planck

In 2021, physicists at the University of Bremen cooled a cloud of rubidium atoms to 38 picokelvin — 38 trillionths of a degree above absolute zero — the coldest temperature ever recorded in a laboratory. At the opposite extreme, the ALICE experiment at CERN produced quark-gluon plasma at 5.5 trillion kelvin in 2012, the hottest temperature ever achieved by human hands. Above both records, the Planck temperature — 1.416 × 10^32 kelvin — marks the point where physics itself breaks down. Between these endpoints, the temperature scale encompasses every phenomenon in the universe, from interstellar clouds barely above nothing to the supernovae that forge heavy elements.

The universe has been expanding for 13.8 billion years, and dark energy is currently accelerating that expansion. If it suddenly reversed and the universe began contracting, we would be heading toward a 'Big Crunch' — but the change would be too slow for any individual to notice.