Okay... when I was young, I learned at school how gravity pulled objects together. I was wondering, how does this happen. What causes things to miraculously be pulled together? My Physics teacher says that it is unknown, but I can tell he is hiding something from me.

<font size=-1>[ This Message was edited by: p9107 on 2002-06-06 10:58 ]</font>

Now that you are old, he should stop hiding gravity from you. In fact, he should let us all see it. I'd like to know what it is too. Einstein said that mass warps space, but I think he's hiding something from us too. Too bad he died fifty years ago--but maybe he gave it to your physics teacher.

The cause of gravity has been an interesting subject for many years. Many arguments on this subject were common in Newton's time. The book: "Pushing Gravity" delves into the history of various thoughts on this. (see http://shop.alpmicro.com/apeiron/) The idea that gravity is a push is my view today. It follows from the idea of a static universe with a Compton effect cosmological red shift, but others have come to this conclusion from entirely different arguments. I personally think Charles Brush's ideas are the right ones. He said the cause of the push was very long wavelength, highly penetrating electromagnetic radiation, much longer in wavelength than radio waves. I think this radiation is there due to the red shift of distant sources from an infinite universe. (Brush was the inventor of street lights, an electric dynamo, and a co-founder of General Electric and Linde Air Products. He called his theory the kinetic theory of gravitation which was published in Science and Nature. He won the Franklin medal.)

Some of the actors in the discussion were Newton, his protege Fatio, Georges Lesage, Huygens, Kelvin, and many others.

<font size=-1>[ This Message was edited by: John Kierein on 2002-06-07 07:49 ]</font>

Whilst personally I suspect John may be right about the "pushing" gravity theory (I may be biased as I had a similar theory in my youth). However, it should be pointed our that the idea that gravity is a pushing force is neither conventional or mainstream.

There is also a promising theory which may be the beginning of an explanation of both gravity and inertia as can be seen from the following Caltech Research Links:

Caltech Research
Zero Point Energy
Origin of Inertia
Gravity

Phobos

Ok - but why do particles, have a force between them, there must be something which pulls them together. I was thinking that maybe everything is magnetic, although only a very small amount. However, in the case of a planet, or even a star, this force is so great that you have enough to attract everything to everything.

Oh, and also, how do I become promoted from a Bad Newbie?

A bunch of us get together & form a peer review group to critically assess your posts every so often...
[img]/phpBB/images/smiles/icon_biggrin.gif[/img] No, its actually just the no. of posts you make, see the FAQ:
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<font size=-1>[ This Message was edited by: Roy Batty on 2002-06-06 11:18 ]</font>

Well, really, that describes it fairly well... Everything is "magnetic" -- except that with gravity there is no "north" or "south" -- everything attracts everything. Gravity is almost exactly like that. And, yes, it's a very small amount, so that, for instance, two peas on a dinner plate have almost no gravitational pull on each other. (They have *some* -- but it's too tiny for us to perceive without very sensitive instruments.) As you note: when you add a little to a little, and do it enough, you get the large effects of gravity.

BTW, the "pushing" theory of gravity fails several very elementary tests: by that theory, the moons of Jupiter should move slightly toward Jupiter every time they are on the other side of the planet from the sun (since Jupiter "shields" them from the sun's "push.") The theory has no observational preference over the standard theory, and thus is unnecessary, but, worse, it has observational drawbacks: it makes predictions which don't come true.

But...don't take my word for it. I'm just a fussy old skeptic who's set in his ways. Pretend I'm a conservative, and John Kierein is a liberal, and, once you've listened to us, make up your own mind. That's the joy of free debate!

Silas


<font size=-1>[ This Message was edited by: Silas on 2002-06-06 11:35 ]</font>

Let me give you my theory of gravity from my early twenties;

First we start with a picture of a radiometer


This device (also called a light-mill) turns at rates proportional to the amount of light falling on it. In principle this is the basis under which I proposed gravity works, but more explanation is required.

First how does the above device work ?

Link to explanation of how it works

For the moment forget the exact nature of the forces concerned, and just accept that movement can be caused by fields acting DIFFERENTIALLY upon the surfaces of an object (push a ball more on one side than another and it moves).

Now consider a solar sail.



Again we have an object moving as the result of differential force. In this case more solar wind strikes one side of the sail than the other, so the satellite moves.

If we were to take our solar sail into deep space we may well find that the sail reaches a point of equilibrium because it receive about the same pushing force from all directions (assuming approx even distances from neighbouring stars).

