We know that ordinary matter is made just 5% of the universe like atoms which make galaxies, stars and planets. The rest of the universe is dark and unknown, composed of dark matter and dark energy. Invisible dark matter makes up 27% of the universe which only interacts with the rest of the universe through its gravity and dark energy makes up 72% of the total mass-energy density of the universe, a mysterious force that drives the accelerating expansion of the universe. When this universe of ours was a very, very compressed globe, with very high temperature, in which mass and energy were so interconnected and compressed that no separate mass and energy could be conceived. In the First place, by special methods, we obtain the initial energy of the Big Bang (by Monte Carlo technique) with appropriate approximation. We found that, the energy in the Big Bang is very, very high. Then, we calculated the amount of energy consumed from the Big Bang to the present, which is 14 billion years. First, creation of subphotons and then electrons, protons, neutrons, atoms and then stars and galaxies and structures, which consumed from the Big Bang's energy. Since the beginning of the equilibrium or homogeneity of the universe, this energy caused the expansion of the Universe so that the structure of galaxies remains constant, but most of the galaxies (99%), due to their structure, are moving away and their speed will also increase. It should be noted that what drives them away is the initial energy that started from the Big Bang and continues to this day and will continue to do so. In fact, dark energy has been around since the beginning of the Big Bang, but after the equilibrium or homogeneity of the universe, we found its effect and now the energy applied in the universe is the residual primary energy or the dark energy.