The Flat Earth Society
Flat Earth Discussion Boards => Flat Earth Theory => Topic started by: fisherman on November 03, 2020, 12:40:40 AM
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I read that quite often and it is true enough, but "level" is a relative term. In RET, it means level with respect to the center of gravity.
In FET, with respect to what is water "level"?
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In FET, 'level' and 'flat' are presented as synonyms.
This is mostly due to the assertion that gravity isnt real, and the apparent force/acceleration we feel is due to constant upward acceleration of the earth's disk at 9.8 m/s^2.
Just dont talk about water 'level' during tidal changes...
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You need to be careful because depending on scale, water can curve quite significantly regardless of FET or RET. At the micro scale, water on a surface can bead up, and against the edges of containers you have a curved meniscus. We all observe this every day when it rains on our freshly waxed cars and when we drink from a glass of water. Of course these effects are different to what you describe at the macro scale.
At the macro scale, let's just all assume that gravity is a real effect for now (I'm a proponent of RET by the way, just so you know). On a sphere, gravity acts towards the centre of the mass causing water to be held against the surface. On a flat disc with a rim around it, the constant acceleration upwards also holds the water against the flat surface. In both cases you can swim around and splash about and any water ejected will return back to the main body of water. Agreed?
Let's now imagine that we have a perfectly smooth sphere and a perfectly flat disc (or dish as is more accurate) and we pour water onto those surfaces. In both cases the water would end up at a constant depth covering both surfaces. Agreed?
In FET, the surface of the water is both level AND flat. As Iceman2020 says, flat and level are the same thing in this context. In RET, the surface of the water can look level but is definitely not flat, it curves around the sphere. The issue is one of scale, as you know. The Earth is so large that even if you absolutely know the Earth is round, when you look out at the horizon at sea, at eye level the water still looks flat/straight/not curved, pick the word that make most sense here.
This is the underlying principle behind the Zetetic Inquiry approach that led to the conclusion that the Earth is flat, and this is where scale comes in. People saw that water in their cups and bathtubs and in lakes was incredibly flat, and I think we would all agree with that. Those same people looked out to sea and saw that the horizon was also flat, and again, we would all agree with that observation. Putting those two together, the conclusion was formed that the Earth itself must also be flat, and no further testing of the hypothesis took place. Everything else in FET stems from there and seems contingent on preserving that core conclusion, but to discuss further here would be woefully off-topic and I want to respect the rules of conduct as best I can.
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In FET, 'level' and 'flat' are presented as synonyms.
I guess that's the problem. They aren't the same thing. A table top can be flat without being level. If you want to say that it's level, you have to answer the question level compared to what? Most people understand that to mean level with the floor.
If water always finds its own level, what determines what water's "level" is?
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In FET, 'level' and 'flat' are presented as synonyms.
I guess that's the problem. They aren't the same thing. A table top can be flat without being level. If you want to say that it's level, you have to answer the question level compared to what? Most people understand that to mean level with the floor.
If water always finds its own level, what determines what water's "level" is?
gravitey
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gravitey
I understand thats the case with RET. I am asking about FET.
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gravitey
I understand thats the case with RET. I am asking about FET.
Strictly speaking, nothing - under FET the Earth is surrounded by (at the very least) an ice wall, so in simple terms you can think of a flat Earth as being like a petri dish - water just fills it up. But, the added theory of Universal Acceleration (the flat Earth explanation for gravity, where the Earth is said to be constantly accelerating upwards at a rate of 9.8m/s^2) is what helps keep that water on the surface instead of floating away.
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The commonly-spouted phrase 'water finds it's own level' is a big part of the issue of understanding things (in my opinion). The phrase implies that water has an inherent property to seek out level or flatness. This is completely untrue, as we know from observation and experimentation.
A better phrase (but still very imperfext) would be "water responds rapidly and predictably to applied stress(es)". Every level surface of water we observe on earth is under an applied stress. We will honour equivalency here and say it's either gravity or upward acceleration. This creates the level (flat-ish) surfaces to everything from puddles to oceans.
Important distinction though: that water is not in it's natural state - it is in equilibrium with the forces applied to it. For a closed, static system, that's gravity/UA. Keep observing that water for a while and you'll see ripples in puddles as a vehicle walks by or a kid walks through it. Waves form on lakes as the wind pulls on the surface, if those are sustained long enough, a seiche can develop, creating up to several feet of difference between water levels in up wind vs downwind shorelines, on the oceans tides go up and down twice daily.
Water's 'natural' state is only observable where the forces acting upon it are net-zero, such as in space, on the ISS. Here we see water forming spherical to amorphous blobs.
That's a long rambling mess just to say that water doesnt do anything except what its told. Take a body of water that has 'found its level', put your face close to it, and just yell at it to do something. With a loud enough voice you'll see what I mean!
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Water's 'natural' state is only observable where the forces acting upon it are net-zero, such as in space, on the ISS. Here we see water forming spherical to amorphous blobs.
I kinda' disagree, in that liquid waters natural state is observable regardless of what forces are acting upon it. When observed on Earth in the presence of gravity, it forms a level normal to the surface (mathematically speaking). In the complete absence of gravity it forms a sphere/globule as approximated in experiments onboard places like the ISS or Vomit Comet, where the effects of gravity are cancelled out.
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A better phrase (but still very imperfext) would be "water responds rapidly and predictably to applied stress(es)". Every level surface of water we observe on earth is under an applied stress. We will honour equivalency here and say it's either gravity or upward acceleration.
OK, I think I get it. In RET, water is level relative to the center of gravity and in FET, it is level relative to UA. The point you make supports the idea that water can curve, if it is only responding to the forces applied to it.
The surface of the water is always perpendicular to the force applied to, then water must curve in order to stay perpendicular to the force of gravity, which follows the curve of the globe.
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@fisherman
Iceman said, In FET, 'level' and 'flat' are presented as synonyms.
but this isn't quite right.
Level and horizontal are the synonyms. Level and horizontal are only ever flat (sort of a square / rectangle relationship). These are facts, and they have no refutation - regardless of perspective on the shape of the world. If you disagree, please provide any demonstration of your belief that level and horizontal can differ. NOT an explanation - a demonstration!
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Level and horizontal are the synonyms. Level and horizontal are only ever flat (sort of a square / rectangle relationship). These are facts, and they have no refutation - regardless of perspective on the shape of the world. If you disagree, please provide any demonstration of your belief that level and horizontal can differ. NOT an explanation - a demonstration!
I don't disagree that level and horizontal are the same. It's that very fact that would allow water to curve on a globe earth. Water conforms to the shape of the force acting upon it. Gravity on a globe earth curves, therefore when gravity acts on water, it must also curve in order to stay horizontal (or level) to the force.
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@fisherman
Iceman said, In FET, 'level' and 'flat' are presented as synonyms.
but this isn't quite right.
Level and horizontal are the synonyms. Level and horizontal are only ever flat (sort of a square / rectangle relationship). These are facts, and they have no refutation - regardless of perspective on the shape of the world. If you disagree, please provide any demonstration of your belief that level and horizontal can differ. NOT an explanation - a demonstration!
Level = horizontal, but neither of those means flat.
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Flat is synonymous with straight
Level is synonymous with horizontal
Jack44556677 is 100% correct in this regard. Something is considered level when it is either normal to a flat surface, or tangent to a curved surface. Level definitely does not necessarily mean flat:
(https://www.industrialconcreteflooring.co.uk/app/uploads/2018/06/image-CBS-floortolerance.png)
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Flat is synonymous with straight
Level is synonymous with horizontal
Jack44556677 is 100% correct in this regard. Something is considered level when it is either normal to a flat surface, or tangent to a curved surface. Level definitely does not necessarily mean flat:
(https://www.industrialconcreteflooring.co.uk/app/uploads/2018/06/image-CBS-floortolerance.png)
I 100% agree with that. My point is that a static fluid cannot have shearing forces. So any force effecting the surface of water must be horizontal to it. On a globe earth, gravity effecting the surface of water would follow a curve, so the water must also curve to remain horizontal to gravity.
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I 100% agree with that. My point is that a static fluid cannot have shearing forces. So any force effecting the surface of water must be horizontal to it. On a globe earth, gravity effecting the surface of water would follow a curve, so the water must also curve to remain horizontal to gravity.
