Warped spacetime and gravity

[The Crow]

just wondering.....constants are generally rtios between quantities..... How can we 'explain' why a constant has the value it does?

It is what it is ... a ratio

[elfmotat]

Santalum, my answer to your question concerning gravity and the indentation in a rubber sheet is as follows. Yes it is only an analogy that directs human thought away from having to imagine orbits to that of a visual experience.

 

The indentation depicts a downhill situation and so to our experiences of gravitational effects. The other effect you refer to is matters inertial property that must be acting under the circumstances dynamically illustrated. For all its pretence of simplicity, practically the whole of physical reality that involves force is included in that illustration.

 

You're taking it too seriously. You shouldn't look at it as anything more than a crude analogy.

 

To begin, there is the question as to what constitutes the mass of the orbiting spherical object?

 

What do you mean? Mass is a property of matter. This is no more a meaningful question than "what is charge really(?)" or "what is spin really?"

 

As a side note, it isn't just mass which affects gravitation: it's the entire energy-momentum distribution.

 

What is acting in an attempt to force the moving spherical object towards the central depression?

 

Again, you're taking the analogy too seriously. There is no "depression." Objects follow "straight" lines in curved spacetime - this produces the effect of what is seemingly mass being "attracted" to other mass.

 

What is compelling the spherical mass to orbit instead of directly rolling downhill?

 

Conservation of momentum/energy.

 

What is enforcing the conservation of momentum and the conservation of energy?

 

Translational and time symmetry.

 

 

With regards the central effect, science sends conflicting messages. On one hand there is the concept generally believed that the warping of space (what enforces the warping and constitutes the reality of space) causes the effect we call gravity to be only an illusion. On the other hand, there are the constant erroneous references to the pull of gravity or gravitational pull being stated by the Ph D from academia when appearing on TV.

 

This is just gravity being presented under two different models. In GR, gravity is a pseudo-force which appears because of curved spacetime. In Newtonian gravity, it's a force of attraction between two masses.

 

Concerning the inertial ability, the measurement (mathematics) regarding inertia is well documented; even so, the fundamental dynamics as to what circumstances ensures the realities of the laws of motion are not now known by academia.

 

I have no idea what you mean by this. What are "the realities of the laws of motion" ?

 

Some of the statement in the replies to your question state that the fundamental dynamic nature of gravity is not known and may never be known.

 

I really hate it when people say stuff like this. The question "but what's really happening(?)" is not a physically meaningful one. Science does not answer such questions.

 

In that regard, the fact that the General theory of Relativity is considered to be beyond reproach and therefore generally accepted as correct, provides the reason why other concepts of gravity, however logical, unless provided by a well known Ph D, will always be ignored as pseudoscience.

 

This is just not true. If you do good research then you can always have it submitted to a journal for peer-review. No PhD required. Granted, it will probably be difficult to know what to research if you're not in the loop, academically.

 

My 16 year attempt to have my 160 page work evaluated by those in academia has been met with only two replies thanking me for the offer but stating that they cannot spare the time.

 

If I am asked why I do not explain my concept of gravity on this thread; that is because it would require at least ten pages to do so and I am cautioned not to provide the address to obtain a free download of the published paper.

 

I'd be interested in giving it a glance-over, if possible.

 

just wondering.....constants are generally rtios between quantities..... How can we 'explain' why a constant has the value it does?

It is what it is ... a ratio

 

It depends on how deep you want to go. For example, "why does this spring have its particular spring-constant?" You could go into detail about materials it's made from, its dimensions etc. But then I could ask the next question, "why does such and such material have said properties?" Then you could go into detail about the chemistry of the material. I could then ask why chemistry works that way, to which you could explain the nature of atoms, the electromagnetic force, quantum mechanics, etc. Eventually you get to a point where you're forced to say "that's just the way things are."

 

For fundamental constants like G, c and h, you just have to say "that's just what they are."

[juanrga]

Something just occured to be with this.

 

In the analogy of the elastic membrane and heavy objects warping the surface such that smaller objects circle the heavier one around the indentation it creates in the membranes requires a force (gravity) to elicit that circular movement around the indentation.

 

If mass causes an analogous indentation in the fabric of spacetime then wouldn't there need to be a force to cause another object to move around the 'indentation'.

