Astronomy 121 - Exam 1 Review

Scientific Notation

A method to express large and small numbers using powers of ten.

Astronomical Unit (A.U.)

The average distance from the Earth to the Sun, approximately 149.6 million kilometers.

Light Year

The distance that light travels in one year, approximately 9.46 trillion kilometers.

The Scientific Method

A systematic process involving Observation, Question, Hypothesis, Experiment, Analysis, and Conclusion.

Theory vs Hypothesis

A theory is a well-tested explanation, while a hypothesis is an untested educated guess.

Placebo Effect

A psychological phenomenon where individuals experience changes due to their belief in a treatment.

Fermi Problem

A rough estimation problem using approximate values.

Celestial Sphere

An imaginary sphere surrounding Earth on which celestial objects appear to be projected.

Circumpolar Stars

Stars that never set and are visible all night, determined by the observer's latitude.

Kepler's First Law

Planets follow elliptical orbits with the Sun at one focus.

Kepler's Second Law

Planets sweep equal areas in equal times, indicating varying speeds in orbit.

Kepler's Third Law

P² = a³; the square of a planet's orbital period is proportional to the cube of its semi-major axis.

Newton’s First Law

An object in motion remains in motion unless acted upon by a net external force.

Newton’s Second Law

The force acting on an object is equal to the mass of that object times its acceleration (F = ma).

Newton’s Third Law

For every action, there is an equal and opposite reaction.

Escape Speed

The minimum speed needed to break free from a celestial body's gravitational pull.

Electromagnetic Spectrum

The range of all types of electromagnetic radiation, including gamma rays, X-rays, visible light, and radio waves.

Photon

A particle representing a quantum of light or electromagnetic radiation.

Wein’s Law

A formula to find the peak wavelength of emission of a black body related to temperature (λ_peak = 2.9 × 10^6 / T).

Nuclear Fusion

A process where nuclei combine to form a heavier nucleus, releasing energy, primarily occurring in the Sun.

Neutrinos

Subatomic particles produced in nuclear reactions, particularly during fusion processes in the Sun.

Auroras

Natural light displays in the Earth's sky, primarily caused by solar wind interactions with the Earth's magnetic field.