Flat Earth counter-arguments

No, you're not listening, I did not imply "common sense" meant the certain knowledge of gravity, I implied that when referring to Round Earth theory you have to take gravity into account, because common knowledge is that gravity applies in a Round Earth theory, and thus common SENSE would be taking that into account when trying to argue against it.

Besides who would be stupid enough to believe in a place where trees grow downwards and rain falls upwards exept for believers in a spherical earth as illogical and unscientific as it is in denial of all common sense?

Are Unimportant and I the only ones who see some problems in relying on so-called "common" sense?

No, you appear to be the only ones who are not correctly grasping the concept despite my attempts to explain.

No you are amongst the only people who have no common sense, that is, a basic grasp of for example what it means to test the shape of an object in space by gathering information and observations about its surface.

Saying I'm right cos I am is your field of expertise, not mine, even if I laid out step by step how to prove these things, you would merely redefine terms like "light" "speed" and "line" in some convoluted attempt to confuse people, blindsiding the dumbest into following you.

That's ok though, this site provides many good jokes to share with my equally deluded "RE" buddies...

No, you appear to be the only ones who are not correctly grasping the concept despite my attempts to explain.

No you are amongst the only people who have no common sense, that is, a basic grasp of for example what it means to test the shape of an object in space by gathering information and observations about its surface.

Did you two Nobel-prize laureates read both quotes or just the first one?

I read them both. The second was of no importance to me, and uses the term "common sense" differently to mine. Mine was referring to "common knowledge" of round earth theory, and the fact that it needs to be known and referred to if attempting to argue against it (which is would be commonly thought of as a sensible thing to do). The "common sense" referred to by Dionysios was that it seems non-sensicle for trees to be able to grow "downwards" and rain to be able to fall "downwards", which is accounted for by gravity theory.

This could go round in circles forever...

My only addition is I think this:

Relying on "common-sense" is a bit weak, but often it is intended to mean  "understanding what is clearly intended by a statement.

Sometimes what you mean can be LESS obvious to us, just because we're not as used to hearing it, and working with it.

Relying on calling the entire world a conspiracy and relying on calling practically everything humanity knows as "fake" is in my opinion weaker, and rather harder to defend. As you demonstrate in fact by very rarely defending it... rather you use defensive argumentation to say something like.

"You don't know everything and you haven't been everywhere so we're right cos we disagree with you."

Relying on calling the entire world a conspiracy and relying on calling practically everything humanity knows as "fake" is in my opinion weaker, and rather harder to defend.

Actually I think we condemn very little of what humanity "knows" as fake... I mean, our theory of gravity is the same as yours, for example.  Obviously we consider lots of modern physics to be true.  It's just that it's hard to tell when so much of it is beyond the grasp of the "common man".

-Erasmus

Your theory of gravity has WHAT in common with RE?

Especially given that there are two schools of thought equally common on this site?

i.) Unidirectional "universal down" gravity
ii.) Constant acceleration idea  (exposed as wrong on numerous occasions but explanation ignored)

Your theory of gravity has WHAT in common with RE?

Especially given that there are two schools of thought equally common on this site?

i.) Unidirectional "universal down" gravity
ii.) Constant acceleration idea  (exposed as wrong on numerous occasions but explanation ignored)

Man it's about time somebody called me on this one.

So here it is.  Objects unaffected by any force are in an inertial state.  They travel along geodesics.  If the Earth were a black hole of the same mass, then objects on geodesics would have a mutual acceleration with the centre.  The only reason inertial objects do not fall to the centre of the Earth is that the Earth is not a black hole but has a solid surface; it gets in their way.

Thus, objects on the Earth's surface must be in accelerated frames of reference (since they are not travelling on spacetime geodesics).  The source of this acceleration must be a parallel force (says Newton) -- you can feel it as the force of the Earth pushing up on your feet.  Thus, the Earth must be accelerating upward -- this is the only possible explanation for the sensation of gravity on a round Earth, and, interestingly, is the same explanation for the sensation of gravity on a flat Earth.

QED.

You've used some language I find it hard to follow, so sorry about that, but this stuff about the Earth accelerating just doesn't follow at all,

As it happens the Earth is an accelerating reference frame because it orbits the sun and is thus also under going a central force motion.

Incidentally the Earth DOES follow a "space-time geodesic" (as I understand it... which might be flawed) because those so-called geodesics refer to the space-time warped by gravity...

So an object accelerated by gravity follows one of these "generalised straight lines in curved-space" the generalised line being a bit like a generalised distance when we deal with Lagrangian Mechanics.

