[Steely Tom]

Since (the sum of) dark matter and dark energy supposedly makes up 99.5% of the universe, and since we NASA just sent the JWST on an exquisitely calculated trajectory up a gravitational mountainside to a precise rendezvous with a point at which it will orbit around an incredibly subtle gravitational potential well, I have this question: did NASA account for dark matter in their calculation of the orbital mechanics in setting up this trajectory, and in adjusting it with mid-course correction burns MCC-1a and MCC-1b?

If they did, how much effect did it have?

If they didn't, why not?

And if they didn't, why am I supposed to believe that the matter in our immediate vicinity, out to a distance of one million miles at least, is devoid of the effects of "matter" that's supposed to make up 200 times more mass than the earth, moon, and sun?

[Campion]

I think you're assuming that "dark matter" (however much of it exists) is spread evenly around the universe. But there's no reason for it to be.

Objects like the earth tend to clear their immediate surroundings, so close to the earth (a million miles is close in space terms) you aren't going to find any matter that isn't either orbiting the earth or soon-to-be colliding with it.

Way over 99% of the gravity the Webb telescope "sees" is due only to the earth and the sun. Everything else is too far away, too small, or too thinly spread out.