--- title: The Most Misunderstood Concepts in Physics description: "Physics can get extremely complicated. While the mechanics we experience in our daily lives are relatively easy to understand, it gets much more confusing when we examine things on either the smallest or largest scales. Quantum physics and astrophysics are two of the hottest fields right now as far as public interest, but ideas within these realms are frequently misunderstood.\n\n## Theory vs. Hypothesis\n\nThe word theory gets bandied around a lot, but it's frequently used incorrectly. This misconception isn't limited to physics but rather extends through all of science. Many terms you have heard described as theories are actually hypotheses, and there is a very important scientific distinction.\n\nA hypothesis is just an educated guess. They often represent the best possible answers we have available at the time, but it's still just a guess. These ideas are either untested or untestable. Thought experiments also tend to be grouped into this category, as they rarely have the ability to be tested.\n\nFor example, you've undoubtedly heard of Simulation Theory and Holographic Universe Theory as principles by which our entire existence is not what it seems. Despite their commonly used names, these thought experiments are not theories as there is no viable way to test them.\n\nSimilarly, even something as famous as string theory isn't actually a theory; it's more of a hypothetical framework for the universe. This is a much more scientific hypothesis than the thought experiments we mentioned, but it is extremely difficult to test. There are very few experimental results related to string theory, so it doesn't actually reach the level of being a scientific theory yet.\n\nIn order for something to be a theory, it has to be able to withstand scrutiny and be supported by a large body of experimental results. Basically, a hypothesis will be used to make predictions, and experiments will either confirm or refute those predictions. If the predictions don't match the experimental results, then either something was wrong with the experiment or the hypothesis needs to be reworked. But if that hypothesis is able to consistently make accurate predictions, it can eventually be upgraded to a theory.\n\nThere's no specific time limit for how long this takes, but it is an extremely rigorous process. The hypothesis needs to be repeatedly confirmed through experimental testing, face peer review and replication of the experiments, and still hold true in the face of scientists designing experiments specifically created to disprove it. Eventually, as evidence continues to mount, a consensus will form among scientists and this hypothesis will become a theory.\n\nWe have seen this countless times with things like Einstein's theories of relativity and effective field theory. These theories have consistently predicted results about phenomena in our universe, having amassed a mountain of evidence to support them. However, this brings us to a related misconception, which is the belief that theories are facts. Theories are used to explain facts, meaning the results of experiments and observations, but they themselves are not facts.\n\nAs such, theories are subject to change no matter how well established they may be. General relativity has been seen as the law of the land for over a hundred years, but it's also incomplete. We are rapidly approaching a time when general relativity may either be adjusted or supplanted by a new theory entirely.\n\nSo remember, whenever you hear discussions about things like dark matter, dark energy, or any supposed \"theory\" that is highly contested or controversial, these things are actually just hypotheses. It may seem like meaningless semantics, but it's the scientific equivalent of \"beyond a reasonable doubt\" versus \"this is just a hunch\".\n\n## The \"Unbreakable\" Speed of Light\n\nEverybody knows that nothing can travel faster than light. The speed of light is often referred to as being the unbreakable speed limit of the universe, so how can we explain Cherenkov radiation? For those unfamiliar, Cherenkov radiation is essentially the visual equivalent of a sonic boom; it's a flash of blue light that occurs when something travels faster than light.\n\nThe misunderstanding stems from the overly simplified version of the initial statement. A more accurate, though much less catchy, way of phrasing it would be to say that nothing with mass can travel faster than the speed of light in a vacuum. More simply, nothing with mass can exceed speeds of 300,000 km/s. That is the fastest speed at which light can travel, and it is a speed that we can never reach.\n\nHowever, the reason an optical sonic boom can exist is because the speed of light isn't the same in all mediums. Just like you can run faster on a track than you could underwater, so too does light slow down when it meets with resistance. And in certain instances, such as when passing through water or glass, it is possible for particles with mass to travel faster than light can in that medium.