The Solar System (including the Earth) formed from a large, rotating cloud of interstellar dust and gas called the solar nebula. It was composed of hydrogen and heliumproduced in the Big Bang at 13.7 Ga, as well as heavier elements ejected by supernovas. About 4.6 Ga, the solar nebula began to contract, possibly due to theshock wave of a nearby supernova. Such a shock wave would have caused the nebula to gain angular momentum. As the cloud began to accelerate its rotation, gravityand inertia flattened it into a protoplanetary disk oriented perpendicularly to its axis of rotation. Most of the mass concentrated in the middle and began to heat up, but small perturbations due to collisions and the angular momentum of other large debris created the means by which protoplanets up to several kilometres in size began to form.
The infall of material, increase in rotational speed and the crush of gravity created an enormous amount of kinetic heat at the center. Its inability to transfer that energy away through any other process at a rate capable of relieving the build-up resulted in the disk's center heating up. Ultimately, nuclear fusion of hydrogen into helium began, and eventually, after contraction, a T Tauri star ignited to create the Sun. Meanwhile, as gravity caused matter to condense around the previously perturbed objects outside the gravitational grasp of the new sun, dust particles and the rest of the protoplanetary disk began separating into rings. Successively larger fragments collided with one another and became larger objects, ultimately becoming protoplanets. These included one collection approximately 150 million kilometers from the center: Earth. The planet formed about 4.54 billion years ago (within an uncertainty of 1%), and the planet was largely completed within 10–20 million years. The solar wind of the newly formed T Tauri star cleared out most of the material in the disk that had not already condensed into larger bodies.
Computer simulations have shown that planets with distances equal to the terrestrial planets in our solar system can be created from a protoplanetary disk.
