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# My Theory for How Gravity Works Answered

So I've never really found out how gravity actually works, why it happens. But a few days ago I had a epiphany. I don't know if I spelled that right. So everything is at least a little bit magnetic, even stuff like wood, no matter how little. So all of this stuff would be attracted to all the other stuff electromagnetically, right? Even a little bit? So when you get huge amounts of this stuff (I'm thinking planets here) there is enough electromagnetic attraction to pull it together, and voila! We have gravity! Plus when you have planets, there's tons of stuff like iron and other metals and metaloids, that could be very strong, magnetically. So if I'm wrong (which I probably am), can someone explain how gravity actually works to me? I'm constantly thinking about stuff like this, I get theories like this every once in a while, many of them right. But not this complicated, more stuff like figuring out how air pressure and vacuums work, but basic principle stuff.

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## 50 Replies

Zaphod Beeblebrox (author)2010-02-06

makes sense to me.i'm pretty gullible.

hungyhipo 2 (author)2010-01-31

basically what kiteman is saying is every object has mass and the more mass something has the more it has a pull on other objects so technically my computer is pulling me to it but the affect is so little that it can not be seen but the earth has so much mass that it pulls things down get it ok

Kiteman (author)2008-08-30

If you managed to properly describe gravity in terms of electromagnetism, you'd be more famous than Einstein!

The "simple" model is that gravity is not actually a force (although it's effects can be treated like one in Newtonian physics).

Instead, mass distorts spacetime; the more mass, the more bending.

This is the bit that plaits most peoples' minds: objects move in straight lines through spacetime, but because mass has distorted the spacetime, the straight lines are actually bent, so (to those animals that only evolved to see three dimensions of spacetime and live along the fourth, they appear to move in curves such as the arc of a thrown ball or the orbit of a Moon.

Weissensteinburg (author)2008-10-28

I understand his theory (at a low level), but in physics we've been talking about circles, including centripetal force. Does it have anything to do with gravity?

kelseymh (author)2008-10-29

As Kiteman wrote, "it depends." The analysis of circular motion you are working through in class is completely general. You don't need to know what kind of force is involved, just that there is a force (specifically, a force applied perpendicular to the velocity. If it is always perpendicular to the velocity (as the velocity vector changes due to the force), it's called a central force.

For the problems you're solving, I'll bet that most of the time the central force you're considering is from a string, or maybe friction on car tires, or some such thing. Gravity is one particular example of a central force. It has the interesting added complication that it's not a fixed, constant force, but depends upon the distance from the center (1/r2).

Kiteman (author)2008-10-29

For little circles, no, for big circles, yes - it depends what is providing the centripetal force - a piece of string, or the gravitational attraction of planets.

Kelsymh?

Weissensteinburg (author)2008-10-29

I forgot about that, the gravity would be the force

kelseymh (author)2008-10-28

Minor nit-pick. You wrote, "objects move in straight lines through spacetime, but because mass has distorted the spacetime, the straight lines are actually bent..." That sort of paradoxical phrasing is inherently confusing, particularly to non-technical readers.

Trajectories in GR are curved, not straight: they have non-zero second derivative along the metric-element (ds) direction. Technically, they are called "geodesics" and are the paths of minimum or maximum distance through the curved spacetime. In particular, they are curved in the full four-dimensional spacetime, not just in the three-dimensional spatial slices of a particular rest frame.

A more familar example of geodesics (and the reason for the name!) involve minimum distance paths on the surface of the Earth. To get from point A to point B on the surface of a sphere in the shortest time (shortest distance at constant velocity) you want to follow a Great Circle trajectory. This path is the intersection of the plane defined by points A, B, and the center of the sphere, with the surface of the sphere.

The Great Circle path is curved in the "flat" three-dimensional space containing the sphere, but it is also curved in the frame of the spherical surface itself. Except for the special cases of travel along the Equator or directly North or South, any great circle route involves a constantly varying compass heading, and is therefore "curved" in the canonical East x North coordinate system.

