Wikipedia is the largest general reference work on the Internet ,  and one of the 15 most popular websites as ranked by Alexa ; in , it was ranked as the 13th most-visited. Wikipedia was launched on January 15, , by Jimmy Wales and Larry Sanger ; Sanger coined its name as a portmanteau of "wiki" and "encyclopedia". The English Wikipedia , with 6. Wikipedia has been criticized for its uneven accuracy and for exhibiting systemic bias , particularly gender bias against women. Other collaborative online encyclopedias were attempted before Wikipedia, but none were as successful.
The Big Bang theory is a cosmological model of the observable universe from the earliest known periods through its subsequent large-scale evolution. Extrapolating this cosmic expansion backwards in time using the known laws of physics , the theory describes a high density state preceded by a singularity in which space and time lose meaning. Detailed measurements of the expansion rate of the universe place the Big Bang at around After its initial expansion, the universe cooled sufficiently to allow the formation of subatomic particles , and later atoms. Giant clouds of these primordial elements — mostly hydrogen , with some helium and lithium — later coalesced through gravity , forming early stars and galaxies, the descendants of which are visible today. Besides these primordial building materials, astronomers observe the gravitational effects of an unknown dark matter surrounding galaxies. Most of the gravitational potential in the universe seems to be in this form, and the Big Bang theory and various observations indicate that this excess gravitational potential is not created by baryonic matter , such as normal atoms.
Geology can also include the study of the solid features of any terrestrial planet or natural satellite such as Mars or the Moon. Modern geology significantly overlaps all other Earth sciences, including hydrology and the atmospheric sciences , and so is treated as one major aspect of integrated Earth system science and planetary science. Geology describes the structure of the Earth on and beneath its surface, and the processes that have shaped that structure.
In the field of Geology, dating is an important term as it is a technique through which evaluation regarding the age and period about the fossil, remains, the archaeologists do valuables and artifacts. At first, there were not many methods of dating were available, but now with advancement in the technology, we mainly have two types of techniques to ascertain ages of ancient belongings. Relative Dating and Absolute Dating are two types of such techniques which are under practice to determine the age of the fossils, objects or civilizations. The relative dating is the technique in the Geology through which the age is determined with relation to the other objects.