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Chart of relative sizes of planets
10^-43 seconds 200 seconds 200 mil years 9.1 bil yrs
10^-43 seconds: The beginning of the Universe. All basic forces(gravity, electromagnetism, strong and weak)are unified into one “superforce”.
200 seconds: protons and neutrons come together to form nuclei.
200 million years: Cosmic gas starts to collapse and begins to form the first stars in the universe.
9.1 billion years: The Milky Way galaxy begins to form.

For centuries scientists and philosophers imagined the Universe unchangeable and existing forever. However, as telescopes became more powerful, allowing us to see further and further, astronomers no longer held on to this view. According to Einstein's theory of relativity, nothing can travel faster than the speed of light. If we observe a galaxy that is 5 billion years away, we actually see it as it was 5 billion years ago, not as it is now. So seeing farther into space, means we are seeing into the past. Astronomers can observe galaxies that are 13 billion years way. Surprisingly, they noticed that the farther galaxies have bigger red shifts, meaning these galaxies are moving way of us. Our Universe is expanding. Astronomers now agree that the Universe was born about 13.7 billion years ago as a result from Big Bang.

In the very beginning all the matter in the Universe was compressed into a space the size of a subatomic particle. The temperature and density were so unimaginably high, that the common laws of physics were inapplicable. Scientists are still looking for theories and laws that could help explain this and what caused the huge explosion called the Big Bang. During this explosion the first subatomic particles that make up matter and energy were created. Space and time were born and the cosmic clock started to run.
At first, the Universe was extremely hot and dense with stuff flying in all directions with unimaginable speed. Scientists call this the inflationary epoch. In less than a millionth of a second the Universe expanded from the size of a subatomic particle to a trillion times bigger than the Solar System. At this time the Universe was almost smooth and expanding symmetrically in all directions. However, astronomers think that small clumps in density caused the formation of the first stars and galaxies. The first few seconds were so hot that the four basic forces were unified. At 10^-11 seconds the weak nuclear force split form the others, allowing formation of the first quarks, the building blocks of subatomic particles. Later on, at 10^-4 seconds the first protons and neutrons were formed. After 100 seconds, it was cool enough for the first protons and neutrons started to link, however the first atoms were very unstable and quickly broke apart. After three minutes the temperature dropped to a billion degrees and hydrogen and helium atoms formed. At the end of Radiation era the temperature dropped to 10,000K and the Universe became transparent. A billion years later, the first stars and proto galaxies were formed.
What is the future of the Universe? This is a hard question to answer. The problem is that we don't know the true density of the Universe and consequently the rate of expansion. Depending on its value, there are two main scenarios. The so called Big Crunch, proposes that eventually the Universe will stop expanding and start contracting until reaching a super dense and hot state. However, recent astronomical observations don't support this model, since we can register only one percent of the mass necessary to drive such a contraction. It seems that the Universe not only expands, but this expanding accelerates, faster and faster. If this is the case the Universe will expand infinitely. Eventually, the bigger galaxies will 'eat' the smaller ones, while empty spaces between them will grow bigger and bigger. When all the matter in the galaxies burns out, the stars they gradually will cool. Even the black holes will "expire". Finally, our universe will end like a vast emptiness.
Current observations of dark matter and dark energy suggest that there are large portions of the universe that we still can't detect. Since the mass and energy balance is still being studied, it is impossible to tell the ultimate fate of the Universe.
While some astronomers spend most of their time making observation, others attack problems theoretically. In searching for the answer how our Universe was born, they came up with the idea that there might be other Universes besides ours. Building different scenarios based on different initial conditions, astronomers concluded that most of these universes will be very boring. They would collapse soon after they are born, or exist like a uniform feature without galaxies and stars. It might be coincidence that our Universe happened just right, so that galaxies, stars and planet were formed and of course intelligent life, able to appreciate the beauty of the Universe.
sparkles in an empty space

The Universe may simply have emerged from energy trapped in a vacuum. When you hear "vacuum" you probably envision emptiness. However, physicists think that vacuums consists of subatomic particles that are born spontaneously, live a very short time and then disappear again. So you can think of a vacuum as small sparkles in dark and empty space. It's possible that one of these particles may for some reason became stable and be the source of our whole Universe.

Big Bang

Cosmic background radiation, first detected in 1962, is the echo left behind from the Big Bang. Even though the heat from the gigantic explosion cooled during last 15 billion years it is still detectable). The Cosmic Background Satellite launched in 1990, measured background radiation mapping the whole sky. Initially, radiation appeared to be very smooth, however very small fluctuations, about a millionth of a degree, were detected. These fluctuations may have sparked the formation of the stars and galaxies.

Dark matter

Dark matter is something that we can't see, but astronomers are convinced it exists. Galaxies and stars appear to be pulled by this dark matter. It may consist of dead or failed stars, known as brown dwarfs, Jupiter size planets and even black holes. Other exotic candidates for dark matter are a mass of subatomic particles, like neutrinos. However, even if we add together all possible candidates, they will make up only the 5% of all dark matter.

Red shifts

The shifting of an object's spectrum toward longer wavelenghts due to its motion away from an observer.

Four Basic Forces

Also known as the four fundamental interactions, they describe the ways in which particles interact with one another.

  1. Strong force: Binds protons and neutrons together and is thus responsible for forming of nuclei in atoms.
  2. Electromagnetic force: the force that dictates how particles with an elecric charge behave with one another.
  3. Weak force: responsible for the radioactive decay in subatomic particles.
  4. Gravitational force: the force which causes objects to be attracted to one another and is directly related to an object's mass.

Quark

A hypothetical particle believed to be a fundamental part of hadrons (particles such as protons and neutrons).
There are six different types (flavors) of quarks: up quark, down quark, top quark, bottom quark, charm quark, and strange quark.

Proton

A positively charged subatomic particle that is located inside the nucleus of an atom.

Neutrons

Nuclear subatomic particles located inside the nucleus of most atoms; simple hydrogen is the exception.

hydrogen

The most common element in the Universe and the main fuel of stars.

helium

A colorless and oderless single-atom gas, it is the second most abundant element in the universe.

Proto galaxies

Huge clouds of gas which are on their way to forming galaxies.