Gravity questions re infinite plates.

[madmac]

We have an infinite (thin)(flat) plate.

1. Newton is standing on the plate. Does he feel a g-force?

2. Einstein is standing on the plate. Does he feel a g-force?

3. madmac is standing on the plate. Does he feel a g-force (madmac is an aetherist).

 

And, are these three g-forces (a) zero, or (b) mansized, or (c ) very large, or (d) infinite?

 

I have my own ideas re the theoretical answers. But i am interested in other's ideas.

Edited February 20, 2017 by madmac

[swansont]

I have my own ideas re the theoretical answers. But i am interested in other's ideas.

 

 

!

Moderator Note

Then let's be clear here. As this is posted in a mainstream section (relativity), we will not be discussing your ideas in this thread. (And you will not be responding to this modnote here, either)

[Strange]

We have an infinite (thin)(flat) plate.

1. Newton is standing on the plate. Does he feel a g-force?

2. Einstein is standing on the plate. Does he feel a g-force?

3. madmac is standing on the plate. Does he feel a g-force (madmac is an aetherist).

 

 

They will of course, all feel the same thing.

 

 

And, are these three g-forces (a) zero, or (b) mansized, or (c ) very large, or (d) infinite?

 

None of the above. (What does "mansized" even mean?)

 

The force depends on the density of the plane. Without specifying that, it isn't possible to answer more specifically.

I have my own ideas re the theoretical answers. But i am interested in other's ideas.

 

 

It would be interesting to hear your guesses and then we can see how they match up with the predictions of (1) and (2).

 

(Of course, number 3 doesn't have a prediction and it couldn't be discussed here, anyway)

[madmac]

Strange.

Yes of course they will all feel the same thing, but my meaning was what do the 3 theories say.

I am happy to mention my guesses. This is before i googled. But even after googling i am still not sure re Einstein.

 

Re Newton my guess was good. At first i thought an infinite g. Then i reasoned that as g reduced per square of distance then there might be some sort of finite limit (& of course google says that there is a limit, & as u say the equation includes the mass per square meter etc).

 

And even better, i guessed that Newton's g might not depend on how far clear he stood. I don't know why i even thought of this, but i was pleased to see that google indeed says that a test mass will show the same g for all clearances (ie the equation for the attractive force or g does not include distance). Just a lucky guess by me here.

 

A side issue. I am thinking that the g felt by Newton here is equivalent to inertial g, not (common) gravitational g. On Earth gravitational g would be stronger near his feet (nearer Earth) & weaker near his head (further from Earth). On the plate the g forces would be the same in every part of Newton's body, ie as per inertial g.

 

I think that the above refers to Newtonian theory, & perhaps not to Einsteinian. Google doesn't make this clear.

Re Einstein, my guess was that he feels zero g. I reckoned that bending of space-time would cancel along the length & breadth of the plate, giving zero bending, giving zero g.

 

I found at least one Einsteinian analysis on google. I couldn't understand it. If i remember aright the explanation even mentioned clocks at different distances. And in the end their equation included a term for distance (unlike the Newtonian equation).

Einstein is standing still (on that plate), he isn't running along (at a uniform speed)(nor non-uniform speed), hencely, some might reckon that Newton & Einstein should agree here re g. But i still prefer my zero g answer. But google says that both are wrong.

[Strange]

You are right, there is no tidal force because the acceleration due to gravity is independent of distance (I assume that is what you mean by "inertial g", which is not a phrase I have come across before).

 

The GR solution is, inevitably, complex. My understanding is that the GR solution reproduces the same acceleration as the Newtonian formula, but doesn't readily produce the expected time dilation (which, obviously, doesn't apply to the Newtonian case). Note that there are very few exact solutions to the Einstein Field Equations, because they are non-linear. So people often have to take a known solution and use that as a basis to approximate a solution for another case. That may explain why it doesn't produce the expected result.

 

It sounds like this might be the page you found: http://www.mathpages.com/home/kmath530/kmath530.htm

[zztop]

We have an infinite (thin)(flat) plate.

1. Newton is standing on the plate. Does he feel a g-force?

2. Einstein is standing on the plate. Does he feel a g-force?

3. madmac is standing on the plate. Does he feel a g-force (madmac is an aetherist).

 

And, are these three g-forces (a) zero, or (b) mansized, or (c ) very large, or (d) infinite?

