Justices can absolutely be impeached, but Congress has three other levers they can pull to reign in a rogue court
- Re-size the court, as you stated.
- Specifically deny the court jurisdiction over certain matters.
- Define exactly what "good behavior" means
- Amend the constitution to do even worse.
The first is most likely because it's simplest and there's precedent. The last is least-likely because there hasn't been a successful amendment proposal since before Roe.v Wade.
The middle two are fuzzier and more uncertain, and would need congress to either impeach or stand firm with a clear consequence if the court attempts to ignore such action. Either can start with a simple majority vote action of Congress, however, which makes them possibly more likely than the others.
(Or maybe the Dems will sweep the 2028 midterms and President Jeffries can have a two-year term as "president fuck you". Although I don't think he has the temperament for it.)
I wish more pop science reporters would report on "dark energy" and "dark matter" as the questions they are.
Dark energy is "our best models of physics say redshift is due to movement away, and when we apply that model to our best observations the furthest galaxies appear to be accelerating, what the fuck is making them accelerate"?
(Dark matter is, simpler, "why are all these galaxies rotating as if they have way more matter than we can see -- and why the fuck can't we see that matter?")