Page:Illustrated Astronomy.pdf/9

 HOW DID WE GET TO THIS DATE? A very brief history of the Universe

Our Universe was born about 13.7 billion years ago. During the first stages, there was no matter, neither atoms, and in a certain way, all the energy, gravitational and electrical forces were all together. Then, in a matter of seconds, the very first particles formed.

It is almost unlikely to believe that, at that very moment, all the matter of the Universe was made up of hydrogen (75 %), helium (25 %), and a pinch of lithium (less than 0.001 %), and a temperature of hundreds of billions of Celsius degrees.

From that moment, and for the next 380,000 years, the Universe only kept growing and getting colder, without forming any new elements.

DID YOU KNOW THAT…

''the antimatter is very alike to the ordinary matter? They have the same mass in general, but they differ in their electric charge signs. For instance, both an electron and a positron (or antielectron) have opposite electrical charges. When the matter and the antimatter bind together, they annihilate each other, generating a vast amount of energy.''

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