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The Doctor and Rose arrive in a very odd place, where even the TARDIS can’t translate certain writings they find; something the Doctor has never seen happen before. They find a crew of humans, working in a planetary outpost, who tell them they are investigating the mysterious planet’s ability to remain in orbit around a Black Hole. Something that is quite impossible!
They find the human crew is attempting to learn the source of the ultimate power that keeps this planet out of reach of the forces of a Black Hole, which is drawing in surrounding solar systems. The power source of the planet appears to be located at the planet’s center, under miles of hard rock.
But, then after one of many reoccurring earthquakes destroys the section of the base the TARDIS materialized in, the Doctor and Rose must accept that they may have no means of escape, or return to any other time or space.
And even worse, an evil force, and not technology, might be behind the planet’s unexplainable power to orbit the Black Hole.
The TARDIS materializes in what appears to be a closet. It reacts oddly, and the Doctor notes that it's acting queasy. They set out to explore and the Doctor quickly realizes they're in a deep-space sanctuary base. They enter a central area and hear the sound of drilling. Rose sees the words "Welcome to Hell" written on the wall, surrounded by writing in some other language. The Doctor doesn't recognize it and notes that it goes beyond the range of the TARDIS's knowledge. They open another door and are confronted by a series of humanoid creatures with tentacles for mouths. They advance on the Doctor and Rose, saying "We must feed." The creatures close in and then pause, adjust their translation spheres, and say they must feed them if they're hungry. The creatures, the Ood, note the electromagnetics interfere with their speech systems...Read the full recap
Rose: if you think there's gonna be trouble, we could always get back inside and go somewhere else.
(she and the Doctor laugh hysterically)
The Doctor: A black hole is a dead star. It collapses in on itself. In, in, in, in, in, until the matter’s so dense and tight, it starts to pull everything else in too. Nothing in the universe can escape it. Light, gravity, time. Everything just gets pulled inside and crushed.
Rose: So they can’t be in orbit. We should be pulled right in.
The Doctor: We should be dead.
Ida Scott: And yet… here we are. Beyond the laws of physics. Welcome on board.
The Doctor: There we go! D'you see? To generate that gravity field, and the funnel, you need a power source with an inverted self-extrapolating reflex of six to the the power of six every six seconds.
Rose: That's all the sixes.
The Doctor: And, it's impossible.
Zachary Cross Flane: It took us two years to work that out.
The Doctor: I'm very good.
The Ood: The Beast and his armies shall rise from the pit to make war against God.
Rose: I'm sorry?
The Ood: Apologies. I said I hope you enjoy your meal.
Rose: Don't forget to breathe! Breathing's good.
Ida Scott: We’ve come this far. There’s no turning back.
The Doctor: Oh, did you have to? "No turning back"? That’s almost as bad as "nothing could possibly go wrong" or "this is going to be the best Christmas Walford’s ever had".
Just before the Doctor and a crewmember goes down you can see an Ood walking among them. But a few scenes before, they are all locked down and a few scenes after you can see the waking up. So where did this walking Ood came from ?
Just after the Doctor and Rose see the star consumed by the black hole, they are talking while sitting on a table. Written on the table, just near the Doctor, you can see four Maxwell's equations in differential form.