Why Does Light Exist? What is Its Purpose?

this video is sponsored by bespoke post a monthly membership club delivering a box of awesome top shelf products from under the radar Brands click the link in the description to find out more let me give you something to ponder look around the room that you're in what you're seeing is not matter you can't really see matter what you're seeing is the light bouncing off that matter that enters your eyes that your brain then interprets as matter as objects so you're not seeing the objects themselves but the light bouncing off of it nearly all the information that you have about your room is carried by tiny Quantum objects that make up that light called photons and this information needless to say is traveling at the speed of light if light did not exist you would not be able to gather any visual information about the universe the entire universe would be completely dark to you but it would be much worse than that because you also would not exist without light in fact No Life as we know it would exist light plays a crucial role in the existence of the universe we're going to take a closer look at what that is what is the purpose of life how does it work and why does it exist that's kamea right now [Music] there had been a controversy regarding whether the true nature of light was particles or waves in the 17th century many scientists like Dutch astronomer Christian Huygens thought that light was a wave vibrating in some kind of ether ether was presumed to exist because all ways were thought to need some kind of medium but around the same time other scientists most prominently Isaac Newton believed that light was composed of a stream of corpuscles which are little particles that travel at a finite speed about a hundred years later in 1801 Thomas Young's double slit experiments seemed to show that light must be a wave because when a beam of light was split through a double slit the resulting overlapping beams of light created an interference pattern this phenomenon could only be explained if light was a wave however about a hundred years after Young's experiment and 200 years after Newton's corpuscular theory none other than Albert Einstein showed that wave Behavior or not light must come in discrete packets of energy which today we call photons because that's the only way to explain the photoelectric effect the photoelectric effect is when electrons are ejected from the surface of a metal when a certain frequency of light is shown on it whether the electron is ejected it is not affected by the intensity of the light only its frequency if light were a classical wave the energy of the light would depend on its intensity not its frequency what Einstein showed is that the energy of light comes in discrete quanta defined by Planck's equation energy equals a plus constant times the frequency in other words light consists of photons with the energy of each determined by its frequency so light has characteristics of both waves and particles today we call this phenomenon wave particle duality but it's a bit unfortunate though that wave particle duality is taught in schools today it's okay as a stepping stone to get an intuitive understanding but it's really not the correct explanation it's more a statement of the problem to say that light appears to behave like a particle and a wave the reality is that it's neither it's a different kind of thing altogether it is a type of quantum object and it behaves as all Quantum objects do it obeys the Schrodinger equation which has something called a wave function in it this function does not show Quantum objects as waves in the traditional sense of waves but that their Quantum states such as position momentum spin Etc are in flux similar to the way that the amplitude of a classical wave is in flux if anything a Quantum object such as a photon is a wave of probability the probability of finding it at any particular location if we look there but about 50 years before these developments with quantum mechanics around 1865 James Clark Maxwell had come up with his laws of electromagnetism which revealed that light was an electromagnetic wave and that its speed could be determined precisely by two constants which are part of electromagnetic Theory the dielectric constant and the Magnetic constant which are now also known as the permittivity and permeability of free space this realization that the speed of light is determined by the innate property of empty space led Albert Einstein to hypothesize that the speed of light in space is the same for every reference frame and this is the essential postulate which led to the theory of relativity so light and the discovery of its properties played an important role in development of both quantum mechanics and relativity which together are the best understanding we have today of how the universe works but we're not done yet because light is even more profound in the role that it plays in our universe it is an essential way that our universe uses to transfer energy from one thing to another what do I mean by this let's take the Sun how does it Shine where does the light come from in the core of the Sun four hydrogen atoms combine to form a helium nucleus through a process called Fusion this process releases a lot of energy because a single helium nucleus is more stable and is in a lower energy State than the four hydrogen nuclei used to create it much of this energy released is in the form of gamma rays which are very high frequency or high energy photons these gamma rays however never reach us because their energy is absorbed in the dense plasma of the sun although these photons are traveling at the speed of light it still takes them thousands of years to reach the surface of the Sun due to the random motions they experience within the cortisone such that by the time they reach the surface their energies are down in the visible light range which is what we see here on Earth so this describes the origin of light from the Sun but what about artificial sources of light like we create on Earth such as from a street light or lamps that you turn on in your home at night or fire how are photons produce in these processes almost all the light created on Earth is the result of electrons collapsing to lower orbits in an atom after they have been excited by some source of energy into a higher energy state in an atom electrons are in specific discrete orbits which can be roughly calculated with the help of the Schrodinger equation these electrons can be excited to a higher orbit when absorbing energy often it's excited by a photon now you have an atom with one or more electrons in some excited state thus a higher energy State than the lowest energy state that it could