What causes gravity?

[trini123]

What causes gravity? I am not looking for a formula for gravity; that is well known. The question is if you had to explain the cause of gravity, what would you say? Let's say a five year old asks you what causes a ball to fall when dropped, what would you say? "chile, yuh tink de ball go float up? why yuh so chuppid" is not a valid answer.

[edyle]

My suspicion is that gravity will eventually be found to be a 'side effect' or small left-over effect so-to-speak of electromagnetics.

When one considers the powerfull forces one can observe with magnets or electrostatics (powerfull in comparison to the weight/mass of the objects involved) and consider that the very atoms that stuff is made of consists essentially of charged particles with electrons zipping around all over the place and the corresponding electrostatic forces and magnetic forces involved, it is no surprise that two masses would have either a residual attraction or repulsion to one another.

[BW]

sufficently large objects generate a measurable force of attraction with other nearby objects.

the earth, being massive, exerts a force of attraction to everything on the earth, and we call this force gravity.

[Sirius]

Think of space as a sheet. Now put a marble on it. It sinks in around the marble. Pitch another smaller marble across the sheet, and the second marble will be drawn towards the first. The first has warped the fabric of space (well, space-time to be more accurate), creating this gravity well around it.

Now picture space to be 3 dimensional instead of a flat sheet and think of the marbles being the Sun, Earth, Moon, asteroids, comets, you or me - anything with mass. There you go. Anything with mass pulls stuff toward it -- that force is gravity.

Perhaps if this were really being told to a 5 year old and they were curious about even more details than that, then some illustrated videos might be a great way to spark an early interest in physics...

[lexbarker]

I believe gravity is a force that exists within the heart of every atom.

[kemist]

This article sums it up, has a nice vid on the first page, briefly explains both Newton's gravity on the second page and Einsteins theory on the 3rd page: link (http://science.howstuffworks.com/environmental/earth/geophysics/question232.htm)

Another good brief video:

http://www.youtube.com/watch?v=LoaOHvy5AcA


This wiki article may give a good explanation of: What is space-time? :link (http://en.wikipedia.org/wiki/Spacetime)

In physics (http://en.wikipedia.org/wiki/Physics), spacetime (or space-time, space time) is any mathematical model (http://en.wikipedia.org/wiki/Mathematical_model) that combines space (http://en.wikipedia.org/wiki/Space) and time (http://en.wikipedia.org/wiki/Time_in_physics) into a single continuum (http://en.wikipedia.org/wiki/Continuum_(theory)). Spacetime is usually interpreted with space as being three-dimensional (http://en.wikipedia.org/wiki/Three-dimensional_space) and time playing the role of a fourth dimension (http://en.wikipedia.org/wiki/Minkowski_space) that is of a different sort from the spatial dimensions. According to certain Euclidean space (http://en.wikipedia.org/wiki/Euclidean_space) perceptions, the universe (http://en.wikipedia.org/wiki/Universe) has three dimensions (http://en.wikipedia.org/wiki/Dimension) of space and one dimension of time. By combining space and time into a single manifold (http://en.wikipedia.org/wiki/Manifold), physicists have significantly simplified a large number of physical theories (http://en.wikipedia.org/wiki/Theoretical_physics), as well as described in a more uniform way the workings of the universe at both the supergalactic (http://en.wikipedia.org/wiki/Physical_cosmology) and subatomic (http://en.wikipedia.org/wiki/Quantum_mechanics) levels.

[Sirius]

I might also suggest taking a read of Stephen Hawking's "A Brief History of Time"

[lexbarker]

We have not seen a clear definition of what is actually gravity. We can define electricity as the movements of electrons, a "physical" action. Like electricity, we can see the effects and predict the outcome of an action. Within the atom there is that force that gives us gravitational properties, just as the movement of electrons would give us electrial and magnetic properties.

[edyle]

This article sums it up, has a nice vid on the first page, briefly explains both Newton's gravity on the second page and Einsteins theory on the 3rd page: link (http://science.howstuffworks.com/environmental/earth/geophysics/question232.htm)

Another good brief video:

http://www.youtube.com/watch?v=LoaOHvy5AcA


This wiki article may give a good explanation of: What is space-time? :link (http://en.wikipedia.org/wiki/Spacetime)

What you can get from such descriptions refering to the space-time continuum to describe gravity, is that the nature of gravity is connected to the nature of time itself.

That may not be intuitively enlightening. What is more enlightening is we know that the nature of gravity is connected to the nature of time itself BECAUSE of the connection to the SPEED of LIGHT. Gravity can intuitively be seen as untimately related to ELECTROMAGNETICS. And that is how teleportation, and antigravity will be developed.

