Toy boats float along the bottom of a levitating liquid

Going bottom-up is no problem for a boat on the underside of a levitated liquid.

In a container, liquid can be levitated over a layer of gas by shaking the container up and down because the repeated, upward jerking motion keeps fluid from dripping into the air below.

Lab experiments have revealed a curious consequence of this antigravity effect. Objects can float along the bottom of a hovering liquid as well as along the top, researchers report in the Sept. 3 Nature.

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B. Apffel et al/Nature 2020

Creating an antigravity effect in the lab allows objects like toy boats to float upside down on the bottom of a layer of levitating liquid.

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Source: B. Apffel et al/Nature 2020

“I was very surprised” to see the effect, says Vladislav Sorokin, an engineer at the University of Auckland in New Zealand, who coauthored a commentary on the study that appears in the same issue of Nature.

Sorokin has studied another paradoxical phenomenon in vibrating liquids — the fact that bubbles sink to the bottom of the liquid rather than rising to the top.

The discovery of this new phenomenon hints that perhaps other counterintuitive effects are yet to be discovered in vibrating systems, he says.

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Physicists knew it was possible to keep a layer of liquid levitated over a cushion of air by vigorously shaking the layers up and down in a container.

But new lab experiments have revealed a surprising effect of that antigravity trick. Toy boats and other objects are able to float along the bottom surface of a levitated liquid as well as its top.

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