A little background based on a few articles about this plus my recollection of PBS Space Time videos on this: There are at least two ways to try to figure out the rate of expansion of the universe (which is called the Hubble Constant).
• From variations in the cosmic microwave background (CMB) which are the result of certain conditions in the early universe it is possible to figure out what the expansion rate should be now.
• From looking at very distant galaxies and noting how far away they are and how fast they are receding from us the expansion rate can be calculated.
Theory says that these should give the same expansion rate. When the rates were first found using those two methods they gave different results, but the error bars on both were large enough to overlap. People expected then that further refinement of both methods to decrease the error bars would converge to some common value.
That did not happen. Refinement of the CMB measurements got to 67 +/- 0.5, and refinement of the galaxy distance/speed method got to 73 +/- 1. Those do not overlap.
This non-overlap between the possible ranges given by the two methods is called the Hubble tension, and it is one of the most irksome problems in cosmology.
Possible explanations include:
• Some sort of error in how we measure the variations in the CMB.
• Some sort of error in the distant galaxy distance or speed measurements, which until the James Webb telescope were almost entirely Hubble telescope measurements.
• We're missing something in our understanding of the physics.
These new results add a bunch of data from the James Webb telescope, which observes in different wavelengths than Hubble. These results fit with the Hubble measurements.
They do not resolve the Hubble tension. What they do is remove most doubt that the distant galaxy results involve some sort of Hubble measurement error. I believe cosmologists are pretty confident of the CMB measurements, and so this will be interpreted as telling us that the Hubble tension is not just a problem with our measurements. There is either physics that we got wrong or physics we need to discover.
• From variations in the cosmic microwave background (CMB) which are the result of certain conditions in the early universe it is possible to figure out what the expansion rate should be now.
• From looking at very distant galaxies and noting how far away they are and how fast they are receding from us the expansion rate can be calculated.
Theory says that these should give the same expansion rate. When the rates were first found using those two methods they gave different results, but the error bars on both were large enough to overlap. People expected then that further refinement of both methods to decrease the error bars would converge to some common value.
That did not happen. Refinement of the CMB measurements got to 67 +/- 0.5, and refinement of the galaxy distance/speed method got to 73 +/- 1. Those do not overlap.
This non-overlap between the possible ranges given by the two methods is called the Hubble tension, and it is one of the most irksome problems in cosmology.
Possible explanations include:
• Some sort of error in how we measure the variations in the CMB.
• Some sort of error in the distant galaxy distance or speed measurements, which until the James Webb telescope were almost entirely Hubble telescope measurements.
• We're missing something in our understanding of the physics.
These new results add a bunch of data from the James Webb telescope, which observes in different wavelengths than Hubble. These results fit with the Hubble measurements.
They do not resolve the Hubble tension. What they do is remove most doubt that the distant galaxy results involve some sort of Hubble measurement error. I believe cosmologists are pretty confident of the CMB measurements, and so this will be interpreted as telling us that the Hubble tension is not just a problem with our measurements. There is either physics that we got wrong or physics we need to discover.