JWST is the 2021 James Webb Space Telescope, if, like me, you're not plugged into this stuff.

Excerpt:

It’s looking more and more like the universal expansion was different when it was young than it is now. When it was young it was denser, galaxies were closer together, and conditions were just different. We know that dark energy plays a huge role here, causing the expansion to speed up, but how it does that isn’t clear.