[xasop]

Yes it is. It’s just that either :

a) you don’t understand it,
b) you’re trying to shill me or
c) relativity works differently on a flat earth (which would require a different universe).

In any event, congratulations for picking up something so complicated using only Zetetics.

Your postulations are irrelevant. Let's deal with facts and figures, shall we?

Let’s get this clear – the FE is ALWAYS accelerating at 9.81m/s² in order to replace gravity, but you cannot accelerate and be stationary in the same “frame of reference”.

Incorrect. You can be stationary -- that is, have a velocity of zero -- at one instant in time while accelerating in a given inertial frame of reference. A short time before, you would be moving one way, and a short time after, you would be moving the other, but in between you have acceleration but no velocity. It is perfectly valid to consider what is happening at the instant for which you are stationary using special relativity.

At any given instant, there is an inertial frame of reference in which the Earth is stationary, and it is in that frame of reference that it has an acceleration of 9.8 m s^-2. This is why only the rest mass is relevant.

Now, to perform a complete analysis involving the passage of time, we need to consider that the Earth is really in a non-inertial frame of reference, which is a case explicitly excluded from special relativity. Fortunately, we do not need to complicate our analysis in this way. It is sufficient to note that in this non-inertial frame of reference, we observe a proper acceleration (also known as "gravity") of 9.8 m s^-2, which means that that is the Earth's rate of acceleration within an inertial frame of reference in which it is stationary at any given instant.

The energy need to accelerate the FE is always proportional to its total mass. At a standstill it has only rest mass, but as it accelerates it gains inertial mass. Total mass=rest mass+inertial mass.

This is nonsense. "Inertial mass" is not something you gain by accelerating. What you mean to say is that at non-zero velocities, your relativistic mass exceeds your rest mass, which is true. However, it fails to do anything to counter my point. Indeed, it is an axiom upon which my point rests.

That's the wrong way round. Assuming you mean the beginning of the acceleration, the only mass of the Flat Earth would be its rest mass (although it could still be very heavy). Acceleration would be at 9.81 m/s² in your own time frame, and I agree as I watch you from my frame on Round Earth. However, within a few years I see you still accelerating, but much much less as the Universe stops you reaching the speed of light by adding inertial mass. And slowing down time, etc.

I have no idea what you're trying to say here. You start out by saying I have things the wrong way round, and spend the rest of your paragraph repeating my argument (using incorrect terminology, but nobody's perfect). I appreciate the support, but was hoping you would have some more substance to your asserted disagreement.

No, acceleration in your frame of reference remains at 9.81m/s², otherwise your “gravity” would alter.

Correct, but we're not talking about our current frame of reference, we're talking about the frame of reference we were in 4 billion years ago. More precisely, we are talking about the inertial frame of reference in which the Earth was stationary 4 billion years ago, but I skimmed over that distinction for brevity. Perhaps I overestimated your inferential abilities.

However the Universe is ganging up on you by making your mass increase ( thereby needing more energy), time slow down (so instead of 9.81 m per second every second, it’s 9.81 m per 2 seconds, every two seconds – and increasing) and distances foreshorten (ie 9.81m becomes 8m then 7 …)

Yes, exactly. This happens as measured by an inertial observer. However, we are not inertial -- if you'll recall, the whole premise here is that we are accelerating -- so we would not expect to observe this.

Rejoice! As distances foreshorten, the Flat Earth gets even flatter - even Round Earth becomes disc-shaped 

You are still accelerating, but “meters”, “kilograms” and “seconds” have changed. In my frame of reference, not yours; you can’t zetetically detect anything unusual because it’s happening to everything in your frame of reference.

Everything looks normal to you, as you whizz through the Universe at 99.99999999999999999999999999% of the speed of light, but I see you as short and squashed - you're only a few inches tall. The second hands on rour clocks are barely crawling around their faces, as far as I'm concerned. If you hold a 12" ruler and point it to the ceiling, to me it seems maybe 2" high. But when you point it to the wall, at 90degrees to your acceleration, i see it magically stretch to its full length.

You don't need to explain all this to me. I understand special relativity, apparently better than you do.

Thus the energy requirement for UA goes off the scale. Einstein tells you why you can't exceed the speed of light, but that doesn't mean you can't keep accelerating. That's what your own wiki says; it just seems to stop short of considering the implications.

You've just spent your entire post explaining why this is wrong. To an inertial observer, the energy requirement (or more precisely, the power requirement, that is energy per unit time) does not increase. Instead, the acceleration decreases.

