We use many tools to get us out to the farthest reaches of the Cosmos. Herein, we summarize the various ways we learn to measure these gargantuan lengths. This is part of my complete intro Astronomy class that I taught at Willam Paterson University and CUNY Hunter. • Cosmology Definition: The study of the universe’s origin, evolution, and fate. • Redshift and Distance: Redshift, a shift in light wavelength, helps determine distances to faraway galaxies. • Hubble’s Law: Relates a galaxy’s distance to its recession speed, indicating the universe’s expansion. • Cepheid Variables for Distance Measurement: Cepheid variables, with their luminosity-period relationship, are used to measure distances in the universe, but their range is limited to about 150 million light years. • Hubble Space Telescope Limitations: Using the Hubble Space Telescope to observe Cepheid variables is expensive and requires significant justification due to limited observation time. • Cosmic Distance Ladder: Scientists use a series of methods, including Cepheid variables, to measure distances in the universe, aiming to understand objects billions of light years away. • Distance Measurement Techniques: Spectroscopic parallax and Cepheid variables are used to determine distances to stars and galaxies. • Cepheid Variables as Standard Candles: Cepheid variables, with their predictable brightness variations, serve as reliable distance indicators for measuring distances up to 60 million light years. • Type 1a Supernovae for Farther Distances: Type 1a supernovae, with their consistent brightness, are used to measure even greater distances, up to 70-100 million light years. • Standard Candles in Astronomy: Astronomers use standard candles like cepheid variables and planetary nebulae to determine distances in the universe. • Cepheid Variables: Cepheid variables are crucial for measuring distances to spiral galaxies. • Tully-Fisher Relationship: Spiral galaxies’ luminosity correlates with their rotation speed, aiding in distance measurement. • 21 Centimeter Radiation Application: Used to determine the relative motion of gas clouds in galaxies. • Tully-Fisher Relationship Application: Provides a reliable method for determining cosmic distances by linking a galaxy’s luminosity to its rotation rate. • Hubble’s Law Application: Relates a galaxy’s distance to its redshift, indicating the universe’s expansion. • Galactic Distance Measurement: Cepheid variables and Type Ia supernovae are used to measure distances to galaxies. • Cosmological Measurements: WMAP, Planck, Sloan Digital Sky Survey, and the Holy Cow group have made recent measurements of the universe’s expansion rate. • Precision Cosmology: Scientists can now precisely measure the expansion rate of the universe, leading to new questions about its future and past. Music by Matthew Huffaker used by CCL4.0.