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
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
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
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
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.