The Instigator
captmurk
Pro (for)
Tied
0 Points
The Contender
FourTrouble
Con (against)
Tied
0 Points

Gravity can be defined as pressure resulting from space displacement

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Voting Style: Open Point System: 7 Point
Started: 7/20/2015 Category: Science
Updated: 2 years ago Status: Post Voting Period
Viewed: 1,510 times Debate No: 77909
Debate Rounds (4)
Comments (22)
Votes (0)

 

captmurk

Pro

This is a very loose, underdeveloped theory of mine that may or may not already exist. I expect to be torn apart by someone knowledgeable in GR and physics; however, given the mysterious nature of gravity, and the variety of theories claiming to understand it, I figured what the heck? Here's another one. I have no debate rules, just stay on the topic of gravity, and hopefully we can have a fun, informative exchange. Here is my theory:

Gravity is nothing more than pressure being exerted on an object of mass. The pressure is being exerted by space (assuming that empty space has the ability to exert pressure). The larger the mass, the larger the pressure (gravity). In fact, there is a direct correlation between the amount of space the object is displacing, and the amount of pressure being exerted on the object. In other words, the space that an object displaces pushes back on the object from all sides (hence the roundness of most massive objects in space). Any object that comes near this pressure-sphere surrounding the object, gets pushed into the object, giving the illusion that the object is sucking them into it. This could also explain why very large objects fall at the same speed as much smaller objects. The external pressure being exerted on them is evenly distributed, and therefore the pressure (gravity) affects them equally.

This theory is derived from the concept of how particles naturally move to fill a vacuum and achieve equilibrium (like high pressure systems moving to low pressure systems). In this case, it is the exact opposite. Space itself has a natural desire to fill the objects place that is displacing space. It's easier to visualize if you inverse the make-up of earth and space. Imagine if space was filled with fluid matter (like water), and there is a small spherical vacuum moving through it (Earth), there would be a consistent and evenly distributed pressure being exerted on that spherical vacuum because of the matter it is displacing as it moves through it. That pressure is what we perceive as gravity.

That's kind of the idea. Obviously there's more to discuss, and I'm sure you can't wait to explain all the ways this violates physics and what we already know about gravity. Let's get to it!
FourTrouble

Con

The argument against Pro's theory is simple:

Pressure is based on volume displaced, not mass. In other words, pressure is stronger or weaker based on the size of objects (i.e. which affects how much volume is displaced).

Gravity scales with mass, not volume. In other words, gravity is stronger or weaker depending on the mass of objects.

Volume is not the same as mass.

This alone dooms Pro's entire theory. At this point, you can vote Con. There's no need to continue reading.

But Pro's theory contains so many other problems, and so much nonsense, that it's worth pointing issues out, so as to make the debate more educational.

1. What is a "pressure sphere"? I've never heard of such a thing; it sounds like nonsense. I can't even imagine what a pressure sphere would look like. Pressure just doesn't work like that.

2. Assuming this "pressure sphere" idea somehow exists or is possible, Pro's theory still fails to account for the fact that anything affected by gravity falls with the same acceleration. This is an integral part of the way gravity works, and it's encapsulated by Newton's famous law, F=ma, i.e. force equals mass times acceleration. Any theory of gravity must produce the result that things fall with the same acceleration. Pro's "pressure sphere" cannot produce that result. In Pro's "pressure sphere," the force from pressure is proportional to area rather than mass. This is inconsistent with Newton's law. Pro even admits this: "The external pressure being exerted on them is evenly distributed, and therefore the pressure (gravity) affects them equally." In other words, Pro's saying all objects feel the same force or same pressure due to the uniformity of the pressure from his so-called "pressure sphere." This makes no sense. In Pro's "pressure sphere," where objects experience the same pressure uniformly, the force of the pressure will depend on the surface area of the object. If that's what causes gravity, objects won't fall with the same acceleration. The only way for every object to fall at the same speed is if the force depends on the mass. When force depends on the surface area of the object, the objects will fall at different speeds. In Pro's "pressure sphere," the mass in the equation cancels out. Thus, Pro's theory fails because it cannot account for a crucial part of gravity.