Meanwhile, to us non-inertial observers on the Flat Earth, the Earth's mass remains its rest mass, and the acceleration remains 9.8 m s^-2.

If you need further clarification, I recommend reading your own post again. It contains all the answers you need.

[Boodysaspie]

OK, let's start again:

1) It's not possible to accelerate to the speed of light;

2) If you try to do so the Universe changes the goalposts so that metres shrink, seconds expand and kilograms increase, all in such a way as to negate the effect of your acceleration;

3) Because these factors are working against you, you need more and more energy to maintain your acceleration;

4) Since it's UA, repeat steps 2 & 3 ad infinitum. As speed approaches C, your mass approaches infinity, time slows almost to a halt and meters almost vanish. The only option is to increase the energy input, but this approaches infinite as the mass approaches infinite.

5) Universal Acceleration may be valid, but I'm not aware of an infinite energy source to power it.

============================================================================

(I'm happy to ignore time and distance if you are?).

If I've got this right, you say that mass dilation doesn't affect an accelerating FE from its own inertial FoR, i.e. it doesn't know that it's getting heavier.

But the universe knows it's getting heavier, otherwise it wouldn't have to move the goalposts. So the FoR is from the universe's point of view - to accelerate close to C through the universe you need almost infinite energy.

[AATW]

Interested to know how UA accounts for the differences measured in gravity in different parts of the world.

https://www.newscientist.com/article/dn24068-gravity-map-reveals-earths-extremes/

The general answer from Flat Earthers is "FAKE!", but that is a pretty lazy response and note that multiple agencies in different continents have all reported this.

[Ratboy]

Interested to know how UA accounts for the differences measured in gravity in different parts of the world.

https://www.newscientist.com/article/dn24068-gravity-map-reveals-earths-extremes/

The general answer from Flat Earthers is "FAKE!", but that is a pretty lazy response and note that multiple agencies in different continents have all reported this.

To start, I am not making this concept up.  google "it's turtles all the way down" if you are not familiar with this concept.

I was thinking that if instead of infinite turtles supporting a flat earth, one had an appropriate initial number of turtles that could continue growing and reproducing, the rate of growth would be parabolic. This would give the appearance of gravity to us. If instead of only being one giant turtle per layer, there were many smaller turtles, the growth rate would vary.  This would create heaving of the earth in one area of faster growth (mountains) and trenches where the earth was being left behind a bit. This would cause earthquakes and volcanoes and such things. It would explain local variations in gravity in different areas.

I bemoan that to date, I only get arguments from Round Earthers and perhaps that is what I will get here. This might be a complicated system, but I think for a Flat Earth it pretty much covers  more observations, provides a mechanism for gravity and I am willing to hear better models.

Cheers

[xasop]

1) It's not possible to accelerate to the speed of light;

Correct.

2) If you try to do so the Universe changes the goalposts so that metres shrink, seconds expand and kilograms increase, all in such a way as to negate the effect of your acceleration;

I have to wonder if you really understand what's going on here because of the terminology you are using, and also what you say below (but I'll reply to that in turn). Nothing "changes the goalposts"; length contraction, time dilation and mass dilation are well understood physical effects. The universe also has no sapience with which to do anything.

However, terminology aside, this is fundamentally correct.

3) Because these factors are working against you, you need more and more energy to maintain your acceleration;

Only if you want to maintain a constant acceleration as seen by an inertial observer. This corresponds to an ever-increasing acceleration as observed by someone on the accelerating object.

This is not how UA works; we observe a constant acceleration, therefore an inertial observer would see decreasing acceleration.

4) Since it's UA, repeat steps 2 & 3 ad infinitum. As speed approaches C, your mass approaches infinity, time slows almost to a halt and meters almost vanish. The only option is to increase the energy input, but this approaches infinite as the mass approaches infinite.

5) Universal Acceleration may be valid, but I'm not aware of an infinite energy source to power it.

Step 3 does not correctly represent UA, so this does not apply.

(I'm happy to ignore time and distance if you are?).

It's not that they are being ignored, it's that it massively simplifies our analysis if we consider one instant in time from an inertial frame of reference, instead of trying to model the Earth's non-inertial frame of reference over time. The key point to keep in mind is that we do not specify which instant of time we are talking about, and therefore can draw conclusions spanning all of time (or at least, for as long as the Earth's proper acceleration remains constant) by considering individual instants.

If I've got this right, you say that mass dilation doesn't affect an accelerating FE from its own inertial FoR, i.e. it doesn't know that it's getting heavier.

But the universe knows it's getting heavier, otherwise it wouldn't have to move the goalposts. So the FoR is from the universe's point of view - to accelerate close to C through the universe you need almost infinite energy.

