light. More massivestars would need to be 杭州油压手推 hotter to balance their strongergravitational attraction, making the nuclear fusion reactionsproceed so much more rapidly that they would use up theirhydrogen in as little as a hundred million years. They wouldthen contract slightly, and as they heated up further, wouldstart to convert helium into heavier elements like carbon oroxygen. This, however, would not release much more energy,so a crisis would occur, as was described in the chapter onblack holes. What happens next is not completely clear, but itseems likely that the central regions of the star would collapseto a very dense state, such as a neutron star or black hole.
The outer regions of the star may sometimes get blown off ina tremendous explosion called a supernova, which wouldoutshine all the other stars in its galaxy. Some of the heavierelements produced near the 杭州西湖阁最新 end of the star’s life would beflung back into the gas in the galaxy, and would provide someof the raw material for the next generation of stars. Our ownsun contains about 2 percent of these heavier
elements,because it is a second- or third-generation star, formed somefive thousand million years ago out of a cloud of rotating gascontaining the debris of earlier supernovas. Most of the gas inthat cloud went to form the sun or got blown away, but asmall amount of the heavier elements collected together to formthe bodies that now orbit the sun as planets like the earth.
The earth was initially very hot and without an atmosphere.
In the course of time it cooled and acquired an atmospherefrom the emission of gases from the rocks. This earlyatmosphere was not one in which we could have survived. Itcontained no oxygen, but a lot of other 杭州丝袜按摩的吗 gases that arepoisonous to us, such as hydrogen sulfide (the gas that givesrotten eggs their smell). There are, however, other primitiveforms of life that can flourish under such conditions. It isthought that they developed in the oceans, possibly as a resultof chance combinations of atoms into large structures, calledmacromolecules, which were capable of assembling other atomsin the ocean into similar structures. They would thus havereproduced themselves and multiplied. In some cases therewould be errors in the reproduction. Mostly these errors wouldhave been such that the new 杭州男士私人spa macromolecule could notreproduce itself and eventually would have been destroyed.
However, a few of the errors would have produced newmacromolecules that were even better at reproducingthemselves. They would have therefore had an advantage andwould have 杭州爱情故事spa是飞机吗 tended to replace the original macromolecules. Inthis way a process of evolution was started that led to thedevelopment of more and more complicated, self-reproducingorganisms. The first primitive forms of life consumed variousmaterials, including hydrogen sulfide, and released oxygen. Thisgradually changed the atmosphere to the composition that ithas today, and allowed the development of higher forms of lifesuch as fish, reptiles, mammals, and ultimately the human race.
This picture of a universe that started off very hot andcooled as it exp