Isaac Newton (1542-1727)
The ‘bodkin’ experiment
Cambridge, ca 1669

In his work on light and optic Newton wished to understand the nature of colour, seen in the spectrum from a prism or a rainbow but that also might be produced if, as in this ‘self-experiment’ he pressed a stick against the ball of his eye from behind. Here, in trying to replicate the sensation of colour in normal sight Newton wrote that he ‘…tooke a bodkin gh & put it betwixt my eye & the bone as neare to the backside of my eye as I could: & pressing my eye with the end of it (soe as to make the curvature a, bcdef in my eye) there appeared severall white darke & coloured circles r, s, t, etc.’

Newton’s theory of colour and light postulated particles or corpuscles of light; this idea was later overturned by the wave-theory given mathematical embodiment by James Clerk Maxwell in terms of waves in electro-magnetic fields. In turn Maxwell’s theory lead in some degree to Einstein’s theories of relativity and today quantum mechanics envisages a wave-particle duality – where light is thought of as having the properties of both waves and particles – which Einstein described as “a new kind of difficulty”

The whole of this Laboratory Notebook can be viewed within the Cambridge Digital Library by clicking the link below.

MS.Add.3975, p.15