Dept. Of Physics and Astronomy
The evolution of the Universe from the big bang
The Story of the Universe
The universe is made of everything from smallest things to gigantesque ones. The universe includes humans, animals, plants, planets, dust, stars, galaxies, light, and even time, this makes understand that before the beginning of the universe nothing, even space and time existed. Scientific researches tell that the universe came from a powerful explosion that brought everything into existence and set them in motion.
The universe is unimaginably vast, for example in the known universe, there are billions of galaxies and each galaxy contains millions, or billions of stars, and the place between those galaxies is empty , but clouds of gas and hydrogen atoms can be present between stars. Space also contains radiations and particles. Most of stars are extremely distant, for example, from here on Earth, it would take millions of years for a spaceship with current propulsion system to reach the nearest star, and a spaceship travelling at the seep of light would spend almost hundred thousand years to travel across the our own galaxy Milky Way. With current technology, it is impossible to know the size of the universe because we are not able to see at the edge of the universe, this also makes difficult to know exactly the age of the whole universe. Actually, the size of the known universe is ninety -three billion light years across (a light year is a distance that a light travels in the vacuum in one year).
The size of the universe changes daily, scientists suggest that it started from a powerful explosion that happened around fourteen billion years ago, and it has been expending, which means that space between stars or galaxies is increasing .Scientists believe that this explosion started from nowhere and in nothing and brought everything into existence. According to the theorist Lemaitre, the universe came from something he called primordial atom, or a cosmic egg that was infinitely smaller than a pinhead, and then it exploded giving birth to space-time, mass and energy. And in a friction of a second the universe already had a size of a galaxy, and it continued to expending at incredible speed, and it still is undergoing an expansion.
During the expansion of the universe, it cooled down and the energy was transformed into matter and antimatter, and because of annihilation matter and antimatter were canceled each other, but some matter managed to survive that apocalyptic event. Stable particles such protons and neutrons began to form after one second of the birth of the universe, and after only three minutes, the temperature became one billion degree Celsius, at this temperature, protons and neutrons already formed were able to came together to form atoms , and primary atoms to have been formed were hydrogen and helium nuclei. Hydrogen and helium atoms began to form after three hundred thousand years when the universal temperature was about three thousand degrees Celsius, and that time, the universe was made of cloud of Hydrogen and Helium.
It is absolutely impossible to see something that took place three hundred thousand years, to get information, scientists try to figure out what happened by using the knowledge from particle science and computer simulations. First stars came into existence from hot and dense cloud of Hydrogen and Helium gas about hundred million years just after the big bang. There was higher rate of stars birth than it is today, and first sets of stars became first galaxies. Most sophisticated telescopes such as Hubble Space Telescope can take scientists in the past to observe galaxies that were born one billion years ago, these galaxies were small, and as the universe expands they formed large galaxies such our own galaxy Milky Way, or Andromeda galaxy.
One of the most puzzling phenomena that have taken place since the birth of stars is the formation of black holes. A black hole is a region of space with infinite gravity that nothing even light can escape, everything that approaches a black hole falls in it. A black hole is, in one case, the result of the collapse of matter resulting from an exploded star as a supernova, and black holes are invisible, the only way to know that they are there is using a technique called gravitational lensing( determination of an object's presence by studying how light behaves when it travels around that object) . Scientists are struggling to understand the complete nature of these strange objects that seem to occupy the middle of every galaxy in the universe, but they still do not know much about them, for example, nobody knows exactly what is inside a black hole, and nobody knows what happens to the matter that falls into it.
Other strange objects residing the universe are dark matter and dark energy. It has been found that our universe is not only made with ordinary matter, but also with invisible matter that makes up twenty-five percent of the total mass in the universe. Scientists believe that this form of matter is responsible for holding clusters of stars from collapsing under the pull of gravity. Our universe has been expanding since its birth from an explosion of an infinitesimal bubble, the cause of its expansion was previously not known, recent discovery found that the universe is largely filled with dark energy that makes up seventy percent of the total mass of the universe, and scientists believe that this form of energy is responsible for the expansion of the universe. Nobody has seen dark matter or dark energy, but scientists know that they exist by using the gravitational lensing technique.
The universe came from an infinitesimal egg (simply nothing) that exploded fourteen billion years ago. And since then, the universe has been expanding and undergoing changes that led to the formation of diverse objects, even this moment, it still expanding, and nobody knows exactly its future.
- "The story of the universe". Teaching kids Astronomy. The European Space Agency
- "Dark Energy, Dark Matter" NASA Science: Astrophysics.