According to the big bang theory, matter was an infinitely small point of very high density that burst and extended in all directions at a specific point in time, generating what we now call our Universe, which also encompasses space and time.
The big bang occurred around 13.8 billion years ago. Theoretical physicists have reconstructed this timeline of events beginning 1/100th of a second after the Big Bang.
After the explosion, the Universe expanded (in the same way that a balloon expands to take up more area), and the first subatomic particles were formed: electrons, Positrons, Mesons, Baryons, Neutrinos, Photons, and a lengthy list of others up to the more than 90 particles known today.
Atoms were later created. Meanwhile, due to gravity, matter began to cluster together, forming clouds of these primordial components. Some got so huge that stars and galaxies began to develop.
History of the Big Bang Theory
George Gamow, a naturalized American Russian scientist, refined Lemaître’s hypothesis of the primordial nucleus in 1948.
Gamow suggested that the Universe was created in a massive explosion. The numerous atoms observable today were formed within the first minutes following the Big Bang when the Universe’s extraordinarily high temperature and density fused subatomic particles into chemical components. This formed the big bang theory as we know it today.
According to more recent estimations made by studies of the big bang theory, hydrogen and helium were the initial products of the Big Bang. Stars developed heavier elements like iron later. However rudimentary and eventually corrected, Gamow’s hypothesis offers a foundation for comprehending the Universe’s early phases and its evolution.
In the early stages of the Universe, matter expanded swiftly. Helium and hydrogen cooled and compacted as the Universe expanded, forming stars and galaxies. This explains the Universe’s expansion and serves as the physical foundation for Hubble’s law.
After the Big Bang
The remaining radiation from the Big Bang continued to cool as the Universe expanded, reaching a temperature of roughly 3 °K (-270 °C). Radio astronomers discovered these leftovers of microwave background radiation in 1964, offering what most astronomers consider evidence of the Big Bang theory.
Researchers of the big bang theory appear to have a long way to go. Recent studies of the redshift of supernovae, which have been attributed to dark energy, for the time being, show that the Universe’s expansion is speeding rather than decreasing. The study of black holes and the recent discovery of gravitational waves continue to yield new and intriguing facts.
Is the Universe Infinite?
One of the major unanswered scientific questions in the expanding Universe concept is whether the Universe is open or closed (i.e., whether it will expand indefinitely or contract again).
One approach to resolving this issue is to see if the average density of matter in the Universe is larger than the critical number in the Friedmann model. By measuring the motion of its stars, a researcher can calculate the mass of a galaxy; multiplying the mass of each galaxy by the number of galaxies reveals that the density is only 5 to 10% of the critical threshold.
The scientist may calculate the mass of a cluster of galaxies similarly by monitoring the speed of the galaxies included within it. When this mass is multiplied by the number of galaxy clusters, the density approaches the critical limit, indicating that the Universe “looks to imply” that it is closed.
The distinction between these two techniques reveals the presence of unseen mass, or dark matter, within each cluster but outside of visible galaxies. This approach to deciding the fate of the universe will be unconvincing until the phenomena of hidden mass are understood and cannot be answered by the big bang theory just yet.
Inflationary Universe Model
Much of the typical work in theoretical cosmology is devoted to improving our understanding of the processes that must have preceded the Big Bang. By embracing current developments in fundamental particle physics, the inflationary theory, developed in the 1980s, answers significant flaws in Gamow’s initial method. These ideas have also given rise to audacious predictions such as the potential of an infinite number of worlds formed by the inflationary model.