Maddie

Abstract:

Introduction:

Since Einstein’s work in the 20th century, the universe has traditionally been viewed through a lens that uses space and time as fundamental benchmarks by which everything else is explained. He used his principle of relativity and the constancy of the speed of light to begin defining all other phenomena. By combining space and time into the united idea of ‘spacetime,’ Einstein was able to explain why moving through space in different ways can affect the way something moves through time. Many questions and equations were answered and explained with Einstein’s spacetime. However, as quantum mechanics research grows, these ideas have been challenged. Some experiments have yielded results that over and over again disagree with our current ideas of the framework of the universe. If our equations and laws are applied to environments with strange conditions, like the big bang or the event horizon of a black hole, they stop working. In order to create rules that work in all types of space and time conditions, our ideas of spacetime itself need to change.

Relevant Background Theory

Einstein’s combination of space and time was the result of his theory of relativity. He concluded that moving through space in certain ways can change the way time moves. If something is moving extremely fast through space, close to the speed of light, or is close to a massive body with a lot of gravity, such as a black hole, that object would move through time at a slower rate than an object not experiencing those forces. Space is not a static thing. It can be warped by matter and energy. After combining space and time into the unified framework of spacetime, Einstein was still left with one glaring question: how can we move through space in any direction, but through time in only one? The so-called ‘arrow of time’ flows stubbornly one way: past, to present, to future. Our universe gains entropy, because, by the second law of thermodynamics, systems can only become move from order to disorder. This property of the universe defines the arrow of time. However, the fundamental laws of physics work just as well for events whether they are calculated forwards or backwards in time. If space and time are such malleable properties, building all of physics on top of them might not be the right answer.

Fundamentalism arises from the limits of our own human perception. A good example of this phenomenon is water. On our own, we see it as one giant blob of fluid, but with the aid of sharper and sharper tools, we realize that the water we see is actually an emergent phenomenon. Breaking it down into its more fundamental parts, we get atoms. Then atoms were thought to be fundamental, but we refined our tools even more and realized that that too was an illusion, and quantum particles were the true building blocks. Now we’ve gone further, theorizing that even the space and time through which these particles move is not fundamental, rather emergent. An emergent property is something that does not exist for each individual piece in a system, but does exist for the system as a whole. It might sound like a far leap, but some of the greatest overhauls of physics have come from reframing what were thought to be fundamental parts of the universe—spacetime might just be next in line.

Theoretical Work:

In his theory of relativity, Einstein viewed space as a smooth, uniform surface, something one could zoom in on continuously and never have any bumps emerge. This supposition directly contradicts evidence found by quantum physicists. Our universe is bumpy on the smallest scales. Comparing gravity to another force, such as magnetism, is a helpful analogy. Sticking two magnets together can be described using a smooth classical magnetic field, but the field itself is created by quantum particles, a bumpy swirling mess of interactions. We use gravity like it’s a smooth field, but it’s the only force that has yet to be described in a quantum manner. No one knows for sure what creates gravitational fields or how individual particles act inside them. Therein lies a large question for today’s physicists: quantum gravity. General relativity says space is smooth, quantum mechanics says it is a bumpy mess of particles, and many physicists don’t think it can be both, and that it has to choose one or the other. If, however, space was an emergent property, it could be both. At the fundamental level space would not exist, and would instead emerge as a result of the interactions between quantum particles—such as the proposed but elusive ‘graviton.’ Water again is a good example of this. The ocean is made up fundamentally of H₂O molecules, and tides are an emergent property of the ocean. Just because each individual water molecule has no measurable tide does not mean tides aren’t a very real, measurable phenomenon. Then, much how the ocean has tides due to gravitational interactions between the molecules (caused by the moon), space would emerge as the smooth surface used in general relativity due to tiny interactions between particles. Time is just another dimension through which things move, so it would follow that time as well is emergent, due to the intertwining nature of spacetime.

If space and time are completely relative, that leaves causality as the only marker by which to describe events. Things can only be explained through the lens of other relative events, whether through space, such as one thing influencing another by a force like gravity, or through time, such as an object’s past state evolving into its present state.

