EVERYDAY SCIENCE

Detailed explanation-1: -The universe has continued to expand and cool since the Big Bang, and has a present temperature of only 2.7 Kelvin (K). After the hydrogen and helium created in the Big Bang condensed into stars, nuclear reactions at the cores of massive stars created more massive nuclei up to iron in a series of nuclear reactions.

Detailed explanation-2: -The Universe will expand forever: If the mean density is less than the critical density, then there is insufficient mass within the universe to stop the expansion-the universe will expand forever. Ultimately, the galaxies will move increasingly further apart.

Detailed explanation-3: -But as the universe quickly expanded, the energy of the Big Bang became more and more “diluted” in space, causing the universe to cool.

Detailed explanation-4: -The heat death of the universe (also known as the Big Chill or Big Freeze) is a hypothesis on the ultimate fate of the universe, which suggests the universe will evolve to a state of no thermodynamic free energy, and will therefore be unable to sustain processes that increase entropy.

Detailed explanation-5: -The point of the Big Bang is described as an infinitely hot and dense singularity. The energy from the Big Bang spreads out as the universe expands, which gives us the cooling effect.