Thought Experiments and their Taxonomy

This topic for discussion was prompted by Curiouser and Curiouser, one of the moderators. The background is important but I will be as brief as possible. Please be mindful this is a serious question and could lead to a fruitful discussion.
It has emerged that Curiouser and Curiouser was employed for a number of years on various projects all to do with the manufacture of systems for satellites. Which you may find strange as many of the flat earth representatives here apparently deny their very existence. He stated he values properly constructed and well presented arguments that use logic. In a discussion I had with him he posted a link to a previous post he made. In this post Curiouser and Curiouser along with others admonished a forum visitor for his/her inability to consider the ‘flat earth infinite plane’  and the ‘flat earth ice wall’ through a properly constructed thought experiment.
https://www.theflatearthsociety.org/forum/index.php?topic=81384.msg2173876#msg2173876
In this discussion, if you care to read it, more or less gives  the background to the question.

The question, which I think is an interesting one, so here goes.

Thought experiments have been employed since the time of the birth of philosophy. Experiments such as Newton’s bucket, Heisenberg’s gamma-ray microscope, Einstein’s elevator, Leibniz’s mill, Parfit’s people who split like amoebas, and Thomson’s violinist have all been written about extensively as being useful in the development of scientific thought.
The question is can a flat earth thought experiment such as the ‘infinite plane’ have any logical or scientific validity? In all honesty I’m not sure, which is why I have asked the question.
My immediate thought is that such experiments would due to their initial starting premise fall under the reductio ad absurdum heading and be governed by the law of Law of noncontradiction and as such be null and void. I also thought that such an experiment would exist outside the recognised taxonomy of thought experiments but after thinking about it I’m now not sure. The question is, what do you think?

Curiouser and Curiouser is not a flat earther or a moderator. Calling you out on your terrible arguments does not make someone FE.

Also, you will get out of a "thought experiment" what you put into it. If you're not willing to think there's no point.

This topic for discussion was prompted by Curiouser and Curiouser, one of the moderators. The background is important but I will be as brief as possible. Please be mindful this is a serious question and could lead to a fruitful discussion.
It has emerged that Curiouser and Curiouser was employed for a number of years on various projects all to do with the manufacture of systems for satellites. Which you may find strange as many of the flat earth representatives here apparently deny their very existence. He stated he values properly constructed and well presented arguments that use logic. In a discussion I had with him he posted a link to a previous post he made. In this post Curiouser and Curiouser along with others admonished a forum visitor for his/her inability to consider the ‘flat earth infinite plane’  and the ‘flat earth ice wall’ through a properly constructed thought experiment.
https://www.theflatearthsociety.org/forum/index.php?topic=81384.msg2173876#msg2173876
In this discussion, if you care to read it, more or less gives  the background to the question.

The question, which I think is an interesting one, so here goes.

Thought experiments have been employed since the time of the birth of philosophy. Experiments such as Newton’s bucket, Heisenberg’s gamma-ray microscope, Einstein’s elevator, Leibniz’s mill, Parfit’s people who split like amoebas, and Thomson’s violinist have all been written about extensively as being useful in the development of scientific thought.
The question is can a flat earth thought experiment such as the ‘infinite plane’ have any logical or scientific validity? In all honesty I’m not sure, which is why I have asked the question.
My immediate thought is that such experiments would due to their initial starting premise fall under the reductio ad absurdum heading and be governed by the law of Law of noncontradiction and as such be null and void. I also thought that such an experiment would exist outside the recognised taxonomy of thought experiments but after thinking about it I’m now not sure. The question is, what do you think?

I see thought experiments as the food for non-problem solving, or Kuhnian revolutionary, theory. In a system where one must have less empirical evidence to assert more valid things - as is the case with a revolution of any size - it makes sense to use a non-empirical or a not strictly empirical 'thought experiment' as a basis.

To me then, it seems to be one of the many tools within scientific "method" or scientific anarchy, depending on which side you fall in that argument.

Curiouser and Curiouser is not a flat earther or a moderator. Calling you out on your terrible arguments does not make someone FE.

Also, you will get out of a "thought experiment" what you put into it. If you're not willing to think there's no point.

