Summary of Einstein's General Theory of Relativity | Lecture 1

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00:00:00 - 01:00:00

In this lecture, Leonard Susskind discusses Newton's equation F=MA and how it applies to an object in an inertial frame of reference. He explains that the mass of an object is a conserved quantity and that the equation can be used to calculate the force exerted by an object on another object. Susskind then goes on to discuss how gravity is a very weak force compared to other forces. However, the force of gravity is still felt strongly because the Earth is so heavy. Finally, Susskind explains the concept of the gravitational field and how it is created by all the masses in the universe.

  • 00:00:00 In this video, Leonard Susskind discusses Newton's equation F=MA and how it applies to an object in an inertial frame of reference. He explains that the mass of an object is a conserved quantity and that the equation can be used to calculate the force exerted by an object on another object.
  • 00:05:00 In the first lecture on Einstein's General Theory of Relativity, the speaker covers Newton's laws of motion and gravity. He then explains how Galileo studied the motion of objects in the gravitational field of the earth. The key point is that in the approximation where the earth is flat, the direction of gravitational forces is the same everywhere, and the force doesn't depend on how high you are.
  • 00:10:00 In this video, Leonard Susskind discusses how the force of gravity is proportional to mass, and how this causes objects of different masses to fall at the same rate. He also talks about how the constant G varies from place to place.
  • 00:15:00 Einstein's General Theory of Relativity states that gravity is equivalent between all different objects independent of their mass. This has the interesting consequence that falling in a gravitational field is undetectable. You can't tell that you're falling in a gravitational field by looking at your neighbors or anything else.
  • 00:20:00 In this lecture, Leonard Susskind discusses Newton's law of gravity, which states that the force between two objects is proportional to the product of their masses and inverse to the square of the distance between them. He explains that this law is not dimensionally consistent and that there must be a small numerical constant in order for it to work. This constant is known as Newton's constant, or G.
  • 00:25:00 In this video, Leonard Susskind discusses how gravity is a very weak force compared to other forces. He demonstrates this by showing how an object with a small mass will not be significantly affected by the force of gravity. However, the force of gravity is still felt strongly because the Earth is so heavy. Susskind explains that this is because the acceleration of an object due to gravity is determined by the force of gravity and the mass of the object, and the Earth has a much greater mass than a human.
  • 00:30:00 In this lecture, Leonard Susskind discusses Isaac Newton's laws of motion and how they can be used to explain the behavior of objects in a gravitational field. He also briefly touches on other force laws, such as the electrostatic force law, and how they differ from the gravitational force law.
  • 00:35:00 In this video, the speaker discusses how uncharged particles move differently than charged particles with respect to electrostatic forces, but the same with respect to gravitational forces. He also talks about how to express Newton's force law in vector form, and how the total force on a particle is equal to the sum of the forces from all the other particles.
  • 00:40:00 In this lecture, Leonard Susskind discusses Einstein's General Theory of Relativity. He explains that the force on the Ith particle is the sum of all the forces due to all the other particles, and that the direction of each individual force is toward the other particle. He also explains that if we combine this with Newton's equations, we see that the acceleration of the Ith particle does not depend on its mass.
  • 00:45:00 In this excerpt, Leonard Susskind explains how a person would experience gravity if they were extremely tall. He says that they would feel a sense of stretching, with their feet being pulled away from their head. He also explains that the force of gravity would squish them horizontally.
  • 00:50:00 In this lecture, Leonard Susskind discusses the concept of the gravitational field. He explains that the gravitational field is an abstraction from the formula for the force of gravity. He also discusses tidal forces and how they cause deformations in objects.
  • 00:55:00 The gravitational field is a vector field that represents the force of gravity on an object. It is created by all the masses in the universe and is proportional to the mass of the object. The field can be mapped out by observing how a test particle moves in different parts of the field.

01:00:00 - 01:35:00

In this series of lectures, Leonard Susskind explains Einstein's theory of general relativity. He begins by discussing how the force on a particle is equal to the mass times the acceleration, and how the acceleration is determined by the gravitational field. He then explains how to use Gauss's theorem to calculate the amount of fluid flowing in or out of a surface. He also discusses how a point mass can be thought of as a concentrated divergence of the gravitational field. Finally, he explains how the theory applies to objects with spherical symmetry.

  • 01:00:00 In this video, Einstein's theory of general relativity is explained. The force on a particle is equal to the mass times the acceleration. The acceleration of a particle at a certain point is determined by the gravitational field. Gauss's theorem is used to define the concept of divergence.
  • 01:05:00 The divergence of a field is a measure of how the field changes in space. Gauss's theorem states that the divergence of a field is equal to the derivative of the field with respect to X, Y, and Z.
  • 01:10:00 In this lecture, Leonard Susskind explains what divergence is and how it can be used to determine the direction of flow of a fluid. He gives an example of a lake with water being pumped in from underneath, and explains how the water flowing out on one side indicates that there is a net inflow from somewhere else.
  • 01:15:00 Gauss's theorem states that the amount of fluid flowing out of a surface is equal to the integral of the divergence over the interior of the surface. This theorem is important in understanding the behavior of fluids.
  • 01:20:00 In this lecture, Leonard Susskind explains how to use Gauss's theorem to calculate the A field outside of a sphere in which a divergence is occurring. He gives the example of a fluid flow, and explains that the integral of the divergence is the total amount of fluid flowing in per unit time.
  • 01:25:00 In this lecture, Susskind explains how a point mass can be thought of as a concentrated divergence of the gravitational field. He starts by discussing how the magnitude of the field is equal to the total integrated divergence divided by four pi, and how this is similar to the Newtonian field of a point mass. He then explains how a point mass can be thought of as a concentrated divergence of the gravitational field, and how this explains the fall off of the field with distance.
  • 01:30:00 In this lecture, Leonard Susskind introduces the audience to Newton's theorem, which states that the gravitational field of an object is the same whether the object is a point mass or a spread out mass. He explains that this theorem is important for understanding the motion of an object near the surface of the Earth.
  • 01:35:00 In this lecture, Einstein explains how his general theory of relativity applies to objects with spherical symmetry. He shows how the interior of such an object would be identical to the exterior in the absence of gravity, and how the exterior would be identical to the interior of a black hole.