[Music] imagine you have a magical box that can create anything you want you can ask it for an apple and there's an apple ask for a pencil and there's a pencil even ask for a unicorn and there's a unicorn here's the strange part the Box doesn't decide what to create until you open it and look inside before you look it could be creating anything it's only when you open the box that it chooses and becomes just one thing the apple pencil or unicorn all these possibilities exist simultaneously Inside the Box this is similar to how
particles in quantum mechanics work before they're observed they exist in a state where they could be many things at once when observed they collapse into one state one interpretation of this is the Copenhagen interpretation it suggests that observing a particle is what causes it to take on a definite State this process is known as wave function collapse the Act of measurement interacts with the particle in such a way that it can no longer remain in super position instead it takes on a single definite state in our story opening the box and looking inside is like
observing the particle making it become just one [Music] thing the ancient Greeks thought the basic elements might be air fire or water this was a revolutionary idea at the time attempting to explain the diversity of nature with a limited set of fundamental substances a century ago physicists were sure it was the atom experiments like those conducted by Max plank Albert Einstein Neils bour and others revealed that atoms themselves were made of even smaller particles and that these particles exhibited Strange Behaviors not explained by classical physics modern physics tells us that the building blocks of the
universe are subatomic particles such as electrons quarks and neutrinos these particles are believed to be the fundamental constituents of matter and all the matter we see around us is made up of various combinations of these particles however the story doesn't end there quantum theory reveals that the fundamental building blocks of the cosmos go beyond just particles extending to the very fabric of space and time itself in this framework the universe is not merely composed of particles moving through space but rather a dynamic interplay of fields and forces within the structure of SpaceTime these fields described
by Quantum field Theory are the true essence of what constitutes reality with particles emerging as excitations of these underlying Fields today we believe the deepest layer of reality consists of Elementary particles governed by quantum theory this invisible tiny realm is where everything we see and experience originates it's a world full of wonder and can often feel strange let's start with what we know visible matter is made of atoms which have protons and neutrons at their centers however these protons and neutrons are not the smallest particles according to the standard model of particle physics which explains
reality at the smallest scales there are even smaller particles surprisingly everything in the universe can be traced back to atoms an atom is the smallest unit of matter that retains the characteristics and properties of the larger visible world including physical and chemical properties an atom is fundamentally a Quantum entity with its own energy levels properties and conservation laws it interacts with all four known fundamental forces in many ways all of physics can be seen inside a single atom here's what atoms can tell us about the universe here on Earth about 90 elements occur naturally and
are formed by Cosmic processes each element has an atom with a nucleus made of protons and possibly neutrons and surrounded by electrons equal to the number of protons each element has unique properties such as hardness color melting and boiling points density conductivity electr negativity ionization energy and many others what's remarkable about atoms is that there's only one property that defines what type of atom you have and hence what these properties are the number of protons in the nucleus in everyday life there are certain rules we take for granted cause and effect for instance something occurs
and that causes other things to occur depending on what happens at the start different causes lead to different effects however in the case of quantum physics the standard rules are fundamentally different you can't Define even your starting point to arbitrary precision as there's an uncertainty inherent to certain properties of your system there isn't a predictable deterministic way to describe how a Quantum system evolves over time only a set of probabilities you can calculate if you make a precise enough measurement observation or interaction you will see a single outcome however the act of measuring observing or
interacting changes the state of your system this Behavior has been debated for nearly a century the resolution may be unsettling not to interpret it at all as puzzling as it sounds interpretations might be what prevent us from truly understanding Quantum reality quantum theory for its part is a supremely effective description of the microscopic world of atoms and their constituents disturbingly however it also reveals a profoundly counterintuitive reality in which for instance a particle can exist in a superposition of states where it can do two or more things at once in 1935 Irvin Schrodinger devised his
famous thought experiment to illustrate a consequence of quantum theory he imagined a cat shut in a box with a vial of poison the decay of a radioactive atom could trigger a hammer to smash the vial and as a result kill the cat if the atom was in a super position of decaying and not decaying the cat would be both dead and alive at the same time the only way to find out would be to open the box this thought experiment brought Quantum weirdness from the microscopic realm into the everyday World forcing researchers to confront it
physicists refer to these macroscale superpositions ones involving many atoms or other Quant entities as Schrodinger cat states in the past decade these cats have helped researchers explore the transition between the quantum and classical worlds they have also begun to explain why we don't see everyday objects in two states at once and whether we ever might the idea that a theoretically Quantum animal could be both alive and dead at the same time is a classic example of quantum weirdness questions like how or why does quantum physics work or what if anything do the mathematical objects in
quantum theory represent have as many answers as we care to give them but those arguably say much more about us and our prejudices biases and assumptions about the universe than the reality of the universe itself there are very few things we can actually observe in nature particle properties like position momentum cross-sections scattering amplitudes and individual Quantum States asking about the underlying nature of reality assumes it follows rules that fit our intuition but the opposite may be true our perception of reality is limited by our senses and capabilities and the true rules governing the universe might
be more foreign to us than we can imagine we talk of particles which occupy points in space but they are actually energetic spikes or excitations in underlying Quantum fields for example a photon is an excitation of the electomagnetic field these fields permeate the entire universe meaning there is always some residual phoness everywhere so-called virtual particles that appear briefly and vanish even when there isn't enough energy to create a real particle fields are considered more fundamental because the mathematics doesn't work without them however the quantum nature of a field means it can't be observed directly any
observation requires energy which forces is the field to produce a particle therefore we often talk about particles because they are what we can observe almost every particle has a corresponding anti-particle with the same mass but opposite charge antimatter is rare in the visible universe and is mostly generated in particle collisions the universe is overwhelmingly made of matter and no one knows why the quantum World operates by rules that defy common sense a particle can behave like a wave under certain conditions and even the concept of a particle becomes uncertain upon closer examination attempting to pinpoint
