The no boundary theory of the universe likens the universe to the Earth, in that is impossible to find any boundaries traveling around the Earth or to fall off it. This is possible as a result of theorizing that prior to the Big Bang, the generally accepted laws of physics did not apply and that the concept of time as we know it did not exist.Continue Reading
The no boundary theory of the universe was advanced by the physicists Stephen Hawking and James Hartle. It is called the no boundary theory because it posits that the universe has no boundaries.
The theory says the quantum singularity that gave birth to the universe via the Big Bang was of infinite density. In that strange state of flux, particles appear and disappear spontaneously, and space and time become separated. It is therefore at the moment that the Big Bang takes place that time starts to exist; before the Big Bang, it is nonsensical to talk about time.
Hawking uses the Earth once again to illustrate this point. While on Earth it is always possible to travel south, that is, until you reach the South Pole. Once on the South Pole, "south" doesn't exist. The same concept applies to time before the Big Bang — once you reach t=0, time ceases to exist.Learn more about Universe
The belief of early astronomers that the Earth was the center of the universe stemmed from limited astronomical tools and geocentric attitudes. The Ptolemaic Model, developed around 100 A.D., presented the Earth-centered solar system in which most early Roman astronomers believed.Full Answer >
Whether humans are the only intelligent life to have evolved in the universe cannot be answered with certainty, but a probability can be assigned to the proposition. Accurately estimating the number of advanced civilizations in existence is done by assessing the number of opportunities for intelligent life to evolve and contrasting that with the improbability of various stages in the development of a civilization.Full Answer >
Nicolaus Copernicus was a Polish scientist who is credited with the early 16th-century discovery that the sun is the center of the universe and that Earth and several other planets orbit it. Copernicus' discovery, which subsequent astronomers expanded on, has become known as the heliocentric solar system.Full Answer >
The universe contains three different categories of black holes: stellar, supermassive and miniature, which are further divided according to whether they are spinning. Non-spinning black holes are always spherical, while spinning black holes tend to be more oblate. The degree of equatorial bulge is determined only by the rotational velocity of the object.Full Answer >