The Sun
This invisible force from the Sun pulls on all the planets to keep them orbiting safely around it.
What is gravity?
How long ago did the Earth form?
What is 4.6 billion years ago
The Moon's gravity pulls on Earth's oceans, causing this daily rise and fall of the water level.
What are tides?
Because early Earth was molten, heavy elements like iron and nickel sank to the center to form this layer.
It is believed that a shockwave from the explosion of one of these nearby dying stars triggered the initial collapse of our solar nebula.
What is a supernova?
The Solar System was formed billions of years ago from a giant rotating cloud of gas and dust and called this
What is a nebula?
The protoplanet that crashed into Earth to create the Moon is named this.
What is Theia?
While the inner core is a dense ball of solid metal, the outer core is made of this state of matter.
What is molten/liquid metal?
The Sun is primarily composed of these two light elements, which were the main ingredients available in the solar nebula.
What are hydrogen and helium?
These small, asteroid-like building blocks crashed and stuck together to form the early planets, including Earth.
What are planetesimals
The energy from the impact was so intense that the newly formed Moon was entirely covered in a global ocean of this liquid material before cooling down.
Lighter molten rock floated toward the surface and cooled to form this outermost solid skin of the planet.
What is the crust?
Before achieving full nuclear fusion, the dense, collapsing core of gas that would become the Sun was known by this "early" stellar term.
What is a protosun/protostar?
These carried water to Earth.
What are asteroids.
Because the Moon lacks a significant atmosphere to protect it or weather it down, its surface is heavily scarred by billions of years of these.
What are craters?
Named after the Greek underworld due to its hellish conditions of molten lava and meteor impacts, this is Earth's earliest eon.
What is the Hadean eon?
The Sun weights this much.
What is 2 nontillion?
This is a planetary embryo that forms inside a rotating disk of gas and dust around a young star
What is a protoplanet?
This is the official scientific name for the leading theory that the Moon formed from the debris of a collision between early Earth and a Mars-sized object.
What is the Giant Impact Hypothesis?
Occurring roughly 4.1 to 3.8 billion years ago, this chaotic period involved a surge of asteroid impacts that heavily cratered the young Earth and Moon.
What is heavy bombardment?