## Gravity is an Illusion?

Interdisciplinary science discussions. Also, if you are not sure where to place your thread, please post it here.

### Gravity is an Illusion?

In order to not take NoShips' thread off topic, I start here with a quote from there.

Biv wrote:Regarding my Galileo example and evidence for things that later prove illusory....I guess one could say that his, and later Newton's, evidence for a gravitational force remains valid if we recognize that gravity is what physicists call a pseudoforce. It's still useful to treat it as a force, even if we recognize at the same time that this is an illusion created by the curvature of space and objects taking a trajectory that follows that curvature.

Biv? Gravity is a pseudoforce? Gravity as a force is an illusion? Please explain.
vivian maxine
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### Re: Gravity is an Illusion?

I will boldly try and explain what biv means. If I am wrong/right he can spank me as a punishment/reward :)

We would see a thing fall and impact with force. We call this force gravitational potential force in basic kinetics. We know that things fall and we then say that they fall because of a force X being put upon them.

In time we've come to review this idea and learnt about how the position of objects and relative velocity give the appearance of a gravitational force. We would say that there was a "pull" between objects before where now we say that there is no actually "pull" and that it is an illusion. What we now understand is to say more clearly that the physical "stuff" of the universe "bends and twists" and that objects within this "bent and twisted" physical "stuff" behave in a way that appears to make them act upon each other at a distance a special force (we named gravity).

Of course in classrooms they will still probably teach you about the "forces" of gravity and magnetism for the sake of practicality and to keep the subject related to the mathematics the students understand?

We, being merely practical creatures, still find it hard to assume that matter doesn't act upon space-time anymore than space-time acts upon matter. And further still we find it beyond our day-to-day nature to fully come to terms with "energy" and "mass" as one of the same "thing".

Basically we are still floundering with semi-archaic terms in modern usage. Pedagogy being what is has been due to certain methods and institutions of education.

Biv, would I be "correct" in saying all "forces" are an illusion? And even that it is more practical in physics to refer to "fields" rather than "force" (beyond obvious day-to-day applications to aerodynamics and such).

Would be worth viewing electronics in this regard too. We generally don't talk about electrical "force", but rather a distribution of energy. It seems to my limited brain that fields are essentially just patterns of distributed energy as presented to us via observations. I would imagine some would go further and even argue we are better off saying "information" rather than "energy" given the context of the subject matter!?

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### Re: Gravity is an Illusion?

Then why do we all cling to the planet despite its great speed? And why do things always fall toward the planet instead of being flung into space?
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### Re: Gravity is an Illusion?

vivian maxine » April 30th, 2017, 8:54 pm wrote:Then why do we all cling to the planet despite its great speed? And why do things always fall toward the planet instead of being flung into space?

What? Did you read what I said above?

We don't because we are within a "field". We need enough energy to break away from the field. It is effectively "distribution of energy". Once we distribute enough energy in one place we can break out of this part of the field.

Or more simply put, because of a phenomenon we have called "gravity" that we once viewed as a "force", but that we no longer view as a "force". In does make perfect sense within the realms of the physical of motion to view "gravity" as a force. The same is done for tension, friction, and such things for ease of use in ... that type of mathematics I for ... Vectors! For vectors it makes sense to call them "forces" so we can do the math, and learn about basic kinetic motion.

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### Re: Gravity is an Illusion?

All true but we are forced (oops) to create a force strong enough to overcome the pull of gravity. Gravity comes free. That force we create to overcome the power of gravity does not come free.
vivian maxine
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### Re: Gravity is an Illusion?

So what? Sorry, I don't see your point at all :S

Don't really understand what you mean by saying "gravity comes free" either?

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### Re: Gravity is an Illusion?

BadgerJelly » April 30th, 2017, 8:52 am wrote:So what? Sorry, I don't see your point at all :S

Don't really understand what you mean by saying "gravity comes free" either?

I meant we do not have to create gravity. It comes with the universe. We have to create a strong enough force to overcome gravity and that is not free.
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### Re: Gravity is an Illusion?

vivian maxine » April 30th, 2017, 8:23 am wrote:All true but we are forced (oops) to create a force strong enough to overcome the pull of gravity. Gravity comes free. That force we create to overcome the power of gravity does not come free.

Gravity is said to be a curvature of spacetime that surrounds matter. I like to think of gravity as “shorter space and slower time” because lengths appear shorter and clocks tick slower in the presence of massive bodies. The changes in space and time surrounding a ponderous body are undetectable at ordinary levels because the the changes are so small but we can observe their effect on nearby objects when they fall.