Kiteman (author)2008-10-28

I bow to your superior knowledge!

Guess where I'm I'm going to start passing all the physics questions on to?

Lithium Rain (author)2008-10-28

>Jaw drops< I...buh...wha... kelseymh just replaced Kiteman as the head "Sciency" guy... *sniff* It's the end of an era...

NachoMahma (author)2008-10-28

. Adrian, Adrian, Adrian. Nobody can replace our beloved Kiteman. No more than anyone could replace you. Mr. Kelsey may have taken the position of Reigning Physics Expert, but that just takes a little of the load off of the Head Sciency Guy.
. He certainly doesn't have the tenacity of Kiteman. It appears to me that he's already given up on Ibles' Head YEC, Darth Gecko Man. ROFL

kelseymh (author)2008-10-28

Nor do I want to replace anyone! I'm a newbie here, and extraordinarily uncomfortable with all of the "social networking" jargon, conventions, and assumptions floating around....

As for DGM, I'm waiting for him to actually respond to my last two leaf nodes in that thread (my third question leading to descent with modification, and the trivial logical deduction of selection from observable facts of nature). If he's unwilling to continue the discussion himself, there's not much I can or should do about it. Silence speaks for itself.

Kiteman (author)2008-10-29

From K to another...

...social networking jargon...

Worse, it's in American! Actually, I think you're going to fit right in, Science-wise, and you make stuff. Give it another couple of weeks, nobody will realise you're new.

Lithium Rain (author)2008-10-29

Haha, I thought I had overlooked him, it took me a minute to realize he was new...

NachoMahma (author)2008-10-28

. Don't hold your breath waiting for a reasonable response - hypoxia can be dangerous.

Lithium Rain (author)2008-10-28

Heh, I said that wrong-not that he can replace him, just that he's no longer the top science guy.

YEC? In any event, apart from whatever beliefs he or anyone else has, he appears to me to be a troll looking to argue.

NachoMahma (author)2008-10-28

. Young Earth Creationism/ist
. At first I thought he was trolling. Then I thought he really believed what he was saying and had just been misled. Now I think he's just clueless. He seems to be quite proud of his self-imposed ignorance. :(
. "Refusing to attempt to understand, willful ignorance, that is as near as my worldview can get to 'sin' as I'd care to go." - Kiteman

Lithium Rain (author)2008-10-28

Ah, I see.

kelseymh (author)2008-10-28

Ummm....the comatose Physics Group?

Kiteman (author)2008-10-28

Huh? I didn't see that...

If nothing else, Plasmana should have added his own projects!

kelseymh (author)2008-10-28

Indeed. I've PM'ed him to see if he's interested (and joined the Group myself, just on spec). I wish the PM interface had the ability to CC...

Aeshir (author)2008-08-30

I've heard that theory a lot before. I'm not sure I can believe in a 4th spacial dimension, but of course, that's to be expected. Call me crazy, but I still don't believe time is a 4th dimension. I still think time rules over everything, including light (I'm a determinist, only in the scientificc sense of the word, no theism here!). But I don't know all the math and whatnot, so I suppose that's to be expected too.

Lithium Rain (author)2008-10-28

Well, a lot of this stuff is counterintuitive...

Kiteman (author)2008-08-30

Guess why you hear it a lot...

BoBeaumont (author)2008-10-06

Im not very good at explaining (or understanding) this sort of stuff but I'll do my best to give you my humble take on things.

Lets take black holes for example. In the space surrounding the event horizon of a black hole the extreme gravitational effects make time appear to flow more slowly than is usualy the case.

Let us set up an hypothetical NASA mission to explore the edge of a black hole. Lets say that we have two astronauts, Astronaut A and Astronaut B. And lets imagine that Astronaut A flies his spaceship to within one mile of the event horizon while Astronaut B takes up a positon about 1000 miles away from it.

