The Big Bang theory describes the early stages of the universe's expansion from an extremely hot and dense state, but it does not directly address the specific conditions on Earth or the evolution of life. The Sun's formation and its subsequent impact on Earth and the development of life are separate topics explained by other scientific theories and processes.
The formation of the Sun and the solar system occurred billions of years after the Big Bang. About 4.6 billion years ago, a large cloud of gas and dust known as a molecular cloud collapsed under its own gravity, leading to the formation of the Sun at the center and the surrounding protoplanetary disk. Over time, material from the disk came together to form planets, including Earth.
As for the early human species, they emerged much later, millions of years after the formation of the Sun and the Earth. The earliest human species, such as Homo habilis or Australopithecus, evolved and appeared on Earth around 2-3 million years ago.
During this time, the Sun was already in a relatively stable phase known as the main sequence. The main sequence is the phase in which stars like the Sun spend most of their lifetimes, converting hydrogen into helium through nuclear fusion in their cores. This process releases energy in the form of light and heat, which reaches Earth as sunlight.
The Sun's energy output is balanced by gravitational forces and the energy generation occurring in its core. While the Sun is a powerful source of energy, it is located at a safe distance from Earth to sustain life. The Earth's atmosphere and magnetic field also provide protection by filtering out harmful radiation and maintaining suitable temperatures for life.
In summary, the Sun's formation and the evolution of early human species are separate processes that occurred at different times in the history of the universe. The development of life on Earth is influenced by a variety of factors, including the Sun's energy output, distance, the Earth's atmosphere, and other geological and biological processes.