Because spacetime is curved (shorter space and slower time) this means that spacetime is an energy gradient and objects free to move in an energy gradient will move from an area of high energy to a level of lower energy.

An object, such as a stone, contains a great deal of kinetic energy in the form of internal motion. Atoms bounce and particles spin etc. In gravity, these motions slow as the stone moves through an energy gradient from an area of fast time to slower time but energy is conserved. The internal motions become what we see as a downward motion when the rock falls. When we lift an object, this requires an input of energy to speed-up the internal motions again.

Gravity is free to us but it comes at a price to the universe. As Pascual Jordan explained in the 1920’s, matter is a highly concentrated form of energy so matter and energy are two forms of the same thing that Jordan called “positive energy.” Gravity is what Jordan called “negative energy” since it takes energy to separate one massive body from another. The energy required to create matter comes from the background spacetime leaving an energy debit (negative energy) that follows matter around like an unpaid bill collector and this negative energy is what we call gravity.

Jordan speculated that a star contains equal amounts of positive energy (matter and energy) and negative energy (gravity) so the net energy of a star is zero and, by extension, the net energy of the universe is zero so it takes no energy to create a universe.

“Because there is a law such as gravity, the universe can and will create itself from nothing.
” Stephen Hawking

“Spacetime tells matter how to move; matter tells spacetime how to curve.”
- John A. Wheeler
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### Re: Gravity is an Illusion?

Thank you, bangstrom. I almost understand that. I'll read it again tomorrow. I bought a book about the universe creating itself from nothing - well, partly about that. Other things in it also. Not Hawking's but another. I've not gotten into it yet.
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### Re: Gravity is an Illusion?

Well, can anything in science technically be proven? Cause I don't believe so, in which case, we can't prove gravity
Mattcook15
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### Re: Gravity is an Illusion?

Hi Mattcook15,

Welcome to the Forums.

If you define Gravity, then you can prove it Exists. This doesn't mean we understand Gravity, but rather just the effects we experience and predict.

We have this bad habit of slapping labels on stuff and accepting that if it is labeled.. it must be understood. This happens a lot more than I'm comfortable with.. lol.

Best Regards,
Dave :^)

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### Re: Gravity is an Illusion?

Dave_Oblad » June 18th, 2017, 1:28 pm wrote:Hi Mattcook15,

Welcome to the Forums.

If you define Gravity, then you can prove it Exists. This doesn't mean we understand Gravity, but rather just the effects we experience and predict.

We have this bad habit of slapping labels on stuff and accepting that if it is labeled.. it must be understood. This happens a lot more than I'm comfortable with.. lol.

Best Regards,
Dave :^)

Hmm, sounds a bit suspect to me, Dave. Plenty of definitions for God, say, or the Loch Ness monster, and the tooth fairy, have been provided. Does the availability of a definition imply the existence of a referent?

Actually, it seems to me, the entire premise of the thread may be suspect. To say that gravity is an illusion is to say that our experience of gravity correlates with nothing in the real world. Compare with the case of a rainbow, say. Our experience is real enough, yet there is no "arch in the sky".

But do we experience gravity at all? It's far from obvious to me that we do. We certainly experience sensations of weightfulness, but is that the same as experiencing gravity?

Isn't gravity that which science invokes to explain, among other things, those feelings of weightfulness? And the form that explanation takes varies from theory to theory (something or other - Aristotle; an attractive force - Newton; curvature of spacetime - Einstein). Meanwhile the feelings of weightfulness remain unperturbed.

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### Re: Gravity is an Illusion?

Hi NoShips,

Despite your Strawman input, I can't say I disagree with you. But if I drop a ball and it falls, how many times do I need to do this to say it will always fall and thus requires an explanation and an appropriate label. So we call it Gravity and study it, make predictions and succeed in shooting probes to other planets.

So we have a good grasp on what Gravity does but no clue what Gravity is. We can talk about Curved space but there again is another Label. Do you actually believe Space is Curved? To me, Curved space is a density gradient in the Fabric of Space-Time. It's not literally Curved.

But some will then ask: How can Space have a density gradient if it is made of Nothing? The obvious answer is that Space is not made of nothing. In my book, it's the only real (sort of) solid that exists.

Anyway, back to the OP, no Gravity is not an Illusion. Gravity is just a label that describes a testable and predictable effect. Unlike God, Loch Ness Monster, or Tooth Fairies.

Again, I'm not disagreeing with you. Just because we label something doesn't make it Real. But just because we Label something.. doesn't mean we fully understand it either.

