Creating a black hole horizon analogue on a lab table

Niklas Manz

This project started from an idea of Marc Manheim and Dr. Lindner. Marc worked on a watertank version in his 2017 Senior IS and Sam Nash scaled it down to use reaction-diffusion waves in his 2019 Senior IS.

Marc found a paper proving that gravity waves (Abbott et al., Observation of gravitational waves from a binary black hole merger, Phys. Rev. Lett. 116, 061102, 2016) in water can behave analogously to electromagnetic waves traveling through space-time which had been shown experimentally in a 30x1.8x1.8 m3 tank (Schützhold and Unruh, Gravity wave analogues of black holes,> Phys. Rev. D 66, 044019, 2002). To scale it down, Marc constructed a scaled down water tank inour workshop (2x1 m2). In this experiment, gravity water waves were generated in the tank and propagated in a direction opposed to a flow of varying velocity. The rate of volumetric flow in the channel varies between the minimum and maximum cross-sectional area as shown in the next figure. The point of equal velocities (water flow and created wave) is a very nice visualization of the event horizon.

Watertank sketch

Schematic of the scaled down hydrodynamic analogue. The fluid flow indicated by the blue arrows is inversely proportional to the width. A 'usually' radial wave would be deformed into an elliptical shape by the varying fluid flow.

During Marc's Senior IS, we faced several experimental problems: leakage and rust are solvable but the high speed of water waves and especially the reflection of water waves at boundaries are inherent to this system and were very difficult to deal with.

Therefore, we combined the idea with a two-dimensional reaction-diffusion-advection system and replace the water waves with chemical concentration waves in a Belousov-Zhabotinsky system which are much slower (about 3 mm/min) and, most importantly, will not reflect at boundaries. We will initiate circular waves (target pattern) in the fluid flow, which will deform in the same way as the water waves. Sam Nash started working on this idea in his 2019 Senior IS.

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