How Our Universe Violates a Fundamental Law of Physics! Energy Conservation

this video is sponsored by Magellan TV the best documentary streaming service available click the link in the description to get your first month absolutely free it may be the most sacrosanct principle in all of science something you learned in elementary school the idea that overall energy is always conserved that energy can never be created nor destroyed it can only change form so for example when a car is in motion but comes to a stop the kinetic energy of its motion is converted to frictional heat from the brakes no energy is lost it's just converted from one form to another similarly a swinging pendulum converts its gravitational potential energy when at its maximum height to kinetic energy at its lowest height if there were no friction from the fall Karma air the pendulum could theoretically swing back and forth forever but even with friction overall energy is still conserved when you take the heat from the friction into account what if I were to tell you that although conservation of energy for all practical purposes and applications on Earth is conserved on the scale of the universe this isn't not the case energy is not conserved the universe as a whole what how can this be stay tuned because I'm going to explain that coming up right now foreign conservation of energy is a conservation law that states that in an isolated system overall energy Remains the Same over time there's Sometimes some confusion about isolated system versus closed system in thermodynamics an isolated system is one in which no energy or matter can enter or leave a well-insulated thermos would approximate an isolated system but there's no perfect isolated system we know of a closed system is one in which no matter enters or leaves but energy can a covered pot or cup of tea would approximate a closed system so in an isolated system that is a system where no matter or energy enters or leaves overall energy Remains the Same energy only changes form we see examples of this every day when you're driving and you slam the brakes to a stop what happens to the kinetic energy of your car well it's converted to heat by the friction from the brakes you don't feel this heat because this is not an isolated system the heat is dissipated to the atmosphere but if you could somehow put your car brake Road and atmosphere in a box and measure the heat you would find that the kinetic energy of the car has nearly perfectly transformed into heat energy the same holds true for any isolated system and would apply to other phenomena such as the pendulum I talked about earlier so the question we want to ask is whether this holds true for the universe as a whole can be considered the entire universe a well-defined isolated System since the universe is everything shouldn't it be the ultimate isolated system turns out that the answer is not straightforward let's examine why if we want to include the whole universe we have to include everything from the very small to the very large let's start with the very small the behavior of the micro scale is described by quantum mechanics which is the physics of the smaller scale objects from the subatomic to the atomic and Beyond at the quantum level the concept of energy conservation is explicitly defined this is Illustrated and arguably the most important equation in quantum mechanics the Schrodinger equation this equation is all about energy it shows that the total energy is equal to kinetic energy plus potential energy energy is conserved according to this equation this is just one example but we can invoke other equations as well in order to show that the energy is explicitly conserved in quantum mechanics so there's no problem at micro scales now let's look at the largest scales the best tool we have to describe objects at the largest scales such as the Earth Sun and galaxies is Einstein's theory of general relativity the core of this theory is represented by Einstein's field equations which in its simplified form looks like this I've discussed this in several videos in the past but let me do a quick recap the left side describes the curvature of space-time the right side represents the matter and energy contained in space-time what this equation shows is that matter and energy affects the curvature of space-time this curvature is what we perceive as gravity and the curvature of space-time affects matter and energy the simplest way to summarize this equation is as the famous physicist John Wheeler put it matter tell space-time how to curve and space time tells matter how to move it's as simple as that the matter and energy is contained in this term on the right side of the equation T sub mu Nu this is known as the stress energy tensor also called the energy momentum tensor we need to take a closer look at this because this is where energy is defined in general relativity and general relativity reveals that the derivative of the energy momentum tensor is zero to be more precise the term on the left is called the covarian derivative but for simplification pertaining to what we're discussing you can think of it as the derivative so the simplified way to think of this equation is that the change in energy and momentum remains zero this is called the principle of energy momentum conservation note that this equation is not saying that energy stays the same only that the combination of energy and momentum Remains the Same in other words only the combined energy and momentum is conserved what general relativity tells us is that if space time we're standing still that is if it were flat and not changing then energy would be constant but if space time is curving and changing then the momentum is changing and thus the energy is changing as well so astonishingly it tells us that at large scales energy is really not conserved in the universe we can point to several observations that confirm this the first is the observed expansion of the universe the first empirical evidence of this was gathered in 1929 by Edwin Hubble then in the late 1990s scientists discovered that the universe is not only expanding but that this expansion is accelerating this