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Author Topic: Spacetime - reality, model, or fabrication? What is it exactly....  (Read 9393 times)

Offline yor_on

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As for what a Big Bang is?

A he* of a lot of energy it seems, creating a 3D 'place' for matter to come to be, having one dimension more that we call the arrow, making the processes from energy into matter we see logical (and so also linear), as found in the LHC. To us at least, macroscopically, but also microscopically as it is the outcomes we use to backtrack other possibilities. The ones most consistent seems to be what the universe use to give us what we have, but it also has to do with temperatures and symmetry breaks, assuming a hot Big Bang. Assuming a cold? Then it could be patterns, and how they evolve inside a arrow possibly?

But assuming a lot of energy seems to me to also assume a lot of 'heat', at least when it comes to those first particles of mass moving?
==

(Maybe it would be possible to argue that 'particles' create 'space' though? As in space and mass being some sort of symmetry where you can't have one without the other, including a arrow. Somehow it feels to me as if relativity's approach is this one. But then we also would need some mechanism for how the 'inflationary period' (FTL) slowed down to a accelerating expansion. All of it assuming that 'energy' isn't constricted geometrically, except when (transforming) inside our universe :)
« Last Edit: 24/11/2012 02:05:52 by yor_on »
 

Offline JP

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Zordim, please don't advertise your theories outside of the new theories forum.  This section is primarily for science Q&A in terms of accepted science.
 

Offline JP

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On the topic of the main question here, we (I include myself in the larger group of scientists here) say that matter curves space-time because that's what our mathematical model describes.  We do this because as scientists we understand that our model isn't a universal truth, but that it works for some range of problems.  So when we say gravity curves space-time, we mean that no matter what space-time is on a deeper level, on some level it acts just like a 4D structure with curvature.  If that's confusing or misleading, that's really a problem for the broader education system--there are a lot of people out there who don't understand how science works and don't understand the difference between a scientific model and metaphysical certitude.

So back on the question of what it really is--we know what models work for it, and our "deepest" tested model right now is one that describes a curved geometry, but we'll probably never be able to tell you with 100% confidence that any model is the absolute correct one and that there is nothing further to discover.  At least no model in science so far has yielded absolute truth.
 

lean bean

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that matter curves space-time because that's what our mathematical model describes.  We do this because as scientists we understand that our model isn't a universal truth, but that it works for some range of problems.  So when we say gravity curves space-time, we mean that no matter what space-time is on a deeper level, on some level it acts just like a 4D structure with curvature.  If that's confusing or misleading, that's really a problem for the broader education system--there are a lot of people out there who don't understand how science works and don't understand the difference between a scientific model and metaphysical certitude.

Yes, I buy in to that big time.


Another mathematical model is the one that defines  a particle as a wave or oscillation in a fundamental field. Whatís that field made of? Sorry you have to start somewhere, the field just is.
 Each type of particle having its own field. Even virtual particles may be thought of as ripples or disturbances in fields.
So, if you want your particles solid, thatís too bad.

Tin maybe malleable, but in the mathematical model of fundamental particle fields your just playing with fields all the way down.
And because the field is a mathematical entity or thing, then it can have the property of energy associated with its waves/particles, in other words, energy is a property of the field.
 

Offline zordim

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At least no model in science so far has yielded absolute truth.

What is - really, truly, scientifically - the space?
Well, it is the following:
- that is something that contains everything. And that "everything" is, essentially, the energy, packed in different ways/forms.
- that is something in which we can notice and measure that what we call "lengths". There can exist maximally three straight line segments which are mutually orthogonal (perpendicular) and which cross each other at one and the same point, and that is why we call it the 3D space.
- that is something that has the following two, detected, measured - that is - scientifically proven properties: the lengthwise capacitance 92e4da341fe8f4cd46192f21b6ff3aa7.gif (a.k.a. electric permittivity), and the lengthwise inductance c9faf6ead2cd2c2187bd943488de1d0a.gif (a.k.a. magnetic permeability). Because of these two properties, electromagnetic properties, the space is an electromagnetic phenomenon.

