The Universe is not heading toward a quiet freeze trillions of years from now. A new model built on fresh dark energy data says the cosmos may be on a timer, and it is already halfway done. Physicist Henry Tye and collaborators Hoang Nhan Luu and Yu-Cheng Qiu calculate that the Universe’s total lifespan is about 33 billion years. We are 13.8 billion years in, which means roughly 20 billion years remain.⁠ ⁠ For the next 11 billion years, the Universe will keep expanding, but more and more slowly. Then expansion stops at a maximum size about 1.7 times larger than today. After that, gravity wins. Space itself reverses and everything begins to fall inward. The final act is swift: in about 8 billion years of contraction, all matter, energy, and spacetime collapse into a single point. This “big crunch” would be the reverse of the Big Bang.⁠ ⁠ The turning point lies in the cosmological constant, a term Albert Einstein introduced to describe how space evolves. For decades, measurements suggest...