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Our universe has an estimated age of almost 13.8 billion years, and during this time several things that we will tell you about in this video, have happened; 13.8 billion years, however, is such a large number that it is difficult to imagine: almost certainly not even your grandparents have reached such a remarkable age!
What we can do to give a more concrete idea is to imagine to compress the 13.8 billion years of our universe in a time span of one year of our calendar: in practice, making the necessary proportions, when the various evolutionary steps of the universe happened if it were one year old?
This idea was born from the fervid mind of the famous astronomer and science popularizer Carl Sagan (1934 – 1996), who in this special cosmic calendar imagined placing the Big Bang in the first second of January 1st and our present in the second preceding midnight on December 31st: Using this time scale, each second of the calendar corresponds to approximately 444 Earth years and 31 of its days correspond to approximately one billion of its years.
Our universe is currently expanding: in 1929 the American astronomer Edwin Hubble discovered that galaxies move away with a speed proportional to their distance: more distant they are, faster they move away. The recession law of galaxies discovered by Edwin Hubble had been predicted a few years earlier by two theoretical physicists, the Russian Aleksandr Friedman and the Belgian Georges Lamaitre, who had shown that the equations of general relativity predicted an expanding universe. If the universe is currently expanding, then it means that, going far back in time, matter and energy were concentrated in a very small region of space, with an infinite density. From this singularity the universe originated, 13.8 billion years ago, with a sort of colossal explosion, the Big Bang: in our model of the universe in one year, this moment corresponds to 1st January. It is believed that at the time of the Big Bang the universe was governed by a single force, which united the four fundamental forces known today:
• strong interaction (which holds atomic nuclei together);
• weak interaction (responsible for the beta decay of atomic nuclei associated with radioactivity);
• electromagnetic interaction (the interaction between objects that have an electric charge, responsible for the electromagnetic field; it propagates in the form of an electromagnetic wave at the speed of light);
• gravitational force.
This situation lasted for a very short time: after 10-43 s (the so-called Planck time), the universe underwent a phase transition, during which the gravitational force separated from the other three forces. The temperature was then 1032 degrees, a million billion times higher than the maximum energy reached so far by accelerating machines; in practice billions of times higher than there are in Death Valley! Can you imagine them? Write it in the comments! Since we do not yet have a unitary theory of all forces, we do not know how the universe was made in its first 10-43 s: the known (or at least imaginable) history of the cosmos begins from that instant.
At 10-36 s from the Big Bang, when the temperature was 1028 degrees, the strong force separated
from the weak force and the electromagnetic force.
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Credits: Ron Miller, Mark A. Garlick / MarkGarlick.com
Credits: Nasa/Shutterstock/Storyblocks/Elon Musk/SpaceX/ESA/ESO/ Flickr
3:06 Gravitational force
9:48 the milky way
12:16 The sun is born
#insanecuriosity #historyoftheuniverse #universe