Poem: Invisible

From this angle it doesn't seem possible that something of that girth and weight could lean out over the water and not tremble.
It's what I can't see that holds it there, a web of roots that exceeds the span of its branches. So many invisible things that I rely on:
gravity, oxygen, radio waves, the workings of my mind, of your mind, awareness. Though sometimes one materialises
in front of me when I least expect it: the woman who stepped onto the grass so I could run past safely. Thank you.