Now, the extreme gravitaional pull would try to suck anything and everything (including light) into the black hole. This would mean that the light bouncing off Astronaut A would travel AWAY from the black hole at a much slower rate than normal, while the light bouncing off Astronaut B would travel TOWARDS the black hole at a much faster rate.

This would mean that, to Astronaut B, his companion would appear to be moving in slow motion, while Astronaut A would think his friend was living at hyperspeed. Even though each astronauts "individual" experience of time would be unaffected.

This proves (I hope lol) that the idea that time rules light is actually the other way round. The speed of light determines the speed of time, and thats why time is said to be relative.

I hope that makes some kind of sense

kelseymh (author)2008-10-28

You wrote, "Instead, mass distorts spacetime; the more mass, the more bending."

The late John Archibald Wheeler (co-author of ''Gravitation'', the textbook heavy enough to collapse into a black hole) wrote, "Matter tells space how to bend; space tells matter how to move."

kelseymh (author)2008-10-28

You wrote, "If you managed to properly describe gravity in terms of electromagnetism, you'd be more famous than Einstein!" He tried it himself, as did several other very good theoretical physicsists in the early to mid 20th Century.

Starting from the field equations, you can take the limit of weak gravity (or equivalently, nearly flat spacetime) and derive mathematical analogues to Maxwell's equations. This has inspired any number of crackpots to suppose that EM and gravity are "equivalent".

Lithium Rain (author)2008-08-30

There is a theory, discarded by most scientists, that there are teeny tiny particles, smaller even than atoms, called Gravitrons, and these cause gravity. Accepted answer: Just like Kiteman said. Objects distort space. The more mass they have, the more they distort space, and the higher the gravity.

kelseymh (author)2008-10-28

You wrote: >> There is a theory, discarded by most scientists, that there are teeny tiny >> particles, smaller even than atoms, called Gravitrons, and these cause >> gravity. Not discarded. General relativity is currently our best model for gravity, on length scales from fractions of a millimeter (torsion balance experiments) up to hundreds of megaparsecs (gravitational lensing by superclusters). It's predictions have been tested to extremely high precision (binary pulsars). One interesting feature of GR is the existence of gravity waves: if a massive object moves back and forth, the curved spacetime induced by its mass won't (can't) change instantaneously. Instead, changes in spacetime will "ripple" outward in all directions, in the form of "tensor oscillations" -- objects or localized groups of objects will be compressed in one direction, and stretched in the other, then vice versa, transverse to the direction the wave is moving. For a variety of reasons, GR is basically incompatible (not "inconsistent") with quantum field theory. If you try to construct a theory of gravity which is both consistent with GR and with QFT, an immediate consequence of such a theory (no matter what form it takes!) will be that classical graviational waves are quantized (just as classical light waves are quantized as photons). We have given a name to the quantum of gravity, the "graviton." We don't have a full theory yet to predict its properties, nor (obviously) have we observed its interactions experimentally.

Lithium Rain (author)2008-10-28

It is discarded if you believe Einstein. This theory contradicts general relativity, which explains gravity as the curvature of spacetime. As you said yourself, general relativity is our best model for gravity.

Yes, I am well aware of the difficulties with general relativity and quantum physics. According to some, string theory is the most promising solution to explaining gravity. This theory would allow for the existence of gravitrons (although I was unaware of this when I posted the original comment). Not everyone is convinced string theory is correct, even some who work on it. I do not believe myself sufficiently knowledgeable to judge its merits, but I do know there are some problems with it that may require an even more advanced theory to explain it all.

And are you going through all my comments from months ago?

kelseymh (author)2008-10-28

You asked, "Are you going through all my comments from months ago?" No; I was paging through the list of Forums, and "Science" caught my eye for hopefully obvious reasons. I unfortunately also have a weakness for non-experts (not you, the original post!) who think they've uncovered the secret to everything. If they'd just stick with 42, we'd probably all be better off.

