Turned around, the notion of relativity is stated more complex, as temporal 'now' is stretched or contracted based upon the amount of space being traversed in a given temporal frame ... clocks run slower (from an outside positioned observer) the faster they traverse spatial expanse, time passes more slowly for particles in greater gravitational fields, such as in the neighborhood of black holes (or a meson(?) entering earth's gravitational field).
The only point of perspective for which there could be a 'universal now' must be 'outside' of the spacetime bubble that is our perceived universe. But that assertion in our current science takes as axiomatic that linear temporal reality is all the temporal dimensional reality that there is.
You can show for your own satisfaction that such is not the case by merely remembering a very vivid occurrence in which you participated or which you observed in person. The remembering is not the point of the lesson, the ability to contemplate the memory is the essential proof that there is more than linear temporal reality.
Your mind/brain association accomplishes this even when you sleep, if you dream, even though what is contemplated is not an actual occurrence which you witnessed in person!
Does dreaming something make it a reality in some where/when? No, and that is the essential self-evident aspect that you are actually touching a temporal reality which is not linear, not founded in/relying upon a previous moment of reality. It is planar in nature, not linear. That is what imagination is. That is also the fraemwork of faith. As a writer of fiction works, I do this 'imagining' a lot. But as a person of faith, I can differentiate faith from imagination because faith has effects upon living whereas imagination effects life only if someone adjusts their behavior in irrational ways to fit their imagined reality ... faith effects life in the flow of rational reality, whereas mental derangement expressed in magic thinking results in negative effects in the flow of rational reality.
For some construct of non-linear time, your mind/brain connection accomplishes an alternate temporal frame of reference which is not to be taken as a real where/when but which has a framework which is not temporally linear in nature.
I would submit that such a self-evident proof opens the door for God the Creator to BE outside of our spacetime universe as we conceive of it. Ancillary to that realization is the astonishing notion that there is far more to the universe than is perceived based upon our reliance upon linear temporal framework.
In my earlier post, I mentioned multiple time dimension theories. Some like Vafa's f-theory call for an additional compactified (Kaluza/Klein) dimension of time and some like Wesson's 5D/2T theory call for additional expanded temporal or time-like dimension.
In the expanded theories (though arguably also in the compactified) time is not a line but a plane or volumetric.
In such theories past, present, future actually do exist concurrently and that could be seen as a universal 'now' - though any observer "in" space/time would still not be able to see "all that there is" all at once because he would still be subject to relativity (inertial frames, etc.) He might however be able to time-travel.
So whether one dimension of time or two or three - the total numbers and types (space/time, compactified/expended) knowable only to God - the bottom line is that only God can see "all that there is" all at once.