Yeah I’m not sure this can be refuted regardless of model. On a globe Earth water follows the curve, on a flat Earth it remains flat. Just so happens that when the globe is very large and you’re a tiny human being, water on a curved Earth still looks flat.
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So we all agree that water surfaces on earth are level/ horizontal. This surface develops as an equilibrium response to stress(es) applied to it, and that the surface will be perpendicular to the direction of net stress - in FET this means the direction of our upward acceleration, in RE, this means gravitational pull towards the center(ish) of the earth.
The equivalency of those two options holds for any snapshot in time, if we are considering observations made from the surface of the earth (because we arent going to use satellite or NASA hoax data to shape this discussion).
I would argue that one of the key areas where deficiencies in UA arise, is when you look at the temporal aspect of what we know about water's surface along our ocean coastlines. Tides create water surface variations of up to several meters, twice per day. Regardless of the cause of these fluctuations, we know that for water's surface to change its local elevation (with respect to a tide gauge, for instance), 'level' is not constant. Level, at broad scales, varies through time.
UA clearly does not explain these spatial and temporal changes in water levels, but they do fit with RE and our understanding of gravity related to the relative pulls of the moon and sun, over the course of earth's rotation.
This point is not meant to shift the focus of this thread to debate the origin of tides - search in the wiki and in other fora for numerous past descriptions of Tidal mechanics in FET. The point here was to emphasize that 'level' is observably transient, based on centuries of measurement of water at gauges along our coastlines.
For the curious, I would recommend looking into how we actually define "sea level" for such a common phrase, and the single most important elevation datum we have, its an amazingly complex history!
Here's a link to a video that introduces (but definitely doesnt explain in any real detail) some of the issues
https://www.youtube.com/watch?v=9hciQPtNhD8
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Interesting stuff Iceman2020, and while it might be going a little off-topic, I agree with your sentiments. In any model, FET or RET, tides are complex things because they vary in number and magnitude all over the surface:
https://earthscience.stackexchange.com/questions/16556/why-high-tides-occur-simultaneously-on-opposite-sides-of-the-earth (https://earthscience.stackexchange.com/questions/16556/why-high-tides-occur-simultaneously-on-opposite-sides-of-the-earth)
However, if we just subscribe to the fact that generally speaking gravity causes water to bulge in places, it does raise the valid question of what "level" really means. Perhaps in this context it's better to think of gravity as a vector (has a direction and a magnitude):
Under RET, gravity is a vector pointing directly towards the centre of the Earth. However, the Moon also has gravity. Its vector points towards the centre of the Moon, directly away from the Earth, just smaller in magnitude. Same with the Sun, it too has a vector that points away from the Earth, although smaller in magnitude again due to distance and scale. The resultant gravitational effect on the body of water is the sum of those three vectors, and the surface of the water is always at a tangent to the normal vector. Mathematically you could say it is "level" with respect to gravity, but in reality the surface would still be curved (even if we can't observe it due to scale).
(https://upload.wikimedia.org/wikipedia/commons/thumb/a/a8/Normal_vectors_on_a_curved_surface.svg/310px-Normal_vectors_on_a_curved_surface.svg.png)
Under FET, gravity (caused by UA) also has a vector always pointing directly down towards the surface of the Earth. In this model, my understanding is that neither the Sun or Moon have the property of gravity, so given that the Earth doesn't rotate either, as Iceman2020 says, UA alone clearly does not explain the mechanics. I couldn't find anything in the Wiki here, or much elsewhere to be honest so I'd be interested to know what those mechanics are.
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Under FET, gravity (caused by UA) also has a vector always pointing directly down towards the surface of the Earth. In this model, my understanding is that neither the Sun or Moon have the property of gravity, so given that the Earth doesn't rotate either, as Iceman2020 says, UA alone clearly does not explain the mechanics. I couldn't find anything in the Wiki here, or much elsewhere to be honest so I'd be interested to know what those mechanics are.
It isn't just tides that are a problem for FET/UA model, but the behavior of water in general on earth's surface. Whatever the force is that keeps things "pinned down" on the surface in response to UA (inertia?), it isn't enough to keep water from flowing downhill.
There's a reason why plumbers install pipes on a downward slope. Water in a level pipe doesn't flow. But when it is on a slope, it begins to flow. Movement requires force, which suggests there is a force at work when a pipe is on a slope that is not present when a pipe is level. The Equivalence Principle wouldn't account for this because (among other reasons), it only applies to objects that are in free fall.
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@fisherman, maybe my understanding of UA isn't correct, but doesn't the Equivalence Principle go something like as follows:
- In a rocket in space, not moving, I feel weightless. The equivalent to being in freefall on Earth.
- In a rocket accelerating upwards, I feel weight. The equivalent to standing on the surface of the Earth with gravity.
Neglecting wind resistance and other complexities of where the ground is, in the first example, if I had a glass of water and slowly tried to pour it out, it would pretty much just stay in the glass or at least stay relative to my position. In the second example, the water would pour out onto the surface beneath me. If Universal Acceleration is considered actual constant upwards acceleration of the Earth (much like the rocket) wouldn't water in a sloping pipe just flow as we expect anyway?
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@fisherman, maybe my understanding of UA isn't correct, but doesn't the Equivalence Principle go something like as follows:
- In a rocket in space, not moving, I feel weightless. The equivalent to being in freefall on Earth.
- In a rocket accelerating upwards, I feel weight. The equivalent to standing on the surface of the Earth with gravity.
Neglecting wind resistance and other complexities of where the ground is, in the first example, if I had a glass of water and slowly tried to pour it out, it would pretty much just stay in the glass or at least stay relative to my position. In the second example, the water would pour out onto the surface beneath me. If Universal Acceleration is considered actual constant upwards acceleration of the Earth (much like the rocket) wouldn't water in a sloping pipe just flow as we expect anyway?
Your understanding of UA is the same as mine...won't necessarily say it is correct, though. I'll let a FEr weigh in on that.
The important point that the FE explanation misses is that the equivalence principle only applies to objects in free fall. .
Water in a pipe isn't in free fall (because its movement is constrained by the pipe) unless or until to flows out of the end of the pipe. But there has to be a force that moves it out of the end of the pipe to begin with. Assuming there is no water flowing in from the other end to push it out, if you slope the pipe and there is no gravity to pull the water out of the pipe, it won't go anywhere. No force, no movement.
UA and the EP is an elegant alternative to gravity for objects in free fall, but there are countless effects of gravity that don't involve free fall. Your feet swell when you are on them all day because blood returning to your heart has to work against gravity. Gravity is partially responsible for why plant roots grow down, trees can only grow so high because rising sap has to work against gravity.
The clearest example I can think of is a rollercoaster. They are usually gravity driven. Keep in mind, the coaster itself is not in free fall. It is (hopefully) attached to the ground so it is rising with the surface of the earth and the riders in the cars are rising with it. If the earth, the coaster and the riders are all rising together as one system, what happens after the chain pulls the riders to the top of the first hill if there is no force to pull the riders down? Nothing. The whole system will just continue to rise together as the earth rises.
As the whole system rises, there is no relative change in the distance between the top of the hill and the bottom of the hill. If the riders are at the top of the hill, there is no reason why the relative distance between the riders and the bottom of the hill should change unless there is a force acting on the riders that is not also acting on the rest of the system.
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Perhaps my understanding of the Equivalence Principle is incorrect as well, which is eminently possible (and I know there are weak, Einsteinian, and strong versions which complicate things further!). I thought it was the inability to distinguish between being stood on the surface of a massive body, and being inside an accelerated frame of reference - the key word there being "accelerated".
I do get what you are saying, and I considered the whole "all moving as one thing", but like I said, the key word is "accelerated". A similar analogy could be a ball on the floor of a train. At a constant velocity, the ball, the train, me, the whole system is traveling at the same rate so everything just stays in the same relative position, doesn't matter what the velocity is. We can't feel constant motion. As the train accelerates we are all subject to the same acceleration, I feel the effect of that acceleration but I'm fixed in my seat so I don't move - I'm essentially part of the train. The ball is not fixed to the floor, it's free to move, and so relative to my direction of travel it appears to roll backwards away from me (falls, in effect).
