Among the numerous theories concerning the appearance of the universe, the Big Bang theory takes leading positions. Current technologies allow astronomers to make mere assumptions concerning what the universe looked like billions of years ago. However, they allowed scientists to capture the “echo” of the background radiation left after the Big Bang.
According to the theory, in the first minutes of the universe existence, it contained fundamental particles of protons, neutrons, and electrons. The temperature probably reached 10 billion degrees Fahrenheit. The light appeared only hundreds of thousands of years after the Big Bang when free electrons formed the neutral atoms. Photons which appeared in the result make up the precise “afterglow” detected by the scientists which makes the Big Bang theory probably true.
According to the observations made with the European Space Agency’s Planck satellite, the universe appeared about 13,8 billion years ago. These conclusions are made due to the cosmic microwave background detected by the satellite. It also helps researchers to determine the composition of the universe. Presumably, the universe mostly consists of the dark matter and dark energy – the constants which cannot be sensed or measured by any current techniques. Planets, stars, and galaxies possibly make up only 5 percent of the universe.
After the discovery of the so-called dark energy, scientists concluded that galaxies move away from each other. The universe is inevitably expanding, and after a while, researchers will not be able to detect other galaxies than Milky Way.
Another interesting assumption based on the probability of the Big Bang is that the universe might have been habitable just 15 million years after the Big Bang.