"In physics, spacetime is any mathematical model that combines space and time into a single interwoven continuum. Until the turn of the 20th century, the assumption had been that the 3D geometry of the universe (its description in terms of locations, shapes, distances, and directions) was distinct from time (the measurement of when events occur within the universe). However, Albert Einstein's 1905 special theory of relativity postulated that the speed of light through empty space has one definite value - a constant - that is independent of the motion of the light source. Einstein's equations precisely described important consequences of this fact: both the shape of space and the measurement of time simultaneously change for observers who have different relative velocities, which is to say, for observers who have different "inertial frames of reference."
https://en.wikipedia.org/wiki/Spacetime
Then, since theoreticians find the consequence - Einstein's spacetime - wrong, and want to "split" it, "retire" it, etc., they will have to admit that the underlying premise, Einstein's 1905 constant-speed-of-light postulate, is false (logic forbids the combination "wrong consequence, true premise"):
https://www.edge.org/response-detail/26563
Nobel Laureate David Gross observed, "Everyone in string theory is convinced...that spacetime is doomed. But we don't know what it's replaced by."
https://www.youtube.com/watch?v=U47kyV4TMnE
Nima Arkani-Hamed (06:09): "Almost all of us believe that space-time doesn't really exist, space-time is doomed and has to be replaced by some more primitive building blocks."
https://www.scientificamerican.com/a...me-from-space/
"Splitting Time from Space - New Quantum Theory Topples Einstein's Spacetime. Buzz about a quantum gravity theory that sends space and time back to their Newtonian roots. Was Newton right and Einstein wrong? It seems that unzipping the fabric of spacetime and harking back to 19th-century notions of time could lead to a theory of quantum gravity. [...] But now Petr Hořava, a physicist at the University of California, Berkeley, thinks he understands the problem. It's all, he says, a matter of time. More specifically, the problem is the way that time is tied up with space in Einstein's theory of gravity: general relativity. Einstein famously overturned the Newtonian notion that time is absolute - steadily ticking away in the background.. Instead he argued that time is another dimension, woven together with space to form a malleable fabric that is distorted by matter. The snag is that in quantum mechanics, time retains its Newtonian aloofness, providing the stage against which matter dances but never being affected by its presence. These two conceptions of time don't gel."
https://edge.org/response-detail/25477
What scientific idea is ready for retirement? Steve Giddings: "Spacetime. Physics has always been regarded as playing out on an underlying stage of space and time. Special relativity joined these into spacetime... [...] The apparent need to retire classical spacetime as a fundamental concept is profound..."
http://www.newscientist.com/article/...spacetime.html
"Rethinking Einstein: The end of space-time. It was a speech that changed the way we think of space and time. The year was 1908, and the German mathematician Hermann Minkowski had been trying to make sense of Albert Einstein's hot new idea - what we now know as special relativity - describing how things shrink as they move faster and time becomes distorted. "Henceforth space by itself and time by itself are doomed to fade into the mere shadows," Minkowski proclaimed, "and only a union of the two will preserve an independent reality." And so space-time - the malleable fabric whose geometry can be changed by the gravity of stars, planets and matter - was born. It is a concept that has served us well, but if physicist Petr Horava is right, it may be no more than a mirage. [...] For decades now, physicists have been stymied in their efforts to reconcile Einstein's general theory of relativity, which describes gravity, and quantum mechanics, which describes particles and forces (except gravity) on the smallest scales. The stumbling block lies with their conflicting views of space and time. As seen by quantum theory, space and time are a static backdrop against which particles move. In Einstein's theories, by contrast, not only are space and time inextricably linked, but the resulting space-time is moulded by the bodies within it. [....] Something has to give in this tussle between general relativity and quantum mechanics, and the smart money says that it's relativity that will be the loser."
https://www.amazon.ca/Faster-Than-Sp.../dp/0738205257
Joao Magueijo, Faster Than the Speed of Light, p. 250: "Lee [Smolin] and I discussed these paradoxes at great length for many months, starting in January 2001. We would meet in cafés in South Kensington or Holland Park to mull over the problem. THE ROOT OF ALL THE EVIL WAS CLEARLY SPECIAL RELATIVITY. All these paradoxes resulted from well known effects such as length contraction, time dilation, or E=mc^2, all basic predictions of special relativity. And all denied the possibility of establishing a well-defined border, common to all observers, capable of containing new quantum gravitational effects."
https://www.newscientist.com/article...wards-in-time/
"[George] Ellis is up against one of the most successful theories in physics: special relativity. It revealed that there's no such thing as objective simultaneity. [...] Rescuing an objective "now" is a daunting task."
http://www.guardian.co.uk/books/2013...reality-review
"And by making the clock's tick relative - what happens simultaneously for one observer might seem sequential to another - Einstein's theory of special relativity not only destroyed any notion of absolute time but made time equivalent to a dimension in space: the future is already out there waiting for us; we just can't see it until we get there. This view is a logical and metaphysical dead end, says Smolin."
https://www.perimeterinstitute.ca/re...essons-quantum
Perimeter Institute: "Quantum mechanics has one thing, time, which is absolute. But general relativity tells us that space and time are both dynamical so there is a big contradiction there. So the question is, can quantum gravity be formulated in a context where quantum mechanics still has absolute time?"
https://www.amazon.ca/Time-Reborn-Cr.../dp/0544245598
"Was Einstein wrong? At least in his understanding of time, Smolin argues, the great theorist of relativity was dead wrong. What is worse, by firmly enshrining his error in scientific orthodoxy, Einstein trapped his successors in insoluble dilemmas..."
Pentcho Valev