Is that not the same as your rollercoaster example? Under UA, everything - the Earth, the rollercoaster, the rollercoaster car, the people strapped in the car are all moving upwards as one system. If the Earth were just moving up at a constant velocity, in the absence of any other force your last statement would be correct - there would no reason for the riders at the top of the hill to change their position relative to it. However, if the Earth were accelerating and changing its velocity over time, the car is free to move relative to the track which is fixed to the Earth. Riders strapped into the car at the top would now effectively roll downhill. It's the acceleration of the Earth upwards that gives rise to the apparent force acting on the car, i.e. gravity. This is why they are equivalent, and this is why flat Earth theory uses it in its sub-theory of Universal Acceleration...is my understanding anyway!
I dunno' mate, I might have it all wrong, it's really interesting stuff nevertheless. It's certainly easier to wrap your head around an accelerating body giving rise to the "effect" of gravity I'll give them that!
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However, if the Earth were accelerating and changing its velocity over time, the car is free to move relative to the track which is fixed to the Earth. Riders strapped into the car at the top would now effectively roll downhill.
The car is not in free fall. It's movement is constrained by the track and can only move with the track. If the track accelerates, the car accelerates with it. We aren't physically fastened down to the surface of the earth, either, but apparently we accelerate along with the earth according to UA. Its perfectly possible to stand on a steep hill and not "fall down". That wouldn't be possible if the ground beneath us was constantly accelerating and we were not moving. No matter how subtle the slope, eventually we'd end up at the bottom. Again, the equivalence principle doesn't apply when an object is supported in any way.
Also, roller coasters generally don't move exactly vertically . If the hill is at anything less than a 90 degree angle, there is some horizontal movement that UA can't account for. Think of a box on any 45 degree inclined plane...in order for the box to "appear" to slide down the plane, the plane would have to move horizontally.
Anyway, that's the way I see it. Maybe a flatearther can chime in. Gravity is so ingrained into our everyday experiences, it's hard to visualize how things would behave without it.
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I spoke to a colleague of mine last night who used to be a physics teacher and had this discussion with him. As a hypothetical thought experiment, he agrees that under the equivalence principle, and assuming equivalent atmospheric pressure, there would be absolutely no difference to how a rollercoaster would behave on the surface of a massive body like Earth, and how it would behave inside a constantly accelerating reference frame as per UA.
Under UA, we all accelerate upwards and are effectively “pushed” into the surface of the Earth, but the surface stops us falling through. Using your hill analogy, the hill is part of the Earth. You’re not, you can move independently, just like the rollercoaster car can move freely with respect to the track. The reason you don’t fall down a steep hill is because of high friction between the soles of your shoes and the surface of the Earth. If you were to suddenly remove the hill from the equation, you’d be in mid air. You wouldn’t just keep on accelerating upwards, you’d slow down because the Earth is no longer pushing you. The Earth would accelerate up towards you and you’d appear to fall. If you took the same scenario but instead of removing the hill, you swapped it with smooth ice, this is more analogous to the rollercoaster scenario. Yes you are still being slightly accelerated upwards because now you’re on the surface still, but this time the acceleration forces are enough to overcome the friction forces and so you slide down the hill.
Stuff moving sideways is all explained by the same forces and vectors which have a direction and magnitude. On a horizontal surface the box wouldn’t move. On a slight incline, the box may or many not move depending on how much friction there is, but let’s say it does move, albeit slowly. The steeper the incline, the faster the box slides. At vertical, the box is in free fall. UA would account for this because it’s directly analogous to gravity on Earth pulling us down.
Honestly, I know it’s hard to wrap your head around, but if the Earth were constantly accelerating upwards at 9.81 m/s^2, neglecting all the other complications/contradictions that the Wiki tries to explain, you wouldn’t be able to tell the difference between that, and the attractive force of gravity on Earth as we know it. Things would rise and fall and behave exactly as they do now.
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Honestly, I know it’s hard to wrap your head around, but if the Earth were constantly accelerating upwards at 9.81 m/s^2, neglecting all the other complications/contradictions that the Wiki tries to explain, you wouldn’t be able to tell the difference between that, and the attractive force of gravity on Earth as we know it. Things would rise and fall and behave exactly as they do now.
Things if free fall would rise and fall exactly the same. The EP is restricted to objects that have no net force on them, you can't assume that it applies to objects that have net force.
Stuff moving sideways is all explained by the same forces and vectors which have a direction and magnitude. On a horizontal surface the box wouldn’t move. On a slight incline, the box may or many not move depending on how much friction there is, but let’s say it does move, albeit slowly. The steeper the incline, the faster the box slides. At vertical, the box is in free fall. UA would account for this because it’s directly analogous to gravity on Earth pulling us down
Perfect example...you can't calculate vectors the same way with UA as you do with gravity. Any object on a slope has a net force on it. On a flat surface the normal force and weight from gravity cancel each other out so there is no movement. That works with UA as well.
But on an incline, the normal force will always be some fraction of the weight/gravity/UA, so the forces are unbalanced. When force are unbalanced, there is movement in the direction of the stronger force. With gravity that would be downslope. With the UA, the object would "fall" upslope because UA is the stronger force.
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I've done a bit more digging and reading as the thought experiment is genuinely fascinating, if hard to wrap your head around because as you say, we live with the effect of gravity as part of our daily lives so to think differently literally means thinking outside the dome. Ultimately it only applies to a small region of space and time, but it does state that gravitational mass and inertial mass are equivalent, even if not strictly correct as per the video I linked to below.
I think I got my head around most of it, but I must admit, I can't quite grasp the concept of something sliding "up" a slope under UA. Let's imagine I'm on a flat Earth cliff edge in space, with two boxes at my feet, one "on the ground" and one "over the edge", with no upwards acceleration at all. I'm sure we both agree that in this scenario, this is equivalent to free-fall on Earth. We are all weightless and both boxes just stay put. Now somebody flicks the UA switch and we all start accelerating upwards at 9.81 m/s^2. Both myself and the box on the top of the cliff now have inertial mass because we are in direct contact with the object that is accelerating us, and we experience that force as weight. Being at the top, the box just stays where it is. However, the other box over the edge is still weightless. The Earth accelerates up towards that box, but to my frame of reference it has fallen to the ground. To an external observer outside of the Earth, the falling box didn't really move at all, it was the Earth moving up to meet it.
This represents the two extremes - either the box doesn't move relative to me at all, or the box falls to the bottom of the cliff. It never goes up relative to me, and surely can't go up in the absence of any other force or acceleration acting on it? Now replace the cliff with an incline, where let's say the force of UA is greater than the friction forces between the box and the surface caused by inertial mass. The steeper the incline, the faster it will reach the bottom. Perhaps I'm completely missing something really simple, but another analogy here on Earth could be a wooden ruler held at an incline with a pencil rubber on it. At some angle it will still stay put due to friction. However, if I were to suddenly be accelerated upwards holding the ruler (creating my own "local UA" if you like) that rubber would appear to slide down the ruler from my perspective. To somebody else stood on the ground, it will appear as though the rubber essentially stayed still, and in fact saw the ruler sliding up the rubber. Just depends on your frame of reference. That's how I see things anyway, but the realities could be very different.
I found this page and video interesting though, and it pretty much sums up FET in a nutshell - takes existing science and facts, extracts the bits that fit, warps the rest and skews the consequences accordingly. It does kinda' make sense why on the bigger scale the Equivalence Principle doesn't work in the flat Earth model interpretation of it:
http://backreaction.blogspot.com/2020/08/what-is-equivalence-principle.html (http://backreaction.blogspot.com/2020/08/what-is-equivalence-principle.html)
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Let's imagine I'm on a flat Earth cliff edge in space, with two boxes at my feet, one "on the ground" and one "over the edge", with no upwards acceleration at all. I'm sure we both agree that in this scenario, this is equivalent to free-fall on Earth.
No, only the box “over the edge” is in freefall. The box on the ground is not. In GR, freefall means there is no net force on an object. More technically, it means an object moves unimpeded along a geodesic. If an object is supported, then there is a normal force on it, and it can’t move unimpeded on a geodesic.
We have to consider in our experiment is that a rolling object down an inclined plane is not in free-fall. The inclined plane exerts some force on the object. The larger the inclination of the plane, the smaller the force exerted by the plane, and the closer the object will be to free-fall
https://www.racefitlab.com/Experiment hgAAAA8AAAAgwxxeAAAAAA==#:~:text=We%20have%20to%20consider%20in,will%20be%20to%20free%2Dfall.
Perhaps I'm completely missing something really simple, but another analogy here on Earth could be a wooden ruler held at an incline with a pencil rubber on it. At some angle it will still stay put due to friction. However, if I were to suddenly be accelerated upwards holding the ruler (creating my own "local UA" if you like) that rubber would appear to slide down the ruler from my perspective.
