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https://en.wikipedia.org/wiki/Fictitious_force

When I came across this passage:

"

*This led Albert Einstein to wonder whether gravity was a fictitious force as well.*"

**He noted that a freefalling observer in a closed box would not be able to detect the force of gravity**; hence, freefalling reference frames are equivalent to an inertial reference frame (the equivalence principle)So suppose I am in a free falling closed box and there is no source of thrust. I have a tool to measure centrifugal forces consisting of 3 springs (X,Y,Z), each with 2 weights at each end M1 & M2. I perform a measurement of each spring and determine that one of the springs is stretched. From this single measurement of the state of the spring can I determine with certainty whether fictitious forces are present? How can I differentiate between these 2 scenarios: A) the box I am in is rotating or B) I am near an event horizon and the gravitational gradient between masses M1 and M2 is sufficient to stretch the spring