Forgive me but it does say 'Moderator' on his avatar. Going by your comment you have obviously not read or possibly understood the initial post, I had expected a bit more thoughtful.

Quote from: Space Cowgirl on January 08, 2020, 07:27:46 AM

Curiouser and Curiouser is not a flat earther or a moderator. Calling you out on your terrible arguments does not make someone FE.

Also, you will get out of a "thought experiment" what you put into it. If you're not willing to think there's no point.

Forgive me but it does say 'Moderator' on his avatar. Going by your comment you have obviously not read or possibly understood the initial post, I had expected a bit more thoughtful.

I don’t believe he’s the only one either.  It would be nice to know for certain who the real mods are.

If it says "Moderator" or "Administrator" above the post count that's the real mods.

Thought experiments are only useful for showing the logical conclusions of a model.
This can be used to demonstrate that something is not incompatible with a model, or to show a problem with that model.

The latter is most useful for scientific progress or revolutions, such as the thought experiment exposing the incompatibility of Newtonian relativity and the speed of light being constant.
The former is most useful for understanding and teaching concepts, like Newton's cannonball.

The problem arises when you try and do a thought experiment based upon a hypothesis and make up the results to try and claim it proves you are correct.

Thought experiments are only useful for showing the logical conclusions of a model.
This can be used to demonstrate that something is not incompatible with a model, or to show a problem with that model.

The latter is most useful for scientific progress or revolutions, such as the thought experiment exposing the incompatibility of Newtonian relativity and the speed of light being constant.
The former is most useful for understanding and teaching concepts, like Newton's cannonball.

Good point, they are also useful for understanding and teaching new problem solvers.

The problem arises when you try and do a thought experiment based upon a hypothesis and make up the results to try and claim it proves you are correct.

How do you reconcile your opinion that this is a problem with the fact that historically they have been used in exactly this way and we would not have come about many advances if we were to take your advice that it is problematic and avoid it. For example, Galileo was lousy about this.

Quote

The problem arises when you try and do a thought experiment based upon a hypothesis and make up the results to try and claim it proves you are correct.

How do you reconcile your opinion that this is a problem with the fact that historically they have been used in exactly this way and we would not have come about many advances if we were to take your advice that it is problematic and avoid it. For example, Galileo was lousy about this.

Could you provide a more concrete example of this?

Thought experiments are only useful for showing the logical conclusions of a model.
This can be used to demonstrate that something is not incompatible with a model, or to show a problem with that model.

The latter is most useful for scientific progress or revolutions, such as the thought experiment exposing the incompatibility of Newtonian relativity and the speed of light being constant.
The former is most useful for understanding and teaching concepts, like Newton's cannonball.

The problem arises when you try and do a thought experiment based upon a hypothesis and make up the results to try and claim it proves you are correct.

Based on the reading of a few works on the subject I would have to disagree with your very first sentence as the definition you appear to present I would say is too narrow in its scope. Forgive me if I use this quote as it lays out my my argument much better than I could.

Thought experiments may be used to entertain. This is probably true of short stories or novels which some argue qualify as thought experiments if certain conditions apply (see, e.g., Davenport 1983). Some thought experiments fulfil a specific function within a theory (see Borsboom et al. 2002). Others are executed because it is impossible to run the experimental scenario in the real world (see, e.g., Sorensen 1992, pp. 200–202). Sometimes thought experiments help to illustrate and clarify very abstract states of affairs, thereby accelerating the process of understanding (see Behmel 2001). Again others serve as examples in conceptual analysis (see Cohnitz 2006). And, then there are those that matter in the process of theory discovery (Praem and Steglich–Peterson 2015). The thought experiments that have received most of the attention are taken to provide evidence for or against a theory, putting them on a par with real-world experiments (see, e.g., Gendler 2004). The different ways to use thought experiments, of course, do not exclude one another. Most obviously, for example, a thought experiment can both entertain and make a case against a theory.

The above quote is from a Stanford publication on the subject which is a very interesting read on the subject. https://plato.stanford.edu/entries/thought-experiment/

With that said the question is can one logically conduct a thought experiment on a subject, other than for entertainment purposes, where in reality the answer is already known? The question I’m referring to: Is the earth an infinite plane?

