Think “Sir Isaac Newton” and close your eyes. What is the first thing that springs to mind? By any chance does it have anything to do with a falling apple and the discovery of gravity? Actually, that story is a delightful urban myth, with Newton’s deductions based on logic rather than a ‘Eureka’ or ‘Ouch’ moment. It’s much more likely that Newton realized the moon would fly off into space unless something attracted it back to the Earth. Likewise, he argued a force must act on a stationary object (such as an apple) to make it move from rest to fall to the ground. (1)
But our story concerns how Newton’s dog, a Pomeranian called Diamond, almost changed the course of history by having the zoomies.
Newton was working by candlelight in his study. He was alerted by a volley of barking from his Pomeranian dog, Diamond, to a visitor’s arrival. Leaving his manuscript open on the desk, Newton left the study to answer the door. However, Diamond was so excited by the stranger’s arrival she continued to dash up and down the hall, barking so loudly that conversation was impossible. But Newton’s chastisement only intensified the dog’s frenzy, so he banished Diamond to the study and closed the door. (3)
However, the over-excited dog continued to charge around the room, zooming this way and that, colliding with the table leg. The inevitable happened, and the candlestick fell over, right onto the manuscript. The flame licked at the paper and it ignited. Whatever instinct alerted Newton to the peril, it was too late and by the time he got to the study 20 years of work went up in smoke.
With no cloud storage or memory stick, Newton’s hand-written manuscript expounding his theories on gravity was the only copy in existence. Anyone who has ever had a hard drive crash, with no backup copy of their files (as happened to me) will know the sickening, sinking sensation at the realization the accounts/drafts/notes are gone forever. Interestingly, there is an account of Newton’s reaction (perhaps from the visitor?) which was to say: “Oh Diamond, Diamond, you little know what mischief you have caused me.” Very restrained!
As you might expect, the loss of the manuscript was a difficult blow to recover from. Reportedly it drove Newton into a deep depression which saw him withdraw to bed for several weeks. However, the scientist appears not to have held a grudge against Diamond, who is recorded as staying beside Newton on the bed.
How did the story end? Well, Newton did eventually rally and recover sufficiently to start again. He reconstructed the scientific paper, which was published in 1687 as Philosphiae Naturalis, Principia Mathematica. Subsequently, this discourse on Newton’s theories of gravity and the laws of motion has been described as “one of the most important works in the history of science.”
Or did it? There are inconsistencies about what documents were actually destroyed in the fire. In 2020 a rare Newtonian document that was burnt around the edges was sold by Sotheby’s for £380,000.  This document was part of Newton’s lesser-known research into the knowledge of the ancients and an obsession with discovering the Philosopher’s Stone (which could turn base metals into gold.) So could it be that what actually happened was a little less dramatic than it first appears?
An interesting footnote to all this is that in later life Newton became increasingly prone to debilitating bouts of depression. There is a theory, that the mercury he used in scientific experiments had accumulated in his system and the depression was a side effect of this. This was backed up, in 1979, by an analysis of a sample of Newton’s hair which confirmed it contained abnormally high levels. Symptoms such as depression, mood instability, memory problems, and anxiety are indeed recognized symptoms of mercury poisoning 
Another footnote is that Diamond the Pomeranian would have looked quite different from the breed we recognize today. Over the centuries all dog breeds have changed considerably (See: Pondering Pug Noses) and the Pom is no exception. Whereas the modern dog is pint-sized, their ancestors were much larger and more akin to a larger Spitz-type animal.
(2) Food and Drug Administration Mercury Poisoning Linked to Skin Products
(3) The History of the World in Fifty Dogs. Mackenzi Lee. Abrams Image.
(4) The Guardian: Isaac Newton Notes Almost Destroyed by Fire Sell for £380,000