Lesson 1 Cosmic Origins

The space and time began with the Big Bang—an event not described as an explosion in space, but rather as the sudden expansion of space itself from an extremely hot, dense singularity.

The universe was filled with pure energy. As the universe expanded and cooled, this energy transformed into matter through a process predicted by Einstein’s equation E = mc² (energy can convert into mass).

The first particles to appear were quarks, which then combined to form protons and neutrons. These particles, along with electrons, became the building blocks of atoms. This transformation marked the universe's transition from an energy-dominated state to one where matter could begin to take form.

Stars act as cosmic furnaces where nuclear fusion occurs. Inside stars, hydrogen atoms fuse to form helium, and in larger, older stars, this fusion process continues to create heavier elements such as carbon, oxygen, and iron. This process is known as stellar nucleosynthesis.

However, elements heavier than iron cannot form through fusion alone because it requires more energy than it releases. These heavier elements are created during the violent explosion of a massive star, known as a supernova. In a supernova, the immense energy and pressure forge the heaviest elements, like gold, uranium, and lead, and scatter them across the universe.

This cosmic dispersal enriches space with the elements that eventually form planets, oceans, and even living organisms—including us.

the solar system and Earth began to form from the remnants of older stars, particularly after supernovae scattered heavy elements into space. These elements collected into a giant cloud of gas and dust, called a solar nebula.

Over time, gravity caused this cloud to collapse and spin, forming a protosun at the center. As the material flattened into a rotating disk, particles began to stick together, gradually forming planetesimals—the building blocks of planets. Through repeated collisions and accretion, these planetesimals merged to form the early Earth and other planets in our solar system.

Thus, Earth formed from recycled star material, shaped by gravity, heat, and time within the evolving solar system.