Or, possibly, there’s a problem with how we’re observing it. Either way, something’s fishy. In a nutshell, the Universe is expanding. There’s a whole bunch of different ways to measure that expansion. The good news is these methods all get roughly the same number for it. The bad news is they don’t get exactly the same number. One group of methods gets one number, and another group gets another number. This discrepancy has been around awhile, and it’s not getting better. In fact, it’s getting worse (as astronomers like to say, there’s a growing tension between the methods). The big difference between the two groups is that one set of methods looks at relatively nearby things in the Universe, and the other looks at very distant ones. Either we’re doing something wrong, or the Universe is doing something different far away than it is near here.