What is Gravity? No-One Knows!

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Anonymous

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#1
What is gravity? No-one bloody knows!

Well?

I love the fact that the answer to this has eluded the most intelligent and most active physics brains in the world.

We all know that an apple falls. I think people have always understood that if you let go of an apple...it will fall.

Genius, eh?
 
A

Anonymous

Guest
#3
....which still does not explain it. We all know that it is there. We all know that it makes things attract other things. You and I could have deduced that a force called....."squeege" pulled things towards the ground.

What is Gravity?
 
A

Anonymous

Guest
#4
SYLLABICATION:
grav·i·ty
PRONUNCIATION:
gr?v??-t?
NOUN:
1. Physics a. The natural force of attraction exerted by a celestial body, such as Earth, upon objects at or near its surface, tending to draw them toward the center of the body. b. The natural force of attraction between any two massive bodies, which is directly proportional to the product of their masses and inversely proportional to the square of the distance between them. c. Gravitation


apparently a lot of it is still theory, hence why it's still studied....


use the Force, Luke.....
 
A

Anonymous

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#6
and then there's always this malarky...


home.earthlink.net/~danielemilio/a_shifting_theory_of_gravity.html#ShiftingTheoryDescribed
 
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A

Anonymous

Guest
#8
i'm sure i saw some TV show once were people realised gravity didn't really exist and they all started floating around...something about the whole theory of gravity being a government conspiracy to stop people form flying...daft... maybe i was dreaming....or it could've been The Simpsons... :)
 
A

Anonymous

Guest
#9
Nope, you're right. It was a short film shown at the cinema before the main feature early this year. 'Low Price Gravity' or something like that.
 
A

Anonymous

Guest
#10
Phill James said:
b. The natural force of attraction between any two massive bodies, which is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.
Hmmm... ;)

The above only really applies to point masses. (Or if one mass is a sphere and the other a point mass, and the point mass is exterior to the surface of the sphere.)

In addition GR kinda knocks this one as well, as the source of the gravitational field includes a pressure term as well as a purely mass term. (This is why the gravitational collapse leading to black hole formation occurs. At a certain point, there is a runaway event where the pressure needed to withstand a particular gravitational force leads to an even greater gravitational force and no stable solution exists for a finite pressure.)

And as for Quantum Gravity... ;)
 
A

Anonymous

Guest
#11
gravity is a dark ages concept created to make the average joe think that he must keep his feet on the ground. The church elders could not keep feeding the congregation the concepts they were trying to promote (i.e. ranks of angels, angelic powers being outside the ken of normal humans etc) if any-old-who could fly.

Thus we have the controlling church/governmental/educational system concept of "keeping your feet on the ground" even today.
 
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Anonymous

Guest
#12
Movement explains it

Here is a weird ramble...

If you take an hard-boiled egg and spin it in a shallow plate of water the water "rides" up the side of the egg's shell and, when the water reaches a certain hight, it spins off in a spinkler effect.

Bear with me...

If you move a iron bar in a coil of wire you generate a current.

Gravity could be the function of "movement" through a process that we have yet to understand. Nothing is "not moving" in the universe. A combination of forces, centrifigal, magnetic, etc. etc could all be used to explain gravity.

Einstine(sp?) tried to explain it in his Unified Field theory but from what I remember he did not complete it.

What would happen if all movement in the Universe came to a stop? No spining planets. No orbiting bodies. No galaxies spining and moving through the Universe. No atomic "movement".

Heat is generated through movement. (Atomic exchange of energy)

Magnitisim is generated through movement. (Spining iron in the Earth's core)

Light is generated by movement. (Energy transfer through photons I believe)

And many other examples probably show this fact.

Gravity is probably "movement potental while in a moving state in relation to another movement potental"

Almost like potental and kinetic energy are defined.

Just a thought :)

P.S. Like the egg example above, what would happen if the Earth suddenly stopped spining, stopped orbiting the sun and stopped moving with the sun through the galaxy and the rest of the universe? Would we sit on the planet and freeze to death or would we fly off the surface because there is no movement to generate Gravity?(provided we survived the initial catastrophe of inerta pushing us at miles a second into our house walls etc.)
 
A

Anonymous

Guest
#14
Re: Movement explains it

Originally posted by Gerry Delmo


I've heard the argument before, and it is an interesting idea, though if the implication is that if the Earth stops spinning it would suddenly have no gravity (for example) there should be a way of testing the theory without actually stopping the earth rotating...
I was always taught that the reason every star, planet, asteroid was moving was simply that even the slightest tendency to movement would continue indefinitely with no friction to stop it.
 