If we were to introduce a large moon near to our solar sail in deep space what would happen ?

The moon would cause a ion-wind shadow on one side of the solar sail and it would be "pushed" towards the large moon.

The shadow of the moon would be inversly proportional to the square of the distance, so we would expect the force to be likewise proportional (the further away the solar sail was from the small moon, the smaller the net push would be on the solar sail.

From the perspective of the small moon, the solar sail will also cast an ion-wind shadow. Being comparatively smaller than the moon we would cast a smaller shadow, so we would expect the solar sail to "push" the moon towards it less than the moon "pushes" the sail.

In principle this is my explanation of gravity. Think of all objects as collections of atoms, and in place of the ion-wind we shall just imagine an unknown force (eg. neutrenos).

If we crush a large object like the moon into an object the size of an orange it would still contain the same number of atoms, so the shadow effect remains the same.

This explanation is very similar to the one proposed by John, but again I should point out it is not mainstream.

Mainstream or not it does demonstrate that there are theoretical explanations to explain the effects of gravity without having to introduce any science beyond the ideas of Newton, and atomic structure.

Phobos

<font size=-1>[ This Message was edited by: Phobos on 2002-06-06 12:20 ]</font>

Actually, push gravity and pull gravity are the same for the moon's of Jupiter. The sun and Jupiter pulls add together just as much as the shading of the sun and Jupiter add.
There is a difference for the motion of an object in a field of photons, though. The flux impinging on the forward direction is slightly greater which causes some heating and some slowing for a moving particle. This appears as though the object is gaining weight as a function of its velocity through the field in accordance with special relativity. It shows WHY an object can't go faster than c. It also gives a reason for the definition of the favored frame of reference of Mach's principle as being the "fixed stars", or, actually, the cosmic background radiation seen in the microwave background (and Reber's long wavelength bright background measurements). Push gravity does not fail the tests when the background is photons. Prior to special relativity, it was thought that the pushing particles had to travel at many times c to agree with the problem of objects moving through this field. Brush's theory solves this.
An unusual consequence of the pushing theory is that the General Theory of relativity's principle of equivalence may not be compatible with the pushing theory for the case of light. The principle of equivalence says that an accelerating frame of reference is equivalent to a gravity field. Consider an elevator accelerating at 1 g in outer space between galaxies somewhere. If you drop a ball it will fall at 1 g just like it was in a 1 g gravity field like the surface of earth. And if you shine a laser on a distant wall of the elevator it will fall slightly, the amount the elevator has travelled in the time it takes for the light to reach the wall while travelling at the finite velocity c. Is this the same as gravity on the earth's surface? But, in pushing gravity, the light will only fall if the incoming pushing photons interact with the laser light photons to push them down. These types of photon-photon interactions are not known to occur where there is momentum transfer from the pushing photons. However, it is of interest that photon interactions have been shown to occur in the case of several low energy photons combining to form electron-positron pairs, (http://www.hep.princeton.edu/~mcdona...ience1202.html) so the theory is uncertain on this point as to whether the General Relativity principle of equivalence applies to pushing gravity.

<font size=-1>[ This Message was edited by: John Kierein on 2002-06-06 13:10 ]</font>

In the standard model, the sun's gravity pulls "through" Jupiter. Jupiter could be there, or not be there, and it wouldn't make any difference to the attraction to one of Jupiter's moons.

But "Push Gravity" depends on the concept of "shadowing." Why does a small massive object cast the same shadow as a larger, less dense object of the same mass? How does an object shadow gravity proportionally to its breadth? (e.g., the tidal effect?) When Jupiter and the Sun are both shadowing a satellite, why is the shadowing increased? (And if this is true, then why was it that there were claims that pendulums behaved differently when in the shadow of the sun and the moon?)

The fact that you have to bring in a whole new explanation having to do with photons strikes me as just more evidence against your theory: it fails on the face of it, so you need additional factors.

I know I'm being argumentative and contentious, and I apologize. I clearly don't understand your theory, which is partly your fault and partly my fault. If you could explain it simply and clearly, I'd be willing to try to comprehend it.

Silas

I'm glad you raised that one. I cannot speak for John, but we do seem to be talking about basically the same thing.

The issue with pendulums behaving differently during an elclipse should be expected if push theory is correct.

Well, examine this link from NASA


1999 Solar Eclipse

So you see this effect HAS been detected.

As regards to the problem of shadow for more dense object - there isn't one.

