Maxwell's Fishpond

TL;DR

This paper presents the design and demonstration of Maxwell's Fishpond, a water wave device inspired by transformation optics, capable of reversing wave ripples and reforming disturbances multiple times for educational and experimental purposes.

Contribution

It introduces a water-based analogue of the Maxwell's Fisheye lens using transformation mechanics, enabling wave control and visualization in a tangible, accessible manner.

Findings

The Fishpond can reform wave disturbances up to five times.

Design demonstrates wave manipulation based on transformation optics principles.

The device offers an educational tool for visualizing wave dynamics.

Abstract

Most of us will have at some time thrown a pebble into water, and watched the ripples spread outwards and fade away. But now there is a way to reverse the process, and make those ripples turn around and reconverge again, ... and again, and again. To do this we have designed the Maxwell's Fishpond, a water wave or "Transformation Aquatics" version of the Maxwell's Fisheye lens [Tyc et al. 2011, Luneberg 1964] that is now well-known from transformation optics. These are transformation devices where wave propagation on the surface of a sphere is not modelled on an actual sphere, but in a flat device with carefully designed spatially varying properties. And just as for rays from a point source on a sphere, a wave disturbance in a Maxwell's Fisheye or Fishpond spreads out at first, but then reforms itself at its opposing point in the device. Here we show how such a device can be made for water waves, partly in friendly competition with comparable electromagnetic devices [Ma et al. 2011] and partly as an accessible and fun demonstration of the power of transformation mechanics. To the eye, our Maxwell's Fishpond was capable of reforming a disturbance up to five times, although such a feat required taking considerable care, close observation, and a little luck. What can you see in the video at http://www.qols.ph.ic.ac.uk/~kinsle/files/MFishpond/ ?