The Big Bang model is that theuniverse began in an extremely dense and hot condition and has expanded. The theory suggests that redshift proves the universe is expanding.[1]
TheBig Bang is aphysical theory about how theuniverse started expanding, and then made thestars andgalaxies we see today. The Big Bang is the name that scientists use for the most common theory of theuniverse,[2][3][4] from the very early stages to the present day.[5][6][7]The most commonly considered alternatives are called theSteady State theory andPlasma cosmology, according to both of which the universe has no beginning or end.[8]
According to the theory the Big Bang began as a veryhot,small, and dense superforce (the mix of the fourfundamental forces), with no stars,atoms, form, or structure (called a "singularity"). Then about 13.8billion years ago,[1]space expanded very quickly (thus the name "Big Bang"). This started the formation of atoms, which eventually led to the formation of stars and galaxies. It wasGeorges who first noted (in 1927) that the universe is expanding. The universe is still expanding today, and getting colder as well.
As a whole, the universe is growing and thetemperature is falling astime passes.Cosmology is the study of how the universe began and its development. Somescientists who study cosmology have agreed that the Big Bang theory matches what they have observed so far.[1]
Scientists base the Big Bang theory on many differentobservations. The most important is theredshift of very far awaygalaxies. Cosmological redshift is theDoppler effect occurring in light. When an object moves away from Earth, its color rays look more similar to the color red than they actually are, because the movement stretches thewavelength of light given off by the object. Scientists use the word "red hot" to describe this stretched light wave because red is the longest wavelength on the visiblespectrum. The more redshift there is, the faster the object is moving away. By measuring the redshift, scientists proved that the universe is expanding, and they can work out how fast the object is moving away from the Earth. With very exact observation and measurements, scientists believe that the universe was a singularity approximately 13.8 billion years ago. Because most things becomecolder as they expand, scientists assume that the universe was very small and very hot when it started.[10] This does not take into account other possible (non-cosmological) causes of redshift.
Other observations that support the Big Bang theory are the amounts ofchemical elements in the universe. Amounts of very light elements, such ashydrogen,helium, andlithium seem to agree with the theory of the Big Bang. The same is true, however, for Static State theory and plasma cosmology. Scientists also detected what they call thecosmic microwave background radiation. Theseelectromagnetic waves are everywhere in the universe. This radiation is now very weak and cold, but is thought to have been very strong and very hot a long time ago.[1]
It can be said thattime had no meaning before the Big Bang. If the Big Bang was the beginning of time, then there was no universe before the Big Bang, since there could not be any "before" if there was no time. Other ideas state that the Big Bang was not the beginning of time 13.8 billion years ago. Instead, some believe that there was a completely different universe before the Big Bang, and it may have been very different from the one we know today.[10]
Nonetheless, in November 2019,Jim Peebles, awarded the 2019Nobel Prize in Physics for his theoretical discoveries inphysical cosmology,[11] noted in his award presentation that he does not support the Big Bang Theory due to the lack of concrete supporting evidence, and stated, "It's very unfortunate that one thinks of the beginning whereas in fact, we have no good theory of such a thing as the beginning."[12]
↑Wollack, Eddie J. (10 December 2010)."Cosmology: The Study of the Universe".Universe 101: Big Bang Theory.NASA. Archived fromthe original on 14 May 2011. Retrieved2017-04-15.The second section discusses the classic tests of the Big Bang theory that make it so compelling as the likely valid description of our universe.
