Big Bang Theory

The Big Bang Theory is the prevailing scientific model of the origin of the universe. According to this theory, the universe began as a hot and dense point, known as a singularity, approximately 13.8 billion years ago. At this time, all the matter and energy in the universe was concentrated in a space smaller than the size of an atom. The Big Bang theory suggests that the universe began to expand rapidly and cool down after this initial singularity, resulting in the formation of subatomic particles, atoms, stars, and galaxies. As the universe expanded and cooled, it also became less dense, the particles that remained began to combine into atoms which eventually formed into galaxies and clusters of galaxies. One of the key pieces of evidence supporting the Big Bang theory is the cosmic microwave background radiation, which is a faint, uniform glow of microwave radiation that fills the universe. This radiation is thought to be the leftover heat from the Big Bang, and its characteristics match the predictions of the Big Bang model. This all began roughly 13.8 billion years ago, and is thus considered to be the age of the universe. Through the testing of theoretical principles, experiments involving particle accelerators and high-energy states, and astronomical studies that have observed the deep universe, scientists have constructed a timeline of events that began with the Big Bang and has led to the current state of cosmic evolution. The Big Bang theory is a cosmological model that describes the universe's evolution from its earliest moments to its present state. It is based on a few fundamental principles of physics and cosmology, such as general relativity, the laws of thermodynamics, and the concept of cosmic inflation. The theory suggests that the universe began as a singularity, which was an infinitely hot and dense point. This singularity contained all the matter, energy, space, and time that exists in the universe. Then, the universe began to expand rapidly, and as it did so, it cooled down, and matter and energy began to form. As the universe expanded, it went through different phases of development, and different structures emerged. After the initial phase of expansion, the universe was dominated by radiation, and particles and antiparticles annihilated each other. Another important concept in the Big Bang theory is cosmic inflation. Cosmic inflation is a period of exponential expansion that is thought to have occurred in the very early universe, just moments after the Big Bang. This rapid expansion is thought to have smoothed out any irregularities in the universe and created the uniformity that we see in the CMB. This is a faint radiation that is present throughout the universe, and it is thought to be a relic of the intense heat and energy released during the Big Bang. The CMB was first discovered in 1965 by Arno Penzias and Robert Wilson, and it is now one of the most important pieces of evidence supporting the Big Bang theory. Most cosmological models suggest that the Universe at this point was filled homogeneously with a high-energy density, and that the incredibly high temperatures and pressure gave rise to rapid expansion and cooling. This began at 10-37 seconds, where the phase transition that caused for the separation of forces also led to a period where the universe grew exponentially. It was also at this point in time that baryogenesis occurred, which refers to a hypothetical event where temperatures were so high that the random motions of particles occurred at relativistic speeds. As a result of this, particle–antiparticle pairs of all kinds were being continuously created and destroyed in collisions, which is believed to have led to the predominance of matter over antimatter in the present universe. After inflation stopped, the universe consisted of a quark–gluon plasma, as well as all other elementary particles. From this point onward, the Universe began to cool and matter coalesced and formed. The theory predicts that that definite amount of hydrogen, helium and lithium were produced. The radiation that also filled the universe was then free to travel through space. Somehow, some excess matter survived—and it's now the stuff that people, planets, and galaxies are made of. Our existence is a clear sign that the laws of nature treat matter and antimatter slightly differently. Researchers have experimentally observed this rule imbalance, called CP violation, in action. Physicists are still trying to figure out exactly how matter won out in the early universe.

FIRST STARS TILL TODAY:

There wasn't a single star in the universe until about 180 million years after the big bang. It took that long for gravity to gather clouds of hydrogen and forge them into stars. Many physicists think that vast clouds of dark matter, a still-unknown material that outweighs visible matter by more than five to one, provided a gravitational scaffold for the first galaxies and stars. Even now the universe is expanding, and to astronomers' surprise, the pace of expansion is accelerating. It's thought that this acceleration is driven by a force that repels gravity called dark energy. We still don't know what dark energy is, but it’s thought that it makes up 68 percent of the universe's total matter and energy. Dark matter makes up another 27 percent. In essence, all the matter you've ever seen—from your first love to the stars overhead—makes up less than five percent of the universe.

Today, the consensus among scientists, astronomers and cosmologists is that the Universe as we know it was created in a massive explosion that not only created the majority of matter, but the physical laws that govern our ever-expanding cosmos.