Physicist might well say... we infer size of original unit that expanded by projecting 'backwards' in time measured changes in universe and perhaps even similarities between current observations and "Big Bang" ..CERN..
Yet none would deny the possibility of multiple "Big Bangs" both in space and time... but how to think of such things..?? Must there always be contact between"Big Bangs" ? through Mega universe?
In Newtonian space no problem.. no contact needed...
Perhaps we are on road to Multiverse thinking??
This forum is brief followup to Newtonian Space number 1
The " Big Bang"
Approached from Newtonian space there are co-ordinates that locate 'Big Bang' and even determine its size..
But from Einsteinian view point there is no "O" Observer who can determine the position of 'Big Bang' and if in theory there existed such an observer there would necessarilly be a physical connection between that observor and the "Big Bang'. This would mean a mega universe larger than that contained in "Big Bang"
But when we visualize the "Big Bang" we seem driven to see it in Newtonian terms...
Otherwise we view "Big Bang" as minute observing constituent of incredibly small original object that exploded..
Naturally it is just to observe after the fact but how to visualize during the event? But as we transport our selves into the past the Newtonian frame of reference seems to be neede to visualize...
..or assume some wrap around reality for which no evidence of its existence appears to exist.
The forum is done with intent of exploring in simple clear terms what is meant when we contemplate 'Big Bang" ..there will be a 3rd forum only if some not present insight develops...