Here's why:
* Formation from a disk: The Earth formed from a swirling disk of gas and dust around the young Sun. Over millions of years, this material clumped together, gradually growing larger.
* Early bombardment: In the early solar system, there were many planetesimals (small, rocky bodies) and asteroids. The Earth was constantly bombarded by these objects, which added to its mass.
* Differentiation: As the Earth grew, its internal heat increased. This led to a process called differentiation, where heavier elements (like iron) sank to the core, while lighter elements (like silicon) rose to the surface. This process contributed to the Earth's overall size.
* Gravitational pull: The Earth's growing mass also increased its gravitational pull, attracting more material from space.
So, the Earth was much smaller at its inception and grew over billions of years through accretion, bombardment, and differentiation. The Earth's size has likely stabilized, but there are still minor changes due to processes like tectonic plate movement.
