Gravity and Orbits
This invisible, attractive force exists between all objects with mass and holds our solar system together.
What is gravity?
Equal to about 150 million kilometers, this unit of measurement equals the average distance from Earth to the Sun and simplifies large space calculations.
What is an Astronomical Unit (AU)?
This is a massive system of billions of stars, gas, and dust held together by gravity.
What is a galaxy?
About 4.6 billion years ago, Earth began forming when cosmic dust and rocks clumped together due to this force.
What is gravity?
These preserved remains or traces of ancient organisms help scientists piece together the story of life on Earth.
What are fossils?
These two factors determine the strength of the gravitational pull between any two objects in space.
What are mass and distance?
These small, rocky bodies leftover from planet formation are mostly found orbiting the Sun in a belt between Mars and Jupiter.
What are asteroids?
Our solar system is located in the Orion Arm of this specific spiral galaxy.
What is the Milky Way Galaxy?
Scientists tested radioactive decay in this ultra-tough mineral found in ancient Australian rock to prove Earth is at least 4.3 billion years old.
What is zircon?
This geological law states that in undisturbed rock layers, the oldest layers are on the bottom and younger layers are on top.
What is the Law of Superposition?
The Sun has the strongest gravitational pull in our solar system because it contains approximately this percentage of all solar system matter.
What is 99%?
Often called "dirty snowballs," these objects are made of ice and dirt and form glowing tails when they get close to the Sun.
What are comets?
This category of galaxy has pinwheel-like curved arms swirling out from a central point.
What is a spiral galaxy?
This thin, solid outermost layer of Earth is where all life lives.
What is the crust?
Geologists organize Earth's 4.6-billion-year history using this calendar divided into eons, eras, and periods.
What is the Geologic Time Scale?
A planet's high-speed forward motion combined with the Sun's gravitational pull keeps it moving in this curved path.
What is an orbit?
This is the specific term for a space rock that survives passing through Earth's atmosphere and actually lands on Earth's surface.
What is a meteorite?
Galaxies that look smooth and are shaped like stretched circles or footballs are classified as this type.
What is an elliptical galaxy?
Early Earth was kept in a partially melted state due to intense heat caused by gravitational compression and these cosmic events.
What are collisions (or impacts)?
Evidence of high iridium levels and a 180-kilometer crater in Mexico suggest this event caused the mass extinction of dinosaurs 66 million years ago.
What is an asteroid impact?
If the distance between two orbiting objects increases, the gravitational attraction between them will do this.
What is decrease (or get weaker)?
While gas giants like Saturn have over 80 of these natural satellites orbiting them, inner planets Venus and Mercury have zero.
What are moons?
Galaxies with no clear, defined, or symmetric shape are placed in this category.
What is an irregular galaxy?
Name the four main layers of Earth's interior in order from the surface to the center.
What are the crust, mantle, outer core, and inner core?
Evidence from heavy water isotopes suggests that ancient collisions with these icy bodies delivered much of Earth's surface water.
What are comets?