The Earth is believed to have originated approximately 4.5 billion years ago through a process called accretion. The most widely accepted scientific explanation for Earth's origin is the nebular hypothesis, which suggests that the Earth and other planets in our solar system formed from a rotating disk of dust and gas known as the protoplanetary disk. Over time, the particles in this disk collided and gradually accumulated, forming larger bodies that eventually became planets.
The Earth is roughly spherical in shape, but its shape is not a perfect sphere. Due to the rotation of the Earth, it bulges slightly at the equator and is slightly flattened at the poles, making it an oblate spheroid. The equatorial diameter of the Earth is about 12,742 kilometers (7,918 miles), while the polar diameter is slightly shorter at approximately 12,713 kilometers (7,900 miles). The Earth's circumference is approximately 40,075 kilometers (24,901 miles). It has a total surface area of approximately 510 million square kilometers (197 million square miles) and a volume of about 1.08 trillion cubic kilometers (260 billion cubic miles).
It's important to note that these dimensions may have slight variations depending on the reference used, as the Earth is not a perfectly uniform object. Additionally, the Earth's tectonic activity and erosion processes continuously shape its surface, resulting in ongoing changes over geologic time scales.