 Hello everyone and welcome to our universe. Today we'll be answering the question, how does the sun produce energy? So we've all seen the sun burning bright in the daytime sky, unless you live in England. But people don't quite question where does the sun get all of its energy from? I mean we know right now that our sun isn't some kind of fire in the middle of the solar system. So what is powering this massive sphere that holds all the planets in place? So the sun contains most of the mass in the solar system and this is quite critical. The sun stands apart from all the planets because it's the only object in the solar system where nuclear reactions are really occurring. So what exactly is a nuclear reaction? Under extreme conditions it is possible for several atoms of one type of element to merge together to form a different element and it's also possible for a single atom to be broken up into several individual atoms. These are all known as nuclear reactions and there are two types, the fusion reactions and the fission reactions. These nuclear reactions can release a large amount of energy. The total mass of the atoms weighs slightly less than what they did before the atoms went into the reaction. This extra mass is converted into energy and this is what we see in the equation of E equals mc squared where E is the energy and m is the mass and c is the speed of light. Since the speed of light is a very large number, even a small amount of mass can result in a large amount of energy. Putting two small atoms together to make one bigger atom releases energy and this can happen to the mass of an iron atom. The fusion of smaller atoms is what produces the energy in stars, like our sun. And splitting apart a bigger atom to make two smaller atoms releases energy for atoms that are more massive than iron. This fission of large atoms is what produces the energy in nuclear power plants. This means that low mass atoms release energy by fusion reactions and higher mass atoms release energy by fission reactions. The iron atom seems to fall between these two groups. This is because no nuclear reaction involving iron can release energy. However, you can't quite expect nuclear reactions to occur so easily. To understand why, we need to know how the atom is actually structured. So inside the atom we have protons and electrons and these have a property called electric charge. Electric charge can come in two different signs, positive and negative. The protons are positive charge and the electrons are negative charge. There is also a fundamental force in nature which acts as an attractive force between objects with an opposite charge and also has a repulsive force between objects with the same charge. So in an atom the electrons are held to the nucleus by the electromagnetic force. But inside the nucleus all the protons have a positive charge but they manage to stick together despite the repulsive electromagnetic force. This is because there is another fundamental force that is taking charge and this is called a strong nuclear force. This holds protons and neutrons together and this force is stronger than the repulsive electromagnetic force between the protons. But this only happens if two protons are brought very close together and the only way to get protons in different atoms close together is that the strong nuclear force must overcome the electromagnetic force. This means that it allows two nuclei to stick together. This basically looks like the two atoms have collided at very high speeds. The nuclear reaction in our sun is probably most known as the proton-proton cycle in which four hydrogen atoms are combined in a series of reactions to form one helium atom. This chain of reactions also produces energy and can produce other particles known as neutrinos. But these reactions can only occur in the central regions of the star and this is where it's the hottest. Energy is generated in the central region and this keeps it very very hot. The energy that is generated in the central regions of the sun gradually works its way throughout the layers of the star. In the inner parts of the sun the energy gets out by radiation while the outer regions gets it out by convection. Eventually though it makes it to the surface of the sun and is radiated out into space. This means that the energy that we received from the sun was originally created by nuclear reactions in the core of our star. This radiation in convection can also be seen from the surface. For example things like granulation and sunspots. The sun also goes through a cycle known as a magnetic cycle. This takes around about 22 years to complete. This cycle seems to affect the solar activity. This means that it can have an increase of radiation and sunspots and it can also affect us here on earth. For example knocking out things like radio communications. The basic structure of the sun can be categorized in several layers. So you've got the core, the radiative zone, the convective zone, the photosphere, the chromosphere and the corona. Somewhat bizarrely the very outer layers of the sun, the chromosphere and the corona are hotter than the photosphere. This is probably because of the heat that is generated from the magnetic field of the sun. So you might be thinking to yourself why is the inner part of the sun hotter than the outside? Well this is due to the atoms in the central region moving a lot faster. This means that it has a kind of pushing out effect known as internal pressure. But also the sun is always fighting with its own gravity. This means that the internal pressure is higher than the external pressure. So the sun is literally being held up against a gravitational collapse. This internal pressure will continue to go on for another 4.5 billion years. Until the sun ceases to stop its nuclear reactions. And when this happens the gravity can take over and the sun will lose its nuclear reaction energy. So I hope that's given you a great insight into how does the sun produce energy. And of course if you want to know any more about the sun, how it produces energy, and nuclear power itself I'll put some links in the description below. And as always if you've enjoyed the video click the like button and if you want to support the channel click subscribe and support our patreon page. Thank you for watching and thank you for your support.