Even the Master has to agree that the dinosaurs are brilliant. Those are not his exact words, not really, his exact words are more along the lines of "not a complete waste of time like everything else", but coming from him it means he's enjoying himself. The Doctor grins as he watches him feed a magnolia branch to a huge long neck dinosaur (an Apatosaurus) while half a dozen smaller carnivores (Coeluruses) hop around in the distance. Then again lately he's always grinning, even more so than usual, can't help it if he's in a good mood. He's still in a good mood when, some time later, a big mean dinosaur with too many teeth that they haven't bothered to identify chases them back to the TARDIS.
"Next stop?" the Doctor asks as soon as he catches his breath.
"What's the furthest back that you've ever been?" the Master asks. "Did you ever go to a time before the dinosaurs?"
"Once or twice," says the Doctor, who has been most everywhere and everywhen in this universe.
Despite himself, the Master is interested. He leans forward and peers at one of the screens on the TARDIS's console. "How far back can it go?"
The Doctor grins. "Want to see?"
The Master doesn't ask to go anywhere. As much as he wants to, he never actually says "I want to go there" and "take me to that time", he's almost childlike in his refusal to admit that he's curious too, that he wants to see it, all of time and space. Sometimes the Doctor turns it into a game, suggesting that they visit random places and times instead (never boring places and times, because nothing is ever boring, just places and times that aren't quite as interesting as what the Master has in mind) just to see how long it takes for the Master to outright admit that dinosaurs aren't too boring, let's go see the dinosaurs instead.
Sometimes the Master has a great idea and the Doctor can't wait, doesn't tease him one bit, he just punches in the coordinates and off into the time vortex they go.
It's a bit like going to see a newborn baby, except without all the family members fussing around and worrying that you might drop the baby on its head. (A valid concern given his track record, the Doctor has to admit.) They open both doors and sit side by side, legs dangling into the void, staring at the newborn cosmos.
"The colours are very pretty," the Doctor says. "But it's not that big. More like a small bang. And no noise either because there is no air to carry it, so really it should've been the small noiseless event." The Master doesn't say anything, so the Doctor adds, "Small noiseless event doesn't roll off the tongue, though."
"What happens before?" the Master asks after a while. "Could we go further back?"
The Doctor shrugs. "You don't want to do that, it's dull and there's not as many pretty colours," he replies. "Popcorn?"
The Master stares at the proffered bowl. "Popcorn?" he asks, lifting an eyebrown. "You're witnessing the beginning of this universe and you brought popcorn?"
"I like popcorns," the Doctor says, propping one into his mouth. The Master takes a handful.
For a while the only sounds are popcorns being munched and a universe being born, which, as stated, doesn't make any sound.