And here's where things get really wonky. You don't seem to understand the most basic principle of relativity, despite the fact that it is written in the name. Measurements of length, time and mass are relative to the observer. The Earth is not "getting heavier" in any objective sense; its observed mass depends on the observer, and so does its acceleration.

The problem with your argument is that you are using the Earth's mass in one frame of reference and its acceleration in another. Of course this is going to lead you to absurd conclusions.

The simplest frame of reference to use in order to see what is going on is the one in which the Earth is stationary (for an instant). In this frame of reference, it has only rest mass and is accelerating at 9.8 m s^-2. If you want to switch to a frame of reference in which its mass is greater, you must also calculate its acceleration in that frame of reference.

[Boodysaspie]

There are plenty of posts on this forum where FET disagrees with RET. It really doesn't matter what I say because it's not my theory; all I'm doing is providing my understanding of it.

My absurd conclusion is based on what I've been taught and what I've read, and it matches every reputable source on this matter. However, if you think it's possible to continuously accelerate to c then I'm surprised that you're too diffident to publish this more widely. If you're correct, write a paper, get some kudos for the society and win yourself a Nobel prize.

[xasop]

There are plenty of posts on this forum where FET disagrees with RET. It really doesn't matter what I say because it's not my theory; all I'm doing is providing my understanding of it.

This has nothing to do with FET or RET, this is basic relativity.

My absurd conclusion is based on what I've been taught and what I've read, and it matches every reputable source on this matter.

Your conclusion is based on mixing and matching observations from different frames of reference. Please provide one reputable source which backs up this methodology.

However, if you think it's possible to continuously accelerate to c then I'm surprised that you're too diffident to publish this more widely. If you're correct, write a paper, get some kudos for the society and win yourself a Nobel prize.

I don't think that, nor is that even close to an accurate representation of what I said.

[Boodysaspie]

Forget observers. They aren't necessary and only lead to confusion.

Universal Acceleration defines a Flat Earth constantly accelerating at g=9.81 /s².

After 1 year it will have accelerated to 0.77c and its mass will have increased by a factor of 1.58
After 2 years it will have accelerated to 0.97c and its mass will have increased by a factor of 3.99
After 3 years it will have accelerated to 0.996c and its mass will have increased by a factor of 11.01
After 4 years it will have accelerated to 0.9995c and its mass will have increased by a factor of 30.79
After 5 years it will have accelerated to 0.99993c and its mass will have increased by a factor of 86.22

After 16 years it will have accelerated to 0.9999999999999999c and its mass will have increased by a factor of 7194825 (and my spreadsheet runs out of resolution).

If the FE wants to continue accelerating at g, then as its speed approaches c its mass will approach infinity and the energy needed to maintain g also approaches infinity.

Universal Acceleration needs almost infinite energy.

[xasop]

Forget observers. They aren't necessary and only lead to confusion.

Observers are fundamental to relativity because mass is relative to the observer. If you do not understand this, you have no business talking about relativity at all.

After 16 years it will have accelerated to 0.9999999999999999c and its mass will have increased by a factor of 7194825 (and my spreadsheet runs out of resolution).

If the FE wants to continue accelerating at g, then as its speed approaches c its mass will approach infinity and the energy needed to maintain g also approaches infinity.

After 16 years of accelerating at g, an object will have accelerated to over 16 times the speed of light. You have correctly surmised that, due to relativity, its acceleration decreases over time in the frame of reference you are using. Why, then, are you still saying that it is accelerating at g?

[Ratboy]

Relativity has been proven by such things as time shifts on satellites, light bending as it approaches the massive sun, and other things that do not exist in an FE world.  Therefore it does not have to exist.  A way to get UA is to put two holes in the ice wall, attach strings and give it to a giant kid to spin like a yo-yo.  That is basically how they got the effect of gravity on 2001 A Space Odessey.

The thing about relativity in a round earth world is that everywhere is the center of the universe.  Nothing is moving from its frame of reference as we can see since the speed of light is the same in every direction.  No matter how long you have accelerated (we appear to be going .9 c to galaxies far from us) it still requires the same amount of energy to accelerate as it did before you accelerated.  You are always basically not moving in relation to yourself as a reference. 

People who do not accept evolution point to how scientists cannot agree on tiny details of their theory.  If you cannot decide if pandas are bears or raccoons, how can evolution be true?  On this site, there is a lot of arguing between round earthers.  I have seen very little debate on the Flat Earth side.  If we accept that FE is based upon just being part of an old society that is like the Volunteer Fire Fighters on the Flintstones (how can houses made of stone burn?) the bickering by REs seems irrelevant.  Play respectfully.