Some argue that ‘fictions’ or fictional works can be viewed in some instances as thought experiments

Some have placed “literary fiction on the level of thought experiments.” (Swirski 2007, p. 6) There are two readings of such a claim. According to the first, some literary fiction may be of cognitive power due to the fact that they are thought experiments. In other words, we shouldn’t outright reject the idea that literature can be of cognitive value.

I recently read a series of novels by sci fi writer Peter Hamilton, His Commonwealth Saga, in which he describes hidden walkable pathways between planets, allowing those entering the hidden entrances to go on an almost infinite walk. The question again is could this fiction be considered a thought experiment or is it just a fiction? The same could be said of the idea that the earth is an infinite plane, while it may be amusing to think about it, can one actually construct a meaningful and logical thought experiment about it?
Pierre Duhem, the great historian of physics, is almost alone in what has been understood as an outright condemnation of scientific thought experiments, he says in the world of science a thought experiment is no substitute for a real experiment. Does he have a valid point to make in this instance? I would say yes.
Currently with enough money one can purchase a round the world ticket for flights or cruises or a combination that will allow you to circumnavigate the world. If fit enough one could cycle or even walk around the world. Alternatively one can stay at home and read the exploits of those who have sailed around the world.
I can stand on a mountain top with a telescope on a clear night and look at the heavens and the great void between us , the moon, the planets and the stars.
While flat earth advocates shrink back from the reality of satellites, they are in plain view for all to see with no thought experiment required, information obtained from them for daily weather forecasts, ground surveys and data updates for maps I think show the reality of the world in which we live.
In my opinion, and that of the whole scientific community, the world is not an infinite plane. If one put any store in science and it’s findings a thought experiment on the idea that the earth is an infinite plane has no scientific value in it at all and could only be done for purposes of entertainment.

Quote from: JackBlack on January 08, 2020, 01:37:05 PM

Thought experiments are only useful for showing the logical conclusions of a model.
This can be used to demonstrate that something is not incompatible with a model, or to show a problem with that model.

The latter is most useful for scientific progress or revolutions, such as the thought experiment exposing the incompatibility of Newtonian relativity and the speed of light being constant.
The former is most useful for understanding and teaching concepts, like Newton's cannonball.

Good point, they are also useful for understanding and teaching new problem solvers.

Quote

The problem arises when you try and do a thought experiment based upon a hypothesis and make up the results to try and claim it proves you are correct.

How do you reconcile your opinion that this is a problem with the fact that historically they have been used in exactly this way and we would not have come about many advances if we were to take your advice that it is problematic and avoid it. For example, Galileo was lousy about this.

I don’t quite understand how you consider Galileo to have been as you say ‘lousy’ at this when his own thought experiment on free falling objects revealed a truth, overturning conventional thought at the time and what Aristotle had taught: that heavy objects fall faster than lighter ones. We now know, thanks to Galileo that this is not the case.
The truth as revealed by Galileo is one easily replicated by a couple of steel balls of differing sizes an electro magnet and a couple of switches linked to timers, or a high speed camera.

As I and more importantly others have said for a logical or valid scientific thought experiment to be carried out other than one just for amusement, it has at some level to integrate or communicate with some concept(s) of scientific truth, rather than just existing on its own as a unconnected free floating idea or fiction.

Dressing what is only a fictionalised idea up in a thought experiment costume does not automatically turn it into a credible idea. At some moment in time the idea has to face some kind of scientific scrutiny.
Nice little video on the subject
https://www.pbslearningmedia.org/resource/nvmm-math-fallingbodies/galileos-falling-bodies/#.XhbxOcqnyhA

Based on the reading of a few works on the subject I would have to disagree with your very first sentence as the definition you appear to present I would say is too narrow in its scope. Forgive me if I use this quote as it lays out my my argument much better than I could.

The problem with just taking a quote is that they often don't actually address what was said.

For example, how does it entertain? By showing the logical conclusion of the model?

Especially note the last part, that the different ways do not exclude from one another.

