Biography earth scientific short

While Earth is only the fifth largest planet in the solar system, it is the only world in our solar system with liquid water on the surface. Just slightly larger than nearby Venus, Earth is the biggest of the four planets closest to the Sun, all of which are made of rock and metal.

Earth is the only planet in the solar system whose English name does not come from Greek or Roman mythology. The name was taken from Old English and Germanic. It simply means "the ground." There are, of course, many names for our planet in the thousands of languages spoken by the people of the third planet from the Sun.

Namesake

The name Earth is at least 1,000 years old. All of the planets, except for Earth, were named after Greek and Roman gods and goddesses. However, the name Earth is a Germanic word, which simply means “the ground.”

Potential for Life

Earth has a very hospitable temperature and mix of chemicals that have made life abundant here. Most notably, Earth is unique in that most of our planet is covered in liquid water, since the temperature allows liquid water to exist for extended periods of time. Earth's vast oceans provided a convenient place for life to begin about 3.8 billion years ago.

Some of the features of our planet that make it great for sustaining life are changing due to the ongoing effects of climate change.

Size and Distance

With an equatorial diameter of 7926 miles (12,760 kilometers), Earth is the biggest of the terrestrial planets and the fifth largest planet in our solar system.

From an average distance of 93 million miles (150 million kilometers), Earth is exactly one astronomical unit away from the Sun because one astronomical unit (abbreviated as AU), is the distance from the Sun to Earth. This unit provides an easy way to quickly compare planets' distan

Overview of Earth's history

For more detail of the geological history of Earth, see Geological history of Earth.

For more detail of the biological history of Earth, see History of life.

The natural history of Earth concerns the development of planetEarth from its formation to the present day. Nearly all branches of natural science have contributed to understanding of the main events of Earth's past, characterized by constant geological change and biological evolution.

The geological time scale (GTS), as defined by international convention, depicts the large spans of time from the beginning of Earth to the present, and its divisions chronicle some definitive events of Earth history. Earth formed around 4.54 billion years ago, approximately one-third the age of the universe, by accretion from the solar nebula. Volcanic outgassing probably created the primordial atmosphere and then the ocean, but the early atmosphere contained almost no oxygen. Much of Earth was molten because of frequent collisions with other bodies which led to extreme volcanism. While Earth was in its earliest stage (Early Earth), a giant impact collision with a planet-sized body named Theia is thought to have formed the Moon. Over time, Earth cooled, causing the formation of a solid crust, and allowing liquid water on the surface.

The Hadean eon represents the time before a reliable (fossil) record of life; it began with the formation of the planet and ended 4.0 billion years ago. The following Archean and Proterozoic eons produced the beginnings of life on Earth and its earliest evolution. The succeeding eon is the Phanerozoic, divided into three eras: the Palaeozoic, an era of arthropods, fishes, and the first life on land; the Mesozoic, which spanned the rise, reign, and climactic extinction of the non-avian dinosaurs; and the Cenozoic, which saw the rise of mammals. Recognizable human

By the time of the moon-forming impact, the Earth was already separated into these rock and metal layers. However, the intense force and heat of the impact re-melted the proto-Earth, re-mixing the separated rock and metal. After this mixing, the Earth was still hot enough for separation to occur again and form new rock and metal layers - this is the key to dating when the moon formed!

When rock and metal mix, they are able to swap certain elements. Elements like hafnium prefer to be mixed in with rock than with metal. Hafnium decays over about 10 million years to form tungsten. The first time the Earth cooled and separated into rock and metal layers was early in the solar system’s history, so lots of hafnium was present in the Earth’s rocky layer because it hadn’t had time to decay to tungsten yet. By the time the moon-forming impact occurred, much of this early hafnium had decayed to tungsten. Elements like tungsten prefer to be mixed in with metal, so when the impact remixed the Earth, the newly formed tungsten sank into the metal core. This created a rocky outer layer with a lower concentration of hafnium than before, and a metal core with much more tungsten in it.

Today, all of the hafnium is gone because it has a short half-life compared to the age of the Earth. However, not all is lost - this makes it very useful for working out the timing of events in the first hundred million years of the solar system’s history. The concentration of tungsten in Earth’s rocks depends on when the most recent separation into rock and metal layers occurred. The concentration of tungsten in Earth’s rocks is too low to be explained by the metal and rock separating early on, which means something must have re-mixed the Earth’s layers. The best explanation for the heat and energy needed to do this is a giant impact about 60-175 million years after the solar system was born.

What did the early Earth look like?

After the moon-fo