Regards,
Dave :^)

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### Re: Gravity is an Illusion?

Dave_Oblad » June 18th, 2017, 10:23 pm wrote:Hi NoShips,

Despite your Strawman input, I can't say I disagree with you. But if I drop a ball and it falls, how many times do I need to do this to say it will always fall and thus requires an explanation and an appropriate label. So we call it Gravity and study it, make predictions and succeed in shooting probes to other planets.

So we have a good grasp on what Gravity does but no clue what Gravity is. We can talk about Curved space but there again is another Label. Do you actually believe Space is Curved? To me, Curved space is a density gradient in the Fabric of Space-Time. It's not literally Curved.

But some will then ask: How can Space have a density gradient if it is made of Nothing? The obvious answer is that Space is not made of nothing. In my book, it's the only real (sort of) solid that exists.

Anyway, back to the OP, no Gravity is not an Illusion. Gravity is just a label that describes a testable and predictable effect. Unlike God, Loch Ness Monster, or Tooth Fairies.

Again, I'm not disagreeing with you. Just because we label something doesn't make it Real. But just because we Label something.. doesn't mean we fully understand it either.

Regards,
Dave :^)

Oh gosh, I hate this. Before we go any further could you please explain where I strawmanned? LOL

Happens a lot, and gets a bit tiresome.

Don't take that the wrong way, Dave. I do enjoy reading your posts and you're a super-nice dude.

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### Re: Gravity is an Illusion?

People will have to start paying for ungrounded strawman allegations. Wotcha got? *drool*

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### Re: Gravity is an Illusion?

Hi NoShips,

Do you ever sleep? (lol).

I have to go to bed like now.. but to be fair..

We are talking about Gravity as a real verifiable effect that has been labeled. I wasn't trying to support the concept that all labeled things are Real. That's why I saw you opening reply to be of the strawman sort.

Then again.. I could have been more clear with my original sloppy statement.. but that's what comes out when one is really sleepy. Catch ya later buddy.. Snooze time.. yea!

Best wishes,
Dave :^)

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### Re: Gravity is an Illusion?

Dave, I quoted you directly:

"If you define Gravity, then you can prove it Exists."

This is not a strawman, it's you. The claim is obviously false.

But I do agree, who really cares, as long as my good name remains unblemished and you get the beers in.

"Do you ever sleep? (lol)."

Yes, and guess who I dream of. Told you I was sick. LOL

And if none of my counterarguments work, "exist", at least, should not have a capital "E".

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### Re: Gravity is an Illusion?

Dave_Oblad » June 18th, 2017, 10:50 pm wrote:
We are talking about Gravity as a real verifiable effect that has been labeled. I wasn't trying to support the concept that all labeled things are Real. That's why I saw you opening reply to be of the strawman sort.

Still sounds piscine to me. Is gravity not the cause that we postulate for certain effects? For example, Ken's dropping pianos on me that unfortunately do not levitate, and me, not only falling down a lot, but piano martyrdom

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### Re: Gravity is an Illusion?

I did mention Dawkins somewhere else, who really deserves a piano, and his idiotic argument to the effect that "gravity is not a version of the truth; gravity is truth" (I parachute from memory; don't quote me just yet)

Should I elaborate?

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### Re: Gravity is an Illusion?

No ships, if we are 10 miles apart, standing on each side of, let's say, Topeka, Kansas, and each begin walking due north, what happens. We seem, at first, to be movng along parallel paths, but after a while, we discover we are approaching each other. Somewhere on Ellesmere Island we are able to see each other, if we each stand on a tall ladder and wave orange flags. At the North Pole, we finally meet. Is there a mysterious force that is causing us to be pulled together, a strange effect of the Earth we will call "globality"? Or is this strange attraction just an illusion, resulting from the curved surface of the Earth?

Is "globality" real?

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### Re: Gravity is an Illusion?

First of all, everyone except stegosaurs uses kilometres these days. However, as a counterargument, you probably want better...

Hmm, you're far too clever to give this a flippant response after 9 Germans beers. No doubt a trap, LOL

See ya tomorrow.

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### Re: Gravity is an Illusion?

Before proceeding to your post, BiV, I feel it might be instructive for us all to contrast a similar case, that of heat, in an attempt to get a grip on the right questions we want to be asking here. This turns out to be vastly more complex than it appears. Might even need to drag in Kripke at some point...