\n\nCherenkov radiation is named after Soviet physicist Pavel Cherenkov, the first person to detect it experimentally back in 1934. It had been hypothesized before that multiple times and even witnessed by Marie Curie among others, but little came of this. Those that witnessed it never tried to identify the source, and those that hypothesized it were dismissed because it was believed that it violated the theory of relativity. Let that be a friendly reminder that physics is so complicated it is even misunderstood by physicists sometimes.\n\nAnyway, Cherenkov radiation is the result of charged particles traveling through something like water at extremely high speeds, faster than light's maximum speed through water. The resulting blue glow can be easily observed in any underwater nuclear reactor, and it is believed to be perceived by astronauts as well in a phenomenon known as Astronaut's Eye.\n\nAstronauts will occasionally perceive a sudden flash of bright blue light originating from within their eyeball. Your eyes are 98% water, so it is believed that these flashes are Cherenkov radiation from stray particles passing through the astronaut's eye at high enough speeds to create the sonic boom effect. The magnetosphere helps protect Earth from these particles which is why we haven't all experienced this same effect, though it has also been reported by patients receiving radiation therapy for brain cancer.\n\nBut this isn't the only way that the speed of light is misunderstood. Something with mass can travel faster than light does through specific mediums like water, but something without mass can travel faster than light does even in a vacuum. Of course, even there it gets a little more complicated.\n\nThere are only two particles known to be massless: photons and gluons. There are also hypothetical gravitons, but those have yet to be detected. However, even if gravitons do exist they would behave exactly the same way photons and gluons do. As massless particles, they would all travel at the speed of light at all times, unable to either speed up or slow down; that's just how these particles work in a vacuum. But if that's true, how can we say something without mass can travel faster than light in a vacuum?\n\nIt turns out that there's something without mass that also isn't a particle, and that's spacetime. Despite general relativity imposing this speed limit on everything in the universe, that limit does not constrain the universe itself. This is one of the reasons we are able to measure that the universe is expanding faster than the speed of light.\n\n## Schrödinger's Cat\n\nIf there is only one thing you know about quantum physics, it's probably the Schrödinger's Cat thought experiment. The thought experiment was devised by Erwin Schrödinger in 1935 in a letter he wrote to Einstein in response to an article he had published. For those unfamiliar, here is how the thought experiment goes:\n\nYou have an opaque, steel box containing a cat, a Geiger counter, a hammer, a vial of poison, and a tiny piece of radioactive material. The radioactive sample is so small that over the course of an hour there is a 50/50 chance that one of the atoms will decay. If no atoms decay in that time, nothing happens. If one of the atoms does decay, it is picked up by the Geiger counter which then triggers the hammer to break the vial of poison, killing the cat.\n\nBecause the box is an isolated quantum system, the cat is both dead and alive at the same time. This is referred to as a quantum superposition, where something is simultaneously in multiple different states until observed. Once the box is opened, the system will collapse to one of the two probabilities revealing that the cat is either alive or dead. This is obviously just a thought experiment and not something that anybody should ever try on their own, but this metaphor is ubiquitous for its use in explaining the concept of quantum superposition.\n\nSchrödinger won a Nobel Prize for his work in quantum physics, yet most people are completely unfamiliar with his work outside of this thought experiment. On the surface, that still doesn't seem that bad. Quantum physics is an extremely advanced subject that goes well beyond even most college educations. For Schrödinger's thought experiment to have made him a household name should be considered an incredible feat, but that wasn't his intention at all.\n\nAfter all, Schrödinger's Cat first appeared in his personal correspondence with Einstein, so it's not like he needed to include a beginner's guide to quantum superposition for that dummy Einstein. Schrödinger's Cat was essentially the 1930's equivalent of a shitpost, designed to show how ridiculous and incomplete he believed the contemporary interpretation of quantum physics was. Einstein lauded Schrödinger for his elegantly designed thought experiment, stating that obviously the cat was either dead or alive regardless of whether it was observed and jokingly asking if the state of the cat could only be determined after being investigated by a physicist.\n\nUnfortunately for Schrödinger, people loved this explanation of quantum superposition. While he was trying to create a ridiculous and impossible example, it was seen by others as posing the question of how long superpositions collapse, when they collapse (assuming they do at all), and how large a system in a superposition can be. These systems are even referred to as \"cat states\" in honour of the thought experiment, though no experiment has resulted in superposition of anything even approaching the size of a cat; the largest \"cat state\" created thus far was only about half the mass of an eyelash.