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Asked by dandav to Angus, Christian, Hannah, Laura, Simon on 21 Jun 2013. This question was also asked by dionnehplol123, 1luckyegg.
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Laura Roberts Artal answered on 21 Jun 2013:
The main theory about how the Universe formed is called The Big Ban Theory.
We think the Universe started forming 13.798 billion years ago as a really small bubble that was hot and dense. It then exploded and grew to be bigger than a galaxy and kept on growing. It is still growing today. The explosion lead things to cool down a bit and this meant it was possible for particles of matter and antimatter to start forming. Protons and neutrons, the building blocks of atoms, formed. It took three minutes for the temperature to lower enough for the neutrons and protons to come together and capture electrons to form atoms of helium and hydrogen. The Universe then filled with clouds of hydrogen and helium.
Scientist don’t have any direct evidence for the Big Bang, they can just see a faint glow in space that supports this theory.
As millions of years passed, the dense areas pulled in material because they had more gravity. Finally, about 100 million years after the Big Bang, the gas became hot and dense enough for the first stars to form.Take a look at this website, it has lots of information about the Universe. http://www.esa.int/esaKIDSen/index.html
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Simon Holyoake answered on 21 Jun 2013:
very complex question! I’ll try to give an answer but it may be long!
I tend to agree with current scientific and cosmological theory about this, approximately 13.8 Billion years ago, was the beginning of time as we know it, the entire universe was compressed into a very small region, very similar to a singularity in the centre of a black hole
As it was so small, it did not obey the laws of physics as we typically understand them, it behaved more along the lines of quantum mechanics (which can be very difficult to get your head around!) and did not have a causal set of behaviours as a result (ie, cause and effect, nothing ’caused’ the big bang to occur, it was behaving differently to the way the universe works today….)
suddenly, this tiny singularity expanded and inflated rapidly, it happened so rapidly we had to invent a new unit of time, called Planck time, to measure it, one planck unit is ridiculously tiny (zero with dozens of zeros after the decimal point!) after approximately 10^-37 seconds, a phase change occured, which caused the universe to rapidly and exponentially inflate
After the early inflation period ended, the unverse was full of tiny elementary particles and a plasma made mostly of quarks and gluons (tiny particles which combine to form protons) most of these particles annihilated each other, and when I say most, I mean only 1 in 30 million survived!
this all happened within a few minutes of the big bang! it took nearly 400,000 years before the first hydrogen atoms were formed
over a much longer period, these clouds of hydrogen atoms condensed under the influence of gravity to form galaxies and stars, the early stars were very pure, being composed almost entirely of hydrogen, they burned very quickly and brightly, and formed other elements inside them, which were scattered widely through the universe when they exploded in colossal supernovae, new stars were formed from this debris as well as planets and other bodies
This model of the universe is widely supported by a great deal of evidence, the abundance of light elements, cosmic background radiation (essentially the ‘echo’ of the big bang) and many observations made by astronomers today
wow, long answer, hope you made it through without falling asleep!!
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