Oh how he loved that beautiful old planet, Gallifrey with its great glass dome and snow-capped hills of red grass. He used to skip class at the academy sometimes, sneak off into the hills on his own to watch the rising of the second sun, which would pour liquid fire over the lands. Those memories are hard to reach now, eclipsed by ones of very much real fire, his planet blazing.
So he tries to bring back that original scene through his words, pouring out the image of his memory, syllable after syllable to Martha, forcefully holding back the heat and burning. He shares the lost beauty in the only way he thinks he can, reliving it through the subtle smiles and wistful expressions on his companion’s face.
As he leaves again on his TARDIS, always running, never looking back, he doesn’t see the sun rise over a newly revived New New York, the sky a burnt orange reflecting off the silver forest of skyscrapers, making the entire city aglow with fire.