Modernity was usually felt to be the first page in a book not yet fully written , the gateway to "The World of Tomorrow".
But it could be argued it better represents the very last page of a very, very long book more than 3000 years old.
Definition time: I consider Modernity to be a mode of thought, not a time period.
Yes, it predominated in the period 1880-1980, but it had strength before (1840-1880) and after (1980 - 2020 ??).
It shared the hundred years between 1880-1980 with Pre-Modernity and Post-Modernity but towered well over them in its undisputed hegemony.
It held, along with the ancient Greek scientists (& Newton) the idea that both macro and micro reality consisted of a solid, resilient material that acted and felt rather like metal or rock or wood or a living body.
In objects like the human body, it consisted of a constantly and smoothly curving unbroken structure - made up (perhaps) of tiny granular objects ( atoms) that were as solid and as resilient as the entire body itself and were packed so closely together as to appear and act as if they were all one big solid object.
Hardened cement, solid but yet visibly made of tiny grains all stuck together is as good a visual representative of this vision of ultimate reality as any we commonly see.
There was no "inside detailing" to these atoms and their outer edges were clearcut and definite.
Simple and unchanging (by no coincidence,rather like the definition Modernists held of bacteria), these micro objects were complied into sub-assemblies which became assemblies and then systems - from atoms to molecules to all the way up to human beings
Macro Reality - when they thought it was working - was a vast Lego or Meccano Set, an additive form of complexity, in strict hierarchical order.
When it wasn't working, Macro Reality was disordered and "dirt" resulted : atoms out of place.
If you were born in 1880 and completed your education before Queen Victoria died you would only have read, later in life, in the newspapers about changes proposed by some scientists to this way of looking at the world but you won't have and couldn't have accepted those changes, deep down in your bones.
You were simply too old but unfortunately, not quite old enough:
you would have been 53 when Hitler came to power, 60 in 1940, 65 in 1945.
In whatever you did (as long as you were a professional class male) you would have been at the top of your profession (the boss) and would have run the world, along with other men roughly your same age and with roughly the same kind of scientific education, throughout World War Two and the ten year lead-up to it.
Quantum science was happening during the Modern Era but was not a part of it, in its day to day workings.
Newton still ruled all through the Modern Era.
Don't believe me?
Millions of parents and their kids believed in this view of ultimate Reality:
check out when the sales of Meccano sets,Erector kits,Tinkertoy and their ilk first became popular and when those sales suddenly died, and you can mark the timeline of Modernity at its peak and at its decline...