Take wings of fancy, and ascend, And in a moment set thy face Where all the starry heavens of space Are sharpen'd to a needle's end;
Take wings of foresight; lighten thro' The secular abyss to come, And lo, thy deepest lays are dumb Before the mouldering of a yew;
And if the matin songs, that woke The darkness of our planet, last, Thine own shall wither in the vast, Ere half the lifetime of an oak.
Ere these have clothed their branchy bowers With fifty Mays, thy songs are vain; And what are they when these remain The ruin'd shells of hollow towers?
Now Tennyson wants us to have imagination time. He's asking us to use our imaginations and rise up to where "all the starry heavens of space / Are sharpen'd to a needle's end." Nifty—but what does it mean?
Well, he seems to be imagining seeing all of space and time as a needle, drawn out and sharp. When you think of things in this grand scheme, nothing really matters.
Even the most significant songs ("deepest lays"), presumably written by the greatest poets, are silent compared to the lifetime of a yew tree.
They won't be remembered for even half the time that an oak tree lives. So what good is any of this? Maybe we'll get an answer in the next canto…