Understanding Our Universe - Chapter 1

Vocabulary flashcards covering key terms and concepts from the lecture notes.

Planets from the Sun (Mercury to Neptune)

The eight planets in order: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune.

Interstellar object

An object that originates outside the Solar System; not from within the Sun’s gravity well.

3I/ATLAS

The first confirmed interstellar object detected; tracked against the background of stars.

Apollo 13

NASA Moon mission that suffered an oxygen-tank explosion; popularized in film starring Tom Hanks.

Eye of a hurricane

The calm, central region of a hurricane.

International Space Station (ISS)

A habitable artificial satellite in low Earth orbit where experiments are conducted.

Streaks of light (night city lights from ISS)

White trails in time-lapse photos caused by city lights as viewed from space.

Astronaut qualifications

Typical prerequisites to become an astronaut: STEM background, advanced degree, physical fitness, leadership and teamwork skills, resilience, and substantial flight experience.

Pilot-in-command time

Hours of flight time where an individual is legally in command of the aircraft.

Tiangong

The Chinese space station.

Mir

The former Russian space station, a major orbiting platform in past decades.

Skylab

NASA’s first space station (launched in the 1970s).

Salyut

A series of Soviet space stations; earliest long-duration orbital platforms.

Laniakea

The Milky Way’s surrounding supercluster; a large cosmic structure.

Cosmic calendar

A scale that compresses 13.8 billion years of cosmic history into one year.

Big Bang

The origin event of the universe, marking the start of cosmic expansion.

Radio telescope

A telescope that detects radio waves from space using antennas rather than optical lenses.

Electromagnetic spectrum

The range of all wavelengths of electromagnetic radiation (radio, infrared, visible, ultraviolet, X-ray, gamma).

NASA

National Aeronautics and Space Administration, U.S. space agency.

JPL (Jet Propulsion Laboratory)

A NASA center that develops robotic space missions.

Perseverance

NASA’s Mars rover exploring the Red Planet; active as of the notes.

Curiosity

NASA’s Mars rover earlier in the Mars program; predecessor to newer rovers.

Gravitational waves

Ripples in spacetime produced by accelerating masses, detected by LIGO.

LIGO

Laser Interferometer Gravitational-Wave Observatory; twin detectors that detected gravitational waves.

Scientific method

A systematic process: observe, hypothesize, predict, test, evaluate, and refine.

Hypothesis

A testable educated guess explaining a pattern in nature.

Prediction

A specific expectation derived from a hypothesis that can be tested.

Experiment

A procedure to test a hypothesis and gather data.

Falsifiability

The quality of a theory being testable and potentially provable false.

Occam’s Razor

The principle that the simplest explanation with the fewest assumptions is preferred.

Polaris

The North Star; located near the celestial north pole and useful for navigation.

Independent variable

The variable deliberately changed in an experiment to test its effects.

Dependent variable

The variable measured in an experiment to assess the effect of the independent variable.

Unit

A standard quantity used to express measurements (e.g., meter, kilogram).

Astronomical Unit (AU)

Average Earth-Sun distance, about 149.6 million kilometers.

Scientific notation

A compact way to write very large or very small numbers using powers of 10.

Light-year

The distance that light travels in one year (about 9.46 x 10^15 meters).

Scale map of the Solar System

A model where each object’s distance from the Sun is represented on a reduced scale (e.g., 1 cm per AU).

Proxima Centauri

The nearest star to the Sun, about 4.2 light-years away.

Artemis program

NASA effort to return humans to the Moon, including missions Artemis I–V and beyond.

Artemis I

Uncrewed test flight of the SLS/Orion to validate systems for crewed missions.

Artemis II

Crewed lunar flyby mission planned to test the spacecraft with people aboard.

Artemis III

Planned crewed lunar landing mission, targeting the lunar south pole.

Trans-Lunar Injection (TLI)

Maneuver that sends a spacecraft from Earth orbit toward the Moon.

Splashdown

Return of the crew and capsule landing in Earth's oceans.

Orion

NASA’s crewed spacecraft used in Artemis missions.

SLS (Space Launch System)

NASA’s heavy-lift rocket powering Artemis missions.

Earthrise

Iconic Apollo 8 photograph showing Earth rising above the lunar horizon.

Astrogeology of Mars rovers

Rovers like Curiosity and Perseverance explore Mars and collect samples.