea of lava. Eventually the distended surface of the sun may extend all the way to the earth. The increased drag causes the earth to spiral in toward the center of the sun and is vaporized. Thus the planet which once was blue and teeming with life and human civilization reaches its unequivocal end. Meanwhile our sun is enjoying its red giant phase but this will last an astronomically brief period of some 250 million years. All this time the sun has been exhausting its supply of hydrogen. But when the hydrogen runs out it begins consuming helium. The sun shrinks once more but will still be 10 times its current diameter. As the helium runs out the sun consumes other elements, including oxygen, which are byproducts of nuclear fusion. As each element is consumed in turn the temperature of the sun increases. Eventually the outer layers of the sun's atmosphere are driven away by an intense solar wind exposing its very core. The discharged solar atmosphere forms a huge cloud that may expand to more than one light year across. Our present day sky is peppered with these so-called "planetary nebulae" the end product of sun- like stars. Many such nebulae are visible in amateur-sized telescopes. The remaining core of the sun is an object called a white dwarf star. It has most of the original mass of the sun but is only the size of Earth. A sugar cube of this material would weigh as much as several automobiles. The material is in what physicists call an "electron degenerative" state meaning that its atoms are compressed so much that the electrons are liberated thus allowing the protons to be squeezed even tighter together. Although a white dwarf is hot it does not radiate much energy due to its small size and surface area. Any remaining human life would need to come ever closer to the sun to keep warm. The white dwarf sun will continue cooling and growing dimmer. Billions of years later the sun ceases to glow entirely having become a black dwarf, a cinder of a star that was once the center of all known life which it nourished with its free outflow of energy. Any humans still in existence would have since left a long time before in search of a newer, younger star with planets to seed. This process might repeat from star to star as long as there are stars in the universe. Next month: The end of the universe as we know it.