The problem is that in order for it to appear that the rubber “slides down”, the ruler would have to move horizontally to some degree, and UA can’t account for horizontal movement, only vertical.
The way I visualize it is an object suspended from the ceiling by a string, just touching a wedge. If you raise the wedge straight up (creating your own UA, as you say), the object won’t slide down (the string would counteract gravity). It would just stay where it is and rise up with the wedge. In order for it to appear to “slide down”, while actually remaining stationary, the wedge would have to move up and either to the left or right (depending on the direction of the angle on the wedge).
I think that is the major fault with the concept of UA=gravity. The effect that gravity has on an object will shift and change as the position of the object changes. I don’t think UA can do that. It has to always be exactly vertical and effect the whole object with exactly the same magnitude.
Anyway, I don’t pretend to have it all figured out, but I do know that the knee jerk reaction of “...but the equivalence principle...” on this site whenever someone raises a question about the effect of gravity is not justified. It only applies to free falling objects and we see too many effects of gravity that have nothing to do with freefall...from saggy body parts to how plants grow.
I found this page and video interesting though, and it pretty much sums up FET in a nutshell - takes existing science and facts, extracts the bits that fit, warps the rest and skews the consequences accordingly. It does kinda' make sense why on the bigger scale the Equivalence Principle doesn't work in the flat Earth model interpretation of it:
Exactly, they take the bits and pieces of a concept that fits their narrative and ignore the rest. Einstein’s concept of the EP and GR went through several iterations before the final theory was developed. One of the last (maybe even the last) definition of the EP he made is
Principle of Equivalence. Inertia and gravity are phenomena identical in nature. From this and from the special theory of relativity it follows necessarily that the symmetric “fundamental tensor” determines the metric properties of space, the inertial behavior of bodies in this space, as well as the gravitational effects.
Einstein didn’t say that from the equivalence of gravity and inertia, it necessarily follows that the earth is accelerating upwards. But that's exactly what flatearthers want to pretend that is what he said.
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I think I get where you are coming from, and nor do I profess to have it all worked out either. I'm not thick, but I do have limits and gaps! What's obvious though, reading what you've said and from elsewhere, is that you cannot just take the Equivalence Principle as refined and twist it around to fit the UA narrative - just doesn't work.
It would explain why water is "level" on a flat Earth per the subject, but doesn't explain tides because they shot themselves in the foot by rejecting gravity so need an alternative theory for that.
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Level and horizontal are synonyms, I am glad we agree on this.
Level and horizontal are both always flat, by definition and, more importantly, in manifest objective reality.
Yes, I am aware of the incorrect definition of level being taught in "schools". There is no curve-a-level. Level is always both flat and horizontal.
If you disagree, and believe that your definition is correct - then please provide a demonstration in reality of level and flat ever differing.
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Level and horizontal are synonyms, I am glad we agree on this.
Level and horizontal are both always level, by definition and, more importantly, in manifest objective reality.
Yes, I am aware of the incorrect definition of level being taught in "schools". There is no curve-a-level. Level is always both flat and horizontal.
If you disagree, and believe that your definition is correct - then please provide a demonstration in reality of level and flat ever differing.
You could do your best, on a calm day, to align a rod to the level of the sea, then align another rod at exactly a 90 degree angle with the first. That second rod would result in a vector pointing upwards. If you did that experiment once in Los Angeles, USA and again in Shanghai, China the vectors would point in completely different directions. If the earth were flat, both of the upward pointing rods would be parallel. If the earth were spherical, they would be at a much different angle. This is what's effectively happening when you observe a gyroscope. This is an unbiased observation, it's just the information produced by an instrument that couldn't care less what the earth's shape happens to be. Now we are not talking about a single gyro but dozens, all producing the same results. If you travel in any direction upon the high seas in a ship the gyros will indicate that the center line between the bow of the ship will relentlessly tilt further & further with the bow going down and the stern going up.
It's a bit more difficult to make an exact determination of what is level while underway on a ship because the ship's tilt is always changing. However it is certainly possible to observe a change in angle of 90 or 120 degrees with no ambiguity. It's also possible to see the level when a ship is at the dock. Strangely enough ships always have large & accurate levels aboard. Why? Because when they are at the dock and cargo & fuel are being loaded, it's important to keep the ship level to reduce stresses on the hull and not break any dock lines. This is done by pumping ballast water from tank to tank.
Perhaps there's another explanation for these actual observations under real world conditions that I don't know about. It would appear to me that the gyro is indicating that the ship is navigating on a very large sphere. The size is large enough for the human eye to be unable to detect any curvature or a change in the Z axis, but the much more sensitive gyroscope is able to measure a change over days & weeks which would be expected because of the speed of the vessel and the size of the earth.
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Level and horizontal are synonyms, I am glad we agree on this.
Level and horizontal are both always level, by definition and, more importantly, in manifest objective reality.
Yes, I am aware of the incorrect definition of level being taught in "schools". There is no curve-a-level. Level is always both flat and horizontal.
If you disagree, and believe that your definition is correct - then please provide a demonstration in reality of level and flat ever differing.
What's your definition of flat? Flat in this context to me means "free of raised areas or indentations", in which case even the flat Earth cannot be considered flat because it has hills and valleys. But, if we remove that level of pedanticity (that's a word now!) and let's just say that a flat Earth is indeed flat. Well, then so is the side of of my house. That's flat, but it is almost certainly not level, and doesn't really need a demonstration - just go outside yourself and have a look at your own. The surface of the monitor I'm looking at now is very flat, much flatter than the side of my house, but is far from level. That's two examples of level and flat differing.
The fact of the matter is that level and flat are two different things, regardless of the shape of the Earth. I completely understand what you are attempting to drive towards, but being flat relates to the surface itself, and being level relates to the surface being at the same height, perpendicular to the centre of gravity. But, since you don't believe in gravity either I suspect the debate could be rather moot.
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pedanticity (that's a word now!)
https://dictionary.cambridge.org/dictionary/english/pedantry
What's your definition of flat?
In this context, it's pretty obvious what a flat surface of water is, and, assuming FET, it will indeed be synonymous to a level body of water. You'll struggle to find a vertical, or otherwise askew, surface of water.
rejecting gravity
Whoah there, cowboy. Nobody's "rejecting" gravity. And, since you almost certainly meant gravitation, nobody's "rejecting" that, either.
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https://dictionary.cambridge.org/dictionary/english/pedantry
Don't be so pedantic ;)
In this context, it's pretty obvious what a flat surface of water is, and, assuming FET, it will indeed be synonymous to a level body of water. You'll struggle to find a vertical, or otherwise askew, surface of water.
Synonymous in that context maybe, but still doesn't mean they have the same definition. Even in RET, for a normal person stood on the surface, the same can be argued - it looks flat and level. However, on the larger scale, the surface of the water follows the curvature of the Earth, and it does so because of gravity. Thus completing the never-ending cycle of debate, because under FET, water cannot "curve", despite there being plenty of references I can make to water surfaces being askew in nature.
Whoah there, cowboy. Nobody's "rejecting" gravity. And, since you almost certainly meant gravitation, nobody's "rejecting" that, either.
Errr, nope, I certainly meant gravity, and jack44556677 has plenty of references to gravity around words such as "fiction", "not real", "concocted", "there is none", "if it were real", "Newton would have scrapped it" etc. Excuse me for interpreting that as anything other than rejecting the concept of gravity. This is backed up with a similar rejection of the concept of mass, leading to the conclusion that weight is an intrinsic property of matter - something you'd know if you took the time to understand why I might have written what I did instead of putting words into my mouth again.
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If you disagree, and believe that your definition is correct - then please provide a demonstration in reality of level and flat ever differing.
It happens all the time. I live in an 110 year old house. Put a carpenter’s level on the floors, they will be flat, in that, both ends of the level will rest on the floor, but I guarantee you that many places aren’t level.
Flat is a description of the surface of an object. A planar surface is flat. Level is about the orientation of an object relative to some reference.
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Synonymous in that context maybe, but still doesn't mean they have the same definition.
Technically correct, but entirely irrelevant, given that you yourself already acknowledged the importance of context. I'm not sure why you'd waste our time like that.
