a sworn foe

Some space missions cool the propellant to almost freezing to densify it, so they can fit more fuel and oxidizer in the tanks.

She was only sixteen, and he was perfectly splendid, and she has plenty of money, and every one talked about it; and when she went anywhere, people looked, you know, and she liked it; but her papa is an old poke, so he's sent them all away. It's too bad, for she was the jolliest thing I ever knew .

If we are another footnote to Plato, Plato was himself already a footnote to still earlier footnotes, in an endless chain of footnotes to footnotes