[edyle]

We have not seen a clear definition of what is actually gravity. We can define electricity as the movements of electrons, a "physical" action. Like electricity, we can see the effects and predict the outcome of an action. Within the atom there is that force that gives us gravitational properties, just as the movement of electrons would give us electrial and magnetic properties.

I don't think so.
Well not exactly; I mean I don't think a single atom or neutron for example exerts a gravitational force; I think gravity is a macroscopic phenomenon; the statistical result of numerous atoms.

[trini123]

Thanks for all the links. I agree electricity is sort of obvious +/- charges etc but gravity when you think of it does not make sense. Why would a big object attract a small object? It can not be easily explained like a fat bottom woman /man or some other example that we see a lot of of this forum. I spent the weekend trying to slope water away from my home and it is very easy with a spirit level and some extra limestone but explaining why rain falls and objects drop still eludes me and I can not explain.

[Sirius]

trini123, consider again the analogy of space-time as a rubber sheet with a bowling ball on it. The mass of the bowling ball sinks the sheet in further than a tennis ball would; therefore the tennis ball is drawn toward the bowling ball. The mass of an object is directly connected to the size of the dent made on space-time. That dent is the gravity well. Therefore, when the rain falls it is drawn toward the center of Earth's gravity well, thereby hitting the ground instead of going up.

The most difficult part of the analogy is to now picture that sheet as a three dimensional space instead of a two dimensional one. In fact - four dimensional. Time is after all a dimension, too.

Now what actually causes mass to dent space-time, well, that's a much more complicated question.

[lexbarker]

I don't think so.
Well not exactly; I mean I don't think a single atom or neutron for example exerts a gravitational force; I think gravity is a macroscopic phenomenon; the statistical result of numerous atoms.

It does not matter how small it is the gravitational attraction is there but how big it mass has to be before it starts to attract other smaller masses.

[edyle]

trini123, consider again the analogy of space-time as a rubber sheet with a bowling ball on it. The mass of the bowling ball sinks the sheet in further than a tennis ball would; therefore the tennis ball is drawn toward the bowling ball. The mass of an object is directly connected to the size of the dent made on space-time. That dent is the gravity well. Therefore, when the rain falls it is drawn toward the center of Earth's gravity well, thereby hitting the ground instead of going up.

The most difficult part of the analogy is to now picture that sheet as a three dimensional space instead of a two dimensional one. In fact - four dimensional. Time is after all a dimension, too.

Now what actually causes mass to dent space-time, well, that's a much more complicated question.

What actually causes mass to 'dent space-time' is exactly what the question really is. The analogy to rubber sheets and the space time model provides no explanation at all; they are just descriptive analogies.

I believe the real answer to the question lies in the nature of time, and of electromagnetics.

[lexbarker]

trini123, consider again the analogy of space-time as a rubber sheet with a bowling ball on it. The mass of the bowling ball sinks the sheet in further than a tennis ball would; therefore the tennis ball is drawn toward the bowling ball. The mass of an object is directly connected to the size of the dent made on space-time. That dent is the gravity well. Therefore, when the rain falls it is drawn toward the center of Earth's gravity well, thereby hitting the ground instead of going up.

The most difficult part of the analogy is to now picture that sheet as a three dimensional space instead of a two dimensional one. In fact - four dimensional. Time is after all a dimension, too.

Now what actually causes mass to dent space-time, well, that's a much more complicated question.

So, if we really go down to the basic building block, then an atom has its own space-time dimention.

[lexbarker]

What actually causes mass to 'dent space-time' is exactly what the question really is. The analogy to rubber sheets and the space time model provides no explanation at all; they are just descriptive analogies.

I believe the real answer to the question lies in the nature of time, and of electromagnetics.

I think the properties of electromagnetics is different from that of gravity.

[edyle]

It does not matter how small it the gravitational attraction is there but how big it mass has to be before it starts to attract other smaller masses.

Yes I understand what you are saying, but I'm just saying I do not believe that gravity is actually a subatomic force; You are saying or assuming that it is but that it is merely small.
I'm saying I do not think it is there AT ALL, and the Gravity is actually a macroscopic phenomenon.

I think that gravity is an effect, ultimately of electromagnetics. The electromagnetic forces are present at the atomic level. With gazillions of atoms and molecules bonded together in 2 separate objects, it is no surprise that there is a residual average attraction between the two objects as the end result.

To assume that a singe proton or neutron exerts a gravitational force is quite a big assumption, and not one that you will likely see in acknowledged Physics.

[Sirius]

So, if we really go down to the basic building block, then an atom has its own space-time dimention.

No, it occupies height, breadth, depth and time in the space-time dimensions. String theory calls for other little curled up dimensions beyond the standard 3 spacial dimensions and time dimension, but I am not aware of those other dimensions being attached to individual atoms...

