physics can get extremely complicated while the mechanics we experience in our daily lives are relatively easy to understand it gets really really confusing where we examine things either on the smallest scales or the largest ones Quant physics and astrophysics are two of the hottest Fields right now as far as public interest is concerned but ideas Within These Realms are frequently misunderstood so let's have a look at some of those shall [Music] we 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 guest they often represent the best possible answers that we have available at the time but it is 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 is more of a hypothetical framework for the universe this is a much more scientific hypothesis than the thought experiments that 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 just yet in order for something to be a theory then it has to be able
to withstand scrutiny and be supported by a large body of experimental results basically 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 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 well that 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 and that's a fact as such theories are subject to change no matter how well established they may be general relativity has been seen as the lore of the land for over a 100 years but it's also incomplete we're 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
now this might all seem like meaningless semantics but it is literally the scientific equivalent of Beyond A Reasonable Doubt versus it's just a bit of a hunch the speed of light is often referred to as being the unbreakable speed limit of the universe so well how can we explain cherenov radiation for those of you unfamiliar like I was before making this video cherenov 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 a second 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 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 cherenov radiation is named after Soviet physicist pavl cherenov the first person to detected experimentally back in 1934 it had been hypothesized before that multiple times and even witnessed by Marie curri 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 and let that be a friendly reminder that physics is so complicated that it is even misunderstood by physicists sometimes anyway Chingo radiation is the result of charged partic 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 astronauts 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 cherun of 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 the 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 mask can travel faster than light does through specific mediums like water but something without mask can travel faster than light does even
in a vacuum of course even there it gets a little bit more complicated there are only two particles that are 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 that 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 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 well it turns out that there's something without mass that 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 that we're able to measure that the universe is expanding faster than the speed of light if there is one thing you know about quantum physics it is probably the schinger cat thought experiment the thought experiment was devised by win schinger in 19 35 in a letter
he wrote to Einstein in response to an article it published for those unfamiliar here is how the thought experiment goes you have an opaque steel box that contains a cat a Geer counter a hammer and 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's 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 Gea counter which then triggers the
hammer to break the p the poison killing the cat because the box is in an isolated Quantum system the cat is both dead and alive at the same time this is referred to as Quantum superposition where something is simultaneously in multiple different states until it's observed once the box is opens the system will collapse to one of two probabilities revealing that the cat is either alive or dead now 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 explaining the
concept of quantum superposition schinger 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 shring has thought experiment to have made him a household name should be considered an incredible feat but that wasn't his attention at all after all shing'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 shring as cat was essentially the 1930s equivalent of a post designed to show how ridiculous and incomplete he believed the Contemporary interpretation of quantum physics was Einstein lorded schinger 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 Schrodinger people love this explanation of superp position 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 superposition can be these systems are even referred to as cat States in honor of the thought experiments though no experiment has resulted in the 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 shring as 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 1930s the prevailing opinion today is that Quantum phenomena such as superposition don't require a conscious Observer the mechanical device like the Gea 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 even gets much more complicated than that which is the last
thing that Schrodinger 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 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 similar multaneously known the more accurately you know where something is the less accurately you will be able to know its momentum it sounds pretty 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 this 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 shoing as cat is a very real quantum phenomenon this highlights another reason that the uncertainty principle is so misunderstood which is that quantum physics is just really bizarre and unintuitive we live in the macroscopic worlds worlds 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 are not the final reason the uncertainty principle is so misunderstood is because it's also often just
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 the result of quantum particles simultaneously behaving both like particles and waves and because
of quantum superposition we can't not 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 Sim mously have many different speeds and positions existing in all of them at once with varying degrees of probability the wave represents the quantum particles momentum and the further we zoom out the better we can measure the entire wave function but what is the 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 could only see one peak of the wave representing our particle that would give us a definite position for 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 valys 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 and 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're measuring or observing these 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 and like we said and I've said many times throughout this video quantum physics is complicated and [Music] weird