3. Presumably, Pro's "pressure" is caused by some substance. If there exists such a substance capable of applying pressure due to its displacement, this same substance should apply a friction force to things moving through it. Friction makes things slow down. So, under Pro's theory, we'd expect to see objects slowing down. But the earth isn't slowing down. So Pro's theory is wrong.
Debate Round No. 1
captmurk

Pro

I first want to say that I didn't really expect to win this debate. As I said in the first round, this is a very loosely organized "theory", and I never really claimed that it was scientifically backed. I just wanted to hear some scientific arguments against it, and Con did exactly that. That said, I do have some rebuttals for Con.

What I am proposing very much has to do with mass, not volume. The example I used in R1, where I imagined space as water, and the earth as a vacuum-sphere moving through it (which is more in line with volume displacement), was only to help visualize the concept. It wasn't the concept itself; it was actually the inverse. What I am saying is that when matter displaces space, the removed space pushes back on that matter. The displacement of space (in this theory) has everything to do with mass, not volume. The greater the mass, the greater the displacement, regardless of the surface area. In other words, a massive object could have small dimensions and surface area, but because of its great density, it displaces more space. Therefore, we are not taking about volume in terms of size and surface area; we are talking about how much space is being displaced, which is directly correlated with the mass and density of matter.

To address your other points:

1) The term "pressure sphere" IS nonsense. It is a term I made up because I couldn't think of a better one to describe the uniform pressure being applied to all sides of any piece of matter. As far as what it is, essentially it is a uniform layer of space-pressure being exerted on the object. If the object is a sphere, like Earth, then this layer of pressure would be a sphere surrounding it, kind of like our atmosphere. If fact, I think our atmosphere, and layered earth, serves my theory well in some ways. External pressure from space would ensure that more massive objects get pushed until they settle at the "bottom", or core, while the less massive particles (air, gas, liquid, dirt, etc.) would be pushed and held in place just above the more massive core; which is why you see greater density starting at the Earth's core, and less and less density as you move away from it (which is indicative of external pressure). The "pressure sphere" would also mean that the further you move away from the massive object (the primary source of displacement), the lighter the pressure would be. In other words, as you move further from earth towards the outer layers of the "pressure sphere," the pressure would diminish at some quantifiable rate; which might explain why astronauts stop getting pushed (i.e. falling) towards earth almost as soon as they escape the external pressure layers of our atmosphere. As far as precise calculations regarding the amount of pressure (gravity) exerted at different distances from the source of displacement, I'm not that mathematically inclined. I only know that the pressure (gravity) is weaker as you move further from the source of mass.

2. Con's entire second point is predicated on the misconception that the kind of pressure I'm talking about is tied to surface area and volume. I explained above how this is not in line with my theory. When space is being displaced, the only thing that determines the amount of pressure space pushes back with, is mass. The size and density of matter is what determines how much space it is displacing. To reiterate, this pressure from space has everything to do with the mass of an object, not it's surface area, because the pressure is derived from displacement, and only mass can truly displace space. It doesn't matter if it is large and hallow like a beach ball. If it is truly hallow, then the hallow portion isn't displacing space...it is space.

As far as how this uniform space-pressure, caused by space displacement, specifically affects the way other objects are pushed towards the more massive source? That's a little more difficult to understand because we don't exactly know how or what "space-pressure" is, or if it even exists at all. It's the least concrete aspect of my theory (among others I'm sure). I just assume that because this pressure is relatively uniform, it pushes all objects down uniformly regardless of their size (hence Newton's law), so long as friction (other already-settled-objects) doesn't interfere with the inward (i.e. downward) movement of the "falling" objects.

