The expansion of the observable universe began with the explosion of a single particle at a definite point in time. According to Georges Lemaître, (1894-1966), Belgian cosmologist, Catholic priest, and father of the Big Bang theory.
The universe contains organized structures on all different scales, from small systems like the earth and our solar system to galaxies that contain trillions of stars, and finally extremely large structures that contain billions of galaxies.
The Universe: Big Bang to Now in 10 Easy Steps:
Step 1: How It All Started
Step 2: The Universe’s First Growth Spurt
Step 3: Too Hot to Shine
Step 4: Let There Be Light
Step 5: Emerging from the Cosmic Dark Ages
Step 6: More Stars and More Galaxies
Step 7: Birth of Our Solar System
Step 8: The Invisible Stuff in the Universe
Step 9: The Expanding and Accelerating Universe
Step 10: We Still Need to Know More.
Or, to put it another way: The universe originated at a single point of infinite density that expanded into time/space:
Singularity
Inflation Epoch
Cooling Epoch
Structure Epoch
Long-term Predictions
The universe began when a singularity expanded rapidly. During the expansion, it was too hot and it had to cool down before atoms could form.
The universe contains organized structures on all different scales, from small systems like the earth and our solar system to galaxies that control trillions of stars, and finally, enormous structures that contain billions of galaxies. The Universe consists of three types of substance: ordinary matter, dark matter, and dark energy. Normal matter consists of the atoms that make up stars, planets, human beings, and every other visible object in the Universe. The universe encompasses all of space, time, matter, and energy. The universe contains everything that exists, from particles of matter smaller than an atom to the most prominent stars. The universe may be much bigger than it looks. When we look out into the Universe, the stuff we can see must be close enough for light to have reached us since the Universe began.
In the early years, everything was made of gas. This gas, mostly hydrogen and helium, expanded and cooled. Over billions of years, gravity caused gas and dust to form galaxies, stars, planets, and more. The matter that spread out from the Big Bang developed into everything in the universe, including you.
only hydrogen and helium were made in the first 4 minutes after the Big Bang. The universe cooled quickly and became too low in density to forge heavier elements except for a little bit of lithium.
After about 400 million years of expansion following the Big Bang, the universe was cool enough for gravity to begin coalescing clouds of hydrogen into stars, igniting nuclear fusion for the first time
In the first moments after the Big Bang, the universe was extremely hot and dense. As the universe continued to expand and cool, things began to happen more slowly. It took 380,000 years for electrons to be trapped in orbits around nuclei, forming the first atoms. At the very instant of the Big Bang, the Universe started as a rapidly expanding ball of energy at extremely high temperatures (trillions of degrees). Thus, just some 3 minutes after the Big Bang began, the Universe was composed of hydrogen and helium nuclei with a great deal of excess energy.
In the first three minutes of cosmic history, the whole universe was the arena of nuclear reactions. A mixture of three-quarters hydrogen and one-quarter helium evolved. A slight change in the balance between the strong and weak atomic forces could have resulted in no hydrogen.
Each light speck is a galaxy, some of which are as old as 13.2 billion years – the observable universe is estimated to contain 200 billion to two trillion galaxies. There are likely to be many more planetary systems out there waiting to be discovered! Our Sun is just one of about 200 billion stars in our galaxy. That gives scientists plenty of places to hunt for exoplanets or planets outside our solar system.
The universe contains organized structures on all different scales
The universe contains organized structures on all different scales
There are four main types of galaxies: Spiral galaxies, Lenticular galaxies, Elliptical galaxies, and Irregular galaxies. A universe is a massive collection of gas, dust, and billions of stars and their solar systems, all held together by gravity. … It’s a small part of the Milky Way Galaxy. A galaxy is a massive collection of gas, dust, and billions of stars and their solar systems.
While stellar collisions may occur very frequently in certain parts of the galaxy, the likelihood of a crash involving the Sun is minimal. Astronomers say that if a stellar collision happens within 100 light-years of the Earth, the resulting gamma-ray burst could destroy all life on Earth. Stars are not scattered randomly through space; they are gathered together into vast groups known as galaxies. The Sun belongs to a universe called the Milky Way. Astronomers estimate there are about 100 thousand million stars in the Milky Way alone. Outside that, there are millions upon millions of other galaxies also! A supergiant elliptical galaxy at the center of the Abell 2029 galaxy cluster and is one of the most giant known galaxies. Its halo extends about 600 kiloparsecs (2 million light-years) from its core, and it has a mass of about 100 trillion stars.
Quasars inhabit the centers of active galaxies and are among the most luminous, powerful, and energetic objects known in the universe, emitting up to a thousand times the energy output of the Milky Way, which contains 200–400 billion stars. Laser beams travel at the speed of light, more than 670 million miles per hour, making them the fastest thing in the universe.
