Key Scientific Theories: Universe Expansion & Continental Movement
Cosmology: Understanding the Universe
Cosmology describes the universe using mathematical models. These mathematical models are a set of equations used to describe physical systems, like the universe, allowing us to predict the properties of new states when modifying some of its variables.
Measuring the Recessional Speed of Galaxies
When light reaches Earth from stars in galaxies, it contains a mixture of radiation of different colors or wavelengths. This light can be separated by a spectroscope, leading to a spectrum.
Each spectrum consists of the seven colors of the rainbow (red light having the longest wavelength and violet the shortest) and displays a series of dark absorption bands. These bands correspond to the presence of certain chemical elements in the interstellar gas of the galaxy, which absorb part of the radiation.
These spectra are similar to barcodes; they are a kind of fingerprint, as each element has its own unique pattern. The wavelength of the chemical wave bands appearing in absorption is a constant feature of each element.
Scientists measured the position of the spectral absorption bands of certain chemical elements present in several galaxies located at different distances from Earth. These spectra were then compared with those obtained in a laboratory for the same chemical elements.
It was discovered that absorption bands shifted to higher wavelengths, and these shifts were more pronounced in more distant galaxies.
The Doppler Effect and Redshift
This phenomenon, where spectral lines are displaced towards the red end of the spectrum, is known as redshift and is due to the Doppler effect. This, in turn, means that galaxies are moving away from each other.
The Big Bang Theory
The phenomenon of redshift implies that the universe is expanding. If the motion of galaxies were reversed for a time equal to the age of the universe, it would lead to the conclusion that all galaxies were at one point in the same origin, marking the birth of the universe.
The Big Bang model, deduced from the current rate of expansion, posits that at t=0, the entire universe, along with the four fundamental forces acting on it (gravity, strong nuclear force, electromagnetic force, and weak nuclear force), energy, space, and time, existed as a singularity: an infinitesimal, infinitely dense, hot point. Conditions were so extreme that current laws of physics find it very difficult to describe.
From this singularity, a massive explosion occurred: the Big Bang. At that moment, space and time were born, and from this point, the universe formed and has since continued to expand.
In these first moments, the energy of the universe was so intense that radiation spontaneously transformed into tiny particles of matter.
As time and space expanded, this hot primordial soup of matter gradually cooled down and generated huge clouds of hydrogen and helium gas, from which galaxies formed. (A type of matter known as dark matter also made its appearance.)
The universe has been cooling slowly until reaching its present form. The appearance of elementary particles and the four forces that govern their behavior is the result of the gradual cooling of the primary energy released in the Big Bang as a result of the expansion of spacetime.
Continental Drift Theory
Alfred Wegener formulated the hypothesis of continental drift, proposing that continents move like boats drifting through the mantle. He presented consistent evidence and solid arguments, the majority of which were and remain correct.
Evidence for Continental Drift
Paleontological Evidence
Based on the identity of fossils of land plants and animals that have appeared on different continents now separated by oceans. It is logical to think that in ancient times, all these organisms occupied a common habitat.
Geographic Evidence
If the continents were united, there would be an almost perfect coupling of their coastlines.
Geological and Paleoclimatic Evidence
This union explains the continuity of mountain ranges and rocky deposits between Antarctica, South America, and African continents, as well as the distribution of glacial deposits.