Classroom Aid - Gravitational Time Dilation
Channel: David Butler
Date: 2023-04-10

Text  http://howfarawayisit.com/wp-content/uploads/2015/12/General-Relativity-II-Effects.pdf
Credits http://howfarawayisit.com/wp-content/uploads/2013/05/Credits-and-Research.pdf
In this segment of the “How Fast Is It” video book, we cover the effects of general relativity and how they differ from what Newton’s gravity predicts. Our first effect is the orbit of Mercury that precesses more than Newtonian gravity predicts. To understand the non-Euclidian space that Mercury orbits in, we introduce the Schwarzschild metric and compare it to the Minkowski metric for flat space-time. We illustrate the positive curvature around the Sun using concentric circles with shrinking circumferences. We then show how this slight difference in curvature produces additional movement in the precessing perihelion of Mercury’s orbit that exactly fits the measured number. Our next effect is the bending of light. We cover Arthur Eddington’s famous measurement during a total eclipse of the Sun and show how the amount of starlight bending matched Einstein’s calculations better than Newton’s. We extend this bending effect to show how Einstein Rings and gravitational lensing work. And we show how this effect tips over light cones and changes world-lines. Our third effect is gravitational time dilation. We show how it works and cover how our GPS uses it. We also cover the Pound-Rebka experiment used the Mossbauer Effect to showed how this time dilation impacts gravitational redshift. We also illustrate how this effect resolves the Twin Paradox we introduced in the Special Relativity segment. Our final implication involves frame-dragging. To understand this effect, we introduce the Kerr Metric that covers rotating energy densities that literally drag space along with them. We use Gravity Probe B to illustrate how it works and how it is measured. We finish with an in depth look at the black hole Gargantua from the movie Interstellar.