cosmology big bang Definition and 2 Threads

  1. nomadreid

    Undergrad FLRW metric challenged, Einstein-Euler equations as alternative?

    The question concerns the article "The instability of critical and underdense Friedmann spacetimes at the Big Bang as an alternative to dark energy" by Alexander, Vogler & Temple in Volume 482, Issue 2338 (May 2026) of the Proceedings of the Royal Society A, found in the link...
  2. J

    Undergrad Where did the early photons go?

    Since photons travel at c, where did they travel to, or was the universe expanding at the speed of light (or faster)?