The universe, according to physicists, is flat.
Experts told Live Science that there are several lines of evidence that point to a flat universe, including light left over from the Big Bang, the rate of the universe’s expansion at various locations, and the way the cosmos “looks” from various perspectives. David Spergel, an emeritus professor of astrophysical sciences at Princeton University and a theoretical astrophysicist, has spent decades exploring the structure of the cosmos. Spergel measured anomalies in the cosmic microwave background (CMB), light remaining from the Big Bang, which were seen by NASA’s Wilkinson Microwave Anisotropy Probe (WMAP) and later by the European Space Agency’s Planck spacecraft, in a 2003 study published in The Astrophysical Journal. In a flat universe, the positive and negative energy levels are identical and cancel one other out. One would be higher than the other if there were a curvature to the universe. According to Spergel, “a flat world corresponds to a cosmos with zero energy.” The rapid expansion of the universe, which is captured by the Hubble constant, is another factor that leads Spergel to believe the universe is flat. The universe was flattened, or at least as flat as it could be, as a result of the universe’s transformation from a compact ball of matter to expanding outward at extraordinary speeds.