NYSSA: I thought we couldn't change history.

DOCTOR: This place. All decay and despair. It feels like an end. Yet you and I know what's coming afterwards. So it's not an ending. Just an alternative.

NYSSA: So we can't change history.

DOCTOR: Who says? I think history's old enough to take care of itself.

THOMAS DODD: We all want immortality, don't we? But with a chrome finish?