Also, the Earth's surface accelerates, but (obviously) towards the centre of the Earth's axial rotation as this is also a central force motion, this time due to the reaction force of the Earth's substance against the tendency of its components to continue in different straight lines.

The explanation of people sticking to the surface is that of the body-force gravity pulling them towards the Earth's centre of mass. The soil and rocks have gone as far as they can, and thus are compressed when the gravity tries to force us through them, hence the normal reaction force.

I SUSPECT you are using flowery language to obfuscate again, and I suspect your statement about "only explanation" is a serious non-sequitur...

Feel free to tell me that I don't understand and don't really exist anyway though.

You've used some language I find it hard to follow,

Yeah I was a bit worried about that.

As it happens the Earth is an accelerating reference frame because it orbits the sun

This is not the motion I'm referring to.  For the sake of this discussion, I'm only describing the effects of a single large body and a single small one.

Also, the Earth's surface accelerates, but (obviously) towards the centre of the Earth's axial rotation as this is also a central force motion, this time due to the reaction force of the Earth's substance against the tendency of its components to continue in different straight lines.

This is also not the motion I'm referring to.  Again, for the sake of this discussion, consider the larger body to be nonrotating.

The explanation of people sticking to the surface is that of the body-force gravity pulling them towards the Earth's centre of mass.

That's just the problem.  Gravitational attraction is not a force, according to general relativity.  In GR, being in freefall is being subject to no forces at all.  So if you're not in freefall, you must be subject to some force.  If the force is an upward one, it must correspond to an upward acceleration.

The only differences between FE gravity and RE gravity are the geometry of spacetime and the fact that some masses do not warp space in the FE theory.

I SUSPECT you are using flowery language to obfuscate again, and I suspect your statement about "only explanation" is a serious non-sequitur...

No, really, I'm serious about this, FE BS aside.  It's the way gravity "really" works.

-Erasmus

The disagreement here is whether GR defines gravity as a force or not.

I haven't read enough about it to dispute your claim, but IF you rely on GR, which in saying Gravity isnt a force contradicts newtonian mechanics, you can't then go on to rely on Newtonian mechanics.

I know you weren't referring to the motions I talked about but I've had too much experience on this site of people picking up on small inaccuracies and capitalising on them to insult my intelligence. So sorry for those bits.

I think that anything that makes you start moving faster and faster when you were standing still has to be considered "a force" in newtonian physics... if you don't do that, then it obviously won't work. It's kinda the definition of forces... if I drop something and it accelerates downwards, there IS some FORCE there... by definition.

Now if you play with that definition nothing works anymore, just like if I allow straight lines to be curved I can wreck the discussion. As you I think pointed out too these thinsg eventually rely on certain axioms, and being aware that there is still SOME doubt as to the validity of those axioms especially under EXTREME circumstances is important...

For example I was reading something about gravity and they'd written that they were certain that there was no deviation from the "inverse square law" up to at least a certain point, at least under certain conditions.

They included a very REAL doubt, about there POSSIBLY being an inverse exponential term in the gravity that we just didnt have the means to observe yet... scientists largely really DO know that things have inherent doubt associated with them...

I'm sorry I really am for this not being entirely on-topic, but frankly I think this amounts to fiddling around with definitions again... I mean... the world is dark if sunlight doesn't "count" as light... That's not clever...

This space-time geodesics thing I thought, was just there to help explain how with BODY forces one can't TELL one is being "pulled"... I don't think it discounts it as a FORCE... you standing on the earth is a BODY force... acting on ALL mass equally, being balanced by a SURFACE force... something that acts only ona  boundary and therefore causes deformation which one FEELS...

But the point is... if GR really redefines gravity, then likely it redefines other things too.. one can't just theory-hop.

IF you rely on GR, which in saying Gravity isnt a force contradicts newtonian mechanics, you can't then go on to rely on Newtonian mechanics.

Why not?  Newton's Laws of Motion are distinct from his Law of Universal Gravitation.  I can accept the former yet refuse to accept the latter.

I think that anything that makes you start moving faster and faster when you were standing still has to be considered "a force" in newtonian physics...

Yeah that's okay.  While you're in freefall, you're not going faster and faster (in GR).  Your speed is constant -- you're travelling at the speed of light.

This space-time geodesics thing I thought, was just there to help explain how with BODY forces one can't TELL one is being "pulled"... I don't think it discounts it as a FORCE...

You're right.  It's not a force, in GR.  But it's not supposed to be an explanatory aid, either.  Rather, it's a description of the way things "really are".

But the point is... if GR really redefines gravity, then likely it redefines other things too.. one can't just theory-hop.

