How Many Days Were in a Year When Earth First Formed?

The formation of Earth is a fascinating topic that spans billions of years, starting from dust and debris in space, culminating in the creation of a planet that we know today. This process, known as runaway accretion, saw Earth taking shape over a period of 10–20 million years, approximately 4.54 billion years ago.

The Formation Process

During the early stages of Earth's creation, the planet went through several significant events, including the Giant Impact about 97 million years after the initial formation, where it was hit by a Mars-sized body named Theia. This impact added a substantial amount to the Earth's mass, between 2 and 10%. Another significant event was the Late Heavy Bombardment, which took place around 3.95 to 3.85 billion years ago, adding one last percent of mass over about 100 million years.

Theories of Earth's Formation

One of the most accepted models to explain the formation of Earth is the core accretion model. According to this model, gravity caused material to collapse, creating a spinning object that eventually turned into a rocky planet. The core accretion model also suggests that Earth began to form around 4.54 billion years ago, while the sun formed about 5 billion years ago, leading to a time of about 10–20 million years for Earth to take its current recognizable form.

Gigaannal of Time

If we consider the time since the Big Bang, which is approximately 13.8 billion years, it would mean that Earth formed around 3.3 billion years after the Big Bang. Alternatively, if we focus on the formation of the solar system, which began about 4.5 billion years ago, Earth would have taken just 10–20 million years to develop. However, due to geological activity, Earth has continuously changed since its formation, making it an active geologic body.

Rotation and Days in a Year

The rotation of Earth has influenced the number of days in a year over time. For instance, 620 million years ago, the Earth had about 400 days per year, as evidenced by fossil records. As Earth's rotation has slowed, the length of a day has increased, consequently reducing the number of days in a year.

Evolution of Earth

The continuous evolution of Earth means that its geological state has changed significantly since its formation. Several million years after the initial formation, Earth continued to develop, making it a dynamic planet with ongoing changes. The oldest Earth rocks are about 4 billion years old, while the Hadean eon, the period of extreme heat and volcanic activity, ended around 3.8 billion years ago. This geologically active nature has shaped the planet into what it is today, an ever-evolving celestial body.