The Big Bang is the leading scientific theory explaining how the universe began about 13.8 billion years ago from an extremely hot, dense, and small point (a singularity), then expanded and cooled suddenly, forming matter, stars, galaxies, and everything we know today, and continues to expand today. This was not an explosion in space, but rather an expansion of space itself, with all places at the center.
This is not an explosion in space, but rather an expansion of space itself, where all places are the center.
The universe originated from a singularity, a point of infinite density and temperature.
About 13.8 billion years ago, this point began to expand very rapidly and continues to expand.
As it expanded, the universe cooled, allowing small particles to form atoms, then stars, and galaxies.
Supporting evidence includes the leftover light from the explosion (cosmic background radiation) and the observation that galaxies are moving away from each other (redshift).
What Happened:
Beginnings:
The universe was a mass of hot, light, and energetic particles at a single point.
Matter Formation:
As it expanded and cooled, particles combined into atoms. These atoms then formed stars and galaxies.
Structure Formation: Through gravity, stars died and formed planets, comets, asteroids, and black holes.
Not an Explosion in Space: The Big Bang was about space itself expanding.
not an explosion at a specific location; everywhere experienced this expansion.
Scientific Explanation: This is the most accepted model for explaining the origin and evolution of the universe.
According to physics: This process is characterized by the expansion of the universe which causes cooling and the formation of particles, atoms (especially hydrogen), stars, and galaxies, supported by evidence such as the cosmic microwave background radiation (CMB) and galactic redshift.
The universe began at a very dense and hot singularity point.
Titik tersebut meledak dan mulai mengembang (ekspansi ruang) secara eksponensial, membawa materi dan energi bersamanya.
As the universe expanded, the temperature of the universe decreased, allowing the formation of subatomic particles, then atomic nuclei (nucleosynthesis), and finally atoms.
Matter began to gather to form gas clouds (nebulae), which then condensed into stars and galaxies.
Microwave Background Radiation (CMB):
The residual heat from the early universe detected as microwave radiation from all directions, discovered by Penzias and Wilson.
Galactic Redshift:
Edwin Hubble's observations showed galaxies receding, proving the universe is expanding.
The bottom line: The Big Bang was not just an explosion in space, but the event that gave birth to space and time itself, as well as the evolution of the entire universe.
Stephen Hawking was a key figure in understanding the Big Bang Theory, proposing that the universe began at a singularity, as well as formulating the no-boundary proposal which states that time began at the Big Bang, making the question of "before" irrelevant, similar to asking where is "north" of the North Pole. Together with Roger Penrose, he proved that the universe must have begun at a singularity, and his theory helped integrate classical physics with general relativity, although he also clarified that the Big Bang was a cosmological event of an expanding universe, not an explosion in space.
Hawking's Major Contributions to the Big Bang:
Initial Singularity:
Working with Penrose, he showed that Einstein's theory of General Relativity implies that the universe must have originated from an infinitely dense and hot point called a singularity, which was the beginning of the Big Bang.
No-Boundary Proposal:
With James Hartle, he proposed that the universe had no boundaries in the past. Time and space bend near the Big Bang, so there is no "before" the Big Bang in the ordinary sense of time. This eliminates the need for a "cause" outside the laws of physics.
Time's Arrow Theory:
Developed the concept that the universe has no end, but rather a series of calculable probabilities, as explained in his book, A Brief History of Time. Opposing God as a Direct Creator: In his book, The Grand Design, Hawking argued that the Big Bang was a natural consequence of the laws of physics, without the need for divine intervention, challenging the traditional view of cosmic design.
In Summary:
Hawking explains that our universe began in a superdense state about 13.8 billion years ago and continues to expand, and he provides a mathematical and conceptual framework for understanding this initial singularity and the nature of time itself before and during this event.
More about the big bang can be found in Stephen Hawking's book, A Brief History of Time.