 

I have my own ideas re the theoretical answers. But i am interested in other's ideas.

Yes, they all feel [latex]F=2 \pi G \rho m[/latex]. Read here. It is a standard exercise given in intro to physics.

[madmac]

Strange & zztop.

Yes that was one of the pages i googled (after starting this thread). Re-reading it i see that i missed a couple of things. It seems that an infinite wall (plate) presents difficulties for Einsteinians (even compared to an infinite sphere). I wouldn't hold this against SR & GR, an infinite wall is a silly notion anyhow. They seem to say that an infinite sphere produces zero curvature (of space-time i presume), & that an infinite wall would do likewise, giving a...

"perfectly uniform and constant acceleration field. Such a field in the context of relativity, had no intrinsic curvature....... ".

So here i return to my original guess of zero g. I don't see how zero curvature can equate to a uniform field -- it equates to zero field in my opinion.

 

And i see that they worry re clocks. It seems that clocks (& frequencies) will vary if we have velocity, despite their uniform field. And they would vary if we have (my) zero field too i guess. But that is probably all irrelevant here.

 

Most of this refers to test masses. But in my 3 cases i have a man. This wasn't intentional, but i suspect that replacing a test mass with a man makes things more difficult.

 

And, madmac Einstein & Newton are (were) all aetherists, but perhaps they spelt it differently (aether, field & ether).

Edited February 20, 2017 by madmac

[Strange]

And, madmac Einstein & Newton are (were) all aetherists, but perhaps they spelt it differently (aether, field & ether).

 

 

Nonsense.

 

Before Newton, Christiaan Huygens had hypothesized that light was a wave propagating through an aether.^{[citation needed]} Newton rejected this idea,

https://en.wikipedia.org/wiki/Luminiferous_aether

 

And, of course, in Maxwell's equations (and therefore special relativity) an aether is (a) not necessary (b) not supported by any evidence. But you shouldn't be dragging your quasi-religious beliefs into this thread anyway.

[swansont]

And, madmac Einstein & Newton are (were) all aetherists, but perhaps they spelt it differently (aether, field & ether).

!

Moderator Note

In case I wasn't clear before, we aren't going to discuss, or mention, aether in this mainstream science thread.

[madmac]

Strange.

Yes, i have read that Maxwell was the key to Einstein's foray into the STR.

I have also read -- Maxwell's Original Equations -- by Tombe -- 2011 -- especially page 5.

 

Yes, Newton believed that light was corpuscular, ie that it wasn't a wave.

But his beliefs re light had nothing to do with his beliefs re gravity, quite the contrary.

[Strange]

Yes, Newton believed that light was corpuscular, ie that it wasn't a wave.

But his beliefs re light had nothing to do with his beliefs re gravity, quite the contrary.

 

 

1. You should start a new thread to discuss this.

 

2. Gravity has nothing to do with the "luminiferous aether" (the clue is in the name)

 

3. Newton (very explicitly) said nothing about the nature or cause of the gravitational force.

 

So stop making stuff up to support your religious beliefs.

[zztop]

Strange.

Yes, i have read that Maxwell was the key to Einstein's foray into the STR.

I have also read -- Maxwell's Original Equations -- by Tombe -- 2011 -- especially page 5.

 

Yes, Newton believed that light was corpuscular, ie that it wasn't a wave.

But his beliefs re light had nothing to do with his beliefs re gravity, quite the contrary.

Tombe is yet another internet crank, it is time you stopped.

[Strange]

Strange.

Yes, i have read that Maxwell was the key to Einstein's foray into the STR.

 

 

I posted this in another thread. You might find it useful:

 

This video explains how the speed of light falls out of Maxwell's equations:

 

Note that the equations don't include anything about the position or the speed of the "things" generating or interacting with the electric or magnetic fields. So the equations are the same wherever you are and whatever your state of motion (Galilean relativity). So the speed of light is invariant. So, special relativity. Simples.

[swansont]

!

Moderator Note

Let's keep this thread about gravity

[mistermack]

Can an infinitely thin plate exist?

Can a massive particle have zero dimensions? Or can a two-dimensional plate actually have any mass, or exist at all?

 

( I don't know, I'm just asking )

[madmac]

Strange.

Nice video. But, Maxwell never saw them 4 equations. He i think had 8 (or 20), & they were variant.