The elementary existence manifestation, the most elementary entity, which manifests its existence within the space, is the photon.
Photon's properties are: energy, EM-oscillation period, wavelength. It moves. "Moving" is the way it exists. There are no photons which do not move. And they move with the velocity which is determined with 92e4da341fe8f4cd46192f21b6ff3aa7.gif and c9faf6ead2cd2c2187bd943488de1d0a.gif properties of space.

Time is that what gives sense to existence. (Without it, we could not determine, we could not define the existence. Without it, some entity could pass some distance "in no time", so it could be throughout the space. So, that entity would be everywhere. Everything would be everywhere. So, space and that what has energy could not be distinguished. There is no need to continue this elaboration, since it is obviously absurd).
Time is the axiom of existence. How is it related to existence? Well, it is one of five axioms of existence, four of which are related in the following way: d5ab8e994c68189025fd02ad67f50c48.gif. The fifth axiom of existence is energy. Its elementary manifestation is the photon. The time is related with energy in the following way: 6e9f3dc333cc693040f10b5dc47289b2.gif, and that directly follows from fec5ba0bf5af436050d2818707df8996.gif.
03c7c0ace395d80182db07ae2c30f034.gif, 92e4da341fe8f4cd46192f21b6ff3aa7.gif, and c9faf6ead2cd2c2187bd943488de1d0a.gif are axiomatic properties of the space. Hence, due to the relation d5ab8e994c68189025fd02ad67f50c48.gif, e358efa489f58062f10dd7316b65649e.gif is also an intrinsic, inherent property of the space. That is why the space is the spacetime.

All of the five axioms of existence: lengths, time, 92e4da341fe8f4cd46192f21b6ff3aa7.gif, c9faf6ead2cd2c2187bd943488de1d0a.gif, and energy, affect each other, and all of them change continually.

"We are to admit no more causes of natural things than such as are both true and sufficient to explain their appearances. Therefore, to the same natural effects we must, so far as possible, assign the same causes."Sir Isaac Newton

And, we do not need the Minkowski spacetime postulation to explain the reality. Minkowski's idea was right, but the model of that idea is wrong. With Minkowski spacetime postulation, and Einstein's postulated tensor equation, we can only approximately model the reality, and we cannot understand it in that way. It is just some nice, abstract mathematics, which produces approximate results, which model but do not explain anything. The goal of science is to understand, and not just to model. Ptolemy's helicoids described the movement of celestial bodies well. But that provided no understanding at all.
"A man may imagine things that are false, but he can only understand things that are true, for if the things be false, the apprehension of them is not understanding."Sir Isaac Newton
"The noblest pleasure is the joy of understanding."Leonardo da Vinci
The results, the final equations that Einstein-Minkowski postulates yield, are not in accordance with continuity principle, and with energy conservation principle. (And there are even worse consequences. And being worse than non-compliance with the continuity and energy conservation is really, really bad situation. And accepting that as science is extremely bad situation).

P.S.
"We canít solve problems by using the same kind of thinking we used when we created them."Albert Einstein
"The important thing is not to stop questioning. Curiosity has its own reason for existing."Albert Einstein
 

Offline old guy

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JP:
Quote
So when we say gravity curves space-time, we mean that no matter what space-time is on a deeper level, on some level it acts just like a 4D structure with curvature.

In other words science grants itself enough freedom to assert that mass curves something without saying what that something is. I understand the function of a model. As I said earlier, I also understand that a model models something. It is the "something" which is the issue here.

GR asserts that the "something" "acts like"... "a 4D structure with curvature." You totally ignored my post above asserting that space is the 3-D void* in which all things exist and move. (* A void is no-thing, not some-thing. A void has no "curvatgure.")

Likewise my ontology of time as a non-entity (which you ignored.) Yet you assert (GR asserts) that spacetime "acts like a structure" and you further describe it as curved. Surely a curved structure is an entity of some kind. I have mentioned the international society which strongly contests that universal assertion among GR theorists. Yet you speak of it as a given. That is not "discussion" but GR's version of dogma.
 

Offline JP

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Old Guy, I'm ignoring all your posts that try to shove realism into the discussion.  That's why I haven't responded.

