What is the "universe?"
It begins in 1929...
In 1929, Edwin Hubble [1889-1953] had been making astronomical observations with the 100in Hooker telescope at the Mt. Wilson observatory for nearly 10yrs
He had been studying “spiral nebulae” (as they were then believed to be) and had discovered “Cepheid variables” [stars with regular brightness-intervals] could be used to determine the distance to a light-source
Using this discovery he found that the “Andromeda nebula” was some 900K light years distant from earth
This put it light years further away than the farthest stars in our galaxy [the “Milky Way:” so-called because of the band of starlight it produces viewing from earth]
Hubble had discovered other galaxies exist in what was soon to be called “the universe”
A new period of astronomy began with the construction of ever-larger telescopes to detect the light emitted from stars now known to be millions of light years outside our galaxy
[As a boy I watched the shipment of the Palomar telescope-mirror from Pasadena CA to the mountains E of San Diego; it would be the world’s largest for some decades]
In 1964, Bell Laboratories in New Jersey operated the Holmdel-Horn “radio-telescope;” astronomers Arno Penzies & Robert Wilson had for some time been puzzled by the “background noise” that persisted while the radio-astronomy unit was in operation
Eventually they realized they hearing the “background noise” from the origin of the universe: called technically the “cosmic microwave background” [CMB: the photo above is the image of the sounds still emanating from the “big bang”]
Over this period, therefore, the “universe came into being” (in the sense that humans first realized that all existing matter is accelerating away from an original point…)
“Astronomy” is Greek for “naming stars;” only in the 20th c. (on the calendar-system invented in Europe in the 6th c. CE) were humans required to begin considering the earth as merely a small planet orbiting a Type-C star in a single galaxy
That is where we are now, and presumably always will be (providing we cease the destruction of the thin envelope of atmosphere on which our existence depends…)