Some people oppose it because they do not like the physics or do not understand it. I would estimate that most “opponents” of relativity theory fall into this category. These people are either cranks or people that do not understand the theory. In both cases, they are generally not all that interesting.
But, then there is the second category. These people understand special relativity but disagree with many of the interpretations of reality offered by the theory.
Let me explain.
It is evident that the mathematics of relativity, both special and general relativity are beyond any serious doubt. They have been verified time and time again. But, what does the math imply?
Does it imply that time is a dimension? No, dimensionality is a purely mathematical concept. Not an aspect of physical reality.
Does it imply that time dilates? No. Time is not an aspect of reality or something that dilates. It is a purely abstract, relational concept used to measure motion or change.
Does it imply that space distorts? No. Space is also an abstract, relational concept, not a physical aspect of reality.
And so forth.
But, some of you will complain, we have proven that time dilates and space bends!
Have you though? You have shown that time-measuring devices act differently at high speeds. Which is very interesting indeed. But that does not show that time, which is an abstract concept, is affected by high speeds.
You say that you have shown that gravity seems to cause space to bend. Or, at least, that is how you interpret what you observe. But, if space is a relational concept, how can that be?
Perhaps what you observe does not mean what you think it means. Perhaps it implies very different things and we do not understand its implications as well as we think. And we are therefore ignorant of some very important facts…
Worth thinking about, no?
It cannot. This should be extremely obvious.
When we say “nothing” we simply mean that within a given area, there are no things, at least no things of interest, within that area.
In other words, it simply means that there are no entities there. At least not the kinds of entities we are interested in.
But, an absolute nothingness would mean that there would be no entities of any kind. Nothing would exist, at least within this area of alleged nothingness.
That means that there is no “it” to produce anything. To “produce something means that something exists so that it can take the actions required to produce this something. But, if there is no “it”, then there is nothing to produce anything.
So, what the question is actually asking is: “If there is nothing to act, how can the thing that does not exist, produce a something?”. Which makes no sense at all, it is an obvious contradiction.
The question supposes action devoid of entities, as though action can exist without entities to act! As though action can exist devoid of things that act. Which is again an obvious contradiction.
Actions are the actions of entities. Not of the absence of entities.
What do you mean by “the universe?”
If you mean, “all the things we observe” now, I do not think that all of them will exist forever.
If you mean “Everything that exists, at least within the area of space we can communicate with”, then I think the answer is basically the same.
But, properly speaking, the “universe” refers to everything that exists. This would include every “universe” in the sense physicists sometimes mean when they refer to “different” universes.
By “universe” they sometimes mean areas of space which can be observed or interacted with. Those parts of existence are separated out into different universes. Max Tegmark and other cosmologists like to do this.