But I suppose I was too harsh. I was meaning in terms of trying to obtain information about reality.
You can show the logical conclusions of a model. This can be used to help explain something from reality, or it can be used to

With that said the question is can one logically conduct a thought experiment on a subject, other than for entertainment purposes, where in reality the answer is already known? The question I’m referring to: Is the earth an infinite plane?

Does everyone know? If not, then you can use it to show problems with that idea.
You can also use it to show problems with arguments raised against it.

But such a topic has no place in science as science has conclusively shown Earth isn't flat.

Quote from: Timeisup on January 09, 2020, 12:51:12 AM

Based on the reading of a few works on the subject I would have to disagree with your very first sentence as the definition you appear to present I would say is too narrow in its scope. Forgive me if I use this quote as it lays out my my argument much better than I could.

The problem with just taking a quote is that they often don't actually address what was said.

For example, how does it entertain? By showing the logical conclusion of the model?

Especially note the last part, that the different ways do not exclude from one another.

But I suppose I was too harsh. I was meaning in terms of trying to obtain information about reality.
You can show the logical conclusions of a model. This can be used to help explain something from reality, or it can be used to

Quote from: Timeisup on January 09, 2020, 12:51:12 AM

With that said the question is can one logically conduct a thought experiment on a subject, other than for entertainment purposes, where in reality the answer is already known? The question I’m referring to: Is the earth an infinite plane?

Does everyone know? If not, then you can use it to show problems with that idea.
You can also use it to show problems with arguments raised against it.

But such a topic has no place in science as science has conclusively shown Earth isn't flat.

Entertaining? Yes I think that a thought experiment on the earth as an infinite plane could be said to be entertaining.
the earth is an infinite plane it would therefore follow;
the earth would have infinite mass
the earth would have infinite gravity as a result of the infinite mass
light would not be able to escape the infinite gravitational field
the earth by implication would have to collapse into a black hole to obey the laws of physics
We would not and never have existed due to the earth being a black hole

If a thought experiment is to have any ultimate logical scientific credibility at some time it has to engage with known scientific truths. In this instance we can see through just thinking about it the earth could never be an infinite plane in this universe obeying its rules. An infinite earth could only exist in another universe with very different laws or exist in someone’s imagination.

ergo, in this universe the earth is not an infinite plane, flat or otherwise.

An infinite plane would not inevitably collapse into a black hole. That's where your thought experiment breaks down. You can't introduce invalid assumptions and expect to arrive at a valid conclusion.

Quote from: John Davis on January 08, 2020, 01:48:51 PM

Quote

The problem arises when you try and do a thought experiment based upon a hypothesis and make up the results to try and claim it proves you are correct.

How do you reconcile your opinion that this is a problem with the fact that historically they have been used in exactly this way and we would not have come about many advances if we were to take your advice that it is problematic and avoid it. For example, Galileo was lousy about this.

Could you provide a more concrete example of this?

It is widely considered true by historians that Galileo never conducted his leaning tower experiment. He simply assumed the results and used them as evidence for his assertion that Copernicus was correct.

His model was also at a less empirical basis than the one at the time - it required more epicycles for it to work, and it had several issues with known measured empirical data - like the number of tides a day, the way the moon looks etc.

Further, he had not yet had the benefit of Opticks by Newton that would have justified his use of his telescope as a valid scientific and empirical tool, by about 100 years. Many of the evidences he put forth using this are directly contradictory to plain sight vision of the moon as well as what we now know due to the benefit of today's technology.

There are a plethora more of examples in Against Method by Paul Feyerabend as well as the paperback pop-science book Free Radicals: The Secret Anarchy of Science by Michael Brooks.

Quote from: JackBlack on January 09, 2020, 01:19:29 AM

Quote from: Timeisup on January 09, 2020, 12:51:12 AM

Based on the reading of a few works on the subject I would have to disagree with your very first sentence as the definition you appear to present I would say is too narrow in its scope. Forgive me if I use this quote as it lays out my my argument much better than I could.

The problem with just taking a quote is that they often don't actually address what was said.

For example, how does it entertain? By showing the logical conclusion of the model?

Especially note the last part, that the different ways do not exclude from one another.