 

Is the warped spacetime thing meant to explain the behaviour objects under the influence of gravity or the nature of gravity itself?

 

The warped spacetime analogy can be used to explain part of the behaviour of objects under the influence of gravitation. At the same time, this analogy reveals the nature of gravitation according to a geometric theory as general relativity:

 

 

An alternative model, sometimes named the non-geometrical approach, the flat-spacetime approach or the field theoretic approach (FTG), considers that gravitation is not due to curved spacetime but due to a force:

 

[IM Egdall]

General theory of Relativity is considered to be beyond reproach and therefore generally accepted as correct, provides the reason why other concepts of gravity, however logical, unless provided by a well known Ph D, will always be ignored as pseudoscience. My 16 year attempt to have my 160 page work evaluated by those in academia has been met with only two replies thanking me for the offer but stating that they cannot spare the time.

 

In order to get the attention of the scientific community with your new theory of gravity, make a specific, detailed measureable prediction -- one which is different from general relativity (GR). If it explains current observations which disagree with GR, it should generate some interest. If it explains an observation which has yet to be made; once that observation is made and it agrees with your theory and not with GR, I think then it will really draw attention to your theory.

 

This is typically how any new theory gets recognized -- through measurements which verify its unique predictions.

[pmb]

I saw elsewhere in this thread that someone was bashing the use of analogies simply because the analogy was ultimately flawed in one way or another. I'd like to point out that analogies are just that, analoges by definition is just that a flaw between concepts. If there were zero flaws then there wouldn't be an analogy, it would simply be that, i.e. i would be the thing being compared.

 

I mention this for two reasons before, because someone spent a lot of time trying to prove to that the analogy I was using was flawed and therefore my argument was flawed for that reason. I think that this point should be kept in mind when using analogies. It's also important to keep in mind the limits of the analogy.

[pmb]

Santalum, my answer to your question concerning gravity and the indentation in a rubber sheet is as follows. Yes it is only an analogy that directs human thought away from having to imagine orbits to that of a visual experience.

That's not quite correct. The embedding diagram for a Schwarzschild geometry can be found in the book Exploring Black Holes by Taylor and Wheeler which is at http://www.eftaylor.com/pub/chapter2.pdf (Moderator - Don't worry. These sections are available to be placed on line by the authors). Download and turn to page 2-26. Look at Figures 6 and 7. Read what is stated in the diagrams for for r, dr, d(sigma). If a collection of rulers was layed down around the Black Hole then you would see a different set of distances than would be there had not the black hole been present.

 

Pete

[derek w]

a quote by D H:- "mass tells space-time how to curve,and space-time tells mass how to move".

 

If I hold a ball 2 metres above the ground that ball is stationary,when I let go how does curved space-time tell the stationary ball to accelerate towards the earth?

 

The analogy with the trampoline and a bowling ball is an example of earth's gravity in action not an explanation of how gravity works.

 

 

 

Edited May 6, 2012 by derek w

[elfmotat]

a quote by D H:- "mass tells space-time how to curve,and space-time tells mass how to move".

 

If I hold a ball 2 metres above the ground that ball is stationary,when I let go how does curved space-time tell the stationary ball to accelerate towards the earth?

 

The analogy with the trampoline and a bowling ball is an example of earth's gravity in action not an explanation of how gravity works.

 

That's where time curvature comes into play. (Actually, the time component of the curvature almost always plays the most important role. Until you start getting up toward the speed of light the space curvature affects you very little. For photons, time and space curvature affect them equally.)

 

 

There's a pretty simple analogy. Take a spacetime diagram of two objects at rest with respect to each other in flat spacetime. The objects trace out two parallel lines that extend vertically to infinity. Now try drawing a spacetime diagram of the same situation, but on a curved surface (such as a ball). This time, the objects start out parallel (at rest), but as you extend their worldlines they eventually intersect. This is because in curved space there are no permanently parallel lines.

 

 

[derek w]

So are you saying that as the ball travels through time(4th dimension) the balls path is already curved waiting for me to let it drop?

 

[pmb]

The rubber sheet analogy is just that -- an analogy aimed at the law audience. Don't try to read anything more into any one of those analogies than the limited thing the analogy is trying to depict...