Heat, according to our best scientific theories, as far as I understand, is (identical with) mean molecular kinetic energy; if correct, a case of successful reduction in science. Heat must not be confused with the sensations, or qualia, that heat causes in creatures like us; feelings of coldness, warmness, burning (i.e. pain), etc. I suggest we all, with great caution, refer to the latter hereafter as HQ (heat qualia). Heat is not identical with HQ.

Q1: Could we be wrong, that is, could we have a false belief, about what heat is? Ans: Of course. Unlikely perhaps but we admit fallibility in science. It's possible heat is not molecular motion.

But what would it mean to ask, "Is heat an illusion?" If simply the same as Q1 then we can stop right now. We already have the answer. But surely there's more to illusion than just a false belief? Illusion need not be accompanied by a false belief. (more in my post below)

Then again, perhaps the question can be construed in terms of HQ:

Q2: Is it possible we might be mistaken about our sensations, our qualia? Heat qualia, like pain, and consciousness in general, do not exist? It's all an illusion, much as Daniel Dennett holds, I believe.

To this question I defer to ma ole pal, John Searle. Illusion is predicated on an appearance/reality distinction. Sometimes things are not what they appear to be. But in the case of consciousness, thus HQ also, no such distinction can be drawn. If it seems to you that you're conscious then you are conscious. Likewise for HQ; if it seems you have a burning sensation then you do have a burning sensation. The answer, then, is no, in my opinion at least. And even if answered in the positive, what is illusory is the heat qualia, not heat.

Finally, consider:

Q3: Are there any non-veridical cases of HQ; i.e., HQ that are not caused by heat? Ans: Certainly. In dreams of being burned at the stake, say. But this is not to say heat is illusory; heat remains molecular motion.

In none of the above cases do we conclude heat is an illusion. In what follows, I'll retain the same nomenclature, mutatis mutandis, for gravity. The word "gravity", if it refers at all, refers to a theoretical physical entity quite independent of us; "WQ" refers to our sensations of weightfulness or weightlessness purportedly caused by gravity. The two must be carefully distinguished. Three more questions, altered accordingly:

Q4: Could we be wrong, that is, could we have a false belief, about what gravity is? Ans: Of course.

Q5: Is it possible we might be mistaken about our sensations of weightfulness, our WQ? Ans: I don't think so.

Q6: Are there any non-veridical cases of WQ? WQ that are not caused by gravity? Ans: Certainly. In dreams of skydiving, say. But this is not to say gravity is illusory; gravity remains, at least as best we can ascertain, the curvature of spacetime.

In none of the above cases do we conclude gravity is an illusion.
Last edited by NoShips on June 19th, 2017, 8:48 am, edited 1 time in total.

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### Re: Gravity is an Illusion?

I wrote the following much earlier, before I realized I was a confused mess, and later wrote the post above. What's below is in need of some surgery, I'm quite certain. But the sun has set and this owl of Minerva can't be bothered. Tear it to shreds. See if I care LOL.

Braininvat » June 18th, 2017, 11:50 pm wrote:No ships, if we are 10 miles apart, standing on each side of, let's say, Topeka, Kansas, and each begin walking due north, what happens. We seem, at first, to be movng along parallel paths, but after a while, we discover we are approaching each other. Somewhere on Ellesmere Island we are able to see each other, if we each stand on a tall ladder and wave orange flags. At the North Pole, we finally meet. Is there a mysterious force that is causing us to be pulled together, a strange effect of the Earth we will call "globality"? Or is this strange attraction just an illusion, resulting from the curved surface of the Earth?

Is "globality" real?

A thought provoking example, Kemosabe, though I believe it needs a little revision to illustrate the point I'm trying to illuminate.

First, let's get ourselves a working definition. The word "illusion", of course, has various usages, but for our purposes, how about this? (holler if you object)

"An illusion is a sensational or perceptual experience whose conditions of satisfaction are not met. Put another way, an illusion is a non-veridical sensational or perceptual experience. You are not seeing what you think you see (hear/feel/etc.)."

(Hereafter, for less laborious typing, I'll speak only of sight, though we recognize illusions involving the other sensory modalities.)

Examples: the non-veridical visual experience of a Pepsi vending machine in the Sahara (a personal illusion), or more relevant to us, a rainbow (a mass illusion).

Now, the question before us is: "Is gravity an illusion?"

I say the question is ill formed inasmuch as we do not have perceptual or sensational experiences of gravity in the first place. No one ever claims to see gravity, much less hear, smell, or taste it. Touch is trickier, but as stated earlier, I feel this is more aptly described in the language of sensations of weightfulness, or even weightlessness if you're an astronaut. "Gravity", I submit, is a theoretical term introduced by science, which purports, among many other things, to account for these sensations. Gravity, we're told, causes these sensations or experiences; it is not the sensations themselves, which are hard to imagine us being wrong about. I don't think we experience a Newtonian attractive force, which is now rejected by science anyway, and I certainly don't experience the curvature of spacetime.

