The Invisible Whirlpool: How a Hidden Center Governs the Motion of a Calm Stream Imagine a vast field of force that flows in perfect circles around a central vertical axis. This field is unique because as you move further away from the center, the strength of the flow weakens. If you were to place a tiny paddlewheel anywhere in this stream, it wouldn't spin, and if you watched the water, it wouldn't seem to be bunching up or thinning out anywhere. Locally, the field feels completely calm and "curl-free". However, this local tranquility hides a surprising global secret that only reveals itself when you take a long journey.
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