Recent content by Sagittarius A-Star

If small bodies follow their geodesics, that is in GR not considered as an interaction force. Consider in flat spacetime two small moving bodies, that try to follow their (intersecting) geodesics. When they crash into each other, forces appear that are not considered to be gravitational...

That are in GR not gravitational interaction forces but electric forces within the extended object.

That's almost correct. It moves a distance ##a (1 \text{s})^2## ahead. Please see above.

That's wrong. Besides the fact, that the physical units on the left and right side of the equation are different, ##x(2s)## cannot be equal to ##x(1s)##, because the body continues to move while the deceleration.

That would be in average the case for electrons in a resistor, but in the OP screenshot, the electron is - according to the problem - in the ionosphere. In the ionosphere, the acceleration of the electron is proportional to E(t). In a resistor, the drift-velocity of the electrons is...

##v(t) = \dfrac{a_0}{\omega} (1 -\cos\omega t)## Assume you repeat periodically: accelerate your car from 0 mph to 65 mph, then press the brake pedal to decelerate from 65 mph to 0 mph. Then your car drifts in average.

The calculation result depends on the direction of movement of things in the moving frame. Assume the two coordinate systems in standard configuration. The easiest case is the following: If things in the "moving frame" (##F'##) move perpendicular to the direction of the relative velocity ##v##...

The relativity (kinematics) chapter of Morins classical mechanics book is also online available: https://davidmorin.physics.fas.harvard.edu/sites/g/files/omnuum12331/files/2025-10/cmchap11.pdf via: https://davidmorin.physics.fas.harvard.edu/books/classical-mechanics

Yes. But ##\Phi_B = \int \int_\Sigma {\vec B \cdot d\vec S}## changes over time, because the angle between the magnetic field and the normal to the rotating surface changes over time. ##\Phi_B (t) = SB \cos {(\omega t + \alpha})##, where ##S## is the area of the loop. ##EMF = - {d\Phi_B...

For geometric intuition: In Geometric Algebra, the electromagnetic bivector can be written in the following way as the sum of a projection on the parallel and a rejection on the perpendicural part. The sandwitch product ##uFu^{-1}## is a reflection with respect to the hyperplane with normal...

I think in GR tidal gravity, it just has to be small enough and insensitive enough.

Is it a matter of adoption of a definition, what a true force is? I think a true force can be measured with an accelerometer.

Why? I think a true force creates a deviation from the geodesic.

I don't think so. If for example an asteroid breaks in tidal gravity, the related forces are electrical forces between parts of it.

This video shows, how to use ##\LaTeX## in MS word.