You wrote, "This theory contradicts general relativity, which explains gravity as the curvature of spacetime. " First minor quibble, we don't even have a "this theory" yet -- there are many, many competing possibilities for "the theory of quantum graviity," including string theory, M theory, loop quantum gravity, causal triangulation, and more.

You also wrote, "This theory would allow for the existence of gravitrons." The mathematically rigorous (I trust the mathematicians who say this :-) statement is actually much stronger than "would allow." No matter what form "this theory" eventually turns out to take, it must include a properly quantized propagator for the gravitational interaction.

You are quite right (as you've implied) that defining a propagator for the structure of spacetime itself (rather than for a field which is embedded in a background spacetime) is difficult and laden with pitfalls and apparent contradictions. I certainly have no idea how to get there from here myself.

Lithium Rain (author)2008-10-28

That was a joke, actually, I figured that. Just messing with you. Are you a physicist? I saw something you said elsewhere that made me think that... Yeah, that gets annoying when people who have maybe a sixth grade science class under their belt think they know more than people who have worked on this stuff for decades. Not that that is 100 % impossible, I suppose it is possible, but certainly improbable. You seem to know way more about this than me, at any rate, so I'll take your word for it. I appear to have been wrong in my first comment, so I'm glad you pointed it out. Thanks for not flaming. It just seems to me (and please correct me if I'm wrong) that the more scientists find out about this, the more complex it gets and the harder to explain. I wonder if we can ever truly understand the answer to it all...

kelseymh (author)2008-10-28

You asked, "Are you a physicist? I saw something you said elsewhere that made me think that..." Yup, I'm an experimental high energy (particle) physicist, on staff at the Stanford Linear Accelerator Center (just renamed the "SLAC National Accelerator Laboratory").

I read a lot of science stuff, both technical articles in Science, Nature, etc., as well as "popular" magazines like SciAm, New Scientist, etc.

NM commented below on your last point, and it's absolutely true. The reason professionals get impatient with the crackpots and apparent crackpots who thing they've discovered The Secret, is that Science is by its nature a cumulative process.

Whether you (the general "you", not AM in particular!) want to build on and expand our existing understanding, or overturn established ideas with a new paradigm, it is your absolute responsibility to know the current field, in all of its detail, and then work to go beyond that.

<soapbox>
If you don't understand the basics, then you are simply not qualified to have an opinion about whether those basics are right or wrong. It is astonishing to me that people can take this concept completely for granted when they take their car to a mechanic, but assume it doesn't apply to understanding the functioning of the universe.
</soapbox>

Lithium Rain (author)2008-10-28

Ha-it must get so frustrating for you guys to keep hearing people say stuff like this:

I've come up with an entirely new and awesome theory to describe the universe and everything in it, despite the fact that I dropped out of third grade after repeating it four times. My theory is actually similar to super string theory, only I call it the Packing Peanuts theory, because I believe all matter is made up of tiny quantum packing peanuts, which are vibrating at exactly the rate of Pi.

The scientists all laughed at me when I described it, but that is only because they are jealous and plan on stealing my theory and are afraid of me being awarded the Nobel prize first.

Lithium Rain (author)2008-10-28

Oh, wow. That's neat! Well, now I feel dumb, having argued about gravity with a particle physicist...and been so wrong on it...your page said you worked on the LHC? Or collaborated on it? On another note, I love your shirt! XD

kelseymh (author)2008-10-28

Don't feel dumb -- you're interested, you ask good questions, and you listen and learn new things. What's dumb about any of that? Besides, "on the Internet, no one knows you're a dog" you wouldn't know I was a physicist if I didn't tell you.

My main experiment for the past 12+ years has been BaBar, which finished running back in April. I'm starting to participate (we call it "collaborate") on the ATLAS detector at the LHC, while continuing data analysis and publications with BaBar.

Thanks (about the shirt)! That headshot was taken when I had a small bit on a NOVA episode a few years ago along with a Web posting. They recently replayed it, and you can see about five minutes of stuff at SLAC at the very end.

