Birth of Universe
Cosmological Theory
The Big Bang is the popular name for the modern cosmological theory. This theory, based on Albert Einstein's (1879-1955) general theory of relativity, posits that nearly 13.8 billion years ago, the universe originated from an extremely hot point (approximately 1032 degrees Kelvin). This hot point would possess an almost infinitely high density, which scientists call a singularity. Simultaneously with the Big Bang, the entities 'space' and 'time' would have originated. Mathematicians can formulate how a three-dimensional space emerges from a point: the surface of a sphere that swells from a point. That surface is curved, it has no edges, and it is finite. Think of the image of a balloon being inflated; this is where the term 'inflation' of the universe is derived from.
The Big Bang theory is based, among other things, on the astronomical observation of the continuously expanding universe. This is notable: the redshift in the spectral lines and the Doppler effect in the light of distant galaxies. However, the general theory of relativity is not yet complete at this point; this is because the idea of an infinitely high density conflicts with the fundamental laws of physics.
The founder of the Big Bang theory was the Leuven priest-professor Georges Lemaître (1894-1966). The term 'Big Bang' was first used by Fred Hoyle in 1950 as a derogatory term to express his dislike of the theory. Hoyle himself was a proponent of the competing but now abandoned steady-state model of the cosmos.
Birth of the Universe
Physical cosmological scientists try to calculate what the universe must have looked like in the past from the location and expanding movements of current galaxies relative to each other. They try to trace the origin of the expansion. Scientists do this by calculating with backward extrapolation of the expansion of the universe (back in time) using mathematical models from the general theory of relativity. This led to the suspicion of an infinite density and temperature at a finite point (singularity) in the distant past.
This singularity conflicts with Albert Einstein's general theory of relativity.
There is much discussion among physicists about how close scientists can extrapolate to the singularity, but certainly not closer than the end of the Planck epoch, about 10-43 seconds after the origin of the universe (Planck time).
The Planck time (10-43 sec.), also called quantum time, is, according to the current state of science, the smallest meaningful unit of time. It is a natural unit, conceived by Max Planck (1858-1947), which is derived only from natural constants. The Planck time plays a particularly important role in theories surrounding the Big Bang and in the unification theory.
The aforementioned singularity (that is, the early hot, dense phase itself) is sometimes called the 'Big Bang', but this term usually refers to the explosion after it (the shattering of the singularity), which can be seen as the 'birth' of the universe.
Scientists have tried to calculate when the universe was 'born'.
They have compared the results of 3 types of measurements, namely:
- Measurements of the expansion rate of current Type 1a supernovae (= exploding stars).
- Measurements of temperature fluctuations in the cosmic microwave background radiation.
- Measurements of the correlation function of multiple Milky Ways.
This yielded a calculated age of 13.772 ± 0.059 billion years for the universe.
The agreement of these three independent measurements strongly encourages the standard model of the Big Bang (Lambda-CDM model) that describes the content of the universe in detail. In 2013, new data from the space telescope (named 'Planck') corrected this age to 13.798 ± 0.037 billion years.
The universe, therefore, would have been 'born' almost 14 billion years ago, or: our universe is almost 14 billion years old. In that time, many galaxies have originated, and our earth is located in one of these galactic galaxies: the Milky Way.