But I suppose I was too harsh. I was meaning in terms of trying to obtain information about reality.
You can show the logical conclusions of a model. This can be used to help explain something from reality, or it can be used to

Quote from: Timeisup on January 09, 2020, 12:51:12 AM

With that said the question is can one logically conduct a thought experiment on a subject, other than for entertainment purposes, where in reality the answer is already known? The question I’m referring to: Is the earth an infinite plane?

Does everyone know? If not, then you can use it to show problems with that idea.
You can also use it to show problems with arguments raised against it.

But such a topic has no place in science as science has conclusively shown Earth isn't flat.

Entertaining? Yes I think that a thought experiment on the earth as an infinite plane could be said to be entertaining.
the earth is an infinite plane it would therefore follow;
the earth would have infinite mass
the earth would have infinite gravity as a result of the infinite mass
light would not be able to escape the infinite gravitational field
the earth by implication would have to collapse into a black hole to obey the laws of physics
We would not and never have existed due to the earth being a black hole

If a thought experiment is to have any ultimate logical scientific credibility at some time it has to engage with known scientific truths. In this instance we can see through just thinking about it the earth could never be an infinite plane in this universe obeying its rules. An infinite earth could only exist in another universe with very different laws or exist in someone’s imagination.

ergo, in this universe the earth is not an infinite plane, flat or otherwise.

Epic fail.

An infinite plane would not inevitably collapse into a black hole. That's where your thought experiment breaks down. You can't introduce invalid assumptions and expect to arrive at a valid conclusion.

Thank you for bringing sense to an otherwise nonsensical argument.

Please remove moderator from your title.

Thanks.

It is widely considered true by historians that Galileo never conducted his leaning tower experiment. He simply assumed the results and used them as evidence for his assertion that Copernicus was correct.

His model was also at a less empirical basis than the one at the time - it required more epicycles for it to work, and it had several issues with known measured empirical data - like the number of tides a day, the way the moon looks etc.

Further, he had not yet had the benefit of Opticks by Newton that would have justified his use of his telescope as a valid scientific and empirical tool, by about 100 years. Many of the evidences he put forth using this are directly contradictory to plain sight vision of the moon as well as what we now know due to the benefit of today's technology.

There are a plethora more of examples in Against Method by Paul Feyerabend as well as the paperback pop-science book Free Radicals: The Secret Anarchy of Science by Michael Brooks.

The only one which comes close to a thought experiment is the leaning tower experiment.
However from what I can see, some people say it happened some people say it didn't.
If it didn't happen then it isn't a valid experiment and shows nothing at all of scientific merit.

However it has been performed by various people, even if Galileo didn't do it.

What I have seen as a thought experiment was a variation on that where there were 2 objects which were tied together. That is valid as it shows the logical conclusion of the model which has heavier objects fall faster, where an even heavier object (formed by combing the 2 lighter objects) cannot fall faster.

But I see no problem with that.

Quote from: John Davis on January 09, 2020, 10:19:20 AM

It is widely considered true by historians that Galileo never conducted his leaning tower experiment. He simply assumed the results and used them as evidence for his assertion that Copernicus was correct.

His model was also at a less empirical basis than the one at the time - it required more epicycles for it to work, and it had several issues with known measured empirical data - like the number of tides a day, the way the moon looks etc.

Further, he had not yet had the benefit of Opticks by Newton that would have justified his use of his telescope as a valid scientific and empirical tool, by about 100 years. Many of the evidences he put forth using this are directly contradictory to plain sight vision of the moon as well as what we now know due to the benefit of today's technology.

There are a plethora more of examples in Against Method by Paul Feyerabend as well as the paperback pop-science book Free Radicals: The Secret Anarchy of Science by Michael Brooks.

The only one which comes close to a thought experiment is the leaning tower experiment.
However from what I can see, some people say it happened some people say it didn't.
If it didn't happen then it isn't a valid experiment and shows nothing at all of scientific merit.

However it has been performed by various people, even if Galileo didn't do it.

What I have seen as a thought experiment was a variation on that where there were 2 objects which were tied together. That is valid as it shows the logical conclusion of the model which has heavier objects fall faster, where an even heavier object (formed by combing the 2 lighter objects) cannot fall faster.

