Astronomers have long understood that the universe is expanding—in other words, the space in between cosmic objects that aren’t bound by gravity is getting ever more vast. Then, in 1998, scientists discovered the universe’s rate of expansion is accelerating.

The availability of the James Webb Space Telescope is finally giving astronomers the tools they need to measure this aspect of space more accurately. A new study led by Nobel laureate Adam Reiss at Johns Hopkins University offers the most accurate assessment yet,

New observations from the James Webb Space Telescope have reinforced the Hubble tension, a discrepancy between different measurements of the universe's expansion rate. Scientists, using Cepheid variable stars,