Those diagrams are called embedding diagrams and they are used to visualize the spatial part of the metric. The one for a Schwarzschild geometry can be found in http://www.eftaylor.com/pub/chapter2.pdf see page 2-24

 

This is not aimed at the "law audience" (whatever that is. what is it anyway??) This diagram shows up in many very mathematical texts and journals. In fact it appears in the Gravitation by Misner, Thorne and Wheeler.

[pmb]

a quote by D H:- "mass tells space-time how to curve,and space-time tells mass how to move".

The person coined that phrase is John Archibald Wheeler. The same person who coined the term black hole.

Sometimes mass say to spacetime - "Don't curve". two examples are the vacuum domain wall and the cosmic straight Cosmic String. There is no spacetime curvature outside the location of the matter. E.g. assume the domain wall is in the xy-plain. Then outside the plane objects accelerate towards the plain. But outside the plain there is no spacetime curvature. However if you placed objects on each side of the wall the particles will accelerate towards the wall and, if placed just right, towards each other!! In that there are gravitational tidal accelerations.

 

Example; wall is in xy-plain. One particle is placed on the plain at x=y=0 and along z > 0. The other is placed at x - y =0 and along z < 0. These particles will accelerate towards each each other.

[imatfaal]

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Moderator Note

PGHarvey's branch on gravity being dependent on movement has been split off to speculations.

[LittleBoPeep]

Something just occurred to be with this.

 

Is the warped spacetime thing meant to explain the behavior objects under the influence of gravity or the nature of gravity itself?

 

Maybe, But we will never be able to construct that deduction until we connect time in the actual 3d space not in a 4d. If you merely change speed (miles per hour) to degree of change you can change the equation of time and place it into the three dimensional realm and start to ask about the nature of gravity.... What the warp is describing is the variation of change in distance traveled at varying altitudes... Again this is key into humanity making the next leap...

 

We know that a greater circumference will produce greater distance but this is not accounted for in the equation of time. (Time = Distance/Speed) Then the next argument comes that math fixed this problem by adding velocity or some other educated answer. THE FACT IS that distance increases as altitude increases while the degree traveled no matter the altitude remains constant. Time should be built upon degrees.... Here is that equation...

 

_________________________

 

Time = ((pi)2r/360)({-+}L) -+ ((pi)2r/360)D

 

pi2r = is the equation for circumference points observed based on altitude position of planet/object it resides upon.

L = is the total Longitudinal degrees to the shortest distance between the current (NOW) starting position to the destination, which never exceeds 180 because that is the defining characteristic for the next step..

{+} = L moves with the gravitation rotation up to 180 degrees Longitudinal from the starting position (if over 180 then repeat step for opposing sign)

{-} = L moves against the gravitation rotation up to 180 degrees Longitudinal from the starting position (if over 180 then repeat step for opposing sign)

+ = Future

- = Past

D = is our current understanding of time expressed in degrees (1 day = 360 Degrees)

_______________________

 

 

Time is the degree of variation between NOW and a second point in space.

Space is 3D. Altitude, Longitude, Latitude and is restricted by position.

 

Time is the 2D representation of Space. Altitude, Longitude and is restricted by motion.

 

Both provide the exact same information but the deference lies in the visual representation... EXAMPLE: Pie graph vs line graph....

 

 

 

ADDITIONALLY, In the equation there are two forms of energy that may eventually use the same formula to explain energy... Force Energy is observer dependent and momentum energy is environmental constant.

 

The force energy of the two points can be combined to create an average but two momentum will require you solve for one and then convert to the other planet size...

 

Time = (Degree of Change)(Force Energy)+-(Degree of Change)(Momentum Energy)

 

Information is received from our senses and is stored by our brain. We can only interpret 3D in the moment if the information is radiated like a wave (Allowing multiple angles of the same point)and all other information is perceived 3D by past/future stored information in the brain.

 

While the equation may allow absolute calculation it is still based on relative reality/information/perception or misperception of the observer...

Edited August 14, 2012 by LittleBoPeep

[imatfaal]

Welcome to the Forum LittleBoPeep. J FYG we do have latex implementation if you prefer. Just surround your code with [math] code [/math]

 

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Moderator Note

Oh and can we keep new ideas and innovative answers to questions within the Speculations forum. Many thanks.