Hmm... I'm not sure in what way I'm theory-hopping.  FE <--> RE, certainly, but I maintain GR in either case.

GR is based on three assmptions: that the laws of physics are the same to all observers, that the speed of light is independent of the speed of the light source, and that gravity is locally indistinguishable from acceleration.  It doesn't "redefine" anything else.

-Erasmus

1.) You don't have to accept universal gravitation to observe that the thing pulling you down IS a force because it accelerates you. The laws of motion (the way I always figured) assume anything that does accelerate you is a force. Universal gravitation isn't that relevant to this is it?

2.) OK I stated that too simply. Freefall is an acceleration, at least under Newtonian mechanics, also note that the origin of the force causing one to free-fall in circles around a body could be anything... electronmagnetic for example, or any other body-force.

According to you no body-force IS a force... (for clarity)?

3.) If space-time had been warped such that no "force" was exerted I think that the same warping would prevent any measurement of the results of the non-force too. Also there ARE gravity gradients, so things can even be torn apart by massive objects nearby, SURELY that has to be accepted as a "force"?

4.) Theory hopping meant that I suspect you of taking aspects of different "theory-universes" and cherry picking quotes you like...  I'm not qualified to say that though really.

1.) You don't have to accept universal gravitation to observe that the thing pulling you down IS a force because it accelerates you. The laws of motion (the way I always figured) assume anything that does accelerate you is a force. Universal gravitation isn't that relevant to this is it?

Hm.  I simultaneously want to say, "Not all accelerations are the same" and "All accelerations are indistinguishable", so I won't say either.

You can talk about acceleration "locally", like, I was travelling along the x-axis at 1/s; or you can talk about it "remotely" like, it appeared that these two objects which at some point were moving together now have different relative velocities than they did before.

Gravity is stretching and bending of the x-axis, so the first notion of acceleration doesn't apply to it.  As you "accelerate" in a gravitation field, your speed never changes.  But the x-axis next to you and the x-axis where the Earth is are not stretched and bent in precisely the same way, so you get observe a mutual acceleration.

According to you no body-force IS a force... (for clarity)?

No... only gravity is not a force.

3.) If space-time had been warped such that no "force" was exerted I think that the same warping would prevent any measurement of the results of the non-force too. Also there ARE gravity gradients, so things can even be torn apart by massive objects nearby, SURELY that has to be accepted as a "force"?

It's not a force.  It's just the components of the things moving at destructively different rates in the relevant directions.  The forces involved are the attractive ones that would otherwise keep these components from travelling along geodesics.

In other words, a cloud of noninteracting dust particles would separate in a gravitational field.

4.) Theory hopping meant that I suspect you of taking aspects of different "theory-universes" and cherry picking quotes you like...  I'm not qualified to say that though really.

If I want to pretend not to believe in GR, I'll probably make a note of it in the post.

In general, you can assume that I'm not going to try to argue that any theories of physics (as opposed to theories of geography) are wrong, but I fully expect to have to retract that assurance later :)

-Erasmus

Well, I feel like I understand the idea of warped space fairly well, like your X axis thing makes perfect sense to me and has done for a fairly long while... I'm not as "into" it as you seem to be, but the concepts always seemed cool to me.

I really can't accept the idea that gravity is NOT a force but say electromagnetism... I think that Einsteins messing around addressed gravity, but nowadays I had thought people were applying the same principle to all forces, after all, at the lowest level all forces are related to one or more of the four fundamental forces, and those are ALL body forces exhibiting similar "free-falling" patterns as macroscopic objects in gravity.

I think the fact that Einstein thought mainly on gravity was an accident... EM is to Charge more or less as Gravity is to mass... and I'm afraid I'm convinced it's unreasonable to claim one of these things "isn't" a force when others are... do you think I'm really dumb for saying that? Seriously?

Look, also those "internal forces" are reaction forces, one can see this because there's no source of energy internally to do the work, some outside influence must be affecting the parts of the object differently, forcing it to react... agin if we use newtonian stuff, then by the equal reaction idea this seems like the right outlook? ....?

after all, at the lowest level all forces are related to one or more of the four fundamental forces, and those are ALL body forces exhibiting similar "free-falling" patterns as macroscopic objects in gravity.

Actually, it's on exactly those levels where GR and nonrelativistic theories start disagreeing with each other.

I think the fact that Einstein thought mainly on gravity was an accident... EM is to Charge more or less as Gravity is to mass... and I'm afraid I'm convinced it's unreasonable to claim one of these things "isn't" a force when others are... do you think I'm really dumb for saying that? Seriously?

