Relativity
an excerpt

“Let me explain something to you.” he said, sitting himself down on the swing. It could barely carry his weight and the black rubber band of the seat distorted around his backside. “You’ve used a swing before, right?”
Michael rolled his eyes and looked at Adam as though he must be kidding. What did he think? A brief swing together will not somehow manage to replace a lifetime of absence. And how old did he think Michael was?
“Yes!” Michael replied, half offended and half confused by his question. “Of course I’ve been on a swing before. I might even be too old for swings now, you know!”
Adam rocked himself back and forth with his legs, gripping his hands around the thin column of rusty chains suspended from the play equipment. He seemed puzzled by Michael’s reaction but continued anyway. “Well do you know how swinging on a swing works? Do you understand what you’re doing with your body, with the swing, rather with the entire universe when you pull your legs back and push them high up into the air and swing?”
Michael hesitated to guess, knowing that swinging was a simple thing, almost instinctive, and he wasn’t entirely sure what Adam was talking about. You push against the ground, you point your feet toward the sky and you swing. Was there anything else to it? Michael knew how to do it, but he did not know what he was doing when it was happening.
“Come sit down next to me.” Adam grabbed the chains of the swing beside him and offered them to Michael. “Now tell me,” he asked. “what do you do first?”
Michael positioned himself on the seat of the swing, careful not to place his body either too far forwards of backwards. He gripped his fingers around each chain.
“First you straighten your legs out against the floor, pull your body back, and that’s it.” Michael said. “You’re off.” He pulled himself back, just like he had described, and swung up into the air. Every movement he made extended him a little bit further than the last, until he was in full flight, swinging back and forth.
“You’re oscillating.” Adam said.