We all live in a very chaotic world. All of our lives are very different. If you think about it, our life is a rush. Every morning some people rush to work, schools, universities. Others are having vocations, relaxing in beaches, dancing in clubs, etc. . A lot of people lives with they‘re eyes shut and they just flow with the monotony of life. But we all have something in common. We are living creatures, in other words we are life. As far as we know it, our Earth is the only planet in all of the universe that has life. For now we are alone and that is what connects us. But what is the universe, planets, galaxies? We live here, it surrounds us, so we need to know at least basic things about that.
Earth is the third planet in the Solar System. The Solar System consists of the Sun and the astronomical objects bound to it by gravity, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune are the eight big planets neighbouhring the Sun. There are also other, smaller planets, known as the dwarf planets (Pluto, Haumea, Makemake, Eris, Ceres) and that is only our Solar System.
For better understanding of our Solar system size, let‘s scale it down ten billion times, now let‘s try to imagine how will planets look like, and how far from the Sun they will orbit. In model like this, Sun would look like 14 centimeters melon. Six meters away we would find Mercury, which would be the size of a half of poppy grain. Five more meters away a size of a poppy grain Venus orbits our melon. Add 4 more meters and we are in the planet Earth, almost the same size as Venus. Continue further on. In the end we would find the last big planet Neptune. Now we are 450 meters away from our Sun. Scale that up a billion times and you will start to understand that the distances are enormous.
Milky Way Galaxy, commonly referred to as just the Milky Way, or sometimes simply as the Galaxy, is the galaxy in which the Solar System is located. As I said our Solar System is very huge, but compared to Milky Way it‘s a needle in a haystack. Glaxy itself contains 100-400 billions of stars like the Sun. I will help you to imagine the massiveness of this complex galaxy. We just simply can‘t imagine sizes like these. So comparisons helps us to do so. Let‘s say our Sun is the size of a dot on the letter i. Now the Milky Way would be the size of the United States of America. It‘s size is enormous. As a matter of fact it‘s so big, that light travels approximetly 100 000 years from one side to another. The speed of light is equivalent to 299 732 458 meters/second. One light year is the distance that light travels per year, in other words 1 light year equals 9.4605284 x meters. The closest galaxy to Milky Way is Andromeda galaxy. It is about 2 million light years away.
Moving further away from our galaxy we would find much more other galaxies and other strange things and all of these form the universe. The universe is commonly defined as the totality of everything that exists, including all physical matter and energy, the planets, stars, galaxies, and the contents of intergalactic space, although this usage may differ with the context. The term universe may be used in slightly different contextual senses, denoting such concepts as the cosmos, the world, or nature. Observations of earlier stages in the development of the universe, which can be seen at great distances, suggest that the universe has been governed by the same physical laws and constants throughout most of its extent and history.
The universe is very large and possibly infinite in volume. The region visible from Earth (the observable universe) is a sphere with a radius of about 46 billion light years, based on where the expansion of space has taken the most distant objects observed. For comparison, the diameter of a typical galaxy is only 30,000 light years, and the typical distance between two neighboring galaxies is only 3 million light years. There are probably more than 100 billion (1011) galaxies in the observable universe. Typical galaxies range from dwarfs with as few as ten million (107) stars up to giants with one trillion (1012) stars, all orbiting the galaxy's center of mass. Thus, a very rough estimate from these numbers would suggest there are around one sextillion (1021) stars in the observable universe; though a 2003 study by Australian National University astronomers resulted in a figure of 70 sextillion (7 × 1022). The most precise estimate of the universe's age is 13.73±0.12 billion years old, based on observations of the cosmic microwave background radiation.
If the universe‘s age is about 14 billion years, from this follows that there was a time when the universe came into existence. This event is called The Big Bang. The Big Bang was the event which led to the formation of the universe, according to the prevailing cosmological theory of the universe's early. According to the Big Bang model, the universe, originally in an extremely hot and dense state that expanded rapidly, has since cooled by expanding to the present diluted state, and continues to expand today. Based on the best available measurements as of 2010[update], the original state of the universe existed around 13.7 billion years ago, which is often referred to as the time when the Big Bang occurred. The theory is the most comprehensive and accurate explanation supported by scientific evidence and observations.
I will try to explain this theory very simply. Imagine super massive and hot dot hanging in the middle of nowhere. Time doesn‘t exist. Something happens and driggers explosion of this dot. Space and time comes into existence. Everyting expands(further expansion is happening every second). This is how the universe and everything started.
As the old saying says: everything that has a begining has an end. There are couple theories about the end of the universe:
The Big Crunch is one possible scenario for the ultimate fate of the universe, in which the metric expansion of space eventually reverses and the universe recollapses, ultimately ending as a black hole singularity.
The Big Rip is other possible scenario, about the ultimate fate of the universe, in which the matter of the universe, from stars and galaxies to atoms and subatomic particles, are progressively torn apart by the expansion of the universe at a certain time in the future. Theoretically, the scale factor of the universe becomes infinite at a finite time in the future.
One more thing that i would like to talk about is ours, as human species, exploration of space. Humans are very curiuous beings by nature. We want to know everything. Curiosity, desire to explore, to know, to learn is coded in our genes.
The early era of space exploration was driven by a "Space Race" between the Soviet Union and the United States; the launch of the first man-made object to orbit the Earth, the USSR's Sputnik 1, on October 4, 1957, and the first Moon landing by the American Apollo 11 craft on July 20, 1969 are often taken as the boundaries for this initial period. The Soviet space program achieved many of the first milestones, including the first living being in orbit in 1957, the first human spaceflight (Yuri Gagarin aboard Vostok 1) in 1961, the first spacewalk (by Aleksei Leonov) in 1965, the first automatic landing on another celestial body in 1966, and the launch of the first space station (Salyut 1) in 1971.
Nowadays the main aim of outer space exploration is to know more about other planets, stars, galaxies, find evidence of extraterrestrial life and eventually colonise other life sustainable planets. This sounds like science fiction, but if humans want to survive, one day Earth will need to be abandoned. Half a century ago, mobile phones and computers looked like science fiction, but nowadays very few people can live without these gadgets. So we need to be optimists, because if something sounds like a science fiction today, it could be a science fact tomorrow.
Space colonization, would be the permanent autonomous (self-sufficient) human habitation of locations outside Earth, especially of natural satellites or planets such as the Moon or Mars, using significant amounts of in-situ resource utilization.
To date, the longest human occupation of space was the space station Mir, which was continuously inhabited for almost ten years, including Valeri Polyakov's record single spaceflight of almost 438 days. Long-term stays in space reveal issues with bone and muscle loss in low gravity, immune system suppression, and radiation exposure.
Many past and current concepts for the continued exploration and colonization of space focus on a return to the Moon as a "stepping stone" to the other planets, especially Mars. At the end of 2006 NASA announced they were planning to build a permanent Moon base with continual presence by 2024.
As time goes on humans will invent new ways of traveling in cosmos. Maby one day we will finally find out that we are not alone in this vast universe, or maby when Earth will be not suitable to live further on, we will be colonizing Mars, or some of our pioneers will travel in time... Possibilites are infinite. We just need to open our eyes and start working together as species for the grater future.