Hello. In this first video, we're going to describe energy in the universe. Universal rules that apply everywhere. Specifically, we'll be talking about components of the universe, before universal forces asking the question, what is energy? And the related question, what is work? We'll talk about generic types of energy and two broad classifications or categories of energy. In the beginning, physicist tell us there have always been four major categories or components of the universe. Time, space, mass and energy. Space and time are connected through theories of relativity, often called space, time. And mass and energy are connected through theories of mass energy equivalence has shown by Einstein's famous equation, E=mc2 where C is the speed of light. And one thing we'll need to note carefully is that mass energy is always preserved. We'll talk a lot more about that in the future. In addition to the four universal components of the universe. Therefore, universal forces. The first of these is the strong force. It holds atomic nuclei together. Let's say it has a relative strength of one. The 2nd, universal force are electromagnetic forces. These electrically buying charged particles positive and negative. That's what binds atoms into molecules. We know that opposite charges attract and the same charges repel each other. The weak force is very weak. It's involved with radio activity. And finally there's a gravitational force. It's the attraction between objects with mass. We're very familiar with gravity of course. It has a relative strength that's very tiny compared to the other three. 10 to the -38. We think of gravity as being a pretty powerful force, but compared to the other three, it's really weak. So now let's ask what is energy and what is work? Energy is a consequence of the universal forces. It comes from those universal forces, the strong, the weak, the electromagnetic and gravitational forces we talked about just now. Energy is often said to be the ability to do work, where energy makes things happen, movement, heat, light, sound radio ways and chemical reactions are all examples of work. Work in many ways can be thought of as the transfer of energy. When turning a wind turbine, sunlight into electrons in a solar PV set up, steam in a geothermal plant, water flowing through a hydroelectric dam, chemicals propelling a rocket, lifting and rolling a bowling ball. All are examples of energy being used to do work. Let's now relate the forces of nature to some typical types of energy. The electromagnetic forests, chemical bonding and electromagnetic radiation show up in chemical energy, mechanical energy, radiant energy, thermal energy, the energy of motion, electrical energy and the energy of sound. Gravitational force the mutual attraction of masses show up as gravitational energy we're very familiar with that. The strong force holds atomic nuclei together and it's involved with nuclear energy. We're not going to talk much about nuclear energy in this course, but it's something to be familiar with. And finally, the weak force radio activity has very limited of application in renewable energy or the topics we're going to be talking about. It has occasional use and we'll talk about those, but it's not terribly important for our purposes. There are two broad categories of energies that are useful. There's kinetic energy which you can think of as active energy or potential energy that we can think of restored energy. Examples of kinetic energy or radiant energy, such as the energy from the sun, thermal energy, such as heating heat from burning wood or fossil fuels or whatever energy of motion, the momentum moving mass, electrical energy such as lightning or electricity and wires, the energy of sounds such as the thumping of a bass drum. Examples of potential energy include gravitational energy. We're very familiar with that energy of objects at a height such as a bowling ball on a shelf. Chemical energy such as the energy and gasoline. Mechanical energy such as a stretch spring or rubber band. And nuclear energy such as the energy in uranium. These are examples of kinetic energy and potential energy and there are many others. In summary, we've been discussing energy in the universe. We've discussed the four universal forces, the strong, weak electromagnetic and gravitational forces. We understand that energy derives from forces work as a result, useful things that result movement results. There are two categories of energy, kinetic or active energy and potential or stored energy. And there are many types of energy motion, radiant energy, thermal energy and so forth. We'll be talking about many of these in the videos ahead. In the next video, we'll be talking about energy on earth. So stay tuned we'll see you there.