[ah4truth2017]

So after thinking y'all must be crazy, then reading a fair amount of the arguments in favor of FET, I've been shocked how well-reasoned the case is, at least at face value. I do have a few questions that I've yet to see even an attempt at explanation.

Question: Given Universal Acceleration, what causes ones stomach to "rise" when stepping off a cliff/bridge as in cliff jumping, bungee jumping, skydiving, etc? RET would say that gravity pulls you down, and the inertia on your inner organs causes them to delay enough to have nerves sense the movement. However, if UA explains the idea of "falling," then the only sensory effect would be the landing on the ground, right?

Side note: I do realize some in the FET-sphere (pun intended) hold to gravity being a thing, just with a different application than RET. However, since the TFES wiki claims UA as the explanation, I am specifically targeting my question at that viewpoint. Also, I do intend this as a real question, but apologize if it should have been posted in the debate forum, since that may be the logical extension of a response.

[Tom Haws]

I think the question is based on a misunderstanding of gravity. The feeling of the stomach rising may just as likely be due to the temporary absence of net forces. I don't mean that the stomach does not actually assume a "higher" position in the abdomen. What I mean is that the question has an imprecise insertion of inertia at an inappropriate point.

It's canonical to Newtonian physics that inertial acceleration is indistinguishable from gravitational acceleration. This is why this site's FE Universal Acceleration position is attractive to a certain point.

[ah4truth2017]

Inertia may be the wrong word. (I'm a mathematician, not a physicist) Can you explain what you mean by "temporary absence of net forces"? As I understand the Universal Acceleration argument, there isn't any "force" acting to "pull me to the ground." Rather, what I perceive as falling is the earth accelerating upward to meet me. If I step out from a cliff or bridge:

• No additional acceleration is applied to my body, as would happen if I jumped.
• From a literal sense, I float there until the Universal Acceleration causes the ground to meet me.

Now, the math of my "fall" would be equivalent between UA and gravity. But if my stomach does "assume a 'higher' position in the abdomen," what caused it to be pushed upwards while my body is (effectively) floating until I land on the ground.

[Roundy]

What property of gravity would make your stomach rise when you fall? Everything should fall at the same rate. A tennis ball and a wrecking ball dropped off that cliff at the same time will land at the same time; they will be equal in level at all stages of the fall; one will never have to catch up with the other. That's how gravity works. If your stomach is leaving that cliff at the same time as the rest of your body, stomach and body will fall uniformly together. So if it feels as if your stomach rises when you jump off a cliff it must be caused by something unrelated to gravity.

[StinkyOne]

What property of gravity would make your stomach rise when you fall? Everything should fall at the same rate. A tennis ball and a wrecking ball dropped off that cliff at the same time will land at the same time; they will be equal in level at all stages of the fall; one will never have to catch up with the other. That's how gravity works. If your stomach is leaving that cliff at the same time as the rest of your body, stomach and body will fall uniformly together. So if it feels as if your stomach rises when you jump off a cliff it must be caused by something unrelated to gravity.

This is pretty obvious, but when you fall, your organs are no longer resisting gravity. They no longer "feel" the usual weight that is experienced when fighting gravity. I don't think it is a rise more a sudden release of pressure. Once the sudden change has passed, the sensation diminishes. That is why skydivers don't feel like they are falling the whole time.

[devils advocate]

What property of gravity would make your stomach rise when you fall? Everything should fall at the same rate. A tennis ball and a wrecking ball dropped off that cliff at the same time will land at the same time; they will be equal in level at all stages of the fall; one will never have to catch up with the other. That's how gravity works. If your stomach is leaving that cliff at the same time as the rest of your body, stomach and body will fall uniformly together. So if it feels as if your stomach rises when you jump off a cliff it must be caused by something unrelated to gravity.

Because your stomach organs have space to move not accorded to the rest of your body as they are essentially bags/tubes of water and muscles thus they experience a less uniform response to falling than say your limbs.

Or maybe earth is flat because it looks flat from my window........