(Those familiar with Saul Kripke may find themselves thinking right now, as I am, of "heat". Heat, science tells us, is mean molecular kinetic energy which, among other stuff that it does, causes in creatures like us certain sensations. It's quite conceivable that in another world, the very same sensations might be caused by a phenomenon other than molecular movement. That phenomenon would not be heat.)

Now, if the question is rephrased as "Could we be wrong about gravity?" we can stop right here and mosey on down to the saloon. Yes or no, the question is at least well formed. And as a matter of historical fact, people have conceded that they were wrong about gravity. Science no longer countenances the Newtonian characterization of gravity as an attractive force acting instantaneously over any distance. We have been wrong about gravity.

Now, to your analogy, BiV, which after some reflection, and given the aforementioned revision, I feel actually serves to support my own position rather than your own. Your analogy, as currently stated, fails, in my opinion, for the reasons just stated: there is no perceptual or sensational experience correlated with "globality". I do not feel myself attracted to you (no offence. Tee hee); a fortiori, talk of illusion is misplaced. Globality, like gravity, is properly regarded as a theoretical postulate, in my view. And unlike gravity, which purportedly is at least the cause of certain sensations in us, globality is correlated with no sensations at all.

While there's no risk of incoherence in telling the globality theorist that he's just plain wrong, I'd personally be hesitant to describe him as the victim of an illusion. He simply has a false belief, not a non-veridical perception or experience (i.e., an illusion). Given that he feels no attraction in the first place, the following sentence would never be uttered: "I thought I was feeling an attractive force, but it turned out to be an illusion. I wasn't feeling what I thought I felt." (See the 2nd last sentence in your post)

By the way, if illusion is defined ad hoc as a false belief, then we can stop right here again, and I answer the OP, "Yes, it's perfectly possible that gravity is an illusion" But an illusion, as commonly understood, is surely not just a false belief or cluster thereof. The fellah who "sees" that Pepsi machine in the desert may or may not have a false belief, depending on his level of thirst and credulity -- I daresay most of us would choose not to "believe our eyes" given background knowledge of Pepsi machines in desert landscapes. He is, however, the subject of a visual illusion.

That revision now. With all due respect to globality advocates, your analogy gets a lot sexier, I think, when we sever all allegiance to globality, and nail our colours, instead, to the sphericality theory mast. Imagine us to be Cro-Magnon proto-scientists way back when men were men and everyone believed the Earth was flat. We've done all the things, and made all the observations that you describe. In a flash of genius, you scream "Eureka!" and run around Kansas naked.

Upon regaining your equanimity and sartorial respectability, you explain to a breathless audience that "my theory is that the Earth is round". Now, what we see happening in all three cases -- gravity, globality, and sphericality -- is the postulation of an unobservable, theoretical entity to explain that which we do observe and experience. Globality has gone the way of the dodo and chest medallions; gravity remains up for grabs. What makes sphericality sexy is that, unlike the case of gravity, the Earth's sphericality has evolved from being an unobservable theoretical postulate to an observable in-yer-face-buster kind of thing; scarcely what can still be described as theoretical.

We can see it! Well, you can if you're Neil Armstrong or David Bowie, at least.

Conclusion: In each of the three cases described (G, G & S) talk of illusion is inappropriate. Our observations were quite correct. It was never the case that we were not seeing what we thought we were seeing. It remains perfectly true that jumping out a tenth-floor window tends to make a mess, as it is true that we'll converge at the North Pole if we both trek due north. We may have had some false beliefs along the way though; the globality fiasco, for one.

Finally, I wish I could claim to be more confident in my assessment here; horrible pangs of doubt remain LOL. Looking forward to hearing your appraisal, BiV. Cheers!

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### Re: Gravity is an Illusion?

Dave_Oblad » June 18th, 2017, 10:23 pm wrote:
But if I drop a ball and it falls, how many times do I need to do this to say it will always fall and thus requires an explanation and an appropriate label. So we call it Gravity and study it, make predictions and succeed in shooting probes to other planets.

This, I think, is exactly right, Dave.

Dave_Oblad » June 18th, 2017, 10:23 pm wrote:So we have a good grasp on what Gravity does but no clue what Gravity is. We can talk about Curved space but there again is another Label. Do you actually believe Space is Curved? To me, Curved space is a density gradient in the Fabric of Space-Time. It's not literally Curved.

