The Versorium Needle

A draft extract from my book using narrative to teach the big ideas of physics:

These are the utterly false and disgraceful tales of the writers.

William Gilbert, 1600

I will start my history of electricity with an utterly false and disgraceful lie: amber, when rubbed, will not attract dried basil.

The ancient Greek philosophers had a method for finding the truth. Observation played a part, but only observation of naturally occurring phenomena. Experiments did not count, because experiments are artificial. Observation combined with reason was the preferred method of finding the truth. This produced excellent mathematics but dodgy science. They claimed that amber would not attract dried basil, but did not test this claim.

This disgraceful falsehood could not be proved wrong without experiment. Medieval scholars could not refute it, because they were suspicious of the senses. The lie remained unexposed for thirteen centuries until a new method for finding the truth was discovered: careful experimentation.

In 1600, William Gilbert began the modern study of electricity. He published a wonderful book which presented a true account of electricity and magnetism. 

He also invented a mysterious instrument for detecting charged objects: the versorium needle.

The needle is made from unmagnetised metal. When rubbed amber is brought towards the versorium, the needle will turn accusingly until it points towards the amber.

The Greeks believed that amber alone could be charged by rubbing. Gilbert used his versorium to prove this wrong. Gilbert’s list of materials include: diamond, sapphire, glass, sulphur, sealing wax and resin. He named these materials electricks because they behave like amber (elektron).

So Gilbert resolved the great amber/basil error and demonstrated that many more substances were ‘electrick’. But then he contributed his own error to the great chain of scientific mistakes:

All electricks attract all things: they never repel or propel anything at all.

This great mistake was not recognised until 1663, when a remarkable scientific inventor, Otto von Guericke, demonstrated repulsion using his powerful electrical sulphur sphere.

Next section…. von Guericke’s Electrical Sulphur Sphere

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5 thoughts on “The Versorium Needle

  1. This is great: I previously only had a very vague idea of Gilbert’s work on magnetism and did not know that he’d also investigated static as well.

    Bearing in mind that this is intended for non-experts, I would advise placing more emphasis on developing the narrative structure. “Rubbed amber does not attract dried basil” seems like such an oddly specific claim to make: who said it? When? And most importantly, why?

    ‘The Ancient Greeks didn’t do experiments’ idea is arguable: certainly, the Greek authors whose work has survived valued the theoretical big picture more than the detail, but what about finds such as Antikythera mechanism which might indicate that Greek thought wasn’t as monolithically anti-experimental as previously thought. You will undoubtedly need to simplify the narrative for clarity, but it would be nice to acknowledge nuance where appropriate.

    Some Greek authors even accepted a form of “action at a distance” for magnets, although they believed air was passed peristaltically through a magnet, producing the observed effects.

    Also, using the history of science to explain science is great: you mention “charge” but don’t explain what Gilbert or modern science understand by it.

    Hope this helps!

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    • Thank you – I need to be careful about over-simplifying.

      You are certainly right about the rubbing amber – I’m editing too far.

      Charge is problematic – I started thinking about my anachronistic use of it, but thought I might get away with it – the fact that you spotted it straight away has made me reconsider.

      Best,

      Ben

      Like

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