\n\nBut despite the popularity of Schrödinger's Cat as a simple means to explain superposition, the cat should never actually be in such a state. Though it was largely believed to be the case in the 1930's, the prevailing opinion today is that quantum phenomena such as superposition don't require a conscious observer. A mechanical device like the Geiger counter would count as an observer, meaning that the system would collapse as soon as the device detected the presence of radiation. Even were that not the case, the cat itself would be an observer of the environment and see whether or not the vial of poison was shattered.\n\nThe discussion gets much more complicated than that, which is the last thing that Schrödinger wanted. He just wanted to show how ridiculous the entire idea was, not to generate nearly a century of debate over what he believed was an obviously absurd premise.\n\n## Heisenberg's Uncertainty Principle\n\nHeisenberg's Uncertainty Principle is one of the fundamental aspects of quantum physics, and also one of the most misunderstood. It states that certain pairs of information, such as position and momentum, cannot be simultaneously known. The more accurately you know where something is, the less accurately you will be able to know its momentum. It sounds simple on the surface, but there are multiple factors that have led to confusion over this topic, not the least of which is the concept's name.\n\nBy referring to it as the Uncertainty Principle, it implies that there is a definite answer and we are simply unsure what that answer is. That is not actually the case in quantum physics. Classical physics is deterministic, which means that with perfect information you can predict exactly how something will behave. If you throw a ball in the air and you know the exact force that was imparted on the ball, the mass of the ball, the wind speed and direction, and so on, you should be able to predict exactly where and when that ball will land.\n\nBut quantum physics is probabilistic, meaning that even if you have perfect information you cannot predict what will happen with certainty because there is an element of randomness involved. This is related to quantum superposition which, despite not really applying to something as large as Schrödinger's Cat, is a very real quantum phenomenon.\n\nThis highlights another reason that the Uncertainty Principle is so misunderstood, which is that quantum physics is really bizarre and unintuitive. We live in the macroscopic world, a world that has been accurately described by classical physics for centuries. While quantum mechanics do apply to things like baseballs and people, the effects are so tiny as to be completely negligible. It's only when we go down to the atomic and subatomic scale where we can measure and observe quantum phenomena properly.\n\nBecause of this, people typically want to apply properties of classical particles to quantum particles. Everything in the physical world appears deterministic and measurable, so it's difficult for us to conceptualize things that aren't.\n\nThe final reason the Uncertainty Principle is so misunderstood is because it's often taught incorrectly. It's frequently explained as a failure of measurement in rather explicit terms. A common explanation is that, by using photons to measure a particle's position, those photons will have imparted some momentum to the particle thus making its current momentum unclear. Or if photons were used to measure the particle's momentum, those photons could have knocked it around and changed its position. However, the Uncertainty Principle exists regardless of whether a quantum particle is being observed or not.\n\nIn actuality, the Uncertainty Principle is a result of quantum particles simultaneously behaving both like particles and waves, and because of quantum superposition. We can't know the precise position and momentum of a quantum particle the way we could with a classical particle because it doesn't have them. Quantum particles simultaneously have many different speeds and positions, existing in all of them at once with varying degrees of probability.\n\nIt gets really complicated, but it's a little easier to conceptualize if we think of how the quantum particle works by existing both as a particle and a wave. The wave represents the quantum particle's momentum, and the further we zoom out the better we can measure the entire wave function. But what is that wave's position? The wave would clearly appear to be in lots of places, so we can't say for certain what its exact position is.\n\nConversely, we could zoom in until we only see one peak of the wave, representing our particle. That would give us a definite position for the quantum particle, but what then is its momentum? Since the momentum would be the frequency of the wave, meaning the distance between two peaks or two valleys of the wave, there's no way to be sure. Since pinpointing a precise position for the wave required restricting our view to a single peak, there's no second peak we can use to measure its momentum.