Errr, nope, I certainly meant gravity
To be completely clear: if you "certainly meant gravity", then you've found someone who claims things don't fall on Earth (regardless of the cause).
https://byjus.com/physics/difference-between-gravitation-and-gravity/
https://www.toppr.com/guides/physics/difference-between/gravitation-and-gravity/
I doubt you have indeed found someone who claimed that, and based on the context of this conversation (and your subsequent statements), it's nigh-impossible that you meant anything other than gravitation.
Christ, one day you'll learn not to just lash out at every disagreement you encounter, but it'll be a long process.
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If I’m remembering correctly, Newton imagined gravity when an apple fell from a tree. But if that apple would have caught on fire would the same gravity pull the smoke down like it did the apple. What would be easier to pull. If you have 2-100’ ropes. With a Bicycle on the end of the first rope and a train on the second rope. The bike would be because it’s 1000’s of times smaller than the train and would require less force.
So why would the force of gravity pull down a bowling ball faster than it would a feather. It should take less force to move the feather.
Gravity doesn’t effect the tides. If it did, when it moves the oceans and seas +/- 10’ it would also move that small pond in my back yard. But It doesn’t move it, not 1”. Just like every other body of water that’s not connected to the oceans.
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Technically correct
I'm glad we agree
but entirely irrelevant, given that you yourself already acknowledged the importance of context. I'm not sure why you'd waste our time like that.
Ah...
If you think it's irrelevant and a waste of time, just skip it then. Regardless of the shape of the Earth, flat means flat, level means level, they don't mean the same thing and never will. Under FET, they are used as synonyms with respect to water at every vantage point, under RET they are only synonyms in certain circumstances because water curves. This is supposed to be the Flat Earth Theory forum, and this discussion relates directly to FET and the very title of the thread, including a direct request for a demonstration of the difference between flat and level.
...Christ, one day you'll learn not to just lash out at every disagreement you encounter, but it'll be a long process.
Not sure where you went with that as I absolutely 100% meant gravity, as clearly written multiple times in black and white. If you want to yet again infer that absence of gravity means somebody thinks things don't fall, perhaps you should understand the impact that intrinsic weight would have in such an understanding.
As for lashing out, you're fond of that term aren't you? Yet, you're the one going around dissecting posts, picking them apart piece-by-piece and taking every chance you can to throw petty insults and derogatory terms around. I'm just reacting in a manner befitting of how you engage with me, so if you want to partake in productive discussions, try to be not quite so destructive.
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If I’m remembering correctly, Newton imagined gravity when an apple fell from a tree. But if that apple would have caught on fire would the same gravity pull the smoke down like it did the apple. What would be easier to pull. If you have 2-100’ ropes. With a Bicycle on the end of the first rope and a train on the second rope. The bike would be because it’s 1000’s of times smaller than the train and would require less force.
So why would the force of gravity pull down a bowling ball faster than it would a feather. It should take less force to move the feather.
Gravity doesn’t effect the tides. If it did, when it moves the oceans and seas +/- 10’ it would also move that small pond in my back yard. But It doesn’t move it, not 1”. Just like every other body of water that’s not connected to the oceans.
You are correct in that remembrance, but if the apple caught fire, the smoke particles would rise up with the hot air causing convection currents above it. The smoke particles are very, very light and may eventually end up back on the ground, but some can stay in the atmosphere for a very long time as the wind and natural air currents continue to blow them about.
The bike would indeed be easier to pull because the train has significantly more mass. The larger the mass, the heavier the weight due to gravity, and so it would be impossible for me to move the train, but possible for me to move the bike. Even if we forget gravity and mass for a second and just assume weight is a "thing", the same effect would be observed.
The reason why gravity pulls a bowling ball down faster is because the feather experiences proportionally much more air resistance. If you get a large enough container and create a strong vacuum and carry out the experiment, you'll find that they fall at exactly the same rate. This is because the bowling ball has a lot more mass than the feather, so is harder to get moving. The lighter feather is easier to get moving, and so the net effect is that both fall together at the same time.
The question about tides is all to do with scale. The Earth is absolutely huge, almost 8,000 miles in diameter, and so a bulge of 10 feet is nothing in relative terms. The water in your pond does rise up, but it is by such a tiny amount it is basically imperceptible and would easily be negated by wind effects at that scale. It's the same effect of the horizon looking flat out at sea - it looks flat simply because the Earth is huge and you are tiny in comparison.
Another thing to consider is that if it’s not the gravity of the Moon and Sun causing tides, what is it? We know tides exist and they generally happen twice a day. I don’t have the answers to tides in the absence of known gravity, the Wiki might help. I should take another look!
Hope those helped your thinking a bit :)
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If you think it's irrelevant and a waste of time, just skip it then.
You forget my role here. If you're wasting people's time with irrelevant remarks, it's my job to stop you. So: Stop it. This is the last time I will ask this politely. Since you have not responded positively to previous requests to date, short bans will follow if you don't start taking this place seriously. I hope I've made myself clear.
Not sure where you went with that as I absolutely 100% meant gravity
You evidently did not. You didn't see anyone claim that things don't fall down to Earth. If you think you did, you need to work on your reading comprehension, and urgently.
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If I’m remembering correctly, Newton imagined gravity when an apple fell from a tree. But if that apple would have caught on fire would the same gravity pull the smoke down like it did the apple. What would be easier to pull. If you have 2-100’ ropes. With a Bicycle on the end of the first rope and a train on the second rope. The bike would be because it’s 1000’s of times smaller than the train and would require less force.
So why would the force of gravity pull down a bowling ball faster than it would a feather. It should take less force to move the feather.
Gravity doesn’t effect the tides. If it did, when it moves the oceans and seas +/- 10’ it would also move that small pond in my back yard. But It doesn’t move it, not 1”. Just like every other body of water that’s not connected to the oceans.
You are correct in that remembrance, but if the apple caught fire, the smoke particles would rise up with the hot air causing convection currents above it. The smoke particles are very, very light and may eventually end up back on the ground, but some can stay in the atmosphere for a very long time as the wind and natural air currents continue to blow them about.
The bike would indeed be easier to pull because the train has significantly more mass. The larger the mass, the heavier the weight due to gravity, and so it would be impossible for me to move the train, but possible for me to move the bike. Even if we forget gravity and mass for a second and just assume weight is a "thing", the same effect would be observed.
The reason why gravity pulls a bowling ball down faster is because the feather experiences proportionally much more air resistance. If you get a large enough container and create a strong vacuum and carry out the experiment, you'll find that they fall at exactly the same rate. This is because the bowling ball has a lot more mass than the feather, so is harder to get moving. The lighter feather is easier to get moving, and so the net effect is that both fall together at the same time.
The question about tides is all to do with scale. The Earth is absolutely huge, almost 8,000 miles in diameter, and so a bulge of 10 feet is nothing in relative terms. The water in your pond does rise up, but it is by such a tiny amount it is basically imperceptible and would easily be negated by wind effects at that scale. It's the same effect of the horizon looking flat out at sea - it looks flat simply because the Earth is huge and you are tiny in comparison.
Another thing to consider is that if it’s not the gravity of the Moon and Sun causing tides, what is it? We know tides exist and they generally happen twice a day. I don’t have the answers to tides in the absence of known gravity, the Wiki might help. I should take another look!
Hope those helped your thinking a bit :)
So when force of gravity moves these massive body’s of water that increases elevation 10’ what replaces underneath the water. You can’t just move water without air,dirt,etc. replacing the area that has moved.
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@Pete Svarrior, believe me, I haven’t forgotten your role here. I answered a question about things being level and flat in this thread, and responded to your resultant critique. If that’s being irrelevant then the boundaries seem skewed, but thanks for letting me know.
As for what I meant, let me repeat for absolute clarity just in case you’re not listening. I 100%, categorically, unequivocally, and without refute, meant gravity, because that is specifically the thing being repeatedly dismissed. Are you not the one who said that if true then I’ve found somebody who claims things don’t fall down to Earth? I don’t ever remember saying I saw someone claiming things don’t fall down, I simply explored your inference of somebody dismissing gravity. But, here you go again, suggesting I work on my reading comprehension, dishing out the childish insults. Very professional of moderator, well done.
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So when force of gravity moves these massive body’s of water that increases elevation 10’ what replaces underneath the water. You can’t just move water without air,dirt,etc. replacing the area that has moved.
Nothing replaces the water, it’s just deeper where the tides are and shallower everywhere else - it just moves around.