A

Anonymous

Guest
#16
Spin it up!

Of course, the corollary of the "gravity is caused by spinning" theory, would be that no spin means no gravitational attraction. Now whilst it would be very difficult (and I suspect that no funding body would support this as a research proposal ;) ) to stop the earth spinning, it is a relatively simple task to take a mass on the earth and stop it "spinning" relative to "the fixed stars" (following Mach.)

This should then become weightless. If it doesn't then the spinning gravity theory has problems.

Anybody want to give it a go and report back? :)

This is actually a great example of the way that science (usually) works, going from a theory to a prediction to an experiment/observation. :)
 

MrSnowman

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#17
Excuse me for my ropey science (HAPPY NEW YEAR TO EVERYONE!!!:) ).

There was an old experiment we did in school that makes you think of gravity on a more 'personal';) level...

Try sitting on a swivel chair, and push yourself off. THere's one of two things you can do...

1) Stick your legs out, you'll notice how quickly you slow down.
2) Pull your legs in.. Egad! You'll keep on spinning!

I dunno if it's just one of my crazy ideas, but, maybe gravity has got more to do with the amount of weight revolving around a particular mass, as opposed to the idea of how much force a body in itself can exert on a mass revolving or sticking to itself. Maybe we could ask the moon to stick it's feet out, just to see.

In all seriousness, the theories of gravity, although mathematically objective to a point, leave a lot to be desired. Where is the consideration of mass Vs mass where the radius of orbit exceeds the optimal amount of swing to produce an effective and and constant inertia?

Thinking on a Bee-bop tip, maybe gravity has got a bit more to do with swing, or is, perchance, more understandable as such.

I hope this makes sense in some sort of twisted fashion; I just got back from a party near Sherwood where I has the pleasure of speaking my native tongue (Welsh) in England for a change! HUZZAH!

May your God love you all :)
 
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Anonymous

Guest
#18
If metal discs whose structures are weak are spun at the right speed, they can stretch and distort due to the (non-existant..) centrafugal force constantly pushing their molecules outward and away from the center. Why is planetary spinning different from this? Why does the spin not have the same power to throw us to the equatorial ring and then out into space? Gravity does it!

We are on a spinning ball, and instead of being pulled outwards, we are being pulled down. No matter where we stand, we are pulled straight down.

I know why certain people get defensive about these questions. It seems to be similar to those attitudes found in religious people whose theology is crumbling. This suggestion is not new, though.

I just think it makes it more fascinating and awe-inspiring.

Its not a threat!:)
 

phi23

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#20
Gravitons are analogous to photons in the theory that gravity, like light, can be a wave or a particle i.e. when two objects are attracted by gravity they exchange gravitons - make sense?
 
A

Anonymous

Guest
#21
A bit of a google, and after running away from some scarily complex looking calculations found this interesting site:

autodynamics.org/new99/Layman/PicoGravitons.html

A nice theory, am a bit worried about all these little particles passing through me at super-light speed whilst spontaneously changing from energy to mass tho...
:)
 
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A

Anonymous

Guest
#22
This last one is the same theory practically as Phill James came up with...
to wit: gravity doesn't pull, it pushes (aka gravity doesn't suck, it blows.)

The medieval thinkers came up with the same explanation-
squillions of tiny angels all pushing against objects-
of course there are fewer wherever another object gets in the way, so the push is weaker.
This results in a net attraction.
Gravity.

Also the opposite of levity, as I understand it.
 