This, on the other hand, doesn't sound right to me, with all due respect. Einstein's theory about curved spacetime, if read literally, is not just a label. It's a claim to what gravity is. Yes, really! As far as I understand, Einstein himself, adopted a Machian-inspired instrumentalist take on his own theory to begin with; after all, the implications are pretty radical if taken at face value: time and space, as traditionally understood, do not exist. Later he switched to a realist position due to well known dissatisfaction with quantum theory.

Dave_Oblad » June 18th, 2017, 10:23 pm wrote:Anyway, back to the OP, no Gravity is not an Illusion. Gravity is just a label that describes a testable and predictable effect. Unlike God, Loch Ness Monster, or Tooth Fairies.

Again, I'm not disagreeing with you. Just because we label something doesn't make it Real. But just because we Label something.. doesn't mean we fully understand it either.

Now this takes us into heavy-duty philosophy of language. Here there be dragons and Loch Ness monsters LOL.

On one account (descriptivism), the definition (or label) we assign "refers" to something out there in reality if and only if that description is satisfied.

On another account (Kripke, Putnam) that label serves only to identify -- to hook onto -- something out there. We may come to learn that the attributes we assigned (our description) was partially or even entirely incorrect. Nonetheless the label can still refer, even if the description (definition) is wrong.

Given that atoms, for example, we no longer believe have (all) the attributes Dalton assigned to them, a strict descriptivist account would conclude the term "atom", as described by Dalton, does not refer. It was a theory about nothing. Bad news indeed for those who would like to think that science progresses through better and better theories about the same things.

Best wishes
Colin

And thanks for some terrific thought provoking posts.

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### Re: Gravity is an Illusion?

NoShips » June 19th, 2017, 8:59 pm wrote: I don't think we experience a Newtonian attractive force, which is now rejected by science anyway, and I certainly don't experience the curvature of spacetime.

What a load of crap! And the same goes for similar remarks you've made. Get a life, idiot!

Erm, something had felt dreadfully wrong in the NoShips gut since posting yesterday. This is it. I now would like to say, instead, that if gravity is indeed the curvature of spacetime, i.e., if Einstein's theory is literally true (as opposed to only instrumentally true), then we do experience the curvature of spacetime, thus we experience gravity too, for they are one and the same thing.

Just as we experience heat (= mean molecular kinetic energy) as sensations of warmth, burning, etc., (assuming also the truth of this theory), likewise we experience gravity as sensations of weightfulness.

Whew! Glad I got that off my chest. The rest of what I said seems largely unaffected by this latest revision. A few more thoughts now, partly inspired by other members' insights...

I now find myself with conflicting intuitions over the appropriateness of describing (the possibility of) gravity as an "illusion". On the one hand, it sounds odd, to my ears at least, to say that "phlogiston turned out to be an illusion". I'd be inclined to say simply that we were wrong; there's no such thing. Strangely enough, though, the adjectival form sounds fine to me: "phlogiston turned out to be illusory".

On the other hand, it doesn't seem so odd to say, "We used to think we were feeling ourselves being held to the ground. This was an illusion. By and large, we do stay on terra firma, yes, and the feelings are/were real enough, of course, but there is no "hold" or "pull"." Thus Badger could say above:

BadgerJelly » April 30th, 2017, 9:39 pm wrote:
In time we've come to review this idea and learnt about how the position of objects and relative velocity give the appearance of a gravitational force. We would say that there was a "pull" between objects before where now we say that there is no actually "pull" and that it is an illusion.

and Einstein did say apropos of time:

"People like us, who believe in physics, know that the distinction between past, present, and future is only a stubbornly persistent illusion." - Albert Einstein

I appreciate other speakers may well have different intuitions from my own. And it would seem, in matters such as these, there exists no higher court of appeal than our own linguistic intuitions.

Another question to ponder: If gravity is simply the name (or label) we have assigned to whatever it is that causes in us certain sensations, as well as being responsible for various other observable effects (apples falling, tides, planetary motion, etc), then is it even possible at all we could come to believe that gravity does not exist?

Thus, we hear Dave quite reasonably assert:

Dave_Oblad » June 18th, 2017, 10:23 pm wrote:But if I drop a ball and it falls, how many times do I need to do this to say it will always fall and thus requires an explanation and an appropriate label. So we call it Gravity and study it, make predictions and succeed in shooting probes to other planets.