\n\nThat's just meant as an example to help you visualize the Uncertainty Principle, but don't be mistaken by thinking that the uncertainty is a flaw in how we are measuring or observing those properties. Even with perfect measuring technology, it is impossible to know both of those properties beyond a certain limit. That limit is a fundamental feature of quantum physics, caused by the fact that quantum particles simply don't have a single, definite position and momentum like classical particles do. Like we said, quantum physics is really weird.\n\n## Key Takeaways\n\n- Theories in science require extensive testing and evidence, unlike hypotheses which are educated guesses.\n- The speed of light is not universally constant; it varies in different mediums, allowing for phenomena like Cherenkov radiation.\n- Schrödinger's Cat thought experiment was intended to highlight the absurdity of quantum superposition, not to explain it.\n- Heisenberg's Uncertainty Principle reflects the probabilistic nature of quantum physics, not measurement limitations.\n- Quantum particles exhibit both particle and wave properties, leading to inherent uncertainties in their position and momentum.\n\n## Frequently Asked Questions\n\n### What is the difference between a hypothesis and a theory in physics?\n\nA hypothesis is an educated guess that is either untested or untestable, while a theory is a hypothesis that has been repeatedly confirmed through experimental testing, peer review, and replication of experiments. A theory must also withstand attempts to disprove it and consistently make accurate predictions.\n\n### Can anything travel faster than the speed of light?\n\nNothing with mass can travel faster than the speed of light in a vacuum. However, particles with mass can travel faster than light in certain mediums, like water, resulting in phenomena such as Cherenkov radiation. Additionally, massless particles like photons and gluons always travel at the speed of light in a vacuum.\n\n### What is Cherenkov radiation?\n\nCherenkov radiation is a blue glow that occurs when charged particles travel through a medium, like water, at speeds faster than light can travel in that medium. It is often compared to an optical sonic boom.\n\n### What is Schrödinger's Cat thought experiment?\n\nSchrödinger's Cat is a thought experiment where a cat in a sealed box is both alive and dead until observed. It illustrates the concept of quantum superposition, where something exists in multiple states simultaneously until measured.\n\n### What is Heisenberg's Uncertainty Principle?\n\nHeisenberg's Uncertainty Principle states that certain pairs of information, like position and momentum, cannot be simultaneously known with precision. The more accurately you know one, the less accurately you can know the other. This is due to the probabilistic nature of quantum physics and the dual particle-wave behavior of quantum particles.\n\n### Why is the Uncertainty Principle often misunderstood?\n\nThe Uncertainty Principle is often misunderstood because it is named in a way that implies uncertainty in measurement, but it is actually a fundamental property of quantum particles. Additionally, people tend to apply classical physics concepts to quantum phenomena, and it is often taught incorrectly as a measurement issue rather than a inherent property of quantum particles.\n\n### What is the significance of the speed of light in the universe?\n\nThe speed of light is considered the ultimate speed limit for objects with mass in a vacuum. It is a fundamental constant in physics that plays a crucial role in theories like relativity. However, the universe itself can expand faster than the speed of light.\n\n### How does the concept of a theory change over time?\n\nTheories in physics are subject to change and refinement as new evidence emerges. Even well-established theories like general relativity may be adjusted or supplanted by new theories as our understanding of the universe deepens.\n\n### What is the role of experimental evidence in upgrading a hypothesis to a theory?\n\nFor a hypothesis to become a theory, it must be repeatedly confirmed through experimental testing, face peer review, and withstand attempts to disprove it. A large body of experimental results supporting the hypothesis is essential for it to be considered a theory.\n\n### What is the significance of quantum superposition?\n\nQuantum superposition is the principle that a quantum system can exist in multiple states simultaneously until it is measured. This concept is fundamental to understanding quantum mechanics and is illustrated by thought experiments like Schrödinger's Cat.\n\n## Sources\n\n- [Original Side Projects video: The Most Misunderstood Concepts in Physics](https://www.youtube.com/watch?v=pLMiYnP-pAA)\n- [Hero image source](https://upload.wikimedia.org/wikipedia/commons/f/fa/Rignano_sull%27Arno_-_Monumento_a_Robert_Einstein_-_2023-09-17_12-10-37_001.jpg) by Repuli / openverse, by-sa.