Shipping News for Physicists

A real physical force that pulls together two metal surfaces separated by empty space does not tug on ships lying close at anchor, according to physicist Fabrizio Pinto, in today’s

The “mysterious” Casimir effect is often illustrated by analogy with two ships floating side by side in a heavy swell and being pulled together, at least that’s how it’s been described in popular science articles. The notion apparently stems from a physics article published in 1996, which describes how an 1836 book, The Album of the Mariner, says ships should not be moored too close together because they will be attracted by a mysterious force.

Pinto is out to stem the tide of pseudoscience, however. He told news@nature that the idea is a simple misunderstanding. The Album of the Mariner says this attraction only happens in calm seas, not a heavy swell, points out Pinto. The only way a Casimir-like effect could be responsible is if the boats were moored in a choppy swell.

So the analogy is false, says Pinto. And there may not be any mysterious force at all pulling two ships together, whatever the conditions. “We have caught physicists in the very act of creating a myth,” he says.

So, what is the Casimir effect? Well, it’s not due to gravity, electrostatic charge, nor magnetism. That’s what it’s not. Essentially, it results from the resonance of the energy fields between the two objects. At least that’s what Wikipedia tells us, but what does it mean? Well it boils down to quantum fluctuations in the vacuum between the plates and for a lucid yet detailed description of how that causes attraction check out this PhysicsWeb article on the subject.

Incidentally, how would anyone navigate two ships in a vacuum to begin with?

One thought on “Shipping News for Physicists”

  1. “Incidentally, how would anyone navigate two ships in a vacuum to begin with?”

    First pump out the air which fills the two bottles which the ships are in.
    Then they can navigate as they usually do.
    Obviously you don’t want to let them get too close together or an attractive force will appear when their bottles break.

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