(Except I suggest "Gravity" is what we call the unobservable, presumed cause of these effects. Gravity is surely not the phenomenon itself of balls and other things falling.)

At first blush, the answer to my italicized question above might seem a resounding "No! It's not possible". After all, something must be causing these effects, even if it turns out not to be an attractive force (as it did), or the curvature of spacetime as many now believe. And that something just is gravity.

But not so fast...

In the 19th century scientists had noticed that the planet Uranus was misbehaving; its orbit was at variance with that predicted by Newtonian physics. It was suggested that a previously unobserved planet, which they named "Neptune", was the culprit. Astronomers pointed their telescopes at where the mathematicians told them it ought to be, and ... voila!

So now, do we have confirmation that the name or label "Neptune" just is that which is causing the anomalous orbit of Uranus, thus we could not conceivably have been wrong about Neptune's reality?

Well, curiously enough, a very similar thing happened with Mercury, also guilty of orbital recalcitrance. Much as they had done in the case of Uranus, scientists postulated a previously unobserved planet which they named "Vulcan", pointed their telescopes, and ... (*drumroll*) found nothing!

They were wrong, and no one these days, not even Star Trek nuts, believes there is a third inner planet; the name (label) "Vulcan" having long fallen into scientific desuetude.

In light of this, the amaranthine persistence of gravity talk in science surely must be regarded as slightly more tenuous.

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### Re: Gravity is an Illusion?

NoShips » June 20th, 2017, 6:13 pm wrote:So now, do we have confirmation that the name or label "Neptune" just is that which is causing the anomalous orbit of Uranus, thus we could not conceivably have been wrong about Neptune's reality?

Uh oh! Dunnit again. The above should read (as if anyone cares):

"So now, do we have confirmation that the referent of the name or label "Neptune" (if it refers at all) just is that which is causing the anomalous orbit of Uranus, thus we could not conceivably have been wrong about Neptune's reality?"

The salient point to note here is this: Our earlier supposition was that a theoretical term/name "X", if it refers at all, refers to just that, whatever that might be, responsible for certain observable effects. Therefore, given this supposition, whatever it is that causes all the observable effects we currently impute to gravity, whether it turns out to be the curvature of spacetime or not, will still be called by the name "gravity".

In other words, on this view, attractive Newtonian forces and Einsteinian spacetime curvatures may come and go. But the name "gravity" is here to stay (unless we give up on causality altogether).

The case of "Vulcan" belies this supposition. There is indeed something causally responsible, we now believe, for the once puzzling behavior of the planet Mercury. But we don't call it "Vulcan".

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### Re: Gravity is an Illusion?

The plot thickens...

The citizens of Scienceville were up in arms. Dead bodies had started turning up one after another. Even though horribly mutilated, the victims were all undeniably Scienceville citizens; DNA analysis and unkempt hair proved this.

The local constabulary, as you might imagine, came under enormous pressure to provide answers. The first officer assigned to the case was a Detective Newton. Months of tireless policework culminated in a profile of the killer as 7-ft tall, left-hander from Wales, which was subsequently issued to the press.

Meanwhile, the name "Gary the Ripper" had come to be associated with the crime spree. It's always hard to say how these things start; perhaps the creation of some tabloid journalist, or even a coinage of Detective Newton himself. Who knows, eh? All that really matters is cracking the case.

Tragically, before any arrests were made, Newton fell ill and died. A Lieutenant Einstein was immediately assigned to take over. After another six months of sedulous inquiry, Einstein's own profile was issued to the media at a press conference:

"The culprit, we now believe, is a right-handed midget from northern England, perhaps even the town of Nuneaton specifically, a town notorious for wanton violence and thuggery", a police spokesman declared.

The press room erupted in a cacophony of howls.

"Are you saying that the first six months of the investigation under the leadership of Detective Newton was a complete waste of time? You've been tracking the wrong man?" a furious phalanx of reporters demanded.

"Not at all. We're tracking the same killer. We're making progress", the spokesman replied with an unscrupulous expression, no visible embarrassment on his face.

The assembled members of the press were at a loss.

"But that's ridiculous", Bertie Russell of the Daily Description snorted indignantly. "How can the killer be both a giant, Welsh southpaw and an English rightie midget?"

Police spokesman, Saul Braininavatke, explained unperturbed, "Obviously he can't. Nonetheless, our dearly departed Detective Newton was onto the right guy; he had a few false beliefs about him, that's all. We continue to make progress in our investigation of Gary the Ripper."

