How and when was the universe made? That is the question people have asked from the first human being without getting an answer. Still there is no sign of coming any closer to an answer.
Many astronomers today think that a big explosion caused the universe to start between 15 and 20 trillion years ago. Every particle in the universe was together as a single, very hot, dense mass. This mass exploded, and the scientists call the phenomenon: the “Big Bang”.
We almost know how the universe was 100,000 years after the “Big Bang,” and we have an idea of how it was after a couple of minutes. It has to have been chaotic with radiation because separate particles could not have existed there. After a billionth part of a second, maybe the first and the basic elements came to be. The temperature had then fallen maybe 100 billion degrees.
Plasma, which is a very warm gas of electric ally charged particles and ions, filled the universe in the plasma period. This period ended about 100,000 years after the “Big Bang.” The temperature had now fallen considerably and it was now free for protons, neutrons, electrons to exist. Another particles created the first atoms after approximately one million years. After that, the atoms created fog, stars and galaxies. That’s the way the universe became what it is today.
Million of years after the Big Bang the first elements were created - hydrogen, and helium. These atoms united in gigantic clouds. After another million years, these clouds drew together and shaped large balls of gas. That was the beginning of the stars.
After a while, the pressure in the stars grew larger; and the temperature also became higher. This resulted in hydrogen merging with the second heaviest element, helium. This process makes some of the hydrogen to convert to energy, and this makes the sun shine and send out other radiation. These stars were either born together in galaxies, or gathered into galaxies. Today there are approximately one trillion galaxies, and each contains 100 billion stars.
Has the universe an outer edge? In that case, what is outside this outer edge? This depends on the form of the universe. The answer would be simple if it could be looked at as a balloon. The balloon would be like the earth; if one were to walk far enough, he or she will finally come back to the starting point.
The universe is expanding the whole time, so, if it has an outer edge, we will never see it. This is because the universe expands with a speed close to the velocity of light. Therefore, will we never be able to catch up with the outer edge.
So the size of the whole universe depends on how old it is. If the universe is between 15 and 20 trillion years, the diameter of the universe will be between 30 and 40 trillion light years.
It’s really hard to understand how big the universe really is. An example will help to understand it. A light-year is the distance light travels in a year at a speed of 186,000 miles per second. That is about 5.9 trillion miles. The distance to Alpha Centauri, the nearest star other than the sun, is 4.3 light years. The distance to Andromeda, the nearest neighbouring galaxy, is 2,000,000 light years. And diameter of the Milky Way galaxy is 100,000 light years.
For the time being we don’t know much about the great “nothing” outside our solar system. In 1977, NASA sent out the space probe Voyager 2 to go where no one has been before. Now, 22 years later, Voyager 2 is still in our solar system.
On board in Voyager 2, there is a recording of voices and sounds from the earth to be used in case the craft meets other life. Instructions on how to play the record are inscribed on the cover of the disc in a hopefully recognizable code. The inscription also shows where in space Voyager came from. When another being plays the disc, they will hear greetings from earth in 60 languages. They will also hear a message from the then President Jimmy Carter. There are also typical sounds of natural and man-made words of earth, from the haunting calls of whales to the roar of a rocket take-off. There is music from the world's greatest composers as well as pop music and folk songs.
What if there is life out there and other being’s hear us? Would they try to contact us? This is just wishful thinking, but nobody knows…
The universe will continue to expand until it reaches a particular point at which it would start to shrink again. When it has shrunk to the starting point of the “Big Bang,” will there be a new “Big Bang?” Dr. Robert Kirshner of Harvard said once: "The truth is out there, and we will find it."