I think we all know that no matter what your stance is on metaphysics, physics describes very precise properties for space-time.  If you're unhappy with that description, New Theories is the place for it.  :)
 

Offline Phractality

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Let me repeat myself, since no one seems to have heard me the first time. Meters and seconds are defined by the constancy of the speed of light and the wavelength and frequency of cesium atom emissions, regardless of where the cesium atom is. The space-time metric of GR is represented by a 4D grid of hypercubes, each measuring 1 meter cube by 1 second. That grid is what is warped, and it is warped because, in a flat space-time metric the cesium atom emission are not constant. By "flat space-time metric" I mean a metric represented by units of distance and time which, by definition, agree with Euclidean geometry. (I am not introducing new theory. Flat space-time is nothing more than a mathematical transformation of warped Minkowski space-time.)

You could define the units of distance and time in a flat metric to be equal to the meter and second at a point of maximum gravitational potential (like the middle of a cosmic void). For convenience, let's call the flat-metric units "fleters" and "fleconds". In the middle of a cosmic void, 1 fleeter = 1 meter, and 1 flecond = 1 second.

Measuring the cesium atom emission relative to those units, you would find that a meter stick at the bottom of a gravity well is shorter than one fleter, and an atomic clock ticking once per second would be ticking slower than one tick per flecond. (Someone please correct me if I got that bass ackwards.) I'm not sure, but it might also be necessary to let the speed of light, in fleters per flecond, to be different in and out of the gravity well. (Wanted: A mathematician to determine whether the speed of light, in fleters per flecond, is constant.)

It has been stated several times, in this thread, that gravity bends light. That is true in a flat metric, but it is not true in GR. In Minkowski space-time, the path of light in a vacuum is the definition of a straight line, so photons can't be bent by gravity. Light follows a straight line thru a gravity well, and comes out in a different direction. That's what a warped metric is all about.

I don't know for sure, but I strongly suspect that my own ontology for the fabric of space-time is uniform relative to a flat metric.
« Last Edit: 25/11/2012 23:03:50 by Phractality »
 

Offline JP

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Phractality, I agree with you in spirit, but disagree on a few nitpicky details.  I believe they're important, though, so I'm going to list them. 

Let me repeat myself, since no one seems to have heard me the first time. Meters and seconds are defined by the constancy of the speed of light and the wavelength and frequency of cesium atom emissions, regardless of where the cesium atom is. The space-time metric of GR is represented by a 4D grid of hypercubes, each measuring 1 meter cube by 1 second. That grid is what is warped, and it is warped because, in a flat space-time metric the cesium atom emission are not constant. By "flat space-time metric" I mean a metric represented by units of distance and time which, by definition, agree with Euclidean geometry. (I am not introducing new theory. Flat space-time is nothing more than a mathematical transformation of warped Minkowski space-time.)
We can argue over definitions, but the basic assumption is that SR is correct and the speed of light is constant over small enough regions in a vacuum (i.e. over flat space-time).  This allows us to define the "second" and "meter" in terms of EM radiation, either distance traveled in a fixed time or the length of time it takes for a given number of oscillations of a wave to pass us.  So I think we basically agree, although we use slightly different terms.  :)

I do disagree with the statement that the space-time metric is a grid of  1 meter x  1 second hypercubes.  It's more correct to say that space-time is a geometric construct that can be represented in terms of a grid of those hypercubes (if it's flat) and in terms of some distorted grid (if it's curved).

Quote
...
Measuring the cesium atom emission relative to those units, you would find that a meter stick at the bottom of a gravity well is shorter than one fleter, and an atomic clock ticking once per second would be ticking slower than one tick per flecond. (Someone please correct me if I got that bass ackwards.) I'm not sure, but it might also be necessary to let the speed of light, in fleters per flecond, to be different in and out of the gravity well. (Wanted: A mathematician to determine whether the speed of light, in fleters per flecond, is constant.)
General relativity assumes that space-time is continuous and is structured so that you can look at smaller and smaller regions without limit.  Under those assumptions, if you look at a small enough region, it looks flat, and the speed of light over that flat region is constant (and equal to "c" if measured by a local observer).  This is analogous to how if you look at the ground under your feet, it looks flat, even though the earth is (roughly) spherical.  The curvature deals with how things move from 1 region to another.