Here’s a thought experiment. Take a sphere with water all around it to a depth of 100m all around its surface. Now apply a Sun and Moon so that it creates tides. Where the tides are, the depth might be 101m now. All around the rest of the sphere the water might be 99 m deep. Make sense?
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So when force of gravity moves these massive body’s of water that increases elevation 10’ what replaces underneath the water. You can’t just move water without air,dirt,etc. replacing the area that has moved.
Nothing replaces the water, it’s just deeper where the tides are and shallower everywhere else - it just moves around.
Here’s a thought experiment. Take a sphere with water all around it to a depth of 100m all around its surface. Now apply a Sun and Moon so that it creates tides. Where the tides are, the depth might be 101m now. All around the rest of the sphere the water might be 99 m deep. Make sense?
Water finds its level. If Water rises from 99m to 101m without gaining any extra water. Then water has to be raised up off the bottom or the land around it has to be pushed down.
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Water finds its level. If Water rises from 99m to 101m without gaining any extra water. Then water has to be raised up off the bottom or the land around it has to be pushed down.
So we need to understand what you mean when you say “water finds its level”, which has been the entire topic of this thread. In both FET and RET, the effects of gravity hold the water down, and “level” means that the water is level perpendicular to the direction of gravity. In both models, regardless of what causes the tides, water just moves around the surface. It gets deeper in one part by getting shallower in another. The land is largely unaffected in comparison.
You can do an experiment with a spherical magnet and some ferrofluid. The ferrofluid surrounds the spherical magnet to a consistent depth let’s say. If you introduce another magnet close to it, simulating gravity, some of the ferrofluid will be attracted towards the other magnet. As the ferrofluid gets “deeper” at the tidal point, the ferrofluid gets shallower around the rest of the magnet. Nothing is raised up off the bottom and no surface is getting deformed. You could also do the same with a disc magnet to simulate a flat Earth, at least the motion and depth of fluid anyway.
Just remember, tides have to happen on a flat Earth as well, and by definition the water can’t be flat at those transition points even if the rest of it is.
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Are you not the one who said that if true then I’ve found somebody who claims things don’t fall down to Earth?
Yes, I provided you with the definitions of the words you were misusing.
I don’t ever remember saying I saw someone claiming things don’t fall down
Indeed. Because you never meant gravity. That much is patently obvious. Perhaps you're not a native speaker of English? If so, I apologise - for some reason I thought you were British.
But, here you go again, suggesting I work on my reading comprehension, dishing out the childish insults. Very professional of moderator, well done.
If you cannot post without resorting to personal insults, do not post. Your inability to internalise information that's presented to you is no excuse for you to lash out like this.
As for what I meant, let me repeat for absolute clarity just in case you’re not listening. I 100%, categorically, unequivocally, and without refute, meant gravity, because that is specifically the thing being repeatedly dismissed.
Very well. Please provide a reference for an individual in this thread who claims things do not fall down (i.e. they deny gravity, rather than gravitation). If you can't do that, I will conclude that you are cynically attempting to derail this thread, and respond accordingly. After all, you were given plenty of chances to clean your act up, and so far you've chosen to double down.
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Very well. Please provide a reference for an individual in this thread who claims things do not fall down (i.e. they deny gravity, rather than gravitation).
If you can't do that, I will conclude that you are cynically attempting to derail this thread, and respond accordingly.
Seriously? Here’s just one reference amongst many where they deny that gravity is real. A quick search over his his post history will show many similar wordings around gravity:
We know and can readily demonstrate this on earth's surface, where "gravity" is presumed and calculated (NEVER measured) to be strongest. Gravity, if such a force were real and not mathematical fiction, does not help with this problem
Here’s another recent one that’s quite pertinent:
So what is gravity then?
Almost no one has any idea. I have figured it out, and I am not alone. It is mathematical fiction with no reality whatsoever. Weight is all there is, an inexorable and intrinsic property of all matter.
I never once said the words, “There are individuals claiming things don’t fall down to Earth”. What I said was, there is somebody claiming that gravity is not real. You took it upon yourself to decide that if I meant what I said, it also means I’ve found somebody who claims that things don’t fall to Earth. Your words and your interpretation, not mine, and it infers that dismissal of gravity is to dismiss things falling to Earth. Not once did I say that, or that anybody else did. I merely replied by saying that dismissal of gravity does not necessarily mean things do not fall, because this individual concerned caters for weight in an alternative manner in his theory of how things behave, which itself would account for why things fall.
If you think the discussion is anything different than that, perhaps get somebody independent to review it because while my initial reply which triggered yours may not have been worded the best, in no way at all was it an active attempt to cynically derail anything, nor anything written subsequently.
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...Those same people looked out to sea and saw that the horizon was also flat ...
As I stood looking out to sea last year admiring the cut-edge look of the horizon, and trying my best to see curvature, it struck me that I was looking for it in the wrong direction, and I'm sure that's the direction you're speaking of. I was looking for the horizon to be lower to my right and left, and to be slightly higher straight ahead. But, for that to be the case, it would mean I was seeing farther out to sea on my left and right than I was in the middle, and all of a sudden I realized my error.
I WAS seeing curvature, but on the wrong plane, which is at a perspective that is imperceivable. The curvature of the earth causes you to see the same distance out to sea regardless of direction, therefore the curvature is at eye level (parallel to the ground, not up and down), and there's no way you can perceive that. Imagine holding a pole out from your body at eye level and then turning in a circle. The pole end stays the same distance from you, but is describing an arc AROUND you. That's what you see when you look out at the ocean, and why it looks flat.
I haven't been on this forum long enough to know if this has been discussed before.
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@stevecanuck, I think I get what you are saying, and yes, from our perspective as being tiny specs on a huge surface, we literally cannot observe curvature directly with our own two eyes. There are, however, a number of different ways you can conclude curvature from down here that don’t need complex maths and physics to understand. I’ve carried out a couple myself.
The real issue being debated here is, what does flat and level mean, and how can water be level on a curved surface? The answer is gravity (or the effects of gravitation to keep the peace). Level just means that the surface is at a constant height in line with the gravity vector. In RET, gravity is caused by the mass of the Earth pulling things down, and in FET, gravity is caused by Universal Acceleration (the Earth constantly accelerating upwards, pushing up on us at a rate of 9.81 m/s^2) In RET, water can conform to the surface of a sphere, in FET it cannot. In RET, gravity accounts for the tides. In FET it cannot. There are a number of differences and discrepancies that warrant understanding on both sides to respect each other’s position.
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@stevecanuck, I think I get what you are saying, and yes, from our perspective as being tiny specs on a huge surface, we literally cannot observe curvature directly with our own two eyes.
I think you missed my point, so I'm going to try again.
Imagine being in a row boat in the middle of the ocean. Now look in any direction and you will be able to see approximately 2 miles from a sitting position with your eye level at 2'6".
If you turn in a full circle you will therefore be the center of a circle with a radius of 2 miles. Every spot on the horizon will look the same to you and will therefore appear to be flat.
Or, hold a hula hoop over you so it's parallel to the ground and at eye level. As you turn 360 degrees you will see the edge of the hula hoop at exactly the same level above the ground and at eye level height, it will be a flat plane.
So, we ARE seeing curvature. It's just on a horizontal plane and NOT down to the left and right. You're looking at the hula hoop from the middle of it looking outward, and NOT from the side with it being held vertically.
I hope that explains it. Bottom line is that it's physically impossible to see left to right curvature because, you would have to see farther to the left and right than you would have to see in the middle.
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@stevecanuck
Thank you for explaining that to everyone! Most people don't understand why the horizon doesn't curve at any altitude (regardless of conception of the shape of the world), and is always a 360 deg circle surrounding you.
So, we ARE seeing curvature.
Sort of. The horizon is an optical illusion, and the edge of nothing but our vision. Assuming mostly uniform weather / air conditions in our viewing "bubble"/sphere, the maximum distance we can see laterally is fixed/static and linear.
The "curve" (of the hula hoop of visible area, NOT the horizon or physical earth/water), also an optical illusion - but mostly indiscernible as you describe correctly, is because of this fixed and linear "seeing distance limit" (dependent on limitations of our eyes / processing, and weather).
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Sort of. The horizon is an optical illusion, and the edge of nothing but our vision. Assuming mostly uniform weather / air conditions in our viewing "bubble"/sphere, the maximum distance we can see laterally is fixed/static and linear.
