Question: how was the earth created

Harrison Prosper answered on 15 Jun 2019: last edited 15 Jun 2019 12:06 pm

Our current understanding is that the solar system formed from the gravitational collapse of an enormous cloud of gas and dust, rather like the one we see in the constellation Orion, M42, in which some stars have already formed and new ones are forming. Gravity pulls things together. When dust and gas get squeezed together by gravity, starting from a large tenuous cloud, we say there has been a gravitational collapse. (By the way, these clouds contain dust from previous generations of huge stars that exploded, injecting elements such as carbon, oxygen, and nitrogen into the clouds.) As the cloud collapses, it flattens into a spinning disk. The densest part of the disk is at the centre and that is where the star forms. Typically, the center hogs most of the matter from the cloud and gets more and more compressed by gravity. Whenever anything is compressed it gets hotter. Since the center of the spinning disk is the most compressed, it is also the hottest part of the disk. If the temperature reaches a few million Kelvin (1 K = 1 C), nuclear reactions are triggered in which four protons stick together (i.e., fuse) into helium. These reactions raise the temperature and, more importantly, they create light which, after thousands of years, streams out from the center of the disk. A star is born! The light from the star blows much of the remaining gas and dust away, but some tiny fraction remains in the disk (about 1 in a 1000) and eventually collapses into much smaller objects that we call planets. In our solar system, the largest planet is Jupiter with a mass about 1/1000 that of the Sun. Interestingly, you can think of Jupiter as a “failed star”. Had Jupiter managed to accumulate about fifty times more dust and gas from the remaining cloud, it would have ignited and become a star. The Sun and Jupiter would then have formed a binary star system. One last thing. For centuries, we did not know whether other solar systems exist. Today, we know that planets are everywhere. Planets outside our solar system are called “extrasolar planets”. So far, more that 3,500 have been discovered. It would be the greatest discovery of all time were we to discover that one of these planets (or one yet to be discovered) contained life.