Changing how we see

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

Extended captions