Einstein’s theory of relativity explains the idea that nothing can travel faster than the speed of light. If all events are relative, then no information or interaction can happen faster than the speed of light. This is known as relativistic causality. There is one phenomenon, however, that breaks the rule of relativistic causality: entangled particles. Two particles are able to influence each other directly and immediately no matter the distance between them, which means the information had to have traveled faster than the speed of light. If a pair of particles interact in some way and then separate, they can sometimes retain matching properties that are not any definite state but are nevertheless the same. If an observer then measures one of the particles, thus causing wave function collapse, this will effect its entangled partner, causing the same wave function collapse, regardless of distance. The information somehow travels faster than the speed of light.

Heisenberg’s uncertainty principle also has something to do with this. He determined that the exact position and exact momentum of a quantum particle cannot be known at the same time. This is because of the wave behavior of particles. Even though we call them ‘particles’ they behave as both a wave and a particle. A particle is most likely to be found in the most intense part of its wavelength, but there is a probability it is anywhere in the wavelength’s area. The more intense the wave is, it’s higher momentum is more easily measurable, but the particle’s less precise position is impossible to know. Attempting to measure the velocity of a particle will inevitably change its position, and thus you can never know both at once. This is not about the tools used to measure either of these properties, but is a literal fact about the nature of quantum particles. Because we can only ever know the probable location of particles or the probable velocity, it stands to reason that causality is not always determined by definite knowledge, but by approximations and extrapolations regarding which particles are likely to be near each other, making them more likely to influence each other.

Just because the laws of causality as we understand and perceive them are strict on what can happen when, does not necessarily mean that the individual fundamental particles have to follow them the same ways. Our rules are merely large-scale averages which are controlled by the emergent regularities of space and time. The common, statistically average event is a thing being influenced by another ‘nearby’ (in space or in time) thing. However, with the sheer number of particles, it is completely plausible that statistical outliers, such as entangled particles, would occur.

If quantum particles can violate relativistic causality, they likely follow different rules of time than we do. Because they don’t inherently have space or time on their own, they may be able to ‘communicate’ in ways we cannot. String theory is a current contender for the ‘Theory of Everything.’ Rather than the smallest bits of the universe being point particles, they are described as tiny strings. Most string theorists believe that there are way more than four dimensions in this universe, and that the quantum particles—or strings—can access more dimensions than we can. Sometimes up to eleven are theorized to exist. They would be too small for us to perceive or understand, but the right size for quantum pieces to interact with. This could be another explanation for entangled particles, as they could still be close enough to effect each other in one of these smaller dimensions, while appearing to move apart from each other in the four dimensions we perceive. Equations in string theory can basically ignore space in their description of interactions, which leads directly to emergent space.

Like entangled particles, wave function collapse also violates relativistic causality. The double slit experiment is a famous experiment which illustrates this phenomenon. When a beam of light, a laser, is shot through two thin slits, it moves out from the slits the same way ripples in water would, creating a wave-like pattern when measured. After thousands upon millions of photons have hit the measuring plate, a dark-and-light striped pattern appears. This is essentially the probability of where any single given photon of this wavelength sent through these slits would land. There is a high probability it would land in the brighter areas, and a low probability it would land in the darker areas. When photons (as well as other fundamental particles) act as waves before detection, it is known as being in a state of ‘superposition.’ Much like Schrodinger’s Cat, the particle lands both to the left and to the right of the measurement tool—as well as to the top and to the bottom—before measurement. We have no way of knowing for certain which it would be unless we measure each particle’s landing place one by one. When we perform this version of the experiment, carefully measuring each individual photon, only then does a specific spot on the measuring tool appear. Until the moment before the photon hits, there is no way of knowing where it will land besides the imprecise light-and-dark probabilities created by the interference pattern. This is wave function collapse. And then, at the moment of impact, the probability of the point where it ‘landed’ is immediately 100% and any other probability of where it could possibly land (whether it was a 10%, 50%, or 95% chance) is immediately 0%. The information communicating at which point this photon landed travelled faster than the speed of light, thus violating relativistic causality.

If wave function collapse is caused by observation, it could also be said that it is caused by consciousness. No particle has to have any definite property unless it is being observed in some way, and any ‘observation’ requires a conscious agent. Consciousness directly effects reality. If time is an emergent phenomenon, then quantum particles may not follow the same past to present to future arrow of time that we do. If they experience or can access all time at once, consciousness forcing a particle to choose a state of being billions of years after the creation of the universe is the exact same as consciousness forcing a particle to choose a state of being at the very beginning of the universe. Space and time are not a structure that one is within, but rather the conscious agent is creating the emergent spacetime phenomenon through observation.

Conclusion: