[Tom Bishop]

I noticed that we did not have a page dedicated to the Equivalence Principle. I started one, and embedded that Classroom Aid explanatory video that either totallackey or iampc suggested to include.

https://wiki.tfes.org/Equivalence_Principle

[Tom Bishop]

An accelerometer tells you how that device is accelerating, as experienced on the stresses on the internal springs. While resting on the surface of Earth it reads 1g. While in free-fall the accelerometer reads zero. It's not accelerating while in free-fall.

In contrast, on a horizontal example, a jet accelerating at 1g is moving, and the stresses on a jet's accelerometer will read 1g of horizontal motion. Such a simple example.

http://gravityprobe.org/GravityProbe%20Links/Galileo-Undone-Mar-10-2020.pdf

[Longtitube]

All very interesting, but the gravity vs acceleration conundrum can only be applied if the Earth is indeed flat. For a round Earth, the proposed Universal Acceleration would mean the world accelerating in all directions simultaneously at 9.81 m/s², which is plainly ridiculous. Did Einstein consider the world to be flat instead of round? I can find no indication he did. Did he protest loudly at the successful application of General Relativity to solving the problem of Mercury's orbit in contradiction of the FE cosmology? No. Indeed, why does this subject absorb so much FE attention when General Relativity is a theoretical description of something called gravity which FE theory repudiates?

The inconsistency of argument here is extraordinary: the Equivalence Principle and Relativity (both special and general) are appealed to in support of a flat earth at the same time as it is used by physicists and astrophysicists in their modelling of a round Earth's behaviour in orbit around the Sun, of the Sun's effect on its satellites and much farther afield in the Universe. Relativistic predictions have been tested again and again over the past near-century and found to be accurate. The huge irony is that relativity started as a thought experiment which has borne out in practice, in measurement, in experiment, what it implies. How very un-zetetic.

The article you linked – thank you for that, it was most interesting as well as diverting – talks at some length of a proposed experiment to be conducted in outer space, a "place" FE theory apparently has no notion of (the extended thought experiment in that article, about Rotonians, is another non-zetetic construct, hence the amusement.) I should like to know what R J Benish is smoking, it's evidently strong stuff, but notice Benish is speaking of a ball Earth, visited by aliens who travel through outer space. Surely you don't intend to justify the FE model by appealing to astrophysics and the mainstream model of the universe?

[JSS]

One of the issues with trying to use the Equivalence Principle to show that we can't tell the difference between gravity and Universal Acceleration is that it only applies to small spaces where you can't observe anything outside of it.

https://en.wikipedia.org/wiki/Equivalence_principle#The_Einstein_equivalence_principle

Here "local" has a very special meaning: not only must the experiment not look outside the laboratory, but it must also be small compared to variations in the gravitational field, tidal forces, so that the entire laboratory is freely falling. It also implies the absence of interactions with "external" fields other than the gravitational field.

This is because while the effects of gravity and acceleration are the same, the objects or methods that produce them are not, and you can tell them apart.

A spaceship accelerating will not have tidal forces, and a planet will. The Earth is also much larger than an elevator, and we can look outside. These all are not permitted, and thus the Equivalence Principle can't be used.