The stream I am standing in does what every natural stream does. It calculates the gradient of the gravitational potential. I can feel its sign as delicate water pressure on my shins. My mind drags me a little deeper, into a meander where the current carves the bed. The river tries. But the carving, the friction, the battle with different layers of rock, they all make it stray, make it only approximate what a frictionless particle would do in the weak-field limit of a curved spacetime metric. I am getting chin-deep into these geophysical musings.

I ponder for a moment the strange inference that just happened: from the water “inferring” the “shape” of the gravitational field, through my shins “inferring” pressure differentials, to the brain integrating bodily sensations with prior knowledge of general relativity. All of that just to look at the trail running along the river and conclude that I will be running uphill. I drag my feet through the gravel to reach the trail.

I have been working recently on my NPM, the Noticings per Minute, so I allow myself one more, before the minute passes. I look at my watch. I have a few seconds left, and as they tick away, I notice a branch, pushed by the current, but held by its elastic, fibrous core. It’s incessantly beating the water’s surface like in a slapstick comedy. “The stick slaps”, I smile a thought! The natural secondhand makes me think of the stream as flowing time. The current of time calculates the gradient of the entropy potential. Its sign points forward. In that case, one could hope to climb against its sign, uphill of time.

“It’s a metaphor, not physics,” I think. But I try to rescue the science. While entropy is not a “potential,” it shapes the free energy landscape. This landscape is often more jagged than the baddest of Badlands, but at the microscale things do occasionally climb “uphill”! Yet that climb against the current is just a descent into lower probability, in a configuration space devoid of time. I can’t rescue the science, but at least I find a symbolic paradox: a climb can be a descent. My watch beeps. My time is up.

With the first step I swing my leg, linked with the rest of the body by its elastic, fibrous core. The forest is flowing through me. Every crack between the leaves is a pinhole camera, and every speckle is a projection of the sun. The reality is speckled, but somehow I make sense of it. I am getting closer to the dam. I can hear the waterfall where the gradient approaches infinity. I run into a clearing, navigating around broken branches scattered by the recent storms. I perceive the scene as a whole, imagining the world flowing into me with the force of the waterfall, millions of bits per second. And then I hear a scream, just below my feet. A man is lying on the ground, basking in the sun. We didn’t notice each other. Him, with eyes closed, getting a few dozen bits per second, me overwhelmed with the richness around me.

We start talking. He is a friendly fellow, probably two decades older than me. He grew up in LA, but moved to Kansas for work many years ago, and only came back to LA, when his kids went to college. They are visiting now, because it is spring break. I tell him about the local trails, and how he could connect them. The conversation is mundane, but for reasons deeply embedded in my human nature, I am absorbed by it. All the nonsense, upstream thoughts about Noticings per Minute, entropic potentials, and rivers calculating gradients is gone. There are just two souls meeting in the wilderness.

“Have a nice run!” he shouts as I accelerate on the path back, downstream, along the river. I notice many things, but I just enjoy them, as one enjoys running downhill, naturally, without effort. As one enjoys meeting a fellow stranger.