When you think of the shadows of object you must think of these objects as clusters of atoms. It doesn't matter how spaced apart the atoms are (ie how dense the object is), what matters is the number of atoms in each object (ie its total amount of shadowing stuff).

Earlier Experiments

Naturally John can expand/correct what I have stated, but I believe our thoughts are in the same direction on this issue.

Phobos

<font size=-1>[ This Message was edited by: Phobos on 2002-06-06 16:30 ]</font>

And, if so, then the moons of Jupiter should also behave differently when doubly shadowed. . .and they don't. John says they shouldn't. But if that's true, then pendulums also shouldn't behave differently.

This fails to explain tides. Tides exist due to the fall-off of the strength of gravity (the inverse square law) over the width of a large object (like the earth.)

How does "push" gravity explain this, if the size and shape of the "shadow-casting" object doesn't matter? If neutrinos or photons are the "pushing agent," then the silhouette, or cross-section, of the shadowing body is of paramount importance.

Blunt question 1: in the "pushing gravity" theory, does the "gravitational pull" that we experience every day, here on earth, come from the earth's "shadowing" of the "pushing" force that would ordinarily come equally from all directions? That's the nub of the theory, as I understand it.

If this is wrong, set me straight. But if this is the theory, then the objections I'm stating are going to be BIG TROUBLE for the theory.

The inverse square law applies equally to shadows as it does to gravity. A radio signal gets weaker, magnetic fields, and effect of shadowing.

Consider the shadow of Jupiter falling on Earth. Being a long way off any shielding effect (ie shadowing) will be much less than during a lunar eclipse, yet the moon is much smaller than Jupiter.

The number of atoms still matter, but distance is equally important.

You have the general gist of the theory, although you will need to check with John in case his interpretation is different from mine (we came to the same idea from independantly but I believe we have the same general concept).

I should also add that whilst I have only pondered on this possibility some years ago, John has gone much deeper into this theory whilst researching his book.

Any experimental data of the effects of shadowing of Jupiters moons would be interesting. I would suspect that any effect would be faily small as the moons contain considerable less matter than Jupiter.

The following Van Flandern link (Paragraph Headed "Gravitational Shielding") does a good job of explaining how Jupiter could prevent detecting such an effect:
POSSIBLE NEW PROPERTIES OF GRAVITY


You may find the following link interesting reading. It summarises the three main theories about gravity. It also gives an insight in how pushing gravity may be the result of zero-point energy of a vacuum interacting with matter.

Gravity: Different Scientific Approaches

Another interesting side-effect of this theory is in interpreting the strange results of the gravitational shielding experiments now being replicated at NASA. Instead of the experiment sheilding some of the gravitational pull of the Earth, we could say that it is replacing some of the pushing field absorbed by the Earth (or shadow effect). If true this is a bit like shining a torch on a shadow to make it less dim.

I also reccomend the following which does a good job of putting forward some of the points in favour of the push gravity theory:

Objections to push theory
First follow-up reply
Second follow-up reply

Phobos

<font size=-1>[ This Message was edited by: Phobos on 2002-06-06 18:53 ]</font>

I hope the links and posts that have been put above help you with your understanding of gravity. As you see there is no single explanation at this point in time, but at least you should have a better feel for what theories are being considered.

As to how to get promoted from a Bad Newbie, just keep posting. As the number of posts goes through certain magic numbers your category changes.

Phobos

Ok, so everything is magnetic... and i know how opposites attract, and everything, but why do they? are there particles shooting out of each atom? Or is it unexplained.

And also, what is light? Some small particle must be hitting the black side of the radiometer to make it spin. What is is?

Thanks

I always was under the impression that "conservation of angular momentum" was the cause of gravity's attraction.

Gotta love that 3dimensional vision thingy our species has going. It makes sphere's look flat, and vice versa.

Everything is at a right angle to everything else, so everything falls in on itself. We just perceive it the way we do because of our eyes. But where we're going, you won't need eyes!

DJ

<font size=-1>[ This Message was edited by: DJ on 2002-06-07 14:33 ]</font>

Precisely. The world is flat, but astronauts perceive it as a sphere because, in space, they're deceived by a lack of reference points. All angles appear to be right angles, inscribed within a hemisphere, and so they're tricked into seing a hemispherical earth.

This also applies to time: the year is actually A.D. 1, and always will be, but we perceive time as linear. Time is actually at right angles to what we think it is, and "the future" is, in fact, the direction east by north north east.

Silas