Earlier this year the British Association for the Advancement of Science held a competition for poetry on the theme of space, time and energy, all in the name of celebrating "Einstein Year". I entered but did not win, oddly enough. The actual winners can be found here.
As you cruise round the galaxy
At near light velocity
There's a problem I think I should mention
When from planets far flung
You return, you're still young,
While your twin would be drawing a pension.
Rob Harper, 2005-07-19