What is an Orbit? Learn the Definition of Orbit - What Low Earth Orbit Is - How Gravity Works - 01

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• published: 09 Jan 2017
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What is an orbit? How do orbits work? We will discuss how low earth orbit can be achieved by launching satellites in space using high horizontal velocity during launch. Launching satellites in orbit is possible by understanding Newton's theory of gravity and how Einstein refined the ideas of how gravity works and the definition of gravity. Finally, we will discuss zero gravity in low earth orbit and how satellites and astronauts float in space. --------------- Hello welcome to get smart in science. here we're going to explain what an orbit is and i have a few key questions that i want to point out to you that we're going to answer here and the goal is to take something seemingly complicated and break it down so that it's understandable and only a few minutes. First thing we're going to talk about it how it is in orbit work we're going to talk about how orbits can exist and go on and on forever seemingly without stopping. We're going to talk about why astronauts seem to be weightless when they're in orbit and how does the spacecraft enter in orbit and stay the there and along the way we'll talk a little bit about history of orbits and kind of the evolution of those ideas. So the first thing here is we all know that we have the Sun at the center of the solar system. Right that's what we know today in the 21st century and the planets go around the Sun so here we have mercury venus here's earth with the moon there Mars Jupiter Saturn Uranus Neptune and Pluto. Now if you zoom in even further any spacecraft satellites, space station anything like that that's in orbit around the Earth is going around and around the earth itself. So just like the moon goes around and around the earth all satellites whether their weather satellites space shuttle space stations are always in motion are always going around the earth in low earth orbit. Later in 1687 the famous Isaac Newton which I know you've heard of who lived between these years and two 1726 published his very famous law of gravitation which again we still use today and the big thing about it i'm going to talk a little bit more about what his law of gravitation really is but the takeaway from it is this right here he basically used his law of gravity to correctly predict using math that the orbit of the planets always follow an elliptical path. so whereas Kepler looked at the night sky and figured out that the planets must be moving in ellipses Isaac Newton developed a theory of gravity and an equation that describes gravitational force and he used that equation to again predict that all the planets should move that way so he knew he was on the right path and that his law of gravity must be pretty close to being correct because he used his law of gravity to predict how the planets actually move in real life. now here's where things get interesting we're going to take a few minutes to talk a little bit about Newton's law of gravity now there's a lot of stuff on the page here so don't worry too much about absorbing it all at once let's take it one step at a time basically what Newton said is that everything that has mass in the universe whether it's a planet or a peanut or a tree they all exert a gravitational force on everything else in the universe and that gravitational force is calculated or can be calculated by this equation. Now I'm not going to do a bunch of calculations here but i do want you to know that there's an equation that exists that Isaac Newton developed and this is basically what it is so the illustration here you can see in one just means mass number one so this could for instance be the earth and this could for instance be a space station or a moon let's call it the moon. that's we all know going around the earth but forget about the fact that its orbiting Earth it's just some moon out there right so what Newton's laws basically saying gravitational laws saying that there's a force that exists between these two things just because they have mass and just because we live in this universe where gravity exists. so if you look at it here this mass here is pulling on this moon with some force we call it f it's pulling at this direction right because gravitational force is attractive and then of course we have this moon here also pulling on the earth so gravity always kind of works in pairs like that each body is pulling on the other one. right so let's go down this list and i'll talk a little bit more about the equation Newton's law of gravity basically says that all objects with mass attract each other. everything whether it's a peanut a bumblebee a bulldozer a planet a black hole if it has mass it's always has this attractive force we call the gravitational force number to gravity is always attractive that means that gravity never repulses we never have repelling bodies pushing away from each other.