Obviously we can explore more into what exactly "space pressure" is, and how it affects objects under the influence of it. Is there a mass-less field or force particle that permeates throughout all of space? Is that what defines space? Because of these mass-less qualities, is that why we don't observe the friction you brought up in point 3? These questions open the door to many other interesting topics. But I did want to make clear that mass, not dimension or surface area, is what determines the true displacement of space, and therefore, is what determines the space-pressure (i.e. gravity) being exerted back on the object of mass.
FourTrouble

Con

Pro's theory is entirely meaningless. It's too vague and ill-defined to even be attacked. It literally says nothing, because Pro is just defining or redefining terms to mean whatever he wants.

As I explained in the previous round, pressure as defined by actual physicists cannot be the basis of gravity because it scales by volume displaced rather than mass.
Debate Round No. 2
captmurk

Pro

I was disappointed to read Con's R2 argument. I expected more from a top debater on this website. It was lazy and dismissive. After thoroughly addressing each point Con made in R1, his response sounded like he just threw up his hands and said, this is all just too stupid and ridiculous to continue discussing. Which naturally leads me to the glaringly obvious question: Why did Con take this debate to begin with? In the opening round (prior to acceptance), I was fairly clear in describing exactly what this theory entails. I was also clear that it was not backed by current scientific theory, that it was loosely defined and abstract, and that it would be difficult for me prove or win. So again, I ask, why did Con take this debate?

Perhaps Con accepted this debate because he thought it would be an effortless win (let's face it, someone in the 99th percentile is likely very strategic about the debates they accept). But here's where Con went wrong. His "nail-in-the-coffin" argument (which happens to be the most sound aspect of my theory) is based squarely on Con's misunderstanding that matter displacing space is the same as matter displacing other matter. The type of displacement Con keeps referring to is when an object of mass is displacing another object of mass (i.e. a submarine displacing water), where the size and shape (surface area) of an object determine the amount of displacement, not its density and mass.

On the other hand, when we are talking about matter displacing space, the amount of space displaced is directly dependent on how much matter an object is made of; and the object's size and density, and therefore, the object's mass, is the measurement that tells us how much matter an object is made of, which tells us how much space it is displacing. As I said before, matter could even be described as, "where space isn't." This understanding, regarding space displacement, is not "meaningless," nor is it an arbitrary redefining of words or concepts; and there are many scientific forums and articles that explore this concept thoroughly.

That being said, one of three things is happening here: 1) Con simply cannot understand that the greater the mass (size and density), the greater the space displacement. 2) I haven't explained space displacement well enough for Con to understand. Or, 3) Con is now aware of this misunderstanding, but decided to double-down for tactical purposes (i.e. admitting error could cost him votes).

There is one other avenue Con can take (which is the one Con SHOULD be exploiting to win this debate): The idea that space can't be displaced because it is a perfect vacuum, and therefore, there is nothing to be displaced. Additionally, how can a perfect vacuum such as space exert pressure? What exactly is doing the exerting? There, I gave you a head start. I'd appreciate a little more effort in your next round.
FourTrouble

Con

Pro is right that my response was "dismissive" but it was not "lazy." I value concision. And anyone who plays mafia in the forums knows that about me. While Pro is free to interpret my conscious choice to be concise as laziness, that interpretation is simply wrong. I exercised judgment about what needed saying. And by focusing directly on what matters, I emphasized certain points that otherwise would be lost in the fray.

In R2 and R3, Pro admits repeatedly that he doesn't expect to win this debate. That's why my tone is dismissive. How can Pro expect anything but a dismissive tone after admitting he expects a loss? Ironically, Pro asks why I took the debate. I took the debate to negate the resolution. That is the purpose of debating. I also took the debate to teach Pro a thing or three about physics. Pro says he wanted to be destroyed by someone who knows stuff about physics. Well, for the record, the person writing this debate (i.e. me) is nearly done with a PhD in physics, focusing on AMO. And I also have fa number of friends who specialize in GR -- and my neighbor for 4 years who is a professor in cosmology -- who I asked about Pro's theory. Every single person said exactly what I already said in R1 and R2: pressure and gravity operate in a fundamentally different way.

A better question would be why Pro started a debate he expected to lose. I'm at a loss to answer that one.

