Timeline & Age
The estimated age of our universe today according to current scientific models.
What is 13.8 billion years?
As the early universe expanded, this is what happened to its overall temperature and density.
What is decreased / cooled down?
The shift observed when a celestial object moves toward Earth, compressing light waves.
What is Blueshift?
What the acronym "CMB" stands for in astronomy.
What is Cosmic Microwave Background?
Distance unit defined by how far light travels through space in one Earth year.
What is a light-year?
The nuclear process that occurred within minutes of the Big Bang to form the lightest element nuclei.
What is Big Bang Nucleosynthesis?)
The two primary elements that made up virtually all matter created in the early universe.
What are Hydrogen and Helium?
The shift observed when light wavelengths stretch as a galaxy moves away from Earth.
What is Redshift?
How the wavelengths of CMB radiation have changed over time as space expanded.
What is stretched out / lost energy?
Approximate distance in kilometers equal to one light-year.
What is ~9.46 trillion km?
This event occurred roughly 380,000 years after the Big Bang when protons captured electrons to form neutral atoms.
What is Recombination/Decoupling?
The primary reason Big Bang nucleosynthesis stopped, leaving heavy elements to be created much later inside stars.
What is the universe becoming too cold and low-density?
The law stating that a galaxy's receding velocity is proportional to its distance from Earth.
What is Hubble's Law?
The Big Bang theory predicted that CMB radiation detected today would be highly redshifted and extremely this.
What is cold?
The primary reason astronomers use light-years instead of kilometers.
What is expressing vast interstellar distances compactly?
The state of the universe during its first 380,000 years where light interacted heavily with charged particles.
What is an opaque plasma soup?
The approximate ratio of hydrogen to helium formed during the initial nucleosynthesis phase.
What is ~3:1 or 75% to 25%?
Features of star light used by astronomers to measure redshift and determine galaxy motion.
What are absorption spectra/emission spectra/spectral lines?
Thermodynamic laws used to model energy changes in the CMB over cosmological time.
What are Conservation of Energy & First Law of Thermodynamics?
Groups of stars near each other in space that move together at equal velocity.
What are star clusters?
The temperature of the universe at the exact time when photons were able to begin traveling freely across space.
What is 3,000 Kelvin?
The process responsible for building elements heavier than helium.
What is Stellar Nucleosynthesis?
Edwin Hubble's discovery regarding Andromeda proved this about the universe's structure.
What is that the universe extends far beyond the Milky Way?
The satellite observatory that captured key detailed thermal images of the CMB.
What is the Planck satellite?
Daily Double: Provide a concise statement describing how the universe changed from immediately after the Big Bang to today regarding size, temperature, and contents.
What is: "Right after the Big Bang, the universe was tiny, extremely hot, dense, and composed of a plasma of subatomic particles; today, it is 13.8 billion years old, vastly expanded, cold, low-density, and filled with neutral atoms, stars, and galaxies."