"So why don't you think there is a boundary (edge) and a beyond for the universe?"
I will now do my best to answer your question in a polite and constructive manner. By that, I am conveying that it will be polite, and I will try to answer it in an understandable way.
As you will see, there are many views in the article quoted.
All about Space, Issue 104. There are unknowable things in the Universe and this may be one of them. My personal view is that there are problems of semantics. Our vocabularies (I include all humanity's) are incapable of describing certain issues. This may be one of them and, I believe this was the root of our communication difficulties. I would point you here to the science of General Semantics as introduced in
Science and Sanity by Alfred Korzybski.
You mention straight lines and meeting yourself etcetera. I will not go back to my view that if you propose impossible starting conditions, such as being at the edge of the Universe (Who knows where that is, etc,) you will not get productive answers,. Take that off the table.
Let us assume you are at Quito. Your 'straight line' is around the Equator, governed by gravity. If you take the flatlander analogy, this means that you do return to your starting position - Quito. If you apply that to the Universe (or
our universe, if you prefer - that is irrelevant in this example), and if the Universe is circular then you will return to the same place Not mentioning that there is no way whatsoever to know where that place is / was. Meeting yourself in Quito is not actually possible, but you could have left a marker saying "I was here". So your argument stands, there. Going around 'our universe' there is no way to identify that location.
Let me go back to the Quito analogy. If we were flatlanders, and all this stuff is widely discussed and available, we would behave and return exactly as you described.
Now, to the flatlander, there is no 3rd space dimension. He (or she, hereinafter assumed) has no appreciation of what we call our 3rd space dimension. There is
no edge to his universe.
Whilst not engaging in the flatlander assumption, I quote from the article referenced above:
QUOTE
There is no current reason to suspect that the Universe ends with our cosmic horizon, just as we know that the Earth doesn’t end just because the rest of the planet is hidden from view by its curvature.
QUOTE
If we return to our flatlander analogy, we can say that the flatlander will know of the existence of the surface of the sphere, which will be the
whole discoverable universe to him (granted it continues in a 3rd time dimension).
We know that the flatlander has no spatial sense to discover a non-existant (to him) 3rd space dimension.
He may face the same dilemma that we face, namely that if his universe is expanding (as ours may be) then distances on the surface will increase, measured by his local measuring sticks.
INTERPOLATION begins
We do not know why this happens. If everything were to expand, including our rulers, then our measurements of the Universe would show no expansion. If we measure a table in our living room and it measures 4 feet and it expands x 2, our rulers tell us 8 feet. If the ruler itself also expanded x 2, then the table would measure 4 new (or x 2 expanded) feet.
INTERPOLATION ends
Now, don’t forget that the flatlander cannot perceive a dimension perpendicular to his sphere or, more correctly, to the surface of his sphere.
He cannot perceive inside or outside that surface. (Leaving aside his time dimension). If we are super beings with that extra perception ,
we can say that his universe is expanding - the radius of his universe is increasing as well as the area of his universe. His universe has no edge.
He is totally unware of expansion perpendicular to his surface.
His universe is limited to the surface of a sphere which has no edge.
If you,
as a superbeing, can postulate that his universe
as seen by us has an edge which
is the two-dimensional surface of his world. I would not consider this assertion to be safe – others might. Please see Korzybski below.
Coming back to the flatlander, whilst we can postulate ‘an outside’ which allows expansion along the radius as well as expansion of the area (being his entire universe)
he does not have the sensory equipment or understanding to operate mentally.
If you now postulate that we are living in a closed universe, we have directly analogous limitations. There may be expansion of the Universe in some postulated dimension that we do not have the sensory equipment to understand, and some super being with extra senses may say that there is ‘an outside’ into which our Universe is impinging
but these observations are not open to us and we cannot perceive an edge or an outside. It is meaningless to contrive some combination of words which endeavours to circumvent this.
It is a shame that General Semantics is not a compulsory subject in schools. Its catch phrase is
The map not the territory. In this case it would be immediately visible to the GS student that to use words to describe an imaginary event is futile. The map (the words, the verbal description) IS not the territory (the reality). You cannot create a reality just by wrapping words around a verbal assertion.
QUESTION
"So why don't you think there is a boundary (edge) and a beyond for the universe?"
RESPONSE
Such a thing is unknowable to any being with the limitations imposed upon us by our physical makeup.
Any such enquiry is exacerbated by introducing assumptions of conditions unattainable in reality e.g., reaching an assumed edge of the Universe and possibly returning to it.
Mr. Franks.
I hope you will agree that I have taken a lot of time writing the above, and that it contains no criticism (explicit or implicit) of your good self. My motivation has been to explain and reply to your final stated question. I hope that I have succeeded in this and that you may have benefited from my efforts. Nevertheless, if I have not achieved that result, then I am sorry for my failure and I am willing to do my best to answer any further points you may wish to raise. The offer is of course open to any other members who may wish to join in.
With sincere best wishes
Cat