As for the resolution itself, I'll repeat what I said in R1 and R2: Pro cannot win this debate because he misunderstands what pressure is. I took the debate to address that very specific and narrow issue. Pro attempts to define gravity as "pressure resulting from space displacement." This "theory" cannot be for a number of reasons. However, the main reason, and the most important reason, is because pressure scales with volume displaced, whereas gravity scales with mass displaced.

This simple fact dooms Pro's entire theory. It doesn't matter what Pro says, because if you use the scientific definition of "pressure," as understood by actual scientists, Pro loses the debate.


The reason I'm dismissive is because Pro tries to redefine pressure in R2. And Pro creates concepts out of thin air. When I questioned him about "pressure spheres," he admits it's nonsense. Pro simply defines or redefines things to be however he wants. And at that point, we're not talking science anymore. At that point, we're talking fantasy. We're talking about a fantasy where Pro defines every term however he wants, and by redefining terms however he wants, he gets to argue a theory that simply has no connection whatsoever to reality or science.

And I have no interest in a debate about this "fantasy." I'm interested in a science debate. That's what I thought this was. If Pro wants to address how a scientific understanding of pressure can do what he's saying, then I'll engage him on that narrow topic. But I'm not gonna engage Pro in an argument about how terms are defined, because in the science world, certain terms are predefined a certain way. While the definition of "gravity" is up for debate, because that's what this debate is about, the word "pressure" is not up for debate.

This is why I called Pro's theory "completely meaningless" and proceeded to dismiss it, while repeating my criticism in R1. Pro still wants me to address his points, instead of trying to using proper definitions. Instead, I'll address his definitional problems, because I'm not going to simply accept his definitions.

Pro states that "the greater the mass (size and density), the greater the space displacement." Pro fails to realize that "space displacement," which is related to pressure," has no relation whatsoever to mass. None. Zero. "Space displacement" is caused by "size," not "density." This is a scientific fact. That's the key fact that distinguishes pressure from gravity, and the key reason Pro loses. You can't just define "displacement" in relation to "mass" when that's simply not how reality works. I already said this in R1.

This concept of "space displacement" is literally meaningless as Pro defines it. When space -- or anything else -- is displaced, it's displaced as a result of "volume" or "size." That's literally what "displacement" means. You have an object. If that object is "displaced," it means it's location in space was moved, as a result of something else taking its place. Pro wants to redefine "displacement" as related to "mass" rather than "size." Pro cannot do that. No scientist would ever accept that redefinition. I certainly refuse to do so. Mass is 100% unrelated to displacement. You can have an object weighing 1 million pounds in a space the size of a speck of sand, or you could have an object weighing 1 nanogram in a space the size of our sun. If that doesn't illustrated to you the total irrelevance of mass to "space displacement," then I don't know what else will.

As I said, I'll accept actual scientific definitions, not whatever Pro wants his definitions to be. Again, remember this is a science debate, and defining and redefining stuff into existence in a non-scientific manner, as whatever you want, is against the spirit of this debate.

If Pro wants to talk about how gravity isn't related to mass but is rather related to volume, and if Pro wants to argue that gravity can be explaiend solely in relation to volume and to the way volume scales, then I'm willing to engage Pro. Otherwise, Pro simply isn't talking science.
Debate Round No. 3
captmurk

Pro

Rebuttals:

Con: "Pressure scales with volume displaced, whereas gravity scales with mass displaced"

Pressure scales with volume displaced when the volume being displaced consists of matter (e.g. water, air, soil, etc.). But when the volume being displaced is space, we have an entirely different circumstance. This is what Con has failed to fully understand or acknowledge: there is a fundamental difference between matter displacing other matter, and matter displacing space. When matter displaces other matter, the object's surface area is the only thing that creates displacement; however, when an object displaces space (not space as in dimension, space as in quantity), displacement is determined by the object's quantity of matter.