But I see no problem with that.

It is irrelevant that others after the acceptance of his work have performed it. Without using this methodology of proposing a thought experiment and claiming it proves his work, it would have had no opportunity to have been tested later and his view may not have been accepted.

You are right, I did go off topic on some of his other errors. However, I feel they are relevant to the discussion at large as they form a basis showing that non-empirical work has a taxonomy and a validity in method.

Please remove moderator from your title.

Thanks.

I do not find anywhere in my account settings that allows me a title, or a custom title. I have put "Moderator" into the Personal Text section of my profile. My friends and colleagues value me for my reasoned, even-handed way of thinking and my ability to moderate the sides of a discussion. Given that others include less-than-fully-accurate statements in their personal text, such as "Most Prolific Scientist, 2019" or "Best Ever Scientist" I would prefer to leave my personal text as is.

If you wish me to change my personal text in your capacity as administrator, please let me know.

It is irrelevant that others after the acceptance of his work have performed it. Without using this methodology of proposing a thought experiment and claiming it proves his work, it would have had no opportunity to have been tested later and his view may not have been accepted.

And it remains completely invalid as a thought experiment. It is a hypothesis, nothing more.
Do you have any evidence that this was just a thought experiment and this lead to acceptance of his work, as opposed to the other, actually valid, thought experiment or people actually doing the experiment?

Quote from: John Davis on January 09, 2020, 11:39:39 AM

Please remove moderator from your title.

Thanks.

I do not find anywhere in my account settings that allows me a title, or a custom title. I have put "Moderator" into the Personal Text section of my profile. My friends and colleagues value me for my reasoned, even-handed way of thinking and my ability to moderate the sides of a discussion. Given that others include less-than-fully-accurate statements in their personal text, such as "Most Prolific Scientist, 2019" or "Best Ever Scientist" I would prefer to leave my personal text as is.

If you wish me to change my personal text in your capacity as administrator, please let me know.

I thought you were asking John to remove your personal text for you, so I did it. Now I see that you were asking if you could keep it. SORRY. Anyway, it is confusing to the angry noobs so if you could think up some other personal text that describes your ability to be the moderate voice of reason... hey voice of reason. Also, if you would like a custom title let me know. I have the power.

"unofficial mod", "super mod", "antidisestablishmentarianism mod" (i heard it said thats the longest word, not sure exactly what it means)

An infinite plane would not inevitably collapse into a black hole. That's where your thought experiment breaks down. You can't introduce invalid assumptions and expect to arrive at a valid conclusion.

Can you put forward the scientific basis for your statement, or is it just an uninformed opinion?

Let’s remember in the real universe the gravity on a planetary body is dependent on its mass.
In the real universe objects that have a mass far less than an infinite earth would have find themselves shaped by gravity into a super dense structure that ends up collapsing into a black hole. It is estimated that the collapse would occur in bodies with 3 solar masses or greater. As your infinite earth would have infinite mass and cross that specific mass threshold, just think of the implications.

Let’s imagine for a moment some unknown force prevented your infinite flat earth with infinite mass and infinite gravity from collapsing what effect would it have on the solar system. Before we do that you do realise that life would be impossible on an infinite earth with infinite gravity.
Due to the infinite gravitational field produced all the planets including their moons and of course the sun would be torn from their orbits and would no doubt come crashing into your infinite earth, bearing in mind F = G (m1m2/r2). Pop infinity into the equation and see what happens.
This infinite gravitational field would create havoc throughout the universe....the implications are mind boggling.

What do you think would happen?
 

Quote from: boydster on January 09, 2020, 04:11:55 AM

An infinite plane would not inevitably collapse into a black hole. That's where your thought experiment breaks down. You can't introduce invalid assumptions and expect to arrive at a valid conclusion.

Thank you for bringing sense to an otherwise nonsensical argument.