Lithium Rain (author)2008-10-28

Thank you! Don't tell anyone, but I'm actually Hannah Montana! :D

That is so cool. I've never met a particle physicist!

!
I just watched that episode of NOVA! Except I missed the last 10-15 minutes because it was like 1 in the AM. I'll have to re-watch it on the DVR...

NachoMahma (author)2008-10-28

> the more scientists find out about this, the more complex it gets and the harder to explain . That's 'cuz they've already explained most of the easy stuff. . > I wonder if we can ever truly understand the answer to it all... . I doubt it ... but that doesn't mean we shouldn't keep trying. . . The more I learn, the more I realize just how ignorant I really am. - NachoMahma

Lithium Rain (author)2008-10-28

How true that is! Haha, I just remembered a quote that seems to apply... "Ah, gravity, thou art a heartless (bad word)"

xACIDITYx (author)2008-10-28

Rofl, prolly.

guyfrom7up (author)2008-09-21

BTW the scientific 4th demension is space-time, as in the fabric of time-space. Time and space are interwoven, And I think that it is true. If you were to put a clock on a space ship and it is exactly in sync with one on the ground, and you send that ship into space, i believe that the clock in space will show a different time then the one on earth because of the effect of earth's dent on the fabric of time-space.

NachoMahma (author)2008-09-21

. IIRC, I read that they have proved that by using clocks at sea level and in airplanes. . BTW, there is no gravity; the Earth sucks. heehee

kelseymh (author)2008-10-28

Yes, the original experiments were done with airborne clocks. However, you cando it yourself.

On a side note, your happy GPS system would be off by several kilometers if the software didn't take into account both the special- and general-relativistic corrections necessary to convert the time signals from each satellite into your frame of reference on the Earth.

... when I was a graduate student, my officemate said something that we put up on the board, and it stayed there for at least five years:

Life is a sucking, swirling vortex of despair.

He was British.

skunkbait (author)2008-09-21

Is it gravity that causes certain parts of the earth to suck more than others (or just the politicians)?

Rishnai (author)2008-09-21

Well, since certifiable beermathmaticians have unified the Strong Political Force and the Gravitational force, perhaps both...

gateon (author)2008-09-20

mass is attracted to other mass not magneticly.in very simple terms it is like magnetism but with all the elements not just metal,because look at pluto and the gas giants they have hardly any metals if any and they are attracted by the sun.

Aeshir (author)2008-09-21

All elements are magnetic. Not just metal. Metals are just a lot more magnetic.

Lithium Rain (author)2008-10-28

Not all metals are magnetic.

kelseymh (author)2008-10-28

You wrote, "All elements are magnetic." Not so. Magnetic interactions require a non-zero magnetic dipole (or higher) moment (since magnetic monopoles apparently do not exist in nature).

The magnetic dipole moment of an atom is proportional to the spin of the atom (technically, the total angular momentum of the nuclear spin, electron spins, and electrons' orbitals).

Atoms with zero spin have zero magnetic dipole moment and are consequently not magnetic.

With a sufficiently high frequency RF field, one can probe the spins of the nucleus, or of the individual electrons, rather than just the net spin of the whole atom. This is the basis of NMR (Nuclear Magnetic Resonance).

kelseymh (author)2008-10-28

In your original posting, you write in your last paragraph, "if I'm wrong (which I probably am), can someone explain how gravity actually works to me?" Are you honest about this -- you're actually interested in learning what our current state of knowledge and understanding is? Are you willing to take "on faith" statements from experts, which would otherwise require you to go back to college and grad school (for roughly six to eight years, full time) to learn the mathematics and physics necessary to derive those statements for yourself? If you are, there are definitely several of us here with the training and expertise to try to explain what we currently understand, and have fairly precise measurements to support, and to point out the places (see my replies to Adrian Monk, below) where our understanding stops, and active research begins.