The reason for this difference is that space exists and permeates throughout every dimension of the Universe, which means that space fills all gaps, both the exterior and interior of any atomic structure. Let's use an example to illustrate this difference. If you submerge a submarine in water, the water can't permeate throughout the air-filled inner dimensions of the sub, which results in displacement. Conversely, if that sub is floating in space, the amount of space being displaced is considerably less than the amount of water it was displacing in the previous scenario. The reason being, space already exists inside and throughout the submarine, unlike the water previously. This is because the atoms that make up the entire volume of the sub's dimensions (including the air inside) are already filled with space; and if the object already consists of what it is supposed to be displacing, it won't displace very much of it.

Con: "Pro wants to redefine 'displacement' as related to 'mass' rather than 'size.' Pro cannot do that. No scientist would ever accept that redefinition. I certainly refuse to do so. Mass is 100% unrelated to displacement."

Wrong. Let's examine Con's example to refute this:

An object that is enormous in size (like our sun), but only weighs 1 nanogram , is an object that has virtually no density per volume (mass). In other words, its volume consists of minimal amounts of matter; and space is what fills the gaps between that sparsely scattered matter. Therefore, the large, mostly mass-less object, despite the visibly large size of its "shell" or outline, is mostly made of space, which means it's hardly displacing any space. Conversely, an object weighing 1 million pounds, but is the dimensional size of a speck of sand, is an object that is immensely dense and massive; meaning it consists of large quantities of matter. Because there is almost no space in between these ultra-dense particles of matter, the object is almost purely displacing space, as opposed to displacing scattered specks of space.

Think of it this way. You could theoretically condense the earth to a much smaller dimensional size (similar to a star condensing to a black hole). This new earth would still have the exact same quantity of matter in it, and therefore would be displacing the exact same quantity of space. The only difference is that the displacement would be concentrated into one completely solid ball of missing space, instead of a larger, scattered displacement with vast amounts of space permeating throughout it. In Earth's current state, most atomic structures (even iron) consist mostly of space, which means that most structures aren't actually displacing as much space as their dimensional size would indicate. That's because something that is made of space, can't displace space, and space exists everywhere, permeating throughout all structures; unless all the space gets squeezed out, resulting in a little chunk of pure matter, creating pure space displacement, like the speck of sand you describe. You can also look at it this way:

Imagine a pool of water with a sponge sitting in it that is already completely saturated with that same pool water. Now imagine that you grab the sponge with your hand, hold it under water, and squeeze it until all the water comes out. If we imagine your hand as an invisible, mass-less force, there is no change in displacement in the pool water. The water simply transferred from within the sponge, to outside the sponge; however, the size of the sponge did change. It is now compressed, and therefore, dimensionally smaller, all-the-while, not altering the net displacement of pool water. Similar to the sponge, atoms that make up all structures in the Universe are already saturated with space in between the protons and elections, and in-between the surrounding atoms as well.

Con: "We're talking about a fantasy where Pro defines every term however he wants, and by redefining terms however he wants, he gets to argue a theory that simply has no connection whatsoever to reality or science."

My use of unconventional terms like, "pressure sphere" and "space pressure," doesn't necessarily mean that the concepts behind those terms are invalid. These concepts may very well be invalid, but just because the term is misleading or inaccurate, does not by default mean the concept is misleading or inaccurate. That is why I said "pressure sphere" was nonsense in R2. Not because I believe the concept is nonsense, but because the term I used to describe it was completely made-up.

Additionally, Con's claim that my theory is somehow violating the laws of physics is nonsense. Con keeps trying to ground the validity of his reasoning to settled physics. The problem is that physics has yet to objectively define exactly what space is. There is no settled law of physics regarding the concepts of "space displacement" or "space pressure" at this point, because physics has yet to objectively define what space is.

Con: "Ironically, Pro asks why I took the debate. I took the debate to negate the resolution. That is the purpose of debating."

But Con hasn't negated the resolution, which is why I expected further debate after highlighting his errors in R2. But instead of addressing my counter points, Con basically said, nope, you're wrong, the end. In R3 Con still stands by his fallacious understanding of space displacement; meanwhile the more obscure aspects of my theory (what is space made of? can it be displaced? can it exert pressure?) have been left mostly untouched.