No, I don't think you're dumb, just in disagreement.  The issue is that gravity is universal, whereas some particles are uncharged.  Also, it's universally attractive, whereas electromagnetism can be attractive or repulsive.  There are also very different qualities to the fields themselves -- I'm pretty sure electromagnetism isn't conservative.  Also there's this really odd coincidence that inertial mass (the m in F=ma) and gravitational mass (the m in F=Gm1m2/r^2) are the same -- GR resolves that.

The great thing about GR is that in throwing out gravity as a force, you get one more physical phenomena explained as, "It's not magical, it's just things moving in relation to one another, that's all."  That's really a nice feature because otherwise we're left with the nagging question, "Okay, so, what exactly is a force?  How does it work?"

Look, also those "internal forces" are reaction forces, one can see this because there's no source of energy internally to do the work, some outside influence must be affecting the parts of the object differently, forcing it to react... agin if we use newtonian stuff, then by the equal reaction idea this seems like the right outlook? ....?

Sure, the internal forces are forces.  But they're acting to resist an object inertia.  They're the same thing as the force you feel on your arm when you swing a bucket of water around.  The bucket wants to go off on a straight line, but the internal forces in your arm act to keep your arm in one piece.

-Erasmus

1.) No dude I get that quantum level has some odd rules, although I'm not that familiar with them, I meant to point out that they're all body-forces... ones that would pull on all of an object equally, (neglecting the objects size) rather than acting on one of its surfaces, if such a concept can even be imagined at that size.

2.) Well.. aren't the nuclear forces always attractive too? I think you're right about EM not being conservative, but it usually is. People can make ones that aren't though... which we can't do on gravity... which is a shame

I have a suspicion that there are likely to be a couple of equations, one of which describes the attraction of two objects of opposite charge, and another which says something about the the relationship between field-strength, charge, and current... or rate of change of current, or somesuch, that might be considered analogous. I'm guessing a bit though, and anyway there are going to be differences like the one you mentioned about conservative-ness.

Anyway, that all sounds cool, gravity is then some illusory effect caused by relative motion? Fun stuff, bit deep for me though, can only speculate.

3.) When you swing the bucket you force it to change direction, that is acceleration, and F=ma holds. The F isn't a reaction... there are raection forces in your arm, internal ones, but there is also a resultant on the bucket.

A force is conducted through the arm to the bucket.

When the person stands on the ground the person "tries" to accelerate, but in so doing also "tries" to deform the ground, which deforms slightly and reaches an equilibrium as the internal forces change.

If the bucket was hanging from your arm or rocketting away and being held back by your arm, then it'd be the same idea. As it is, the person standing on the surface isn't changing direction or speed (neglecting earth rotation etc.) so it can't be the same...


there

It's been a little while since I've looked at this thread, and at the moment I only feel prepared to address one of your points... apologies in advance :)

When the person stands on the ground the person "tries" to accelerate, but in so doing also "tries" to deform the ground, which deforms slightly and reaches an equilibrium as the internal forces change.

If the bucket was hanging from your arm or rocketting away and being held back by your arm, then it'd be the same idea. As it is, the person standing on the surface isn't changing direction or speed (neglecting earth rotation etc.) so it can't be the same...

Ah, but they are changing direction.  If you're moving at a constant speed and yet remaining a constant distance from a point, it sounds like you're travelling in a circle, right?  Well, locally at least, you are.

Don't forget: space is curved near massive objects so that other objects travelling locally along straight lines will get close to the massive object.  If something gets in the traveller's way, turning him aside, then it's forcing him away from his straight-line trajectory.  He's not travelling on a straight-line path anymore -- he's accelerating.

I tried to follow along the best i could but i got lost somewhere in the mix.  But let me get this straight (and this is something that i dont understand with RE or FE) if we are constantly moving up (or whatever) then will we someday hit the end, to where we cannot move no more?

Please dont take my words and twist them, changing meanings or whatever. I meant them only simply and if i am completely lost and this is not part of the FE's theory whatsoever just tell me.  My head hurts now. Quantam Physics =Headache

I tried to follow along the best i could but i got lost somewhere in the mix.  But let me get this straight (and this is something that i dont understand with RE or FE) if we are constantly moving up (or whatever) then will we someday hit the end, to where we cannot move no more?

Please dont take my words and twist them, changing meanings or whatever. I meant them only simply and if i am completely lost and this is not part of the FE's theory whatsoever just tell me.  My head hurts now. Quantam Physics =Headache

The universe in the RE and FE model is infinite and constantly expanding, therefore, in the FE model, the Earth will never reach the "ceiling."

In the RE model, objects are moving relative to each other, so even if the universe were finite, Earth's orbit could never "hit the end".