Until the 19 th century, humans were only interested in measuring the size of celestial bodies and their mutual distances. Over time, as the science developed, the human began to explore how the universe was created and what is actually its size.
The origin of the universe is still a topic of research. Scientific minds attributed it to the Big Bang theory or cataclysmic explosion of a ball of enormous proportions. According to this idea, after that explosion, material was thrown in all directions. Since then, the universe always expands. Edwin Hubble first developed the theory of the expanding universe. He claimed that the galaxies are constantly moving away from each other, where their speed of separation is in fact a product of Hubble constant and distance. Big Bang is estimated that would have occurred 13,7 billion years ago. Shortly after galaxies were created.
The proper definition of the galaxy would be a vast cluster of countless stars, planets, rocks, gas and dust, which are held together by gravity. Within galaxies some stars, as they reach the necessary size and age, explode creating more dust from which new stars and other celestial bodies will be born. At the moment of explosion, gravitational force is so strong that it does not release light. So, we do not see that process in the sky. However, shortly after as material starts disbursing around a careful astronomer with a good telescope can catch it and after filtering the information amazing pictures of supernovas are obtained. Of course, this event is more important for the data scientists get as it tells a lot about processes of creation and death of stars, and, in some theories, even the Universe itself. Naturally, there are various sizes of galaxies. However, a general size would be 10,000 to 200,000 light years*. Our solar system is in a galaxy called the Milky Way, which is the most explored region of Space, and not even a significant fraction of its full length.
Human mind is not developed nearly enough to imagine the size of the universe. It is certain that we will once achieve the stage when we will understand it all, if our species survives, as this is something we’ve been exploring and will continue to, as long as we exist. Currently, some scientists say that the Space has spherical shape while others say that it is flat. It is estimated that the edge of the cosmic horizon located 78 billion light years away and that the universe is 13.7 billion years old. All this remains to be proven and determined sometimes in, hopefully near, future.
* speed of light = 300 000 km/s, distance light travels in a year in vacuum = 1 light year = 9,46 x 10¹² km
Appearance of a galaxy
Most probably look of universe