At this point, I think Con took this debate simply because he thought it would be an easy win; not because he actually wanted to explore an abstract theory of gravity. Look, winning is fine. This is a debate website, and that"s perfectly ok. But being dismissive for the purpose of winning greatly underscores what I was hoping to achieve in this debate. We've spent entirely too much time debating the semantics of something Con has simply failed to understand.

Con: "A better question would be why Pro started a debate he expected to lose. I'm at a loss to answer that one."

Because winning this debate wasn't my objective. Having a meaningful exchange about an obscure and interesting topic was my objective.

Final Topic: What is space, and how can it affect anything?

This, in my opinion, is the least concrete aspect of my theory. If matter displaces space (a matter-less vacuum), then how can that displacement affect anything? Well, GR defines space as a pliable entity or fabric that interacts with mass. This "space fabric" (according to GR) has physical characteristics, which means it is made of something quantifiable that can change, which remains consistent with my theory. In my theory, this change resembles inward-pressure resulting from displacement. The light bending dramatically around a super-massive black hole illustrates this distorted "space-pressure" (what most call gravity) nicely.

There is certainly more digging, analyzing, and scrutinizing to be done regarding this theory, and I'm sorry to cut this off so abruptly, but I've ran out of characters.

I would like to thank Con for taking this debate, and any participating voters and viewers.
FourTrouble

Con

"Space" is a "dimension," not a "quantity." Pro's talking about "vacuum," not "space." You can't just define "space" however you want. Pro's theory is nonsense. "Space" refers to distance from A to B in various directions. Pro's "space displacement" concept is meaningless, and misunderstands the nature of space, as I explained in previous rounds.

Pro: "When an object displaces space (not space as in dimension, space as in quantity), displacement is determined by the object's quantity of matter."

This statement is nonsense. "Space" is defined as a "dimension," not a "quantity."

Pro: "The reason for this difference is that space exists and permeates throughout every dimension of the Universe, which means that space fills all gaps, both the exterior and interior of any atomic structure."

Again, this statement is nonsense. Pro's talking about "vacuum," not "space." Space isn't a "substance" that fills "gaps." It's not an object that "permeates" the dimensions. Space is a dimension.

Pro: "If matter displaces space (a matter-less vacuum), then how can that displacement affect anything? Well, GR defines space as a pliable entity or fabric that interacts with mass. This 'space fabric' (according to GR) has physical characteristics, which means it is made of something quantifiable that can change, which remains consistent with my theory. In my theory, this change resembles inward-pressure resulting from displacement. The light bending dramatically around a super-massive black hole illustrates this distorted 'space-pressure' (what most call gravity) nicely."

This is a massive misunderstanding of GR. Take a look at any GR textbook. For example, Robert Wald's. [1] You'll quickly learn that Pro's completely mistaken. GR is about the geometry of space-time. GR is emphatically NOT about a "space fabric." GR never posits a "space fabric" or "space substance."

What GR says is that space is a manifold, and matter then affects the metric of said manifold. A "manifold" is just a fancy term that means a geometry. So, for example, Euclidean geometry is a manifold with a metric given by the equation: d= (x^2+y^2+z^2)^(1/2). This metric gives us the way that distance is measured between two points in a Euclidean geometry. An example of a Euclidean geometry is a flat piece of paper. On the other hand, a ball (or sphere) has a different geometry. The metric for a ball or sphere is given by the equation: ds2=dr^2 + r^2d_2;^2 + r^2sin(_2;)^2db1;^2. As you can see, the way distance is measured between two points on a ball is different from the way distance is measured on a flat piece of paper.