\n\n## Related Coverage" url: https://sideprojects.pub/article/most-misunderstood-concepts-physics.md canonical: https://sideprojects.pub/article/most-misunderstood-concepts-physics datePublished: 2023-11-12 dateModified: 2026-07-28 author: - name: Simon Whistler url: https://sideprojects.pub/author/simon-whistler publisher: Side Projects image: "https://media.sideprojects.pub/cdn-cgi/image/width=1600,height=900,fit=cover,quality=80,format=auto/articles/pLMiYnP-pAA/hero.jpg" type: NewsArticle contentHash: 0d8a8662011d4fb83a6fdb07e1fc5e7c6ae78169ae8fc94699f8ce3cb4aaecac tokens: 5175 summaryUrl: https://sideprojects.pub/article/most-misunderstood-concepts-physics.md.summary.md --- Physics can get extremely complicated. While the mechanics we experience in our daily lives are relatively easy to understand, it gets much more confusing when we examine things on either the smallest or largest scales. Quantum physics and astrophysics are two of the hottest fields right now as far as public interest, but ideas within these realms are frequently misunderstood. ## Theory vs. Hypothesis The word theory gets bandied around a lot, but it's frequently used incorrectly. This misconception isn't limited to physics but rather extends through all of science. Many terms you have heard described as theories are actually hypotheses, and there is a very important scientific distinction. A hypothesis is just an educated guess. They often represent the best possible answers we have available at the time, but it's still just a guess. These ideas are either untested or untestable. Thought experiments also tend to be grouped into this category, as they rarely have the ability to be tested. For example, you've undoubtedly heard of Simulation Theory and Holographic Universe Theory as principles by which our entire existence is not what it seems. Despite their commonly used names, these thought experiments are not theories as there is no viable way to test them. Similarly, even something as famous as string theory isn't actually a theory; it's more of a hypothetical framework for the universe. This is a much more scientific hypothesis than the thought experiments we mentioned, but it is extremely difficult to test. There are very few experimental results related to string theory, so it doesn't actually reach the level of being a scientific theory yet. In order for something to be a theory, it has to be able to withstand scrutiny and be supported by a large body of experimental results. Basically, a hypothesis will be used to make predictions, and experiments will either confirm or refute those predictions. If the predictions don't match the experimental results, then either something was wrong with the experiment or the hypothesis needs to be reworked. But if that hypothesis is able to consistently make accurate predictions, it can eventually be upgraded to a theory. There's no specific time limit for how long this takes, but it is an extremely rigorous process. The hypothesis needs to be repeatedly confirmed through experimental testing, face peer review and replication of the experiments, and still hold true in the face of scientists designing experiments specifically created to disprove it. Eventually, as evidence continues to mount, a consensus will form among scientists and this hypothesis will become a theory. We have seen this countless times with things like Einstein's theories of relativity and effective field theory. These theories have consistently predicted results about phenomena in our universe, having amassed a mountain of evidence to support them. However, this brings us to a related misconception, which is the belief that theories are facts. Theories are used to explain facts, meaning the results of experiments and observations, but they themselves are not facts. As such, theories are subject to change no matter how well established they may be. General relativity has been seen as the law of the land for over a hundred years, but it's also incomplete. We are rapidly approaching a time when general relativity may either be adjusted or supplanted by a new theory entirely. So remember, whenever you hear discussions about things like dark matter, dark energy, or any supposed "theory" that is highly contested or controversial, these things are actually just hypotheses. It may seem like meaningless semantics, but it's the scientific equivalent of "beyond a reasonable doubt" versus "this is just a hunch". ## The "Unbreakable" Speed of Light Everybody knows that nothing can travel faster than light. The speed of light is often referred to as being the unbreakable speed limit of the universe, so how can we explain Cherenkov radiation? For those unfamiliar, Cherenkov radiation is essentially the visual equivalent of a sonic boom; it's a flash of blue light that occurs when something travels faster than light. The misunderstanding stems from the overly simplified version of the initial statement. A more accurate, though much less catchy, way of phrasing it would be to say that nothing with mass can travel faster than the speed of light in a vacuum. More simply, nothing with mass can exceed speeds of 300,000 km/s. That is the fastest speed at which light can travel, and it is a speed that we can never reach. However, the reason an optical sonic boom can exist is because the speed of light isn't the same in all mediums. Just like you can run faster on a track than you could underwater, so too does light slow down