Quote
It has been stated several times, in this thread, that gravity bends light. That is true in a flat metric, but it is not true in GR. In Minkowski space-time, the path of light in a vacuum is the definition of a straight line, so photons can't be bent by gravity. Light follows a straight line thru a gravity well, and comes out in a different direction. That's what a warped metric is all about.
That's partway true.  Light follows geodesics, which are a generalization of a straight line to curved geometries.  They are not the same as straight lines because they can't always have all the properties of straight lines.  What they are is the shortest path between two points (or longest path), which in flat space-time is a straight line.  So it is correct to say that gravity bends light because it makes the shortest path between two points a curved trajectory.
 

Offline old guy

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Old Guy, I'm ignoring all your posts that try to shove realism into the discussion.  That's why I haven't responded.

I think we all know that no matter what your stance is on metaphysics, physics describes very precise properties for space-time.  If you're unhappy with that description, New Theories is the place for it.  :)
JP,
It is a misrepresentation of my intent to say that I am "trying to shove realism into the discussion." I hope it is not intentional. I am trying to bring realism into the discussion in a reasonable way for those who still understand that Earth does not change diameters with every possible frame from which it might be observed and measured. The same goes for distances between bodies in this solar system and between stars (and galaxies.)
Different observations of the same object or distance do not make the object or distance change. That is basic here, not "shoving" realism into the discussion. Earth's diameter is just under 8000 miles... not varying with the speed of a passing observer. Same for all the other examples.

A "physics" that describes that diameter as 4000 miles or whatever, depending on the relative velocity of the observer, is the metaphysics of Einstein, who said that there is no reality independent of differences in observation, and that all frames of observation are equally valid.

It is late and this may belong in my other thread, but Earth does have its shape independent of observation; and "spacetime" is still a metaphysical concept... a "model" or concept without observable referents ("time" and malleable space-as-an-entity.)

In other words, we do not " all know that  physics describes very precise properties for space-time."

Non-entities have no "properties." "Spacetime" is not an entity. I can cite literally reams of arguments from the scientific commnunity which agree with that analysis. (I have already.)
 

Offline JP

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Old Guy, I'm ignoring all your posts that try to shove realism into the discussion.  That's why I haven't responded.

I think we all know that no matter what your stance is on metaphysics, physics describes very precise properties for space-time.  If you're unhappy with that description, New Theories is the place for it.  :)
JP,
It is a misrepresentation of my intent to say that I am "trying to shove realism into the discussion." I hope it is not intentional. I am trying to bring realism into the discussion in a reasonable way for those who still understand that Earth does not change diameters with every possible frame from which it might be observed and measured. The same goes for distances between bodies in this solar system and between stars (and galaxies.)
Different observations of the same object or distance do not make the object or distance change. That is basic here, not "shoving" realism into the discussion. Earth's diameter is just under 8000 miles... not varying with the speed of a passing observer. Same for all the other examples.

Sorry, you're just introducing it gently into the discussion despite being repeatedly asked by the moderators not to do so.  :)

Going forward, I will shrink posts on realism in this thread, to keep it on track.
 

Offline simplified

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Your motion between observer and light is speeds for the observer,but something of the speeds is not speeds for you,the something is time for you. :P
Some motion is speed,but some motion is time.Don't forget it!
« Last Edit: 27/11/2012 15:48:26 by simplified »
 

Offline old guy

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Old Guy, I'm ignoring all your posts that try to shove realism into the discussion.  That's why I haven't responded.

I think we all know that no matter what your stance is on metaphysics, physics describes very precise properties for space-time.  If you're unhappy with that description, New Theories is the place for it.  :)
JP,
It is a misrepresentation of my intent to say that I am "trying to shove realism into the discussion." I hope it is not intentional. I am trying to bring realism into the discussion in a reasonable way for those who still understand that Earth does not change diameters with every possible frame from which it might be observed and measured. The same goes for distances between bodies in this solar system and between stars (and galaxies.)
Different observations of the same object or distance do not make the object or distance change. That is basic here, not "shoving" realism into the discussion. Earth's diameter is just under 8000 miles... not varying with the speed of a passing observer. Same for all the other examples.

