Why more physicists are beginning to think that space and time are “illusions”

Last December, the Nobel Prize in Physics was awarded for the experimental confirmation of a quantum phenomenon known for more than 80 years: entanglement. As conceived by Albert Einstein and his collaborators in 1935, quantum objects can be mysteriously related even if they are separated by great distances. But as bizarre as the phenomenon sounds, why does this ancient idea still deserve the most prestigious prize in physics?

Coincidentally, just a few weeks before the recent Nobel laureates were to be honored in Stockholm, a different team of distinguished scientists from Harvard, MIT, Caltech, Fermilab and Google reported that they had run a process on Google’s quantum computer that could explain It’s a wormhole. . Wormholes are tunnels through the universe that can act as a shortcut through space and time and are loved by sci-fi fans, and although the tunnel realized in this latest experiment only exists in a 2D universe game, it could be a breakthrough for future research at the cutting edge of physics. .

But why is entanglement related to space and time? And how might it be important for future physics breakthroughs? The concept of entanglement, properly understood, means that the universe is “monometric,” as philosophers call it, and that everything in the universe, on a fundamental level, is part of one unified whole. It is a defining property of quantum mechanics that its fundamental reality is described in wave terms, and the monadic universe requires a global function. Decades ago, researchers such as Hugh Everett and Dieter Zeh showed how the reality of our daily lives could emerge from such a comprehensive quantum-mechanical description. But only now are researchers such as Leonard Susskind or Sean Carroll developing ideas about how this hidden quantum reality might explain not only matter but also the very fabric of space and time.

Entanglement is much more than just another weird quantum phenomenon. It is the acting principle behind both why quantum mechanics merges the world into one and why we experience this fundamental unity as many separate things. At the same time, entanglement is why we seem to be living in classic reality. It is – in the literal sense of the word – the glue and creator of worlds. Entanglement applies to objects that are made up of two or more components and describes what happens when the quantum principle that “everything that can really happen” is applied to these component objects. Accordingly, the state of entanglement is the superposition of all possible combinations in which the components of the component object can be to produce the same overall result. Again, it is the wavy nature of the quantum field that could help explain how entanglement actually works.

Imagine a perfectly calm sea of ​​glass on a stormy day. Now ask yourself, how can such a level be produced by superimposing two individual wave patterns? One possibility is that the superposition of two perfectly flat surfaces again leads to a perfectly flat result. But another possibility that a flat surface might result is if two identical wave patterns are superimposed by a half cycle of oscillation on each other, such that the wave crests of one pattern eliminate the wave troughs of the other and vice versa. If we just observed the circumference of the vitreous, since it is the result of two bulges together, there would be no way for us to tell the patterns of the individual bulges. What seems utterly ordinary when we speak of waves has even more bizarre consequences when applied to competing realities. If your neighbor tells you she has two cats, one alive and the other dead, that means either the first or second cat is dead and the remaining cat, respectively, is alive – that would be a strange and spooky way of describing pets, and you might not know which one of them is the lucky one, but you’ll get On the drift of the neighbor. Not so in the quantum realm. In quantum mechanics, the same statement indicates that the two cats merged into a superposition of states, including the first cat is alive and the second is dead and the first cat is dead while the other is living, but also possibilities where both cats are half alive and half dead, or that the first cat is A third of them are alive, while the second cats add up to two-thirds of the life lost. In a quantitative pair of cats, the fates and circumstances of the individual animals vanish completely in the case of the whole. Likewise, in the quantum universe, there are no individual objects. Everything that exists is combined into a single “one”.

Quantum entanglement reveals a whole new, vast area to explore. It defines a new foundation for science and turns our search for a theory of everything on its head – to build on quantum cosmology rather than particle physics or string theory. But how realistic is it for physicists to take such an approach? Surprisingly, it’s not just realistic – they actually do. Researchers at the forefront of quantum gravity are beginning to rethink space-time as a consequence of entanglement. An increasing number of scientists have come to base their research on the inseparability of the universe. Hopes are high that by taking this approach they may finally come to an understanding of space and time, in the depths of its foundation, truly.

Whether space is held together by entanglement, physics is described by abstract objects beyond space and time or the space of possibilities represented by the universal Everett wave function, or everything in the universe is reduced to a single quantum object — all these ideas share a distinctive flavor of monism. At present, it is difficult to judge which of these ideas will inform the future of physics and which will eventually die out. What’s interesting is that while the ideas were originally developed in the context of string theory, they seem to have outgrown string theory, and strings no longer play a role in the latest research. The common thread now seems to be that space and time are not essential anymore. Contemporary physics does not begin with space and time to continue things laid out in this pre-existing background. Instead, space and time see themselves as products of a more fundamental projector reality. Nathan Cyberg, a pioneer of string theorists at Princeton’s Institute for Advanced Study, isn’t alone in his feeling when he says, “I’m almost certain that space and time are illusions. These are rudimentary concepts that are going to be replaced by something more complex.” Moreover, in most scenarios that propose emerging space times, entanglement plays the primary role. As philosopher of science Rasmus Yaxland points out, this ultimately means that there are no individual objects in the universe anymore; That everything is connected to everything else: “To embrace entanglement as the world makes relation comes at the price of giving up the possibility of separation. But perhaps those who are willing to take that step should look to entanglement for the basic relation by which it will shape this world (and perhaps all the other world) potential).” Thus, when space and time disappear, a unified one emerges.

On the contrary, from the perspective of quantum monism, such mind-boggling consequences of quantum gravity are not far off. Already in Einstein’s general theory of relativity, space is no longer a stationary phase. Rather, it is the source of the masses of matter and its energy. Much like the view of German philosopher Gottfried W. Leibniz, it describes the relative order of things. If now, according to the quantitative unit, there is only one thing left, there is nothing left to arrange or arrange, and in the end there is no longer any need for the concept of space on this fundamental level of description. He is “the One,” a single quantum universe giving rise to space, time, and matter.

“GR = QM,” Leonard Susskind boldly claimed in an open letter to researchers in quantum information science: General relativity is nothing but quantum mechanics — a hundred-year-old theory that has been applied with great success to all kinds of things but never really was. Totally understandable. As Sean Carroll points out, “Gravity was probably wrong to quantify, and space-time has been lurking in quantum mechanics all along.” For the future, “instead of quantifying gravity, maybe we should try quantum mechanics. Or, more accurately but less excitingly, “find gravity inside quantum mechanics,” Carroll suggests on his blog. Quantum seriously from the start, if understood as a theory that does not occur in space and time but within a more fundamental display device reality, many dead ends in the exploration of quantum gravity could have been avoided.If we had accepted the monistic effects of quantum mechanics – The legacy of a three-thousand-year-old philosophy embraced in antiquity, persecuted in the Middle Ages, revived in the Renaissance, tinkered with in Romanticism—early Everett and Zee would have referred to them rather than stick to the interpretation of influential quantum pioneer Niels Bohr who cut short his mechanics. Quantum into a tool, we’ll be on our way to demystifying the very foundations of reality.

Adapted from One: how an ancient idea holds the future of physics by Heinrich Bass. Copyright © 2023. Available from Basic Books, an imprint of Hachette Book Group, Inc. All rights reserved.