Nonsensical argument! It’s a thought experiment, same as the one you were going on about on another thread.
What do you think would happen on an infinite earth with infinite mass and hence infinite gravity. I think the spacecraft you designed would have one hell of a job obtaining escape velocity. What would your calculated escape velocity be for an earth with infinite mass?
Did the spacecraft you designed not have to rely on gravity kicks to get them to their final destination? By virtue of that you must know quite a bit about orbital mechanics, so what’s your take on the local effect on the solar system if the earth was suddenly infinite?

So far no one else has presented their thoughts on the earth being an infinite plane. As Mr John Davis I believe is the originator of the Davis Plane, perhaps he might put forward his thoughts.

Quote from: boydster on January 09, 2020, 04:11:55 AM

An infinite plane would not inevitably collapse into a black hole. That's where your thought experiment breaks down. You can't introduce invalid assumptions and expect to arrive at a valid conclusion.

Can you put forward the scientific basis for your statement

https://theflatearthsociety.org/home/index.php/blog/infinite-flat-earth-mathematics

I await your review.

Quote from: Curiouser and Curiouser on January 09, 2020, 10:56:35 AM

Quote from: boydster on January 09, 2020, 04:11:55 AM

An infinite plane would not inevitably collapse into a black hole. That's where your thought experiment breaks down. You can't introduce invalid assumptions and expect to arrive at a valid conclusion.

Thank you for bringing sense to an otherwise nonsensical argument.

Nonsensical argument! It’s a thought experiment, same as the one you were going on about on another thread.
What do you think would happen on an infinite earth with infinite mass and hence infinite gravity. I think the spacecraft you designed would have one hell of a job obtaining escape velocity. What would your calculated escape velocity be for an earth with infinite mass?
Did the spacecraft you designed not have to rely on gravity kicks to get them to their final destination? By virtue of that you must know quite a bit about orbital mechanics, so what’s your take on the local effect on the solar system if the earth was suddenly infinite?

Why would you assert that an infinite plane would necessarily also have infinite gravity? Do you have any basis for that, despite there being mathematical models to the contrary?

Quote from: boydster on January 09, 2020, 04:11:55 AM

An infinite plane would not inevitably collapse into a black hole. That's where your thought experiment breaks down. You can't introduce invalid assumptions and expect to arrive at a valid conclusion.

Can you put forward the scientific basis for your statement, or is it just an uninformed opinion?

Let’s remember in the real universe the gravity on a planetary body is dependent on its mass.
In the real universe objects that have a mass far less than an infinite earth would have find themselves shaped by gravity into a super dense structure that ends up collapsing into a black hole. It is estimated that the collapse would occur in bodies with 3 solar masses or greater. As your infinite earth would have infinite mass and cross that specific mass threshold, just think of the implications.

Let’s imagine for a moment some unknown force prevented your infinite flat earth with infinite mass and infinite gravity from collapsing what effect would it have on the solar system. Before we do that you do realise that life would be impossible on an infinite earth with infinite gravity.
Due to the infinite gravitational field produced all the planets including their moons and of course the sun would be torn from their orbits and would no doubt come crashing into your infinite earth, bearing in mind F = G (m1m2/r2). Pop infinity into the equation and see what happens.
This infinite gravitational field would create havoc throughout the universe....the implications are mind boggling.

What do you think would happen?

Since you clearly don't have the physics or mathematics background to do the integral that shows the way an infinite plane with uniform density produces a uniform gravitational field perpendicular to the plane, it's not going to be useful to try to show the mathematics here. Let's just point out that that derivation is simple, and that it's easily found elsewhere.

Let's do this at a very simple step-by-step level.


You understand that a large mass, unchecked by any other force, may collapse and form a black hole.

Why is it that large stars exist right now and are not already black holes? A force (outward pressure from fission) currently prevents it.

Picture any circle of an infinite plane with uniform mass density that is equivalent to several solar masses centered on point P. If it had no external force on it, you might imagine it would collapse as you postulate onto point P.

But it *does* have a force on it. The gravity of all the other mass that is outside the circle is tugging it *outward* preventing it from collapsing.

This is true at any point P on the plane.

Your statement "bearing in mind F = G (m1m2/r2). Pop infinity into the equation and see what happens" is an approximation only valid for masses that can be treated as point sources. It isn't valid for an extended mass.