Image: The cosmic microwave background as seen by the European Space Agency’s Planck satellite. Credit: ESA and the Planck Collaboration
The photo above is quite common among astronomers and astrophysicists. It depicts what is known as the cosmic microwave background (CMB), the very ancient light coming from the beginnings of our universe. It is supposed to be the leftovers of the grand explosion birthing our Universe, called the Big Bang.
When analyzing the expansion of the universe, astrophysicists imagined that the expansion could be rewinded, just like a film, and that this backward movement would show the collapse into a singularity. Together with the astronomical observations of the CMB radiation, they concluded that the universe had to be flat. But recent observations with better precision are showing a different picture. An anomaly in data from the best-ever measurement of the CMB is offering solid (although not yet conclusive) evidence that the universe is closed, and in order to be closed, it would curve gently on itself.
In order to understand the difference between both kind of flatness—that of a flat sheet kept strait, or a flat sheet bended—in both cases the surface seems flat at short distances, but at very long distances, the curvature of the second case will affect and manifest different effects. For instance, two photons could cross at some point when travelling along parallel trajectories. The topology or curvature of a surface plays a crucial role in all that exists within.
As most of the calculations are done considering a flat universe, huge amounts of recalculations would have to be done in order to fine tune the physics concerned. And it seems to be necessary, as according to the latest data, there’s significantly more gravitational lensing of the CMB than expected, and this could be explained by inserting a positive curvature for the universe instead of a flat one.
Results were drawn upon data coming from a 2018 release of the Planck experiment—a European Space Agency (ESA) experiment to map the CMB in more detail—and they were published in Nature Astronomy this month.
RSF in Perspective
Is the universe a giant loop? https://www.scientificamerican.com/article/is-the-universe-a-giant-loop/