This question has recently been discussed in my Physics class, so I was wondering, what do you all think Gravity REALLY is (since we really don't KNOW what it is, it's a lot of theories and opinions atm).

Field
Particle
Bending in Space/Time
something else.

Personally, I think ol' Albert's got the most accurate description to date, considering most of his theories have been proved correct to a small degree. But I heard somewhere it fails on the quantum (quarks) level. Don't know about this, haven't looked into it much either.

Anyways, post on!

Strings of course.

OK, I don't really know much about that but it sounds interesting.

Gravity ... it's really ... a force.

I don't know, all I remember is that among the four elementary (gravitational, strong, weak and electromagnetic) forces, it is the weakest, but the one with the largest range.

What is your question exactly? What creates a force of gravity?

Man, I suck at physics

Explaining gravity. But it's not a force--to be specific things like weight are forces. Gravity is the action of attraction between two masses. Even though it's called one of the fundamental forces. Confusing, no? :p

I think it's a field, like an electric or magnetic field.

The worst thing is that I've done an introductory course to quantum physics, passed with 82%, and I don't remember a damn thing.

<3 Alcohol. You've got to love those end-of-semester parties. They make sure you forget all that crap that you learned.

Fun.

It's an effect, not something physical.

It's part of... THE FORCE!

No?

Ok...
It's nature's way of telling you to keep yer *** on the earth. :p

It's got to be physical, because it has a measureable rate of acceleration (9.8 m/s²).

everybody knows that gravity is just a government conspira*snipe*

its jumpy and sticky and clever, science likes it

it's warm cake.

Its a force acheived by dividing a substances measure of weight by its mass

I have always heard of it more as a bending of space.

I knew I shouldn't have changed my signature.

For those who don't remember, a couple of weeks ago my signature was:


This actually came from a discussion that I was having with another physics student, after I was arguing with the professor about whether the surface of the Earth was actually an inertial reference frame. I said that it wasn't, because objects are held up by the earth's surface, and are therefore constantly accelerating upwards. I mean, it feels like we are accelerating, right?

g ~= 9.8 m/s/s (not a true constant)

W = mg <-- definition of weight (variation of F = ma)

F[g] = G((m1*m2)/d^2) <-- gravitational force were m1 and m2 are the masses of two bodies, d is the distance seperating them and G is a constant equal to 6.67 x 10^-11 (N*m^2)/kg^2

The further you go away from a gravitational field, the weaker the force you experience. Gravitational fields extend out for infinity. So in essence you can calculate the gravitational force of any given two bodies.

http://www.thinkgeek.com/tshirts/science/65a4/

i hope its a wave similar in its properties to magnetism and electrostatics, cos then we can create and direct them, and become the masters of the universe like the great and powerful emperor MING DA MERCILESS!!!



sorry random madness

if(getThingFlags(source) & 0x8){
  do her}
elseif(getThingFlags(source) & 0x4){
  do other babe}
else{
  do a dude}

Higgs boson.

Obviously not, since that's the earth's gravitational acceleration. :p

um... no?

Recap:

Gravity is an acceleration. There is a force attracting two masses to one another. For example, you jump out of an airplane, tne earth attracts you to it, and you attract the earth to you, both with the same force. Due, however, to the extreme difference in masses, the earth will accelerate toward you VERY slowly, while you accelerate toward the earth at about 9.81 m/s² (that's what my class uses).

Now, I have an urge to present a physics "class" at the moment -- pretty much everything I've learned this first half of the course. dunno why, but it will help me remember stuff. And in an organized fashion too (all the unit types, dimensions, and all that good stuff in a single list )

xf = xo + vot + ½at²
vf = vo + at
vf² = vo² + 2ax
F = ma = /\p / /\t
Ff = kFN
p = mv
/\p = m/\v
W = Fx * cos@
E = K + U
K = ½mv²
U = ½kx² = mgh
P = W / t
Fc = mv² / r

