Center Stage
This model places the **Earth** at the center of the universe.
What is the geocentric model?
This scientist used his telescope to see moons orbiting **Jupiter**, proving not everything orbits Earth.
Who was **Galileo Galilei**?
Kepler's First Law says that the orbits of planets follow this specific shape.
What is an ellipse?
This term is the resistance an object has to a change in motion, a concept formalized by Newton's First Law.
What is **inertia**?
To accelerate an object (that is, to change its velocity or direction), a force must be applied. But crucially, no force is needed to sustain motion — only to alter it.
What was one Newton's discoveries?
This model places the **Sun** at the center of the solar system.
What is the heliocentric model?
He made decades of very precise, **naked-eye observations** that his assistant later used.
Who was **Tycho Brahe**?
An object will stay in motion unless a **net force** acts on it, according to this law.
What is Newton's First Law of Motion?
According to the Second Law (F=ma), if you push a shopping cart with a constant force, the cart will do this more quickly if its mass is lower.
What is **accelerate**?
A planet moves **faster** when it is closer to the Sun and **slower** when it is farther away, according to this one of Kepler's laws.
What is Kepler's Second Law of Planetary Motion?
The invention of the **telescope** and seeing the phases of Venus helped prove this model was correct.
What is the **heliocentric model**?
He used his boss's data to discover that orbits are **ellipses**, not perfect circles.
Who was Johannes Kepler?
This physics concept is a change in an object's **momentum** caused by a force over time.
What is an impulse?
This is the other name given to Newton's First Law, which says objects keep doing what they are doing unless a force acts on them.
What is the **Law of Inertia**?
If you double the distance between two objects, the gravitational force between them gets weaker by this factor.
What is **four** (or 1/4)?
The temporary **backward** motion of planets is known by this term.
What is **retrograde motion**?
He gave us the universal law of **gravitation** and the three laws of motion.
Who was Isaac Newton?
This law states that the force the Earth pulls on the Moon with is **equal** to the force the Moon pulls on the Earth with.
What is Newton's 3rd Law of Motion?
For every action, there is an equal and opposite **reaction**; this principle is the core of which law?
What is **Newton's Third Law**?
This scientist was instrumental in creating the concept of **inertia**, which was later called Newton's First Law.
Who is **Galileo**?
Centuries ago people believed in this model because said they could not feel the movement of the Earth.
What is the geocentric model?
This Polish astronomer used math to support a heliocentric model. He died one year after he published his book about this topic.
Who was Copernicus?
This law of planetary motion states that a planet sweeps out equal areas in equal time intervals.
What is Kepler's Second Law?
A force that opposes motion between objects that are touching is called this.
What is friction?
This Polish astronomer is famous for writing the book that changed astronomy by putting the **Sun** at the center of the universe.
Who was Copernicus?