[Sirius]

What actually causes mass to 'dent space-time' is exactly what the question really is. The analogy to rubber sheets and the space time model provides no explanation at all; they are just descriptive analogies.

I believe the real answer to the question lies in the nature of time, and of electromagnetics.

If that is the question being asked then we are far beyond the point of explanations in a way a 5 year old could understand as per the OP. We are now in some how shall I say, deep, theoretical physics.

[edyle]

I think the properties of electromagnetics is different from that of gravity.

Yes, we think of electromagnetics as different; and yet when you look at GRAVITY, and Relativity what POPS UP:
c.
c.
c.

c ? THE SPEED OF LIGHT? THE SPEED OF ELECTROMAGNTIC WAVES ??? What the heck does GRAVITY have to do with Electromatic waves?????????? Well there is the clue! Gravity could be an end result of Electromagnetism. Graviy is a TINY TINY TINY force in comparison to Electromagnetic forces, and therefore it would be no surprise if Gravity is merely the residual macroscropic side effect of the overall electromagnetic forces acting withing an object which is composed of negatively charged electrons and positively charged protons and the electrons are whizzing around all over the place.

[edyle]

If that is the question being asked then we are far beyond the point of explanations in a way a 5 year old could understand as per the OP. We are now in some how shall I say, deep, theoretical physics.

Not at all if you look at the ELECTOSTATIC forces within an ATOM composed of a positively charged nucleus, orbited by negatively charged electrons. With a gazillion of these atoms clumped together in a ball, if you have two such balls adjacent to one another, is it any surprise that there is a small attraction between the objects? One can say that oh, the overall charge of the atom is zero and the overall charge of the objects are zero which is absolutely correct, however the electrons are MOVING.

A moving charge creates a magnetic field. With all these electric forces and magnetic forces going on inside an object, it is no surprise that there may be some small residual, or "integral" - meaning the sum, or net effect, of all these forces, which we perceive as gravity.

[trini123]

Not at all if you look at the ELECTOSTATIC forces within an ATOM composed of a positively charged nucleus, orbited by negatively charged electrons. With a gazillion of these atoms clumped together in a ball, if you have two such balls adjacent to one another, is it any surprise that there is a small attraction between the objects? One can say that oh, the overall charge of the atom is zero and the overall charge of the objects are zero which is absolutely correct, however the electrons are MOVING.

A moving charge creates a magnetic field. With all these electric forces and magnetic forces going on inside an object, it is no surprise that there may be some small residual, or "integral" - meaning the sum, or net effect, of all these forces, which we perceive as gravity.


I would buy that if gravity only worked on conductor/metallic objects. But in fact it works on everything the same way - a rock, ball, coin, feather ...

[Sirius]

If the explanation were so simple then gravity would not be such a hot topic in physics. The use of the word "may" in the explanation using electrostatic forces is vital, because physicists are still trying to figure out exactly what causes gravity. Where does the so-called graviton, should it be discovered, fit into your explanation?

[edyle]

If the explanation were so simple then gravity would not be such a hot topic in physics. The use of the word "may" in the explanation using electrostatic forces is vital, because physicists are still trying to figure out exactly what causes gravity. Where does the so-called graviton, should it be discovered, fit into your explanation?

It doesn't.

[edyle]

I would buy that if gravity only worked on conductor/metallic objects. But in fact it works on everything the same way - a rock, ball, coin, feather ...

You seem to be thinking of MAGNETISM alone. Conductor/metallic objects may be magnetic and eletrons can flow *through* metals, but ALL objects - rock, ball, coin, feather - contain those proton and eletrons and yes the electrons DO move in those objects. The electrons are not stationary in a rock.

[lexbarker]

I got this audio that has an interesting explanation.


http://www.youtube.com/watch?v=t9XwuGQX744

[edyle]

Ok.

I stopped at 7 minutes.
I'll get back to the rest of it later.
But so far, this guy has mentioned quite a few things ;
for one thing he mentioned the Poynting vector!
Then of course there's all the zero point energy stuff and quantum vacuum stuff, and low temperature physics etc.

Anyway, if listeners can get anything intuitive from what he is saying, you can sense that there seems to be a connection between gravity, and electromagnetism.

[edyle]

If the explanation were so simple then gravity would not be such a hot topic in physics. The use of the word "may" in the explanation using electrostatic forces is vital, because physicists are still trying to figure out exactly what causes gravity. Where does the so-called graviton, should it be discovered, fit into your explanation?

By the way, I don't think most people realise just how TINY the 'gravitational force' is in comparison to the electromagnetic force.
If you just think of two magnets for one thing, and look at the powerfull forces of attraction and repulsion that can come from those two magnets between each other and compare that to the gravitational attraction between the two magnets themselves, you can intuitively see that electromagnetic forces and huge compared to gravitational attraction.