when it meets with resistance. And in certain instances, such as when passing through water or glass, it is possible for particles with mass to travel faster than light can in that medium. Cherenkov radiation is named after Soviet physicist Pavel Cherenkov, the first person to detect it experimentally back in 1934. It had been hypothesized before that multiple times and even witnessed by Marie Curie among others, but little came of this. Those that witnessed it never tried to identify the source, and those that hypothesized it were dismissed because it was believed that it violated the theory of relativity. Let that be a friendly reminder that physics is so complicated it is even misunderstood by physicists sometimes. Anyway, Cherenkov radiation is the result of charged particles traveling through something like water at extremely high speeds, faster than light's maximum speed through water. The resulting blue glow can be easily observed in any underwater nuclear reactor, and it is believed to be perceived by astronauts as well in a phenomenon known as Astronaut's Eye. Astronauts will occasionally perceive a sudden flash of bright blue light originating from within their eyeball. Your eyes are 98% water, so it is believed that these flashes are Cherenkov radiation from stray particles passing through the astronaut's eye at high enough speeds to create the sonic boom effect. The magnetosphere helps protect Earth from these particles which is why we haven't all experienced this same effect, though it has also been reported by patients receiving radiation therapy for brain cancer. But this isn't the only way that the speed of light is misunderstood. Something with mass can travel faster than light does through specific mediums like water, but something without mass can travel faster than light does even in a vacuum. Of course, even there it gets a little more complicated. There are only two particles known to be massless: photons and gluons. There are also hypothetical gravitons, but those have yet to be detected. However, even if gravitons do exist they would behave exactly the same way photons and gluons do. As massless particles, they would all travel at the speed of light at all times, unable to either speed up or slow down; that's just how these particles work in a vacuum. But if that's true, how can we say something without mass can travel faster than light in a vacuum? It turns out that there's something without mass that also isn't a particle, and that's spacetime. Despite general relativity imposing this speed limit on everything in the universe, that limit does not constrain the universe itself. This is one of the reasons we are able to measure that the universe is expanding faster than the speed of light. ## Schrödinger's Cat If there is only one thing you know about quantum physics, it's probably the Schrödinger's Cat thought experiment. The thought experiment was devised by Erwin Schrödinger in 1935 in a letter he wrote to Einstein in response to an article he had published. For those unfamiliar, here is how the thought experiment goes: You have an opaque, steel box containing a cat, a Geiger counter, a hammer, a vial of poison, and a tiny piece of radioactive material. The radioactive sample is so small that over the course of an hour there is a 50/50 chance that one of the atoms will decay. If no atoms decay in that time, nothing happens. If one of the atoms does decay, it is picked up by the Geiger counter which then triggers the hammer to break the vial of poison, killing the cat. Because the box is an isolated quantum system, the cat is both dead and alive at the same time. This is referred to as a quantum superposition, where something is simultaneously in multiple different states until observed. Once the box is opened, the system will collapse to one of the two probabilities revealing that the cat is either alive or dead. This is obviously just a thought experiment and not something that anybody should ever try on their own, but this metaphor is ubiquitous for its use in explaining the concept of quantum superposition. Schrödinger won a Nobel Prize for his work in quantum physics, yet most people are completely unfamiliar with his work outside of this thought experiment. On the surface, that still doesn't seem that bad. Quantum physics is an extremely advanced subject that goes well beyond even most college educations. For Schrödinger's thought experiment to have made him a household name should be considered an incredible feat, but that wasn't his intention at all. After all, Schrödinger's Cat first appeared in his personal correspondence with Einstein, so it's not like he needed to include a beginner's guide to quantum superposition for that dummy Einstein. Schrödinger's Cat was essentially the 1930's equivalent of a shitpost, designed to show how ridiculous and incomplete he believed the contemporary interpretation of quantum physics was. Einstein lauded Schrödinger for his elegantly designed thought experiment, stating that obviously the cat was either dead or alive regardless of whether it was observed and jokingly asking if the state of the cat could only be determined after being investigated by a physicist. Unfortunately for Schrödinger, people loved