"Think of it as an illusion, if you like", the spokesman added. "We're now convinced the killer was an English midget and not a Welsh giant, although Newton had excellent reasons for supposing him to be so. He seemed to be a Welsh midget. We're still not quite sure if he's left or right handed. Work goes on."

The scene erupted again. "This is manifest nonsense. Let's face it, Newton was on a wild goose chase. Illusion, my ass! If the man responsible for murdering our citizens is not a 7-ft Welsh southpaw, then Newton was tracking a phantom."

Thereafter no one knew quite what to do and it looked as if the world would end. Are/were Newton and Einstein tracking the same man or not? If not, Einstein's work can scarcely be regarded as a continuation of Newton's. The former was pursuing a ghost; the profile he composed was a profile of no one -- Phlogiston the Ripper!

And how would we ever decide a matter such as this anyway? What criteria should be deployed to determine whether or not a name has a referent?

One madman in the corner, or at least a man widely considered to be mad (according to some reports he was a wicked Creationist, anti-evolutionist, and a misanthropic hater of Scienceville) suggested calling in a philosopher of language to sort out the mess. No one listened.

He might as well have been crying "God is dead!"
Last edited by NoShips on June 22nd, 2017, 2:25 am, edited 5 times in total.

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### Re: Gravity is an Illusion?

After all that, some light entertainment:

Or perhaps not so light.

Q: Is it possible that the person responsible for the recent spate of killings in the Sussex region is not "The Hedgehog"?

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### Re: Gravity is an Illusion?

Braininvat » June 18th, 2017, 11:50 pm wrote:No ships, if we are 10 miles apart, standing on each side of, let's say, Topeka, Kansas, and each begin walking due north, what happens. We seem, at first, to be movng along parallel paths, but after a while, we discover we are approaching each other. Somewhere on Ellesmere Island we are able to see each other, if we each stand on a tall ladder and wave orange flags. At the North Pole, we finally meet. Is there a mysterious force that is causing us to be pulled together, a strange effect of the Earth we will call "globality"? Or is this strange attraction just an illusion, resulting from the curved surface of the Earth?

Is "globality" real?

And so... (thought I'd forgotten you, eh?) :-)

Your question should be correctly rewritten (see below) as, "Is globality real?", or put another way, "Does the name "globality" refer to anything?"

Well, one suggestion, one endorsed by pressman Bertie Russell, might be: "A name refers if and only if the description associated with the name is satisfied."

In your case, the description you've associated with the name "globaility" is "a mysterious force that is causing us to be pulled together, a strange effect of the Earth". (cf. "a Welsh giant who kills people in Scienceville" associated with the name "Gary the Ripper")

As far as we can tell, there is no such force (or Welsh giant), so we must conclude, based on our descriptivist criteria, globality (and Gary the Ripper) is not real inasmuch as the description is satisfied by nothing. In other words, "globality" is an empty name much like "Santa Claus"; neither name has a referent. "Santa Claus" (the name) seems real enough (a real name); Santa Claus (the dude) is not a real person.

But I don't think that's the answer you want to hear, is it? You'd like me to say, "we're wrong about the force, but globality (i.e. the curvature of the Earth) is real enough".

It's not the answer the Scienceville constabulary wants to hear either. They wanna hear what you do.

By the way, BiV, be very careful of marking a name with inverted commas and the putative referent of that name without inverted commas. We're confused enough already LOL. "Bill Clinton" is a name; Bill Clinton is a person. "Pegasus" is a name. Pegasus does not exist.

You use globality twice in your most recent post. Your first usage is correctly marked (a name); the second is not. In the latter case, your question (I can only assume) pertains to the reality of a physical entity, not the reality of a name. It should not be in inverted commas.

For more homework, how would we ever go about determining whether or not Moses is real? In other words, how could we determine whether the name "Moses" refers to a real person? Assume we're both superintelligent aliens with unlimited resources, time machines, etc.

If you're unable to locate a dude around the right time period who led the Israelites out of Egypt, parted the Red Sea, and all the rest, are we forced to conclude Moses did not exist?

Or is there any possibility we might come back and announce, "We've found the right guy. But he didn't do any of that stuff"?

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### Re: Gravity is an Illusion?

Gravity is an illusion of Entropy ... which we have absolutely no idea about other than to say it is "entropy".

Thus stands the priesthood of science neither bowing to nor admitting to this hidden beast of the mind.

God is entropy and entropy is God! What could be more simple folks? No need to pray to it or believe in it, we just swim in its filthy refuse, the stuff of life.

Gravity and Entropy walk into a bar. Gravity asks Entropy "What you doing?", to which Entropy replies, "I dunno."

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