So the limit of our vision is variable depending upon altitude.
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@WTF_seriously
So the limit of our vision is variable depending upon altitude.
Correct!
There are two main reasons for that. One is the angular resolution limits of the human eye, and the other is the "standard"/"normal" density gradient within our air.
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@WTF_seriously
So the limit of our vision is variable depending upon altitude.
Correct!
There are two main reasons for that. One is the angular resolution limits of the human eye, and the other is the "standard"/"normal" density gradient within our air.
So how far can we see at ground level?
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@longitube
Theoretical max, around 200 miles from the top of everest under perfect visibility.
At sea level (where the air is densest) it is typically only a few miles, but it varies with weather.
If you are understanding me, then you also understand why the maximum distance you can see varies depending on the matter you are looking through. We may need to discuss this more, because optics are tricky (smoke and mirrors) and there is more than one optical phenomenon/principle at play.
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@longitube
Theoretical max, around 200 miles from the top of everest under perfect visibility.
At sea level (where the air is densest) it is typically only a few miles, but it varies with weather.
I’m not concerned with standing on Everest (where most folk wouldn’t survive without an oxygen supply) so much as normal observational height. I should have been clearer, I meant an observer standing on the ground, not lying on the ground, sees just a few miles?
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@longitube
I meant an observer standing on the ground, not lying on the ground, sees just a few miles?
Yes. That is, laterally towards the horizon through the densest air you can typically only see a few miles.
The top of everest is still the ground though! I just think it is very interesting, and misunderstood by so many, that from the highest point on earth, under the best visibility conditions possible, you can only see a couple hundred miles (laterally, towards the horizon). That is the max, though at sea level (the min) it's only a few miles directly through the densest air.
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@WTF_seriously
So the limit of our vision is variable depending upon altitude.
Correct!
There are two main reasons for that. One is the angular resolution limits of the human eye, and the other is the "standard"/"normal" density gradient within our air.
So how far can we see at ground level?
I live in Calgary where we can see the mountains that start 40 miles away (as the crow flies) as clear as a bell.
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@longitube
I meant an observer standing on the ground, not lying on the ground, sees just a few miles?
Yes. That is, laterally towards the horizon through the densest air you can typically only see a few miles.
The top of everest is still the ground though! I just think it is very interesting, and misunderstood by so many, that from the highest point on earth, under the best visibility conditions possible, you can only see a couple hundred miles (laterally, towards the horizon). That is the max, though at sea level (the min) it's only a few miles directly through the densest air.
Jack, I don’t mean to be rude and hope you won’t be offended, but air pollution where you live must be appalling. I live by the ocean and can see cliffs and headlands twenty miles away while standing on the beach. I can see large hills inland more than thirty miles away from a roadside viewpoint that’s perhaps 150 ft above sea level. From the same beach on a clear day I can see on the horizon the top of a mountain which is 66 miles away. I know this because I’ve seen these things often with my own eyes, without using binoculars, a powerful zoom camera or Google Earth. Furthermore, at night I can watch the moon and stars setting on the horizon, and how far away are these? A few miles?
You need to do some real research, Jack, do some real investigations, before declaring how little we can see. Sorry to be blunt.
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I just think it is very interesting, and misunderstood by so many, that from the highest point on earth, under the best visibility conditions possible, you can only see a couple hundred miles (laterally, towards the horizon). That is the max, though at sea level (the min) it's only a few miles directly through the densest air.
Jack, I don’t mean to be rude and hope you won’t be offended, but air pollution where you live must be appalling. I live by the ocean and can see cliffs and headlands twenty miles away while standing on the beach. I can see large hills inland more than thirty miles away from a roadside viewpoint that’s perhaps 150 ft above sea level. From the same beach on a clear day I can see on the horizon the top of a mountain which is 66 miles away. I know this because I’ve seen these things often with my own eyes, without using binoculars, a powerful zoom camera or Google Earth. Furthermore, at night I can watch the moon and stars setting on the horizon, and how far away are these? A few miles?
You need to do some real research, Jack, do some real investigations, before declaring how little we can see. Sorry to be blunt.
@jack44556677, I don't find it that surprising really given how large the Earth is and how relatively small Mt Everest is by comparison. The 200 mile visibility is pretty much consistent with what you'd expect on a round Earth.
@Longtitube, what you say you can see there makes absolute sense and is consistent with what I'd expect. At 150ft above sea level you can expect to see about 15 miles anyway, and if you are looking at a large mountain in the distance, I'm not sure how tall it is, but even if it's a small one at just 3000ft, you'd still be able to see at least part of it from 66 miles away. There could also be refraction effects that cause the light to track with the surface of the Earth for a few miles making it appear you can see even further.
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@stevecanuck
I live in Calgary where we can see the mountains that start 40 miles away (as the crow flies) as clear as a bell.
Yes. Because of the density gradient in the air, the angle you look through it alters/determines how far you can see. Of course you can see objects beyond the horizon, but not behind it! The horizon also exists on land, even when there are mountains in the distance. The horizon in that case is what the bottom of the mountain is compressed/obscured into.
@longitube
Jack, I don’t mean to be rude and hope you won’t be offended
Excellent, I feel the same way! Rudeness is mostly about lack of courtesy/empathy. In this case, the courtesy you are lacking is in properly understanding before criticizing and recommending diminutive remedial action/"coursework" of your enlightened choosing.
I do not wish for you to misunderstand my tone, which is intended to be playful and somewhat scathingly sarcastic. I am very difficult to offend, and encourage others (and myself) to speak their hearts and minds freely without censure. I encourage the ruthless/vicious attack of all thoughts and though I do not condone ad hominem, I am most functionally impervious to it (as we all should be).
but air pollution where you live must be appalling.
Though air "quality" (composition, density, refractive index etc.) has everything to do with what we are discussing, you seem to be misunderstanding. The reason we can't see beyond the few miles is to do with the air itself (and the intensity of the distant light source of course), and requires no added help from man made particulate/pollution. When I say we can't see more than a few miles under normal weather conditions, I am talking about specifically towards the horizon - looking through the densest air.
Furthermore, at night I can watch the moon and stars setting on the horizon, and how far away are these? A few miles?
This is a very interesting, and highly relevant unanswered question! One of the reasons I mentioned the 200 mile maximum vision limit (this includes aid / magnification), is to help dispel the common misconception, fostered and encouraged through the pseudoscience mythology of astronomy, that we can (and ought) to be able to see forever. We can't. Through the thinnest air on the surface of the earth, the farthest you can see is around 200 miles.
This does strongly suggest, if not prove, that the lights in the sky are far closer than we have assumed (due to the mythology of astronomy erroneously/disingenuously presented to us as science since childhood), however there is less and less air straight above us to interact/obstruct and we have no idea what the initial/source brightnesses are.
Light attenuates without any matter in the way. This is because light is a pressure wave. Light doesn't travel forever, much to the chagrin of the high priests of astronomy that fancy themselves scientists.
Sorry to be blunt.
You spoke your heart and mind earnestly and to me that IS effective communication (or at least a necessary prerequisite). No apologies necessary, though if you earnestly wish to avoid being rude (a worthy goal) you should try to make sure you fully understand what you are criticizing first before doing so and suggest courses of action / "coursework" earnestly (not for rhetorical ad hominem).
@Rhesusvx
The 200 mile visibility is pretty much consistent with what you'd expect on a round Earth.
This is a different figure than distance to the horizon, but hope springs eternal! In any case, "begging the question" / circular logic is a crummy way to investigate anything. The general format goes like this, and is to be identified and discarded/avoided wherever you see it : If the earth is round, I expect to see "something". I see "something", therefore the earth is round. This is circular logic, and is shamefully embarrassing to scientists and children alike!
There could also be refraction effects that cause the light to track with the surface of the Earth for a few miles making it appear you can see even further.
Not for you, no. Your faith REQUIRES you to believe (and profess, disearnestly, that you KNOW) that refraction is the reason we see too far. It is a dogma of your faith, and no dissent is permitted. The more objective (scientific) of us can indulge and pursue alternative explanations - but not you and the rest of the "educated" - no. For you, there is merely the repeated mantra of "refraction" to keep the bad/inconvenient data at bay.
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I dont want to be a downer but there hasnt been a post about water or level in this thread in a while...
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The 200 mile visibility is pretty much consistent with what you'd expect on a round Earth.