Sorry, you're just introducing it gently into the discussion despite being repeatedly asked by the moderators not to do so.  :)

Going forward, I will shrink posts on realism in this thread, to keep it on track.
JP,
Imatfaal split this thread off from the "What was the big bang..." thread, gave it a title and called me the author.

Here is a breakdown of the questions raised in the title:
What is spacetime? That is an ontological question requiring discussion of the nature and "reality status" of space, time, and the combination "fabric." How can its "reality status" be discussed without referring to realism? Iow, "How real is spacetime?... Discuss without reference to what is real!"

"Is it a model?" Discuss without reference to what a model models or the difference between a model and that which is modeled (the real world)!

"Is it a fabrication?" Discuss how real the "fabric of spacetime" is without presenting the realist side of the argument!

So one moderator allows the ontological discussion (makes the title an ontological subject) while another forbids the argument from realism essential to such a discussion.

This leaves me totally confused about what is allowed here and challenged to a "fight" ("discussion") with both hands tied behind my back.

I think I need a 'referee' with a sense of fairness not forbidding realism in a discussion of what is real.
 

Offline Phractality

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Old Guy,

As a member who has been disciplined for "proselytizing", myself, I caution you that you are skating on thin ice.

You are in good company when it comes to being beaten down for trying to bring ontology in the mainstream of science. Einstein, himself, was beaten down by his peers for the same thing. I think his Leyden Address may have been his last public mention of his conviction that the aether must be a ponderable medium. He reluctantly agreed that the reality of the aether, or lack thereof, is a moot point, given a purely mathematical space-time metric which correctly solves real-world problems.

I agree with you, and with Einstein, that a space-time metric with no ontological significance leads mainstream science up a blind alley. Without a sense of what the fabric of space time really is, there are limits to how far we can develop our theories. However, those of us who feel that way are, for the time being, outside the mainstream. We should consider ourselves lucky to have a New Theories forum in which we may discuss our heretical views.

Perhaps Imatfaal was wrong to place this thread in the mainstream forum. Several of the questions in the OP are not answerable without introducing new theory. These are cosmological questions, and in my opinion, cosmology has always been a matter of philosophy and religion, and it still is.

In my opinion, any theory which is not widely accepted by the mainstream is a new theory, regardless of whether it is championed by a mainstream scientist. Even some very old theories which are trying to make a comeback, like the Fatio/LeSage model, are not mainstream; so they belong in the "New Theories" forum. Maybe it should be called the "Renegade" forum, or the "Heresy" forum, instead.
 

Offline old guy

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Phractality,
Thank you for your support. I have been on thin ice here from the beginning. No one can challenge mainstream SR/GR (or parts thereof) without the threat of banishment. (I've participated on many science forums over the years.) I only challenge specific parts, as evident in all my posts.

And it is good that "The Lighter Side" section can still tolerate common sense, logical, reasoning and 'free thinking' as "New Theories"... though Euclid's  postulates of geometry and implications for cosmology are not new theories but rather old theories not yet totally debunked by non-Euclidean imaginative revisions.
I hope for a reply to my last post clarifying the issue of what they accept in this section and what is still considered "wild speculation" and/or "the lighter side" not to be taken seriously... like asking what spacetime IS, and what the "fabric's" components are. The mods really need to find a consensus on this. Otherwise it is just a "bait and switch" situation. Like go ahead with your argument, and if that mentions or invokes realism, you will fall through the thin ice, by mod censorship.
 

Offline grizelda

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A rabbit pulled out of a hat is an ontological event, but it contains no information which gives a scientific description of that event. There are many theories on this forum which postulate 'just so' explanations of the universe, such as this being a reflection of another universe, but these almost always devolve to being descriptions of the author's thinly disguised wish fulfillment, to see the universe as a substitute for the womb. This is our default mode of consciousness, and serves us well, but it is not science, which opens up limitless knowledge unconstrained by the needs of our ego.
 

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