While Euclidean geometry is the geometry that most of us are familiar with, the geometry of space-time is different. The geometry of space-time is given by the following equation: R_{\mu \nu} - {1 \over 2}g_{\mu \nu}\,R + g_{\mu \nu} \Lambda = {8 \pi G \over c^4} T_{\mu \nu}. In this equation, g is the metric. T is the stress energy tensor, which is approximately the mass of an object. The equation shows that mass (or more precisely, the stress energy tensor) determines the metric. The beauty of GR is that the metric is not uniform (in Euclidean geometry, the metric is always uniform). In GR, the metric's affected by mass. And, remember, the metric defines how to measure the distance between any two points in space-time. Thus, GR shows that the way distance is measured in space-time is affected by matter, because matter affects the metric of space-time. GR also postulates that any object must follow the path of the shortest distance between any two points in space-time. As a result, gravity emerges as a consequence of geometry. Gravity is no longer understood as a force but simply as a result of the geometry of space-time. In GR, "space" is never treated as a "substance" or "fabric." In fact, look through a GR textbook. The terms "space fabric" or "space substance" are nowhere mentioned. These are invented terms that have no relation to actual science.

Pro, I'm gonna help you understand GR, since I feel bad about your misunderstanding. To explain it as best I can, I need you to follow these instructions. Readers interested in learning about GR should also follow the instructions:

Go get a pencil and paper. On the paper, draw a vertical line and a horizontal line. That's your coordinate system. The horizontal line represents space; the vertical line represents time. Now, pick a point and fill it in. That is your object under consideration. Time is always going forward, so the object is always moving vertically. Even if the object is sitting still in space, it's moving forward in time. The only question is whether it will curve horizontally too (i.e. is the object moving through space?).

To answer the question, fill in another point above the first point vertically. The question is how to draw the shortest path from the first point to the second point. In Euclidean geometry, that's easy: you draw a straight line going up. That line represents a movement through time but not through space. The result is there's no gravity on that object; it's sitting completely still. But remember, this assumes a Euclidean geometry. The geometry of space-time is not Euclidean.

In GR, the metric of space-time is affected by mass. As I explained before, that means the distance between two points is affected by the object's mass. As a result, the shortest path between these two points is NOT a straight line. The shortest path is determined by the equation I gave above for the geometry of space-time. The shortest path will be determined by other factors, including the mass of the object.

The important thing to understand here is that the shortest path between these two points in GR will curve horizontally. The object will travel through not only time but also space, which is represented on your coordinate system as a curved line that moves both horizontally and vertically. The horizontal movement shows the existence of gravity. In other words, gravity emerges as a result of drawing a line that represents the shortest path between these points in the geometry of space-time. As such, gravity is a consequence of geometry. It's a consequence of finding the shortest path between two points in space-time.

Finally, just take a look at [2] -- that's the Wikipedia page with the equation for the geometry of space-time. Or take a look at a GR textbook. Either way, you'll see that Pro's entire theory is literally meaningless, and it's predicated on a gross misunderstanding of GR. Nowhere in GR is a "space substance" or "space fabric" ever suggested or implied by the geometry of space-time.

Again, vote Con because pressure and gravity operate in fundamentally different ways. Don't let Pro just define terms however he wants. That's not science. And make sure you punish Pro for his complete misunderstanding of GR.

[1] http://www.amazon.com...
[2] https://en.wikipedia.org...
Debate Round No. 4
22 comments have been posted on this debate. Showing 1 through 10 records.
Posted by tejretics 1 year ago
tejretics
Your explanation of GR is awesome, FT.

Just as a question/note, you say, "In Euclidean geometry, that's easy: you draw a straight line going up. That line represents a movement through time but not through space. The result is there's no gravity on that object; it's sitting completely still. But remember, this assumes a Euclidean geometry. The geometry of space-time is not Euclidean."

