New Theory about Light and Colours

Newton sends Oldenburg his New Theory about Light and Colors

Newton's public debut in optics provoked Robert Hooke's first attack within a week of the paper circulating.

Cambridge, 6 February 1671/72

Isaac Newton sent Henry Oldenburg a letter dated 6 February 1671/72 Old Style — 16 February 1672 by the Gregorian calendar — to be communicated to the Royal Society. England was then ten days behind Gregorian reckoning, and its legal year began on 25 March, which is why contemporaries could file the day under February 1671.

The Society had recently examined Newton's reflecting telescope and elected him a fellow. Oldenburg encouraged further communication, and Newton fulfilled his promise to describe the optical discovery behind the telescope.

Thirteen propositions

The letter described admitting sunlight through a small hole in a darkened room, refracting it with a triangular glass prism, and his surprise that the coloured image was oblong rather than circular. What began as a pleasing divertisement became a problem.

Across thirteen numbered propositions he argued that ordinary light is a heterogeneous mixture of rays with different refrangibilities, and that colour is an intrinsic property of those rays rather than something the refracting medium creates.

Red, yellow, green, blue, violet — and indefinitely more

Newton named red, yellow, green, blue and violet-purple as original or primary colours, together with orange, indigo and indefinitely many intermediate gradations. This is not a scheme of seven sharply bounded bands; the later seven-part arrangement was formalized in Opticks.

Oldenburg thanked him on 8 February Old Style and placed an edited version in Philosophical Transactions no. 80, pages 3075–3087, dated 19 February 1671/72. Hooke's objections followed within a week of the paper's circulation.

Sources

Researched 23 Aug 2026 5 sources 2 audit passes Traditional date

How this was checked

Researched from the web into a fact sheet, rewritten from that sheet, then audited against it by a different model. How the pipeline works →

Traditional date. Conventionally dated here; the research places it at 1672-02-16.

What the sources leave uncertain

The Gregorian date 1672-02-16 is a conversion of 6 February in England’s Julian calendar. England was then ten days behind the Gregorian calendar.
The contemporary date 1671/72 reflects England’s legal year beginning on 25 March: contemporaries could call the day February 1671, while modern historical dating calls it February 1672.
This is the dispatch date, not the publication date. Philosophical Transactions dated the issue 19 February 1671/72 Old Style.