[JohnAdams1145]

I read through Parsifal's posts and I (think) I understand special relativity decently well. Parsifal is correct in that most of the arguments involving "a lot of energy" are wrong -- energy is not an invariant quantity. Neither is relativistic mass (a term often avoided due to the confusion it causes). There is a quantity that is invariant, and that is aptly named invariant mass -- this is the rest mass of an object.

However, wouldn't Universal Acceleration mean that the entire observable Universe had to be accelerating with us? If not, then in the (approximately) inertial reference frame of one of the stars, we would see the Earth getting stupidly close to the speed of light with stupidly high amounts of energy. Additionally, if we were on the Earth, and the rest of the Universe weren't accelerating with us, we would observe obvious length contraction of the distances between the stars.

I'm a Round Earther, and my question to you Flat Earthers is: why would a theory that violates isotropy of space (clearly there is a favored direction of acceleration) be favored over one with a simple explanation: gravity exists, and the Earth is roughly spherical?

Also, this means that an invisible force has to affect everything in the observable universe to make it accelerate with the Earth (otherwise it wouldn't); we feel the acceleration of UA as weight because of the (electromagnetic) normal force exerted on us by Earth to keep us accelerating. Why aren't we just accelerated by the invisible force? Shouldn't we feel weightless? What makes our matter on Earth different from those in the stars?


Of course, none of UA can explain the various experiments done with torsion balances to verify the existence of gravity. Usually these are hand-waved away by criticizing experimental procedure (such as the presence of stray charges, incorrect measurement, bad setup, etc) but in reality most of those criticisms are outright lies or misinformed.

Claiming that the experiment is not repeated is an outright lie, and I don't appreciate that. Claiming that there are problems with the replications requires a lot of proof, and most of those "problems" are misinformation. Claiming that gravity is some sort of EM interaction is displaying ignorance, as all of the balls are intentionally discharged. Claiming that gravity is due to some <insert quantum woo here> does nothing to dispel its existence.

[xasop]

Relativity has been proven by such things as time shifts on satellites, light bending as it approaches the massive sun, and other things that do not exist in an FE world.

Those things are demonstrations of general relativity. We are talking about special relativity, which is observable in (for example) particle accelerators.

The rest of your post is just ranting which is not FED material. I have not split it off because your first sentence is at least somewhat relevant, but please try to remain on topic.

However, wouldn't Universal Acceleration mean that the entire observable Universe had to be accelerating with us?

Yes, this is part of the UA theory. See https://wiki.tfes.org/Universal_Acceleration.

I'm a Round Earther, and my question to you Flat Earthers is: why would a theory that violates isotropy of space (clearly there is a favored direction of acceleration) be favored over one with a simple explanation: gravity exists, and the Earth is roughly spherical?

Why is isotropy of space necessarily a simple quality?

Also, this means that an invisible force has to affect everything in the observable universe to make it accelerate with the Earth (otherwise it wouldn't); we feel the acceleration of UA as weight because of the (electromagnetic) normal force exerted on us by Earth to keep us accelerating. Why aren't we just accelerated by the invisible force? Shouldn't we feel weightless? What makes our matter on Earth different from those in the stars?

The Earth shields us from the UA's direct influence. Please do read https://wiki.tfes.org/Universal_Acceleration.

Of course, none of UA can explain the various experiments done with torsion balances to verify the existence of gravity. Usually these are hand-waved away by criticizing experimental procedure (such as the presence of stray charges, incorrect measurement, bad setup, etc) but in reality most of those criticisms are outright lies or misinformed.

UA cannot do that, but that is because UA does not really say anything at all about interactive forces between masses, so I would not expect it to.

It is evident that a gravitational attraction between masses must exist, otherwise the variances in observed gravity across the Earth's surface could not be explained by UA alone. The point on which FET and RET disagree is whether the Earth has sufficient gravitational attraction to pull itself into a ball. In FET, its mass (or perhaps merely the strength of gravity over long distances) is not sufficient to do this, but local gravity varies due to variation in the density of the Earth.

Following this train of thought, there is no need to deny the validity of such experiments, but nor do they verify anything about the RET model.

[xenotolerance]

Those things are demonstrations of general relativity. We are talking about special relativity, which is observable in (for example) particle accelerators.

Is it possible for the theory of general relativity and the theory of universal acceleration to both be true?

[xasop]

Those things are demonstrations of general relativity. We are talking about special relativity, which is observable in (for example) particle accelerators.