 

But re my OP re a man standing on an infinite plate. I would like to introduce a variant. This is an infinite plate near an infinite plate (i guess that the "near" is redundant). What would the gravity force be, in each of the three theories. This is i think simpler that my original OP of an infinite plate & a man (or a test mass). No equations needed this time i think.

 

I am thinking that Newton would say an infinite force.

And Einstein would i reckon say zero force. But i expect others here will say an infinite force.

 

Mistermack.

That there plate of mine is infinite in extent, not infinite thinness.

 

I don't think i mentioned a thickness, but i suppose that in my thought-experiment it shouldn't make any difference whether the plate had zero thickness (as long as it had mass), or had a sensible thickness, or had infinite thickness.

 

And it goes without saying that the plate needs to have infinite stiffness, or be perfectly stiff (not sure which term offends least).

Edited February 22, 2017 by madmac

[Lord Antares]

Can an infinitely thin plate exist?

 

I assume you mean a plate of infinitesimal thickness. No.

 

 

Can a massive particle have zero dimensions?

 

No.

 

Or can a two-dimensional plate actually have any mass, or exist at all?

 

No.

 

 

/cut

 

A plate of infinite size implies an infinite universe, which is already a big assumption.

Still, the answer would be infinite force. The answer doesn't change.

[madmac]

Lord Antares.

Do u mean that Einstein would say an infinite force tween two infinite plates?? (I reckoned he would say zero force, based on zero bending of space-time).

 

But your comment re an infinite universe reminds me of the elephant in the room.

No, not the BigBang question. No, i mean the speed of gravity question. Gravity takes time, depending on distance.

 

I reckon that the speed is Van Flandern's more than 20 billion c.

Some say the speed of light, c (eg LIGO's Gravitational Waves).

Some say instantaneous at all distances, ie even at infinity.

Some say instantaneous, but only locally, not at infinity.

 

This all affects or can affect my infinite plate thought-experiment, but i am not looking for this complication, & it would rightly need its own thread (has the speed of gravity ever had a thread here??).

[zztop]

 

I reckon that the speed is Van Flandern's more than 20 billion c.

Some say the speed of light, c (eg LIGO's Gravitational Waves).

Some say instantaneous at all distances, ie even at infinity.

Some say instantaneous, but only locally, not at infinity.

 

 

Please stop quoting cranks, the speed of gravity is "c".

[Strange]

Can an infinitely thin plate exist?

 

 

No. But neither can an infinite plane. However, you can calculate the properties of such a thing (in the limit, at least).

 

 

 

Can a massive particle have zero dimensions?

 

All fundamental particles have zero size (if that is what you mean).

Strange.

Nice video. But, Maxwell never saw them 4 equations. He i think had 8 (or 20), & they were variant.

 

Start a new thread. Stop hijacking this one.

But your comment re an infinite universe reminds me of the elephant in the room.

No, not the BigBang question. No, i mean the speed of gravity question. Gravity takes time, depending on distance.

 

Gravity (waves) propagate at the speed of light. There is no reason to think otherwise. (This is consistent with LIGOs results, as you say. And will probably be confirmed once VIRGO and other instruments come on line.)

 

(If van Flandern says it is something, then you can be damn sure it isn't that.

 

 

 

 

This all affects or can affect my infinite plate thought-experiment

 

No it doesn't.

[imatfaal]

!

Moderator Note

No more off-topic forays into non-mainstream science. Next one will just be hidden and the member sanctioned.

!

Moderator Note

 

Lord Antares' response to Madmac's comments on the speed of gravity has been split off to a new thread. It raises some interesting, but wrong, points that members may wish to address - but not here

 

[madmac]

edit -- speed of gravity is now on new split off thread.

Edited February 22, 2017 by madmac

[zztop]

zztop.

I thought that an infinite speed of gravity was mainstream,

No, it isn't.

 

 

 

And Van Flandern's idea that gravity had a speed of no less than 20 billion c is also to my mind not contrary to mainstream's infinite speed.

 

It is full fledged crackpot. Stop posting rubbish.

Edited February 22, 2017 by zztop

[Strange]

The two things being non-contradictory (somehow)(which i could never understand).

 

 

Well, if you make stuff up (or believe cranks like van Flandern, who make things up) you shouldn't be too surprised if you get confused when these fantasies differ from science.