a particle's location obscures its momentum while recording its momentum obscures its location this is Heisenberg's uncertainty principle suggesting that these properties themselves are inherently fuzzy the most surprising aspect of quantum physics is the minimal properties needed to define a particle Mass charge and angular momentum or spin with these a mathematical equation can describe the particle fully through its wave function which predicts Its Behavior probabilities this concept is closely linked to wave particle duality and superposition particles exist in a wavelike range of States until observed at which point their wave function collapses and they adopt a
specific State however the question of who or what is needed to observe this collapse remains unanswered do detectors suffice or does human Consciousness play a role Quantum physicists have proposed various interpretations from the necessity of human consciousness to the idea that wave function collapse is illusory and all possible States exist in parallel universes the many worlds interpretation there is no straightforward answer we learned what we know today about the universe by asking the right questions which means by setting up physical systems and then performing the necessary measurements and observations to determine what the universe is
doing despite what we might have intuited beforehand the universe showed us that the rules it obeys are bizarre but consistent the rules are just profoundly and fundamentally different from anything we'd ever seen before reality if you want to call it that isn't some objective existence Beyond what's measurable or observable in physics describing what is observable and measurable as accurately and completely as possible is our highest goal by creating a theory where Quantum operators act on Quantum wave functions we can accurately calculate the probability distribution of possible outcomes for most physicists this is enough however you
can add assumptions to these equations and come up with different interpretations of quantum mechanics is the Quantum wave function meaningless until you make a measurement do all possible outcomes occur requiring an infinite number of parallel universes can reality Be Imagined as an infinite number of identically prepared systems with measurement choosing which one represents our reality do particles always have real unambiguous positions Guided by deterministic Pilot waves in a non-local manner there are various Quantum interpretations with different assumptions About Properties despite their differences no experiments can distinguish these interpretations from each other although certain interpretations like
those with local real deterministic hidden variables can be ruled out frustratingly all of these interpretations plus others are experimentally indistinguishable from one another there is no experiment we have been able to design or perform that discerns one of these interpretations from another and therefore they are physically identical the idea that there is a fundamental objective Observer independent reality is an assumption with no evidence behind it just thousands upon thousands of years of our intuition telling us it should be so science doesn't aim to confirm our biases but seeks to uncover the nature of reality regardless
of our preconceptions to understand quantum mechanics we should let go of biases and embrace what the universe tells us entangled photons emitted from a source reaching separate observers exhibit random result results but display correlations whether these correlations follow local realism or not depends on whether they obey or violate Bell's inequality understanding the universe isn't about revealing a true reality separate from observers measurements and interactions reality might be intertwined with measurement observation and interaction at a fundamental level to further understand the universe we need experimental tests to dis uish between interpretations so far only interpretations that
require local realism have been ruled out choosing between interpretations is a matter of Aesthetics experimental measurements of polarization correlation agree with theoretical predictions from quantum mechanics indicating that local real correlations between photons cannot explain the observed Precision in science we don't declare what reality is and then adjust observ ations to fit our assumptions theories and models that predict observations with accuracy predictive power and minimal assumptions survive physics isn't troubled by reality seeming puzzling and bizarre the issue arises only if we demand more from the universe than reality provides there's a strange and wonderful reality out
there until we devise experiments that teach us more it's better to embrace reality as we can measure it than to impose additional structures based based on our biases until we conduct that crucial experiment we'll be philosophizing superficially instead of relying on scientific intervention will remain in the dark until then quantum mechanics stands as science's most precise and Powerful theory of reality predicting countless experiments and spawning numerous applications however physicists and philosophers remain divided over its interpretation many physicists perhaps the majority adhere to the the Copenhagen interpretation which suggests physicists should focus on calculations rather than
trying to understand the underlying meaning of quantum mechanics philosopher Tim modlin criticizes this approach highlighting several interpretations of quantum mechanics that offer detailed explanations of how the world functions yet other scientists scrutiny of these interpretations reinforces skepticism as they appear convoluted and implausible they don't explore interpretations that frame quantum mechanics as a theory about information which some find appealing however to others these information-based interpretations seem even less plausible as they introduce Consciousness into physics undermining its objectivity the debate over Consciousness is similarly contentious previously there was a consensus that Consciousness emerges from neural processes but
empirical evidence for these theories has been lacking consequently there's now a multitude of theories including integrated information Theory and proposals suggesting Quantum effects underpin Consciousness although evidence for the latter is sparse moving on the journey into understanding Quantum reality goes beyond the limitations of our rudimentary perceptions it's easy to be seduced by the face nature reveals directly to our senses evidence gathered from our rudimentary perceptions often yield a clouded conception of the world we inhabit assessing existence while failing to embrace the insights of modern physics would be like wrestling in the dark with an unknown
opponent by deepening our understanding of the true nature of physical reality we profoundly reconfigure our sense of ourselves and our experience of the universe quantum physics is captivating because it defies our everyday experiences matter can behave as both waves and particles the universe is composed of indivisible quanta we can only predict prob abilities rather than specific outcomes and it operates non-locally in both space and time its effects are most apparent on the smallest scales making it one of the most peculiar discoveries about the universe yet we often incorporate ourselves into the equation introducing Concepts like
observation measurement and interaction remove ourselves and we're left with equations results and the universe's answers physics can't explain why the universe works as it does it can only elucidate how it functions to understand the fundamental nature of reality ask the universe questions about itself and heed its responses anything else we add is our own construct not the universes well we've covered a lot in this video and one of the key takeaways is that quantum mechanics despite being the most precise and Powerful theory of reality remains shrouded in mystery regarding its true meaning thanks for watching
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