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.
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
The nebular theory of solar system formation suggests that stars and their planets form out of cooling interstellar clouds of molecular hydrogen. As the cloud contracts, it forms a disc of dense material that forms the star. As it forms, the star throws off material that coalesces into planets.Full Answer >
Although the ultimate fate of the universe is a largely debated topic, according to the University of Tennessee, in an open universe the universe will continue to expand forever. This is due to insufficient mass to cause the expansion to stop.Full Answer >
As of 2013, the National Aeronautics and Space Administration determined, with a margin of error of only 0.4 percent, that the universe is infinite in size. The observable universe extends 92 billion light years in diameter. The exact size of the universe, or if there are multiples, is unknown.Full Answer >
As of 2014, the size of the universe is unknown. Clues to its size can only be found within the limits of the observable universe, which is a sphere with a diameter of about 92 billion light-years.Full Answer >