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What is the Geocentric Model?

An ancient Greek belief in an Earth-centered universe with planets moving around the Earth in perfect circles.

What did Copernicus argue in the Copernican Model?

He argued for a sun-centered universe but could not fully explain other types of planetary motion.

What does Kepler's 1st Law state about planetary orbits?

Planets orbit the sun in an elliptical orbit with the sun at one focus.

Define an ellipse in the context of orbits.

An ellipse is like a squashed or stretched circle, characterized by a major axis, semi-major axis, minor axis, perihelion, and aphelion.

What is the perihelion?

The point in an orbit where a planet is closest to the sun.

What is the aphelion?

The point in an orbit where a planet is farthest from the sun.

What does Kepler's 2nd Law describe?

Orbiting planets sweep out equal areas in equal times, meaning they move faster when closer to the sun and slower when farther away.

What is Kepler's 3rd Law?

Planets farther from the sun take longer to orbit, with the period calculated using the equation p² = a³, where p is the period in years and a is the average distance in astronomical units (AU).

What causes the seasons on Earth?

Seasons are caused by Earth's axis tilt, not by its distance from the sun.

What is the principle of Universal Gravitation?

Gravity is a force that attracts all objects with mass, depending on mass and distance.

How does mass affect gravitational force?

Increasing mass increases the force of gravity, but not by a squared amount; doubling mass doubles the strength of gravity.

How does distance affect gravitational force?

Increasing distance decreases the force of gravity by a squared amount; doubling distance decreases the force by 4 times.

What is the difference between mass and weight?

Mass is the amount of matter in an object and does not change when moving to a different planet, while weight changes based on gravitational pull.

What is the formula for calculating speed?

Speed = distance/time.

What is the definition of velocity?

Velocity is how fast an object is moving in a specific direction.

What does Newton's First Law state?

An object in motion stays in motion at a constant speed, and an object at rest stays at rest unless acted upon by an outside force.

What is inertia?

Inertia is an object's resistance to a change in motion.

What is Newton's Second Law?

Force equals mass times acceleration (F=ma), with force measured in Newtons (N).

What does Newton's Third Law state?

Every action has an equal and opposite reaction; applying a force on an object results in an equal force in the opposite direction.

What happens to white light when it refracts through a prism?

It separates into a spectrum of colors.

What is the Doppler Effect?

A change in wavelength due to the motion of the source, indicating whether an object is moving towards or away from an observer.

What does Hubble's Law state?

More distant galaxies are moving away from us faster than nearby galaxies, indicated by redshift.

What is the Big Bang model?

It describes the universe expanding from a hot, dense single point, predicting the universe is 13.8 billion years old.

What caused small particles to stick together into larger particles during the cooling phase of the universe?

Cooling caused forces to separate and particles to combine.

What is the first step in the Big Bang Model regarding the forces?

Gravity separated from other forces.

What significant event occurred 380,000 years after the universe formed?

The first atoms formed, allowing light to move freely through the universe.

What does the Big Bang Theory predict about the current state of the universe?

The universe should be expanding today.

What evidence supports the expansion of the universe according to the Big Bang Theory?

Redshift evidence shows the universe is still expanding.

What is the predicted composition of the first stars according to the Big Bang Theory?

75% hydrogen and 25% helium.

What is the Cosmic Microwave Background Radiation (CMBR)?

A continuous spectrum of microwaves coming from all parts of the sky, leftover heat from the Big Bang.

What phenomenon is causing the acceleration of the universe's expansion?

Dark Energy.

What is a galaxy?

A cloud of billions to trillions of stars, gas, and dust.

What is a globular cluster?

A group of millions of old stars, packed closely together.

What are the four main types of galaxies?

Spiral, elliptical, irregular, and lenticular.

What characterizes a spiral galaxy?

It has a disk with spiral arms containing blue, new stars and a central bulge of older stars.

What is the main feature of an elliptical galaxy?

It is spherical or football-shaped and contains only older, redder stars.

What defines an irregular galaxy?

Oddly-shaped due to interactions with other galaxies, filled with new, blue stars.

What is the primary energy source of the Sun?

Nuclear fusion of hydrogen into helium.

What are the three main layers of the Sun?

Photosphere, chromosphere, and corona.

What is the significance of the solar cycle?

It is an 11-year cycle of sunspot activity.

What is gravitational equilibrium in the context of the Sun?

The balance between gravity and pressure that keeps the Sun stable.

What does the Hertzsprung-Russell (H-R) diagram illustrate?

The relationship between a star's brightness (luminosity) and its temperature (spectral class).

What happens to a star when it runs out of hydrogen?

It expands into a giant and begins fusing helium to carbon.

What is a supernova?

The explosion that occurs when a supergiant star's core becomes iron and fusion stops.

What is a black hole?

A core crushed by a supernova into a single point.

What is the event horizon of a black hole?

The point of no return around a black hole.

What evidence suggests the presence of black holes?

Stars wobbling, X-rays from the accretion disk, and high-energy jets emitted from the galaxy center.