You will need to look at the vid to make sense of some of the text. Basically, infrared light enables astronomers to see through dust:
All of this is pretty cool, but I am personally most excited about the observations on young galaxies, at extremely high redshifts, early in the universe. The youngest galaxy that the Hubble telescope has seen has been estimated to date back to about 400 million years after the big bang. Webb should be able to see back to about 100 million years after the big bang.
That’s very interesting because the way that galaxies form tells us something about the matter in the universe, in particular about dark matter and its role in structure formation. In the currently most widely accepted theory for cosmology, the large galaxies we see today build very gradually by merging smaller galaxies.
This figure shows how astrophysicists think this works. All the symbols here are galaxies and the larger the symbol the larger the galaxy. Time increases from the bottom up. At the beginning you have all these tiny galaxies, and then they join to increasingly larger ones.
What you can see from this graph is that if this theory is correct there basically shouldn’t be any large galaxies at very early times. But is this correct? This figure shows the predictions from the millennium simulation in comparison to data. You can see two things here. One is that there isn’t a lot of data at the moment. But also that it seems like the data is way off the simulation…
If the Webb telescope sees large galaxies anyhow, then that’s going to be very difficult to explain with dark matter. That, in my opinion would be the most interesting discovery the telescope could make. Though, I guess oxygen and water on an exoplanet would be a close second.
Sabine Hossenfelder, “What may the new James Webb telescope discover?” at BackRe(Action) (January 30, 2022)