See theNSCI 170A – Elements of DescriptiveAstronomyBlackboard sitefor aGeneral Relativityreading assignment
Albert Einstein(1879 - 1955)
The gravitational force that one object exerts on another objectcan be thought to occur in either of two ways:(1) Action-at-a-distance – The first object somehow exerts aforce on the second object across the distance between them.Newton’s idea of gravity(2) Gravitational Field – One object produces agravitationalfieldaround itself.A second object then interacts, not withthe first object directly, but instead with thegravitationalfieldproduced by the first object.The second object’sinteraction with the first object’s gravitationalfieldproducesthe gravitationalforceon the second object.Einstein’s idea of gravityNSCI 170A – Elements of Descriptive Astronomy
Field lines represent the gravitational field about the Earth.Where the field lines are closer together, the field isstronger.Farther away, where the field lines are farther apart, thefield is weaker.
Space – TimeAn event (such as a birth) occurs at a particular place inspace and at a particular time.We normally consider space and time to be bothseparate and absolute (the same for everyone).In Einstein’s Theories of Relativity, however, space andtime are not separate (they are intimately related) andthey are not absolute.NSCI 170A – Elements of Descriptive Astronomy
The General Theory of Relativity (1915)Everything is weightless on the inside of anon-accelerating spaceship far away fromgravitational influences → actual weightlessness
Everything is weightless on the inside of a spaceshipthat is in free fall → perceived weightlessness