this explanation of quantum superposition. While he was trying to create a ridiculous and impossible example, it was seen by others as posing the question of how long superpositions collapse, when they collapse (assuming they do at all), and how large a system in a superposition can be. These systems are even referred to as "cat states" in honour of the thought experiment, though no experiment has resulted in superposition of anything even approaching the size of a cat; the largest "cat state" created thus far was only about half the mass of an eyelash. But despite the popularity of Schrödinger's Cat as a simple means to explain superposition, the cat should never actually be in such a state. Though it was largely believed to be the case in the 1930's, the prevailing opinion today is that quantum phenomena such as superposition don't require a conscious observer. A mechanical device like the Geiger counter would count as an observer, meaning that the system would collapse as soon as the device detected the presence of radiation. Even were that not the case, the cat itself would be an observer of the environment and see whether or not the vial of poison was shattered. The discussion gets much more complicated than that, which is the last thing that Schrödinger wanted. He just wanted to show how ridiculous the entire idea was, not to generate nearly a century of debate over what he believed was an obviously absurd premise. ## Heisenberg's Uncertainty Principle Heisenberg's Uncertainty Principle is one of the fundamental aspects of quantum physics, and also one of the most misunderstood. It states that certain pairs of information, such as position and momentum, cannot be simultaneously known. The more accurately you know where something is, the less accurately you will be able to know its momentum. It sounds simple on the surface, but there are multiple factors that have led to confusion over this topic, not the least of which is the concept's name. By referring to it as the Uncertainty Principle, it implies that there is a definite answer and we are simply unsure what that answer is. That is not actually the case in quantum physics. Classical physics is deterministic, which means that with perfect information you can predict exactly how something will behave. If you throw a ball in the air and you know the exact force that was imparted on the ball, the mass of the ball, the wind speed and direction, and so on, you should be able to predict exactly where and when that ball will land. But quantum physics is probabilistic, meaning that even if you have perfect information you cannot predict what will happen with certainty because there is an element of randomness involved. This is related to quantum superposition which, despite not really applying to something as large as Schrödinger's Cat, is a very real quantum phenomenon. This highlights another reason that the Uncertainty Principle is so misunderstood, which is that quantum physics is really bizarre and unintuitive. We live in the macroscopic world, a world that has been accurately described by classical physics for centuries. While quantum mechanics do apply to things like baseballs and people, the effects are so tiny as to be completely negligible. It's only when we go down to the atomic and subatomic scale where we can measure and observe quantum phenomena properly. Because of this, people typically want to apply properties of classical particles to quantum particles. Everything in the physical world appears deterministic and measurable, so it's difficult for us to conceptualize things that aren't. The final reason the Uncertainty Principle is so misunderstood is because it's often taught incorrectly. It's frequently explained as a failure of measurement in rather explicit terms. A common explanation is that, by using photons to measure a particle's position, those photons will have imparted some momentum to the particle thus making its current momentum unclear. Or if photons were used to measure the particle's momentum, those photons could have knocked it around and changed its position. However, the Uncertainty Principle exists regardless of whether a quantum particle is being observed or not. In actuality, the Uncertainty Principle is a result of quantum particles simultaneously behaving both like particles and waves, and because of quantum superposition. We can't know the precise position and momentum of a quantum particle the way we could with a classical particle because it doesn't have them. Quantum particles simultaneously have many different speeds and positions, existing in all of them at once with varying degrees of probability. It gets really complicated, but it's a little easier to conceptualize if we think of how the quantum particle works by existing both as a particle and a wave. The wave represents the quantum particle's momentum, and the further we zoom out the better we can measure the entire wave function. But what is that wave's position? The wave would clearly appear to be in lots of places, so we can't say for certain what its exact position is. Conversely, we could zoom in until we only see one peak of the wave, representing our particle. That would give us a definite position for the quantum particle, but