On Kurhan, the Doctor learns that neither he nor Martha are very good skaters.
He thinks she might learn, eventually, but she is too clinical in her approach, too afraid of falling. She can't get up enough speed to keep warm, and so her attempts are all the more difficult, made as they are from within the confines of a large, puffy coat. The Doctor has neither need nor desire to keep out the cold, but while this body may be good for sprinting and springing, it is apparently bollocks at balance. Wiry, thinnest he's ever been, and he feels like a medicine ball on the tip of a springpole balanced on rollers.
"Doctor!" comes a cry from behind him, and Martha careens in for a landing, gripping his forearm with both hands. Teetering, she throws her center of gravity too far forward, and before he can shout a strangled, "No!", they both go down on the mineral ice in a heap.
"Sorry," comes contritely muffled from underneath a cumbersome, fur-lined hood. Martha lets out a huff of breath against his chest and heaves over onto her back, pinning his arm.
"I'm sure I was better at this, once," the Doctor says, staring up at the black, star-specked sky.
Really, he doesn't mind the fall. This expanse of cold, entropic space at his back is just what he needs. Sky above, sky below; the mineral ice is clear as glass. The only break is from the distant bluish snowdrifts, winds hollowing out the space underneath the tips until they look like waves about to break. And if he closes his eyes...
Rage. Burning, screaming--
"--long has it been?"
The white heat disappears as his eyes snap open. The stars are just stars, just pinpricks in the black.
"Hmm?" His brain catches up with his ears as he drums the fingers of his free hand against the ice. His fingertips haven't yet stopped buzzing and throbbing, like a colony of electric ants have fled the rest of his body and are pooling there, itching to get out. He blinks again, setting off a fraction of a firestorm behind his lids, and processes the context of Martha's question. Ice skating. How long--?
"Oh, centuries," he answers absently. "Must be."
"Centuries? What, like it was the fifteen-hundreds when you visited last year?" The weight is lifted off his arm and he turns his head to find Martha propped on an elbow with her hood thrown back around her shoulders, studying him. She starts to sit up but stops abruptly, her brow furrowing. "Hold on, what year is it? Are we in the future now?"
"I--" he starts, then realizes he doesn't know. He set the TARDIS to keep the current timeline, but he didn't exactly check before bounding out the door into the snow. He searches for an answer, but words wither in his mind, dissipating into newly empty space. Martha removes an oversized mitten to reach for his hand, and there is a flashpan memory of burning agony spiking against every cell, of the dizzying trip to the medbay grounded only in the scrape of boots across the deckplates, and in human hands that felt like ice anywhere they touched him.
He doesn't flinch, but Martha raises an eyebrow at him anyway. Her question lingers close in the cold air, and he can see a tinge of fear behind her nonchalance as they gain their feet. His attention has been wandering since they left the Torajii system. Well, it's always wandered, of course; his brain can easily handle half a dozen orthogonal trains of thought at once. Just, some tracks recently got folded over, or twisted aside, or crushed, melted, or just. . . burned away. When the sun particles left he was literally light-headed, terrified and giddy, scoured from the inside out.
"I'm older than I look," he finally answers. They start off again, away from the snowdrifts. Martha stumbles and falls behind a few steps, but keeps asking questions.
"Really. By how much?"
"Nine hundred years," he says over his shoulder. His ankles wobble, but he straightens and turns to face her. "Give or take," he adds.
He remembers screaming over the atomic roar in his ears, trying to tell her about regeneration. He remembers saying other things as well. He's had bouts of sudden youthfulness before, and he remembers now why he was so reluctant to embrace it. It's been harder since the war not to simply forget, reinvent himself utterly, without the pool of his people's collective history and thoughts to ground him. Youth has its disadvantages, and it has been a very long time indeed since he's run across something ancient enough and massive enough to make him feel like a speck of a child.
Mind of a sun, it's certainly something new. Hardly an excuse, echoes up into the hollows of his mind, repeated in at least three different voices.
On the flat, glistening ice, Martha stares at him, open-mouthed. Then she breaks into a huge smile.
"Oh, you lucky--!" She hollers at the sky, arms outstretched, before catching herself, spinning around to point a finger at him. "Not that I'd put myself into a hypersonic mixer for it or anything, but that's one hell of a natural life span you've got there. And you look better than Yoda."
Her smile is contagious. The Doctor laughs. The sound rushes away across the ice, battering the distant drifts.
"That's not all," he says. He follows an echo of one of those disapproving voices down to a cramped, tiny corner. A memory unfurls into the gloom, slowly at first, but gaining strength-- a detached liquid nitrogen coolant hose, a frozen TARDIS swimming pool, and Peri and Erimem grinning wildly despite his best attempts to be stern.
If he had come back later, tentatively, testing the edges and gliding out onto the ice, it was only the TARDIS who knew.
On Kurhan, the Doctor plants his feet, ankles strong and straight, and with a burst of speed he races twenty meters out and leaps into a single pirouette, landing perfectly on one skate in the black expanse. Martha applauds enthusiastically as he takes a bow.
"Told you I was better at this."
A boy's will is the wind's will
And the thoughts of youth are long, long thoughts.