greywolfe

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#23
The reason that gravity waves, gravitrons etc have not been discovered is because they do not exist. It is because any mass in space contracts the area in which it resides that it gives the illusion of pulling objects together. Imagine a 2 dimensional piece of paper representing an area of space. First draw a vertical line in the middle and then a horizontal line to divide the sheet into 4. Call the intersection at the centre of the page point (A). From point (A) measure 4 inches up the vertical and mark this point calling it point (B).
Now place an imaginary planet Earth at point (A). Immediately point (B) is relocated one inch closer to point (A) as the planet contracts the space between point (A) & point (B). Note it is important to realize thet point (B) has not been pulled to Point(A) but that space has been compressed.
Now place an imaginary Moon at point (B). Its not important to calculate or visualize further contractions of space here as the argument is not effected. The argument under consideration now is that the moon does not orbit the earth but in fact always travels in a straight line.
Starting at point (B) the moon is travelling towards the right and its path is parallel to the horizontal line dissecting the page.From point (B) draw a parallel line to the existing horizontal line to show the straight anticipated path of our moon as it travels through space. At a place 6 inches from point (B) along the moons straight line route you can mark a point and call it (C).
From my earlier argument you will see that point (C) will be drawn closer to (A) as the Earth has compressed the space around it. Now we see that whilst the moon has in fact travelled in a straight line, it appears to have begun to orbit the Earth. The truth is that point (C) has moved.
We can complete the straight line orbit by adding point (D)(E) and so on but its the same deal as point (C). This discussion says that the moon starts at a point on the orbit where it finishes. To expand this ,my reasoning says that if you place a mass in empty space the immediate effect is for that mass to draw-in spheres of space around it like linear rods of space formed into hoops with their ends joined or bubbles if your progressing to 3D imagery.
We can go an interesting step further and regress to the flat Earth philosophy (only with an Einstein like twist). Firstly take another piece of paper and draw a circle on it. Now this circle is a 2D representation of the Earth. Mark a point at the centre of the circle and call it (A). Next mark a point at the very top of the world/circle and call it (B). Imagine a person walking clockwise around the Earth to a point 45 degrees around the circumferance to point (C). Now consider, as with the lunar orbit reasoning above, that our walker has been walking on a dead straight line and not in a circle as at first it might appear. It is the centre of mass of the Earth that has relocated point (C) to appear at a point on the circumferance of our circle. If our man keeps walking he will indeed come back to where he started as the linear track of space occupied by the surface or the planet has been formed into a hoop by the presence of Earths mass. Simple don't you think ?...............
 

Xanatic_

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#24
Well, that´s more or less what Einstein said a hundred years ago. That doesn´t mean gravity waves shouldn´t exist though.
 

azuredoor

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#25
Yes you are absolutely right, Einstein's theory of space time does not envisage gravitons and relies only on the geometry in 4 dimensions. One of the great problems of our time is to join quantum theory with relativity theory. Gravitons might not exist but quantum theory predicts them. If the LHC can't find any then quantum theory has big problems.
 

KarlD

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#26
Gravity in itself is a force which does exist, if it didn't exist then the universe would be an ever expanding mixture of hydrogen and helium from the moment of the big bang onwards.
Gravity as we percieve it is caused by massive objects causing distrotions in space time and a good analagy is to imagine a heavy weight on a rubber sheet, only in four dimentions.
 

Stormkhan

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#27
Now, anyone who knows me well might tell you - correctly - that I'm no award-winning physicist but here's my take on it ...

Gravity - as a subatomic particle might not exist but it patently does exist as an effect of other pyhsical forces. This is similar in phenomenon to a gyroscope. It doesn't have gravity particles or whatever, and it is kept upright by centrifugal effect - note, not force!
Thus, gravity exists (obviously) but as an effect of combined forces and elements, including material mass, movement and - as Einstein impllied - energy supplying movement to mass. What the material mass is can be all sorts of things.

This is a sad admission from one who always wanted to "rediscover" caborite and construct his own starship. If you can get a gravity particle then you can have interaction (and negation) of it.
 

Peripart

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#28
Stormkhan said:
This is a sad admission from one who always wanted to "rediscover" caborite and construct his own starship.
You've been looking for the wrong stuff! It's got a "V" in it, not a "B" - I hope that helps you find it a bit quicker. You could try to contact the inventor, but the last I heard, Professor Cavor was still stuck in the lunar caves, and the Selenites were closing in. Frankly, it wasn't looking good for him...

Back on topic (just about), while the original post is a slightly-more-confusing version of something I was taught at university many years ago, I think I've read it about right. However, the idea that mass contracts space/time does not mean that gravity doesn't exist. Gravity is just a name for whatever mechanism attracts masses over great distances, whether it be waves or whatever. There has to be some means of "transmitting" the effect though, surely - otherwise, how does a mass at B "know" about the mass at point A?
 

KarlD

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#29
The interesting thing about gravity is that it acts instantaniously over any distance, if the sun where to vanish now then the planets in our solar system would start to wander off because of the lack of gravity from the sun immediatly not after the several minutes to afew hours it would take a signal traveling at the speed of light, which is why it has proved so difficult to incorporate a theory of gravity into any postulated Theory of Everything which is the holy grail of physics.
Its like your 4- dimentional sheet of rubber which you have created an indentation in with your massive object has no inertia, so it springs back flat as soon as you remove the massive object.
if you have a large ball bearing on your rubber sheet and a small ball bearing on your rubber sheet they will orbit each other and the gravitational attraction, the size of the depression made in the sheet is proportional to the mass times the inverse of the square of the distance between the two.
 

Xanatic_

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#30
Where have you heard that gravity should act instantaneously? As far as I know gravity waves have not yet been detected, and they are generally believed to move at light speed, not at infinite speed.
 
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