what then is its momentum? Since the momentum would be the frequency of the wave, meaning the distance between two peaks or two valleys of the wave, there's no way to be sure. Since pinpointing a precise position for the wave required restricting our view to a single peak, there's no second peak we can use to measure its momentum. That's just meant as an example to help you visualize the Uncertainty Principle, but don't be mistaken by thinking that the uncertainty is a flaw in how we are measuring or observing those properties. Even with perfect measuring technology, it is impossible to know both of those properties beyond a certain limit. That limit is a fundamental feature of quantum physics, caused by the fact that quantum particles simply don't have a single, definite position and momentum like classical particles do. Like we said, quantum physics is really weird. ## Key Takeaways - Theories in science require extensive testing and evidence, unlike hypotheses which are educated guesses. - The speed of light is not universally constant; it varies in different mediums, allowing for phenomena like Cherenkov radiation. - Schrödinger's Cat thought experiment was intended to highlight the absurdity of quantum superposition, not to explain it. - Heisenberg's Uncertainty Principle reflects the probabilistic nature of quantum physics, not measurement limitations. - Quantum particles exhibit both particle and wave properties, leading to inherent uncertainties in their position and momentum. ## Frequently Asked Questions ### What is the difference between a hypothesis and a theory in physics? A hypothesis is an educated guess that is either untested or untestable, while a theory is a hypothesis that has been repeatedly confirmed through experimental testing, peer review, and replication of experiments. A theory must also withstand attempts to disprove it and consistently make accurate predictions. ### Can anything travel faster than the speed of light? Nothing with mass can travel faster than the speed of light in a vacuum. However, particles with mass can travel faster than light in certain mediums, like water, resulting in phenomena such as Cherenkov radiation. Additionally, massless particles like photons and gluons always travel at the speed of light in a vacuum. ### What is Cherenkov radiation? Cherenkov radiation is a blue glow that occurs when charged particles travel through a medium, like water, at speeds faster than light can travel in that medium. It is often compared to an optical sonic boom. ### What is Schrödinger's Cat thought experiment? Schrödinger's Cat is a thought experiment where a cat in a sealed box is both alive and dead until observed. It illustrates the concept of quantum superposition, where something exists in multiple states simultaneously until measured. ### What is Heisenberg's Uncertainty Principle? Heisenberg's Uncertainty Principle states that certain pairs of information, like position and momentum, cannot be simultaneously known with precision. The more accurately you know one, the less accurately you can know the other. This is due to the probabilistic nature of quantum physics and the dual particle-wave behavior of quantum particles. ### Why is the Uncertainty Principle often misunderstood? The Uncertainty Principle is often misunderstood because it is named in a way that implies uncertainty in measurement, but it is actually a fundamental property of quantum particles. Additionally, people tend to apply classical physics concepts to quantum phenomena, and it is often taught incorrectly as a measurement issue rather than a inherent property of quantum particles. ### What is the significance of the speed of light in the universe? The speed of light is considered the ultimate speed limit for objects with mass in a vacuum. It is a fundamental constant in physics that plays a crucial role in theories like relativity. However, the universe itself can expand faster than the speed of light. ### How does the concept of a theory change over time? Theories in physics are subject to change and refinement as new evidence emerges. Even well-established theories like general relativity may be adjusted or supplanted by new theories as our understanding of the universe deepens. ### What is the role of experimental evidence in upgrading a hypothesis to a theory? For a hypothesis to become a theory, it must be repeatedly confirmed through experimental testing, face peer review, and withstand attempts to disprove it. A large body of experimental results supporting the hypothesis is essential for it to be considered a theory. ### What is the significance of quantum superposition? Quantum superposition is the principle that a quantum system can exist in multiple states simultaneously until it is measured. This concept is fundamental to understanding quantum mechanics and is illustrated by thought experiments like Schrödinger's Cat. ## Sources - [Original Side Projects video: The Most Misunderstood Concepts in Physics](https://www.youtube.com/watch?v=pLMiYnP-pAA) - [Hero image source](https://upload.wikimedia.org/wikipedia/commons/f/fa/Rignano_sull%27Arno_-_Monumento_a_Robert_Einstein_-_2023-09-17_12-10-37_001.jpg) by Repuli / openverse, by-sa. ## Related Coverage