Is it possible for the theory of general relativity and the theory of universal acceleration to both be true?

I don't see why not. However, my understanding of general relativity is much more limited than my understanding of special relativity.

[xenotolerance]

Well, the answer is strictly No, because GR includes gravity. I ask because I'm interested in how one might reconcile the experimental tests of general relativity with another theory that precludes the existence of gravity as GR requires.

[xasop]

Well, the answer is strictly No, because GR includes gravity.

Why is that a problem?

I ask because I'm interested in how one might reconcile the experimental tests of general relativity with another theory that precludes the existence of gravity as GR requires.

Those tests all assume a RET cosmos, as Ratboy has pointed out. The collected data would need to be reinterpreted from scratch with a FET cosmos. As I'm sure you can imagine, the majority of research funding for the past century being directed towards projects which assume RET has left us somewhat behind in this regard, so unfortunately I do not have any ready-to-eat explanations for you.

[xenotolerance]

If it assumes a particular cosmos, and has been repeatedly measured tested in multiple ways, and the assumptions have never led to incorrect or surprising results that were not predicted by the theory, then the assumptions are exceedingly likely to be correct.

If you assume a flat Earth cosmos of whatever design, any experimental prediction will fail, because the Earth is not flat. If one holds the assumption to be true regardless, then there must be some other reason things are the way they are. This is how universal acceleration was conjured out of the bunk aether in the first place. 'If the Earth is flat, then gravity cannot exist, therefore we must experience constant universal acceleration and mistake it for gravity.'

I should point out, your wiki agrees with me that the theories are incompatible. If you think this is wrong, change the wiki.

[xasop]

If it assumes a particular cosmos, and has been repeatedly measured tested in multiple ways, and the assumptions have never led to incorrect or surprising results that were not predicted by the theory, then the assumptions are exceedingly likely to be correct.

This is bog-standard scientific arrogance. The same thing was thought of Newtonian physics, until Einstein came along. Much less time has now passed since relativity was published than elapsed between Newton's time and Einstein's. Just because we have not yet discovered inaccuracies in a model does not imply that they do not exist.

Looking at this from another angle, is it any surprise that a theory which was concocted by someone assuming RET works well with RET assumptions?

If you assume a flat Earth cosmos of whatever design, any experimental prediction will fail, because the Earth is not flat. If one holds the assumption to be true regardless, then there must be some other reason things are the way they are. This is how universal acceleration was conjured out of the bunk aether in the first place. 'If the Earth is flat, then gravity cannot exist, therefore we must experience constant universal acceleration and mistake it for gravity.'

This is gibberish based on your assumption that the Earth is round. I could just as easily say that Newton's theory of gravity was "conjured out of the bunk aether" because he simply thought about what might cause a large ball to attract smaller objects towards it. However, that does nothing to discredit the theory, because it is still perfectly consistent within RET. Assuming the Earth is flat as an axiom when discussing RET will get us nowhere, and neither will the converse.

I should point out, your wiki agrees with me that the theories are incompatible. If you think this is wrong, change the wiki.

The wiki merely states that gravity cannot be responsible for the 9.8 m s^-2 of proper acceleration that we observe, because that requires the Earth to be a ball. It does not rule out the existence of gravity in any form. It is possible that this wording could be improved.

If you think this is wrong, change the wiki.

I have not said that GR and UA can coexist, merely that I do not see any reason why they cannot. I have already stated that my understanding of GR is somewhat limited, so I do not consider myself qualified to state definitively that they can.

[Pete Svarrior]

If it assumes a particular cosmos, and has been repeatedly measured tested in multiple ways, and the assumptions have never led to incorrect or surprising results that were not predicted by the theory, then the assumptions are exceedingly likely to be correct.

Luckily, we don't need to concern ourselves with this hypothetical. https://en.wikipedia.org/wiki/Gravity#Anomalies_and_discrepancies

[xenotolerance]

Arrogant or not, what I wrote about assumptions is correct. Both of you are making the same error. A theory eventually appearing incomplete is not the same as it being wrong. GR doesn't have a ready explanation for the phenomena listed in Svarrior's link, and Newton's physics were phased out in pieces during the last two centuries because it couldn't deal with fields; at no point were the premises found to be faulty in either case.

Parsifal, when you write 'I could just as easily say that Newton's theory of gravity was "conjured out of the bunk aether" because he simply thought about what might cause a large ball to attract smaller objects towards it,' this is child's play. "No, you!" You're right that just saying UA is bunk doesn't discredit anything because it is indeed consistent with flat Earth belief, but that's not the entire argument I put forward, is it?