[Sirius]

By the way, I don't think most people realise just how TINY the 'gravitational force' is in comparison to the electromagnetic force.
If you just think of two magnets for one thing, and look at the powerfull forces of attraction and repulsion that can come from those two magnets between each other and compare that to the gravitational attraction between the two magnets themselves, you can intuitively see that electromagnetic forces and huge compared to gravitational attraction.

I quite understand where you're coming from on this - it does have to be acknowledged though that the jury is still out on just where gravity comes from. It's quite interesting...a fundamental pillar of the universe, yet still so shrouded in mystery...

[edyle]

I quite understand where you're coming from on this - it does have to be acknowledged though that the jury is still out on just where gravity comes from. It's quite interesting...a fundamental pillar of the universe, yet still so shrouded in mystery...

Absolutely. Where exactly gravity comes from (and significantly, how can we develop antigravity) is still a mystery to general science, however the contribution I hoped to make to readers is an intuitive understanding from simple knowledge of atoms and electromagnetic forces, that gravity isn't exactly some complete mystery. What we experience as gravity is not surprising when one considers the electromagnetic force which certainly exists in every single atom of every object;

And it would turn out to be no mere coincidence that both electrostatic and gravitational force should decrease by the same 1/r2 formula.

[kemist]

By the definition of 'space', the electromagnetic explanation and bending of space-time explanation would be mutually exclusive.

[edyle]

By the definition of 'space', the electromagnetic explanation and bending of space-time explanation would be mutually exclusive.

What are you talking about? What definition of space are you talking about? There is nothing in your statement saying what is mutually exclusive about what except a 'definition of space'. But in contradiction, you then go on to mention SPACE-TIME.
And it is SPACE-TIME whereby ELECTROMAGNETICS comes in.

The theory of SPACE-TIME comes from Relativity which has the fabric of the universe being intimately related to "c" - THE SPEED OF LIGHT. Actually not the speed of visible light specifically, but the speed of ELECTROMAGNETIC WAVES. Therein lies your connection between GRAVITY or SPACE-TIME, to ELECTROMAGNETISM.

[kemist]

BY space i meant 'nothing'.
I was hoping to prompt someone into saying that the same thing can be said of mass, but the theory implicates that mass curves space time. So then one can ask why not em waves instead of just mass?

I don't have reservations against the electromagnetism concept, but what is a bit confusing to me is the concept of quantized em and what effect that would/should have.
I've read that even Einstein had to abandon the classical em wave for quantized em. So i'm wondering if electromagnetism is responsible for gravity, would there be points (no matter how small) of zero gravity, say between the sun and the earth?

[edyle]

BY space i meant 'nothing'.
I was hoping to prompt someone into saying that the same thing can be said of mass, but the theory implicates that mass curves space time. So then one can ask why not em waves instead of just mass?

I don't have reservations against the electromagnetism concept, but what is a bit confusing to me is the concept of quantized em and what effect that would/should have.
I've read that even Einstein had to abandon the classical em wave for quantized em. So i'm wondering if electromagnetism is responsible for gravity, would there be points (no matter how small) of zero gravity, say between the sun and the earth?

I don't understand that last part about points of zero gravity; I'm guessing you meant conceptually - zero space-time, if I was following your thinking about quantisation.
Because yes of course there are points of zero gravity; for example there exists a point between the earth and the moon where the gravitational forces from the earth and moon cancel out; of course that is a first approximation; you then have to consider the gravity from the sun and other objects.

[Sirius]

Is it not true that general relativity and quantum gravity are not yet quite compatible?

[edyle]

Is it not true that general relativity and quantum gravity are not yet quite compatible?

I'd say so; as far as I know, and I know less about quantum mechanics that relativity, quantum theory bears little relationship to relativity.

The only sort of theoretical relationship I've heard of would be the quantum vacuum, zero-point energy sort of stuff which seems to relate quantum theory to macroscopic energy and space.

[edyle]

Another simple view of what might cause of be related to Gravity, is the NUCLEAR FORCE.
The force that holds the Nucleus together.

Neutrons and protons get together and form a nucleus. For example the iron atom has 26 protons and typically 30 neutrons.
The nucleus holds together because of the neutrons; there are typically a few more neutrons than protons.
So it would appear that neutrons are
1: attracted to one another
2: most significantly, are attracted SO STRONGLY to protons that a few neutrons can hold together a few protons OVERCOMING the REPULSIVE force that the positively charged protons have.

Now, it is therefore intuitive that one nucleus will be attracted to another nucleus; they are not usually able to get close enough to each other to combine because of the electron shells surrounding them.

So, we are left with the possibility that what we perceive as gravity, might be the same at the nuclear force that causes neutrons to attracted to protons (and other neutrons),

{particularly for the case of small nuclei.)