Universe and universes - some conformity please.


"Science begets knowledge, opinion ignorance.
Many of us are familiar on when it is appropriate to use a capital U or small u. Korzybski (Science and Sanity) clearly teaches that "the map is not the territory". Some find it easier to understand "the menu is not the meal". The words are not the reality they may purport to describe. :)

According to the "Oxford Dictionary of Astronomy" 2nd Edition Revised 2012:
Universe. Everything that exists, including including space, time, and matter. . . . . . . Cosmologists distinguish between the Universe, with a capital 'U', meaning the cosmos, and all its contents, and universe(s) with a small 'u', which is usually a mathematical model derived from some physical theory. . . . . . .

I would prefer to give the following example of a universe. An observable universe (as per this example) is that part of the Universe observable by an individual (or other intelligent entity). As we know, limitations on how much of the Universe can be observed by any observer (from the relevant locality) vary with location. Limitations are also imposed or assisted by our means of observation. For example, telescopes allow observation of more distant objects. Means of observation are also permitting changes in observable universes. For example, visible wavelengths (limited by our eyesight) are being extended to include X-rays, IR, UV and so on. Science is allowing observable wavelengths to be extended by the ability to receive information beyond the visible by providing the necessary equipment.

It is important to understand that our perceptions of the Universe, our views of observable universes, will continue to expand as science provides us with improved equipment.

The early years of the new millenium promise to be a period of intense excitement, with experiments set to probe the microwave background in finer detail, and powerful optical telescopes mapping the distribution of galaxies out to greater distances. Who can say what theoretical ideas will be advanced in the light of new observations.
The icon critical dictionary of The New Cosmology, Ed. Peter Coles, Icon Books 1998.

I have, myself, been guilty of lapsing in to this terminological inexactitude, but will do my best in future to comply, and hope that we might all try to set an example, for science's sake. Failure to do so can perpetuate unnecessary misunderstandings. It is clearly not good to see questions posted asking "if the universe is all there is, how can there be more than one?" And does this "The concept of a multiverse suggests that our universe is just one of many universes, each with its own physical laws. These universes could exist in a vast cosmic landscape, beyond our observational reach" actually mean anything in reality? Observable universes - yes - but as for the rest???

There is an excellent entry in Wikipedia under observable universe, small parts of which read as follows:

The observable universe is a ball-shaped region of the universe comprising all matter that can be observed from Earth or its space-based telescopes and exploratory probes at the present time; the electromagnetic radiation from these objects has had time to reach the Solar System and Earth since the beginning of the cosmological expansion
Cat comment: Of course, there is no reason why the above comment should be restricted to the immediate Earth environs.
Are parallel universes actually real?

Any time a quantum (or subatomic) process occurs anywhere in the universe, this wavefunction splits in two, meaning parallel universes are constantly created. But these interpretations have never been shown to be correct, and they have some major weaknesses that prevent them from being widely accepted.2 Jan 2023

Cat :)
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"Science begets knowledge, opinion ignorance.
It is imteresting to follow some consequences of what we have seen referred to as 'multiverse.
I would now understand parallel universe' as nothing more or less than one of a collection of different observable universes. The sum of parallel universes now becomes the Universe itself, since this is the Universe we already know as the sum total of all observable universes.

In fact, we must make a further allowance for the fact some parts of the Universe may not be 'seen' by any observers. Thus, the Universe would still be the total of all there is - whether this is observed by other observers or not.

We can still make unwarranted assumptions about this - such as different laws may apply in those parts of the Universe not subject to known observation. But this is just the same unwarranted assumption referred to above - and equally without meaning.

IF it is to be forever unobservable (due to the speed of light and the expansion of the Universe) then it has no meaning until such observations might become possible - not possible in our present state of knowledge.

Similarly, multiverse would be simply the collection of 'observable' universes - whether or not there were 'observers' at all locations whence observations might be made. Another possible definition might include all possible 'wavelengths' including those not yet discovered These altered definitions would need attention by the appropriate authority, replacing what some might consider unwarranted assumptions or 'guesses'.

Just compare the Oxford Dictionary (as above) entry.
"Multiverse. A collection of universes which some speculative theories suggest could exist.
If true, our own Universe would be only one member of the larger multiverse.
" It was suggested above that our Universe is the sum total of observable universes. In the following, it is clear that the Universe and its component universes would exhibit the same fundamental constants, leaving nothing to explain. Life appeared under those identical constants Occam's Razor applies."

Cat :)
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