spooky action: we can no longer take locality for granted -- 7/08/20
Today's selection -- from Spooky Action at a Distance by George Musser. Jenann Ismael on the idea that physical locality may not be the deepest level of reality. "One of the strangest aspects of quantum physics is entanglement: If you observe a particle in one place, another particle -- even one light-years away -- will instantly change its properties, as if the two are connected by a mysterious communication channel." The idea of quantum entanglement -- the ability of separated objects to share a condition or state -- was once dismissed by Albert Einstein as "spooky action at a distance." Over the past few decades, however, physicists have demonstrated the reality of this kind of "spooky action" over ever greater distances:
"Maybe particles in an entanglement experiment or galaxies on the farthest reaches of known space act strangely because they're really projections -- or, in some other way, secondary creations -- of objects existing in a very different realm. 'In the kaleidoscope case, we know what we have to do: we have to see the whole system; we have to see how the image space is created,' Ismael says. 'How do we construct an analogue of that for quantum effects? That means seeing space as we know it -- everyday space in which we view measurement events located at different parts of space -- as an emergent structure. Maybe when we're looking at two parts, we're seeing the same event. We're interacting with the same bit of reality from different parts of space.'
"She and others question the assumption, made by nearly every physicist and philosopher from Democritus onward, that space is the deepest level of physical reality. Just as the script of a play describes what actors do on stage, but presupposes the stage, the laws of physics have traditionally taken the existence of space as a given. Today we know that the universe has more to it than things situated within space. Nonlocal phenomena leap out of space; they have no place in its confines. They hint at a level of reality deeper than space, where the concept of distance ceases to apply, where things that appear to lie far apart are actually nearby or perhaps are the same thing manifested in more than one place, like multiple images of a single shard of kaleidoscopic glass. When we think in terms of such a level, the connections between subatomic particles across a lab bench, between the inside and the outside of a black hole, and between opposite sides of the universe don't seem so spooky anymore. Michael Heller, a physicist, philosopher, and priest at the Pontifical Academy of Theology in Krakow, Poland, says: 'If you agree that the fundamental level of physics is not local, everything is natural, because these two particles which are far apart from each other explore the same fundamental nonlocal level. For them, time and space don't matter.' Only when you try to visualize these phenomena in terms of space -- which is forgivable, because it's hard for us to think in any other way -- do they defy comprehension.
"The idea of a deeper level seems natural because, after all, it is what physicists have always sought. Whenever they can't fathom some aspect of our world, they assume they must not yet have gotten to the bottom of it all. They zoom in and look for the building blocks. How mysterious it is, for example, that liquid water can boil to steam or freeze to ice. Yet these transformations make perfect sense if liquid, vapor, and solid are not elemental substances, but distinct forms of a single fundamental substance. Aristotle took the states of water to be diverse incarnations of so-called prime matter, and the atomists -- presciently -- thought they were rearrangements of atoms into tighter or looser structures. En masse, the building blocks of matter acquire properties that, individually, they lack. A molecule of water is not wet, and an atom of carbon is not alive, but lots of them, coming together in the right way, can be. Likewise, space might be built of pieces that are not themselves spatial. Those pieces might also be disassembled and reassembled into nonspatial structures such as the ones that black holes and the big bang are hinting at. 'Spacetime can't be fundamental,' says the theorist Nima Arkani-Hamed. 'It has to come out of something more basic.'
"This thinking completely inverts physics. Nonlocality is no longer the mystery; it's the way things really are, and locality becomes the puzzle. When we can no longer take space for granted, we have to explain what it is and how it arises, either on its own or in union with time. Clearly, constructing space isn't going to be as straightforward as melding molecules into a fluid. What could its building blocks possibly be? Normally we assume that building blocks must be smaller than the things you build out of them. A friend of mine and his daughter once erected a detailed model of the Eiffel Tower out of popsicle sticks; they hardly needed to explain that the sticks were smaller than the tower. When it comes to space, though, there can be no 'smaller,' because size itself is a spatial concept. The building blocks cannot presume space if they are to explain it. They must have neither size nor location; they are everywhere, spanning the entire universe, and nowhere, impossible to point to. What would it mean for things not to have positions? Where would they be? 'When we talk about emergent spacetime, it must come out of some framework that is very far from what we're familiar with,' Arkani-Hamed says."