On Friday, March 14, 2025 at 8:31:55 AM UTC-6 Alan Grayson wrote:
On Friday, March 14, 2025 at 6:46:05 AM UTC-6 Alan Grayson wrote: On Friday, March 14, 2025 at 3:59:42 AM UTC-6 Alan Grayson wrote: Maybe the EP just showed Einstein that graity is not a force, so it must be modeled differently, possibly by geometry? AG No. The EP just shows that gravity is equivalent to acceleration ignoring tidal forces, but the fact that no forces are exerted on a body in free fall is what showed Einstein that gravity couldn't be modeled as a force. I have to check; this might be called the Weak Equivalent Principle (WEP). AG The WEP states that gravitaitonal and inertial mass are equivalent, which is implied by the fact that all bodies, regardless of their mass, fall at the same acceleration in a gravitiational field. Now I am puzzled by the fact that an orbiting body is in constant free fall, or constant acceleration, yet its velocity remains essentially unchanged. Can someone explain this? AG This is the explanation: an orbiting object is in constant free fall and is constantly accelerating, but the acceleration vector is perpendicular to its velocity vector along its trajectory, pointing in the direction of the center of mass. Hence, the *magnitude* of its velocity vector is NOT constantly increasing. For example, for perfect circular motion of an orbiting object, its velocity is constantly accelerating, but the magnitude of its velocity remains constant. AG On Wednesday, March 12, 2025 at 3:37:55 PM UTC-6 Alan Grayson wrote: As precisely as possible, can anyone describe the function and value of the EP in the construction of GR? Alternatively, how are the field equations implied by the EP? TY, AG -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion visit https://groups.google.com/d/msgid/everything-list/2b739a08-39cb-4d80-af81-d92baedefe82n%40googlegroups.com.
