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Relativity - Intro

In physics, the theory of relativity (or simply relativity) encompasses two theories by Albert Einstein: special relativity and general relativity.


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Video Transcript

Welcome to our next unit in physics, one of three in this unit. We're going to be discussing the topic relativity. So if you recall from physics 101 Relativity is the mathematics that we do to account for the motion of one reference frame with respect to another. For example, if we have reference frames and be a reference frame might be a person standing here at a and a person standing here at B except A is holding still relative to the ground, and B is moving relative to a or, in other words, a feels like they are not moving. And they observed that B is moving relative to them with some velocity v b A. And then the two of these people look at a point c and try to figure out its motion based on what they observe. Member ref guy in reference frame be will think that he's not moving. Meanwhile, stick figure in reference frame A will think that they're not moving, and this leads to some transformations for position and velocity Now. Similarly, we had some other examples of relativity. We had the boat attempting to cross the river where the River has some velocity with respect to an observer on the shore, and the boat has a velocity with respect to the river. We also talked about a boy Joe housing up a ball inside of a train. Where to the person who's tossing it, it appears to go up and down. But to a person standing here on the side, what they observe is the ball goes up and then translates to the side before being caught by the person who is also translated because of the velocity of the train with respect to the person on the side. So these are all instances of relativistic motion, and it seems pretty standard. Now. The question of why are we coming back to this? Is that it turns out that when we start to really consider relativity, there's some problems that arise. In particular, problems arise with universal constants. Things like you, not an epsilon, not from physics, one of two that we used to calculate electric and magnetic fields, an electromagnetic radiation. These things are constant and should be the same in every frame of reference. And what does that mean for relativity? So Einstein is one, along with many others who considered this question and came up with water, known as his special in general theories of relativity. We're going to start off by looking at what's known as Galilean relativity, which is what we used in physics 101 And then we will progress into talking about Einstein. What he postulated, what has been found since then, and how we can account for this strangeness that's going to occur because of relative motion.