[Tom Haws]

Inertia may be the wrong word. (I'm a mathematician, not a physicist) Can you explain what you mean by "temporary absence of net forces"? As I understand the Universal Acceleration argument, there isn't any "force" acting to "pull me to the ground."

Right.

Rather, what I perceive as falling is the earth accelerating upward to meet me. If I step out from a cliff or bridge:

1. No additional acceleration is applied to my body, as would happen if I jumped.[/li][/list]

Right. Your body is suddenly free of the force of the earth resisting falling (Round Earth) or accelerating you (UA)

2. From a literal sense, I float there until the Universal Acceleration causes the ground to meet me.[/li][/list]

Almost. You keep on trucking free of outside forces until the earth at its new speed crashes into you again.

Now, the math of my "fall" would be equivalent between UA and gravity. But if my stomach does "assume a 'higher' position in the abdomen," what caused it to be pushed upwards while my body is (effectively) floating until I land on the ground.

Your organs spend your entire standing life squished against your pelvis by gravity. Remove gravity (or UA) and they are no longer squished. They move to assume the position accounted for only by your body tissues.

[ah4truth2017]

Your organs spend your entire standing life squished against your pelvis by gravity. Remove gravity (or UA) and they are no longer squished. They move to assume the position accounted for only by your body tissues.

Plausible, and tough to really use as an argument for either gravity or UA, since we are both describing the impact of relative acceleration compared to surroundings. (Looks like this is called the "Equivalence Principle"?)

However, it seems to me that some experimentation around this might be in order. We're essentially describing the same fluid dynamics as this question: https://physics.stackexchange.com/questions/76222/accelerating-fluid-filled-container. (There may be better resources for the principles of physics, that's just the first I saw and had a nice chart)

Proposed Test (that is, what's being tested)
1. With gravity, my velocity starts at zero, and increases at 9.8m/s^2 as I start to drop.
2. Under UA, my initial acceleration is 9.8m/s^2. As I step off, velocity is the current velocity of the earth, and acceleration becomes 0.

Mathematically, these describe very different positions for my body in space (on its own, position relative to the ground is immaterial) and my gut says the fluid dynamics would play out differently as well. However, a physicist would need to 1) describe the expectations in equations 2) determine a test to confirm the behavior. (I'm envisioning dropping a half-filled 2L bottle in slow motion?)

[douglips]

These two situations are in fact identical.

You could determine between UA and gravity with things like measuring the direction of gravity and finding it is sphere shaped instead of plane shaped, or by observing variations related to latitude (which are clearly observed and support round Earth and gravity). But you can't distinguish between them by just jumping off a cliff, because before you jump you are accelerating at 9.8 m/s^2 and after at 0, in both cases. The cause of the acceleration is either the Earth pushing you against it's gravity or actual acceleration, and you can't tell them apart.

That is the equivalence principle, a well established aspect of Einstein's theories.

[Tom Haws]

Equivalence principle is it. You can't tell. Better to focus on low-hanging fruit like the fact that No flat map can predict commercial airline flight times between New York, Paris, Cape Town & Buenos Aires.

[ah4truth2017]

While my intuition still suggests the equivalence principle isn't the complete answer, looking at Wikipedia's explanation did have more to support that conclusion. Particularly helpful was its discussion of free fall and an accelerometer. https://en.m.wikipedia.org/wiki/Accelerometer As this was just a question and not a debate, I'd say it can be considered answered for now.

[Havonii]

As far as gravity and UA, wouldn't it be true that,if you jumped off an edge, the initial velocity of the Earth(in UA perspective) would add to that of the force of the jump?

Would you even fall, or would your current acceleration become greater than that of the earth?

Without gravitation, there is no force to naturally pull you down once there is increased upward inertia.

[Roger G]

Unfortunately your point doesn't stand up, because your feet give you an initial acceleration, but once your feet leave the ground you have nothing to maintain you acceleration, so either the ground moving upwards catches up with you or gravity pulls you back down, take your pick 

Roger

[juner]

Come on, everyone, there’s a reason it’s called the Equivalence Principle and not the Mostly Equivalent Principle.

