Cosmic time - Topics

Where 13.8 billion years comes from: the CMB and the cosmic distance ladder together The universe is 13.8 billion years old and 93 billion light years wide: how both can be true Lookback time: the sunlight you feel now left the Sun eight minutes ago Recombination 380000 years after the Big Bang: how the universe went from opaque to transparent The Great Oxidation Event 2.4 billion years ago and how it rusted the oceans Distant Type Ia supernovae run slow by exactly their redshift factor The thermodynamic arrow and the cosmological arrow have to point the same way Hubble tension: two ways to measure the expansion rate differ by about 9 percent The cosmic microwave background is the oldest light we can ever see Interstellar's Miller planet: does one hour near a black hole really cost seven years? Heat death vs Big Rip vs vacuum decay: three endings for time Olbers' paradox: why an eternal static universe would make the night sky blindingly bright Asking what happened before the Big Bang may be a question general relativity cannot pose Why a Boltzmann brain makes the arrow of time a problem for cosmology A timeline of the universe needs a logarithmic axis or the last century vanishes The cosmic calendar: if the Big Bang were January 1st all of human history fits into the last 30 seconds Snowball Earth: how cap carbonates record a planet that froze and then baked Cepheid variables and the period-luminosity relation that measured the universe The myth of the first event: how do you prove nothing came before Cosmological redshift is not a Doppler shift: space stretched the wavelength on its way here