# How do we tell the difference between centrifugal forces and gravity?

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So I was watching this lecture [here](https://youtu.be/JRZgW1YjCKk?t=2139) by Dr. Leonard Susskind and he mentions around the 35 minute mark that one way to tell the difference between if an object was in a true gravitational field and an apparent one created by acceleration was if tidal force were crushing or pulling on the object in question. How do we explain artificial gravity systems that rely on centrifugal forces then? I would assume that the centrifugal force would count as an acceleration based apparent gravity field, but objects in such a setup experience tidal forces since the apparent gravity in the center of such a setup is lower than the apparent gravity at the edge. It’s kind of confusing me a little.

In: Physics

That’s not a tidal force. A tidal force is the result of one body stretching another due to a gradient in its gravitational field. The centrifugal force is a fictitious force because it’s a rotating reference frame. It’s not an actual gravitational field. What Dr. Susskind is talking about is linear acceleration, which locally is indistinguishable from gravity. In simulated gravity via centrifugal force, the force is pulling the person *away* from the axis of rotation, as opposed to gravity, which pulls towards the center of mass. Simulated gravity would also make people inside experience the Coriolis force, another fictitious force. This is all assuming you can’t just look at some window and see that you’re rotating.

Centrifugal force is the force that acts outward on a body moving around a center arising from its own inertia.

An example would be how a wheel of a sort is always pushing outward while spinning from it’s center.

Gravity is, yenno Gravity. It is not as a force, but as a consequence of the curvature of spacetime caused by the uneven distribution of mass.

In theory, there is no experiment that can be done to tell the difference between gravity and a space craft accelerating.
But “gravity” generated by a rotating body has some quirks related to it being a rotating body.
Say the floor of the orbital habitat was 10 meters from the axis.
Say you are 1.5 meters tall.
When you stand up, you head is 8.5 meters from the axis, but spins around the axis the same number of times a minute as your feet.
Your head is thus experiencing less acceleration, because it’s essentially a smaller wheel.
So if you wanted to know if you were on a spin station, hold an accelerometer at two heights and see if they don’t match.