I agree that a straight line going up is the Euclidean explanation. The reason the geometry of space-time isn't necessarily Euclidean is the presence of gravity, etc. In Euclidean geometry, the straight line going up is the shortest way to connect the two points because they're on a flat surface. Gravity means the universe isn't necessarily spatially flat. But recent research in cosmology has shown that the universe is spatially flat, because gravity is "cancelled out" by scalar energy and vice versa [http://map.gsfc.nasa.gov...], which means shouldn't the geometry of space-time be Euclidean at large scales?
Posted by captmurk 2 years ago
captmurk
Thanks for the response. Such an interesting topic. Last question I have, that I've thought about quite a bit in the last couple months. GR explains (please excuse any scientific verbiage inaccuracies) how objects of mass will curve, bend (whatever the right word is) space; and, therefore, GR explains beautifully how other objects are influenced by that geometric curvature (orbits, acceleration, etc.). But one thing GR doesn't explain (to the best of my limited knowledge) is WHY mass affects and bends the geometry of space. I figured perhaps the mere existence of matter creates a displacement of that geometry (or whatever it is), which results in a fundamental changing of it. I don't specifically understand the way it warps and bends like you do, but perhaps it is displacement that causes it? Feel free to respond if you'd like. Thanks again.
Posted by FourTrouble 2 years ago
FourTrouble
Also, notice how much more elegant GR is now that you understand it as simply the geometry of space-time. The beauty of gravity is that it just happens. It's not a force. It's just a result of measuring distances between two points in space-time
Posted by FourTrouble 2 years ago
FourTrouble
If you look up GR on youtube, you're gonna find tons of videos representing space is a fabric -- those videos are wrong. Every single one of them.
Posted by FourTrouble 2 years ago
FourTrouble
In popular media, there's this pliable "fabric" idea that has completely ruined a proper understanding of general relativity. There's no "substance" to space. People have been looking for the "substance" of vacuum (of empty space), and they call that the "ether," but nobody has found that yet, and most physicists don't think an "ether" exists (there's tons of reasoning why but I can't tell you what it is personally).

The idea of the "substance" of space simply doesn't make sense; space is a "dimension." You ask "what exactly is that geometry made of," but that's something I cannot answer in anything but mathematical terms, language like manifolds, metric spaces, and so on. What is a geometry? It's a good question, and all I can tell you is that it's not a "substance"; the best I can say is that it's a dimension, it's what allows you to measure distances, and so on. You're saying "mass can bend the geometry of space," which is partially correct. The idea is that mass affects the distance between two objects. You could look at that as a curvature of space-time, or alternatively, of a curvature in the shortest path between those two objects (as I did in the example I gave you during the debate). Either way, the key idea is that gravity is an emergent phenomenon related to measuring distances between two points in space-time. Space-time itself is simply our dimensions.

I think the "fabric" idea comes from trying to represent space-time (four dimensions) in a Euclidean space, but honestly, it's just wrong. There's no truth to it whatsoever. Space is a dimension; it's what gives us a measurement of distance. It's not a substance. I dunno if that helps but hopefully it does.
Posted by captmurk 2 years ago
captmurk
FourTrouble, I enjoyed your thorough explanation of GR and space. I also liked your coordinate system example. Some good knowledge shared in that round. I do, however, recall space being referred to as a pliable "fabric" many times, in many different ways, on topics covering astrophysics. Is there some truth to that, despite it not being a fundamental component of GR? If you are just done with me and this topic, I totally understand. I'm just speaking from a more conversational perspective right now, and your knowledge of GR would be insightful regarding the "substantive" qualities of space that I've heard of elsewhere in theoretical physics. Just to reiterate my question to you: if mass can bend the geometry of space, which in turn effects mass passing trough that bent geometry, what exactly is that geometry made of? Thanks again for the debate.
Posted by captmurk 2 years ago
captmurk
Thank you for accepting. Looking forward to it.
Posted by FourTrouble 2 years ago
FourTrouble
I've wanted to do a science debate for a while, so hopefully this will be fun.
Posted by Discipulus_Didicit 2 years ago
Discipulus_Didicit
@Berend

He is likely talking about Tejretics, whose profile age is 15. Like commondebator said though you can claim
any age you want so its not really relevant.

Who knows if this is the case with tej? As a matter of fact, who cares?

My answer to the second question is 'lots of people do but not me'
Posted by Berend 2 years ago
Berend
Who's this "15"year old that is one of the best debater on religion?
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