This is a different figure than distance to the horizon, but hope springs eternal! In any case, "begging the question" / circular logic is a crummy way to investigate anything. The general format goes like this, and is to be identified and discarded/avoided wherever you see it : If the earth is round, I expect to see "something". I see "something", therefore the earth is round. This is circular logic, and is shamefully embarrassing to scientists and children alike!
There could also be refraction effects that cause the light to track with the surface of the Earth for a few miles making it appear you can see even further.
Not for you, no. Your faith REQUIRES you to believe (and profess, disearnestly, that you KNOW) that refraction is the reason we see too far. It is a dogma of your faith, and no dissent is permitted. The more objective (scientific) of us can indulge and pursue alternative explanations - but not you and the rest of the "educated" - no. For you, there is merely the repeated mantra of "refraction" to keep the bad/inconvenient data at bay.
Perhaps I should have worded things differently rather than use "round Earth" because there's no circular logic in my statement, just merely stating what's consistent with what we broadly measure here on Earth when you factor in, yes, known refraction coefficients and the known dimensions of our water-laden rock. Looking out over a long distance from any given altitude, the only reasons we stop seeing things are:
- Our own visual acuity and ability to resolve something
- Atmospheric distortion/refraction
- Particulates/pollution
- Something getting in the way, like a curved surface
The use of telescopes and binoculars etc. helps with the visual acuity bit, but even those aren't going to help after a point even on the best of days. So what point is that? It either has to be light bending out of our sight due to EA or refraction, or the object is physically being blocked by something - that something being curvature (with curvature based on a number of other observations in nature, not just one).
I have some experimental experience with light and refraction and how it behaves in different mediums of varying density, so we know that light bends according to known laws and can be mathematically modelled. I trust you at least agree with this bit? Regardless of the shape of the Earth, refraction can account for altering the "apparent" distance that you are able to see something at, especially in colder climates and lower altitudes. It's also known that in some locations on Earth, at one time of year you might be able to see that skyline shimmering away in the distance, yet another time of year you might not be able to see it at all. Nothing has changed other than the nature of the atmosphere between the two points. I'm not saying this confirms or denies curvature, but it does provide some objective evidence for atmospheric refraction and how it can cause you to see things further away than you might otherwise expect.
If you know that there is another reason why we can sometimes see objects further away than we otherwise expect, please let us know. I know you proclaim to be purely scientific in your research and conclusions, but throwing away almost everything you have been taught, rejecting what science experimentally shows you, and only ever choosing to trust your own observations, conclusions and interpretations of physical laws takes things to the opposite extreme and into it's own form of conspiracy-like affair. I don't mean that in a derogatory manner either, just saying that maybe, just maybe some things simply are what they are.
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@longitube
Jack, I don’t mean to be rude and hope you won’t be offended
Excellent, I feel the same way! Rudeness is mostly about lack of courtesy/empathy. In this case, the courtesy you are lacking is in properly understanding before criticizing and recommending diminutive remedial action/"coursework" of your enlightened choosing.
I do not wish for you to misunderstand my tone, which is intended to be playful and somewhat scathingly sarcastic. I am very difficult to offend, and encourage others (and myself) to speak their hearts and minds freely without censure. I encourage the ruthless/vicious attack of all thoughts and though I do not condone ad hominem, I am most functionally impervious to it (as we all should be).
but air pollution where you live must be appalling.
Though air "quality" (composition, density, refractive index etc.) has everything to do with what we are discussing, you seem to be misunderstanding. The reason we can't see beyond the few miles is to do with the air itself (and the intensity of the distant light source of course), and requires no added help from man made particulate/pollution. When I say we can't see more than a few miles under normal weather conditions, I am talking about specifically towards the horizon - looking through the densest air.
Sorry to be blunt.
You spoke your heart and mind earnestly and to me that IS effective communication (or at least a necessary prerequisite). No apologies necessary, though if you earnestly wish to avoid being rude (a worthy goal) you should try to make sure you fully understand what you are criticizing first before doing so and suggest courses of action / "coursework" earnestly (not for rhetorical ad hominem).
I don’t do ad hominem, I’m only interested in facts. I may be sharp with opinions I regard as nonsense, but never with the person - there’s far too much of that on the web already, people ridiculed and their convictions mocked without addressing whatever points are under discussion.
To return to how far we can see across level water: if the limit of our vision towards the horizon is just a few miles, how is it possible to see that mountain top on the horizon from the beach on a clear day, a mountain top which is 66 miles away across the water, through the densest air at the horizon?
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If I’m remembering correctly, Newton imagined gravity when an apple fell from a tree. But if that apple would have caught on fire would the same gravity pull the smoke down like it did the apple. What would be easier to pull. If you have 2-100’ ropes. With a Bicycle on the end of the first rope and a train on the second rope. The bike would be because it’s 1000’s of times smaller than the train and would require less force.
So why would the force of gravity pull down a bowling ball faster than it would a feather. It should take less force to move the feather.
Gravity doesn’t effect the tides. If it did, when it moves the oceans and seas +/- 10’ it would also move that small pond in my back yard. But It doesn’t move it, not 1”. Just like every other body of water that’s not connected to the oceans.
@JaySeneca you haven't quite got gravity correct there. Gravity is a mutual attractive force between two masses, with magnitude proportional to the product of the two masses divided by the square of the distance between them.
On earth, for all but the most precise of calculations, we can ignore the distance part of the equation as the variation with elevation above the earth tends to be trivial compared to the radius of the earth. This means that any object feels a force proportional to its own mass which, in SI units, works out as F=mg, where g is a constant, known as the 'acceleration due to gravity', of around 9.8ms-2. So in your bicycle/train analogy above, yes the force required to accelerate the train is greater, but gravity exerts a force in proportion to mass, so objects accelerating in freefall do so at the same rate.
The important thing to grasp is that this only works in a vacuum. If you drop two objects of the same size and shape but very different masses, they will initially accelerate at the same rate, but the heavier one will reach a higher terminal velocity and will hit the ground first. This is because the force due to gravity is different, but the force due to air resistance at any given speed will be the same, and both objects will accelerate until the two forces are in balance. So your burning apple will indeed fall faster than the smoke around it, and a bag of feathers will fall slower than a bag of coins, all other things being equal.
So in your tidal example, yes, each water molecule in your garden pond feels precisely the same gravity force from the moon and sun as the individual water molecules in the ocean. But the aggregate effect of a small movement of all those molecules is far more visible in the sea than in your pond. Probably the best way to think of it is to visualise the moon and sun causing a tiny 'tilt' in the local angle of the gravity force, which in turn causes a tiny change in the gradient of the water. A gradient of fractions of a degree wouldn't be perceptible in your pond, but could easily generate changes in levels of a few metres at the coast when the body of water is many hundreds of miles across. Something of an over-simplification, but hopefully it illustrates the point.
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As a retired Software Engineer I would like to add my 2c. Long ago I was writing computer programs to aim big guns on warships to targets some 30 km away.
Of course all calculations are in a orthogonal frame of reference.
We did have to correct for the earth curvature and also for refraction. (BTW, also for the Coriolis force)
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As a retired Software Engineer I would like to add my 2c. Long ago I was writing computer programs to aim big guns on warships to targets some 30 km away.
Of course all calculations are in a orthogonal frame of reference.
We did have to correct for the earth curvature and also for refraction. (BTW, also for the Coriolis force)
The weakness of this argument is that artillery guns are not first round accurate. See - https://wiki.tfes.org/Coriolis_Effect#U.S._Army_Artillery_Coriolis_Table_Example
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At least they are accurate enough for the customer acceptance tests. Coriolis force was just a parenthetical addition, but I remember a project where the customer paid extra to remove the Coriolis correction but later paid even more to get it back in.
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As a retired Software Engineer I would like to add my 2c. Long ago I was writing computer programs to aim big guns on warships to targets some 30 km away.
Of course all calculations are in a orthogonal frame of reference.
We did have to correct for the earth curvature and also for refraction. (BTW, also for the Coriolis force)
The weakness of this argument is that artillery guns are not first round accurate. See - https://wiki.tfes.org/Coriolis_Effect#U.S._Army_Artillery_Coriolis_Table_Example
I don't see the relevance to the first round being accurate or not. If accuracy is obtained with curvature and refraction being factored into the calculation as mentioned, then it remains strong evidence of the aforementioned curvature and refractive effects. Guns such as these are not point and shoot armaments and require calibration due to the distances involved, which is reasonable to concede.