be in but since all systems in nature prefer to be in their lowest energy State this excited electron will eventually move back into a lower orbit and in this process the excess energy is released as a photon almost all artificial light on Earth is produced by the process of electrons dropping to a lower energy State now the importance of light is not only evident in what we can see but also what we can feel what do I mean by that the theory of quantum electrodynamics developed in the 1940s by Richard feiner and others revealed that the electromagnetic force is mediated by photons in other words when like charges repel each other as in magnets or two electrons the particles carrying this Force are virtual forms of photons the same is true for the attractive Force such as that between photons and electrons or two opposite poles of a magnet virtual photons are carrying that Force too now if you want to know exactly how this mechanism works I have a video on that right up here for now let me just say that a significant number of forces you feel would not be possible without photons so for example the friction between your shoes and the ground which allows you to walk or the friction between your car tires and the road is fundamentally a product of electromagnetism this is because friction is caused by the electromagnetic interactions between the atoms of the two contact surfaces without light you wouldn't feel anything either because touch is a result of electromagnetic interaction between your skin and the surface you're touching since the very atoms in your body are held together due to the electromagnetic interactions between the positively charged nucleus and the negatively charged electrons orbiting them atoms would not exist without light either in other words no light means no atoms no cars no houses no you and me and no universe as we know it so not only would you not see or feel anything you wouldn't exist without light so you wouldn't care about the fact that sound waves may still exist because you wouldn't be there to hear it losing light would be a catastrophe at least for humankind now the universe could still exist if we took the electromagnetic force and threw it out the window but it would not resemble the universe we know we would still have gravity the strong force in the weak Force so we could still form nuclei and have certain nuclear decays very large nuclei could probably form in such a universe since there would be no electrostatic repulsion between protons which prevents very large nuclei from forming Life as we know it would not exist without light but could some other form of life exist hard to say because we know of no other mechanism for life other than what we see in this universe but I don't think we can rule it out so again let me ask the question that I asked at the beginning what is the purpose of life now I want to tell you that this is a philosophical question and not a scientific one so my answer is going to be speculative but it's such an interesting question that I'm going to tackle it anyway I want to First make clear that light is an inanimate object and has no innate purpose it is not sentient and does not exist to do something it simply exists and follows from everything we can tell the mathematical quantum mechanical laws of the universe having said that it appears to me that other than making the universe look the way that it does today light plays a vital role in almost all processes where energy is exchanged whenever energy is either expended or absorbed photons are almost always involved from chemical reactions to thermal radiation to friction even to many nuclear processes photons are involved so for example the heat released in any chemical reaction the sunlight absorbed by plants the energy used in biological processes of your body even the heat released from nuclear bombs all these involve photons in other words light is somewhere in the equation in fact you'll notice that the speed of light is present in Einstein's mass energy equivalence equation equals mc squared the speed of light here is considered a conversion factor that's used to show how energy and rest Mass are really the same thing but let's think about this a little more deeply what does this really mean for example what happens to the mass of the fuel in a nuclear bomb when some of it is converted to energy that energy is manifested in two ways one is in the form of kinetic energy carried by the materials that made up the bomb that are ejected at a high velocity but most of the energy is released in the form of heat and light this heat and light energy is carried mostly by photons and if it were possible to convert 100 percent of the mass of the nuclear fuel to energy in the end it would all be in the form of photons because photons are the only known particles that are capable of having energy and momentum without any rest mass that can also propagate freely unlike gluons which are also massless but are confined to the nuclei of atoms photons are so ubiquitous that in fact every object in the universe radiates photons this is called black body radiation and it's a property of any object above absolute zero and I want to point out that in the process of energy exchange via photons information is also exchanged so when we feel the heat of the Sun's light that light also carries information from the Sun indeed we would have very little information about our universe were it not for the various forms of light that we detect from stars and other objects in our universe this is not just visible light but also infrared ultraviolet X-rays and gamma rays and let's not forget the microwave background light which is present everywhere in the universe it's the leftover Embers of the early universe and provides strong evidence for the Big Bang so if I were to speculate or assign a purpose to light I would say it is the fundamental currency used to exchange energy and information from one part of the universe to another that's a pretty big purpose now stick around for a minute because you're going to want to see what our sponsor bespoke post has to offer it's like getting a Christmas present every month it's a monthly 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Channel: Arvin Ash

Views: 480,937

Keywords: speed of light, quantum mechanics, electromagnetic waves, is light a particle or wave, why does light exist, what is the purpose of light, how is light emitted from an atom, how does the sun produce light, how is light emitted, how do light bulbs produce light, would the universe exist without light, How are photons involved in electromagnetism, how do photons produce a force

Id: uT-6YVrecro

Length: 15min 9sec (909 seconds)

Published: Mon Feb 27 2023