[StinkyOne]

Come on, everyone, there’s a reason it’s called the Equivalence Principle and not the Mostly Equivalent Principle.

This is one of the most annoying traits of FEH. It cherry-picks one principle out of a theory that deals with something it says doesn't even exist and treats it as some sort of validation. Einstein did not believe the Earth was flat and obviously knew gravity was real.

Let's assume UA is real. It pushes the Earth, it pushes the sun and moon, it pushes the stars. Why doesn't it also push bodies on the surface of the planet? What prevents us from also being accelerated? Seems like if it is pushing everything else, we (and other surface objects) would also be affected.

[juner]

Come on, everyone, there’s a reason it’s called the Equivalence Principle and not the Mostly Equivalent Principle.

This is one of the most annoying traits of FEH. It cherry-picks one principle out of a theory that deals with something it says doesn't even exist and treats it as some sort of validation. Einstein did not believe the Earth was flat and obviously knew gravity was real.

Let's assume UA is real. It pushes the Earth, it pushes the sun and moon, it pushes the stars. Why doesn't it also push bodies on the surface of the planet? What prevents us from also being accelerated? Seems like if it is pushing everything else, we (and other surface objects) would also be affected.

In UAT, if the earth was not between you and the acceleration source, you would be accelerated. That seems a bit nonsensical to suggest. It’s like being inside an accelerating rocket and asking why is only the rocket accelerating and not you specifically.

Try harder.

[nickrulercreator]

Come on, everyone, there’s a reason it’s called the Equivalence Principle and not the Mostly Equivalent Principle.

This is one of the most annoying traits of FEH. It cherry-picks one principle out of a theory that deals with something it says doesn't even exist and treats it as some sort of validation. Einstein did not believe the Earth was flat and obviously knew gravity was real.

Let's assume UA is real. It pushes the Earth, it pushes the sun and moon, it pushes the stars. Why doesn't it also push bodies on the surface of the planet? What prevents us from also being accelerated? Seems like if it is pushing everything else, we (and other surface objects) would also be affected.

In UAT, if the earth was not between you and the acceleration source, you would be accelerated. That seems a bit nonsensical to suggest. It’s like being inside an accelerating rocket and asking why is only the rocket accelerating and not you specifically.

Try harder.

Wait, doesn't UAT state that you're also being accelerated upward with the Earth? You stated you'd be accelerated if the Earth WASN'T between you and the acc. source, so is it safe to assume that we aren't being accelerated upward with the Earth?

[Tom Haws]

In UAT, if the earth was not between you and the acceleration source, you would be accelerated.

Wait a minute. Wait a minute. You would not instantly stop accelerating and "fall" behind/from/below the earth?

[StinkyOne]

Come on, everyone, there’s a reason it’s called the Equivalence Principle and not the Mostly Equivalent Principle.

This is one of the most annoying traits of FEH. It cherry-picks one principle out of a theory that deals with something it says doesn't even exist and treats it as some sort of validation. Einstein did not believe the Earth was flat and obviously knew gravity was real.

Let's assume UA is real. It pushes the Earth, it pushes the sun and moon, it pushes the stars. Why doesn't it also push bodies on the surface of the planet? What prevents us from also being accelerated? Seems like if it is pushing everything else, we (and other surface objects) would also be affected.

In UAT, if the earth was not between you and the acceleration source, you would be accelerated. That seems a bit nonsensical to suggest. It’s like being inside an accelerating rocket and asking why is only the rocket accelerating and not you specifically.

Try harder.

You should re-read what I said. If the acceleration source is under the Earth, how are the moon, sun, and stars affected??

[juner]

You should re-read what I said. If the acceleration source is under the Earth, how are the moon, sun, and stars affected??

You should re-read what has been discussed dozens of times here before. Everything in earth's non-inertial frame of reference is being accelerated. "Under" is a subjective and meaningless term.