acceleration is called dark energy the problem with expanding space-time is that empty space has energy if the volume of the space is increasing then energy is increasing we know that the energy density of space time doesn't change but energy density is energy over volume if the volume increases then energy also increases this phenomenon appears to indicate that energy is not being conserved another consequence of an expanding space time is The observed redshift the light from distant galaxies is redshifted as the universe expands the wavelength of light also expands and as we learn from Max Planck E equals H Nu where H is clocked constant and Nu is the frequency which we can rewrite as the speed of light divided by wavelength Lambda thus we see that if the wavelength is longer the energy is lower so the photons have lower energy by the time they reach us this appears to violate conservation of energy where did this loss of energy of the photons go well the energy of the photon is Observer dependent from our perspective the photon loses its energy to the expanding space time between its origin and us now I know some of you are going to ask since we know that dark energy is increasing could it be that the energy that light waves lose turns into Dark Energy thus conserving energy overall well the problem with that idea is that even if you take all the observed light of the universe into account it would not account for the amount of dark energy in the universe dark energy is almost 70 percent of the energy of the universe whereas all the matter and light that we can observe is only about five percent the Lost energy of light would be a minuscule portion of all the energy needed to counterbalance increasing Dark Energy the expansion of the universe presents a major issue with treating the universe as an isolated system we don't even know what the size of the universe really is so we can't Define what the isolated system would be we only know the observable universe which is about 94 billion light years in diameter there's a so-called Cosmic Event Horizon which is at the end of the observable universe the galaxies at the edge of this Cosmic Event Horizon are moving away from us such that the light Beyond it will never reach us I was watching a video on Magellan TV today's sponsor which showed how it's possible that the universe beyond the visible Universe could be infinite and if that's true then the universe would definitely not be an isolated System since we could not put any boundary around it in this case we would have to conclude that the Universe likely does not conserve energy the Magellan TV documentary is called is the universe infinite and it's a fascinating exploration of the question how far do stars stretch out in space and what might be Beyond them you can click the link in the description to check out that documentary for free right now because the first month of your Magellan TV subscription is absolutely free but once you see the rest of their extensive high quality ad-free content I think you'll want to become a member as well it's the highest rated documentary streaming app on Google Play and I would highly recommend it just click the special link in the description or type the URL that's right ahead here on your screen now even if the universe is not infinite it is probably still the case that it is much much larger than the 94 billion light year diameter that we observe so we don't know what the isolated system in which energy may or may not be conserved consists of should the isolated system be just the observable universe if so what about the galaxies that are moving out of the observable universe what about their energy if we consider just the observable universe as an isolated system then we're clearly losing matter and due to E equals FC squared we're also clearly losing energy from our system when galaxies leave our observable universe now I must point out that some experts believe that overall energy is conserved in an expanding Universe because they argue you have to include the energy of the gravitational field along with the energy of the matter and radiation in other words as distances between objects increase the increasing gravitational potential between them can be thought of as a kind of negative energy now how the heck is this considered negative energy legendary physicist Stephen Hawking explained it this way when you pull two objects apart you need to expend energy to overcome the gravity that pulls them together since it takes positive energy to separate them gravity must be negative energy and this increasing negative energy perfectly cancels increasing Dark Energy some argue now this is not an incorrect way to think of it the problem is that unlike dark energy which has a constant energy density there's nothing like a constant gravitational density in the universe the curvature of space-time is not defined at every point in space but is defined locally by whatever matter Energy may be present there so calculating whether the notion of negative gravitational energy counterbalancing dark energy cannot practically be done but the main point against this notion is that since general relativity plainly points out that energy on its own is not conserved we may be better off just letting go of the idea of energy conservation at the scales of the universe even though it's nearly perfectly valid at the human skills in which we operate so practically speaking our energy conservation equations are valid they only begin to show cracks when we start looking at very large scales so we should not be throwing out a thermodynamics books quite yet I'll see you in the next video my friend [Music]

Channel: Arvin Ash

Views: 114,101

Keywords: physics, conservation of energy, conservation of energy physics, conservation of energy and momentum, conservation of energy pendulum, is energy conserved, energy in the universe, Does the universe conserve energy, is energy conserved in quantum mechanics, Is energy conserved in the universe, How energy is not conserved, energy is not conserved, isolated vs closed vs open system

Id: wd2Zkxc_HYc

Length: 12min 41sec (761 seconds)

Published: Sun Jun 18 2023