Variables:
Vectpr - Has a magnitude and direction
Scalar - Has only a maganitude

x = Displacement - vector - linear distance from start point to finish point; note that it is not the distance travelled, but the difference in locations
12345 • xo - meter (m) - Initial displacement
12345 • xf - Final displacement
12345 • h - height; displacement in the y direction
t = Time - scalar - second (s) - time is (money! ) pretty self explanatory
v = Velocity - vector - m/s - speed at which an object is moving; rate of change of position
12345 • vo - Initial velocity
12345 • vf - Final velocity
m = mass - scalar - kilogram (kg) - the quantity of matter in an object as measured by inertia (resistance to change in motion)
a = Acceleration - vector - m/s² - rate of change in an object's velocity
12345 • g - Earth's Gravity: 9.81 m/s²
F = Force - vector - Neuton (kg • m/s²) - change in momentum with respect to time
12345 • Ff - Frictional force
12345 • FN - Surface normal force
p = Momentum - vector - kg • m/s - objects with greater masses take more force to change velocity by some amount
W = Work - scalar - Joule (J)- The product of the magnitude of force and direction
P = Power - scalar - Watt (W) - Work per unit time
E = Energy - scalar - J - total energy of the system
12345 • K - Kinetic Energy - energy of motion
12345 • U - Potential energy - energy stored in the object
k - Coefficient of Friction/Spring constant - scalar - Dimensionless - Varies with springs/surfaces sliding against each other
r = Radius - scalar - m - in circular motion, the radius of the circle of motion
@ = Angle - scalar - degrees/radians - in the case with work, the angle formed between the force applied and the displacement (note -- normally, you would use the Greek letter theta, but massassi doesn't support it so there)

Oh god why dont we just scan the 700 somewhat pages out of my physics text book :/

BTW, Darth Slaw you did nothing but threw out a bunch of definentions and concepts, and didnt explain any of them....real smart :rollseyes:

You mean gravity has an acceleration... maybe... wait... aaaah!

/explodes

I've heard the particle theory, and that alien spacecraft uses "gravity projectors" to manipulate these particles. Or maybe it's a field.

Well, it can't be a field, because Newton's theory of the gravitational field doesn't hold up in all situations (black hole, quantum). It's been rumored to be a particle, but mostly, it's an effect. A bending of space-time. I wanted to see what everyone would say before we got into this.

See Einstein proprosed that space and time were not separate, but were in fact one entity. Space-time. He proposed that gravity was not a field, but was a bending of space-time. If what he says is true (I didn't explain all of it), then the faster you go, the less the amount of time that elapses. We proved this, when we calibrated exactly 2 atomic clocks, sent one into orbit (18,000+ mph), and let it go for a few months, I believe. We then retrieved this clock, and it was a few seconds off. A few seconds. The most accurate piece of equipment we have in the world for measuring time. Was a few seconds off.

Recently, Frame Dragging was also proven true, as well. Interesting stuff.

9.81 m/s² is acceleration due to gravity on Earth, not gravity itself.

Proven true? Interesting.

I believe it's caused by mangets. (Yoshi, Black Holes and that like don't necessarily exist, so... yarr.)

"omg mragnats kanut floot. dat piktar si pohotoschopeecxdded!!!!11"

Hehe...

If you could prove that then you'd be heralded as the greatest genius in the history of science.

At the moment, the big problem is in uniting the force of gravity with the force of electromagnetism. (gravity is a force, I'm not quite sure why anyone'd think it isn't. force is rate of change of momentum, gravity results in a change of momentum, therefor a force is acting).

Electromagnetism can attract or repel, but gravity can only attract, and this is one of the various fundemental differences between the two making it very difficult to unite them.

Perhaps it's simply that we haven't yet found any gravity that repells?

Frame dragging. Its a side effect of the mass and rotation of terrestrial bodies.

Can you say handbook?

That's 9 weeks' worth of material in a very condensed outline.

And a lot of you all probably know this stuff (thrice over) already, or if you don't, well, sorry for confusing you.


Gah! And after thinking REALLY hard about that, gravity is, indeed, a force, not an acceleration as I had originally stated.

Yeah "acceleration due to gravity" is the acceleration, and gravity is the force that causes that acceleration. I was still half right though, because I also said all objects have an attractive (gravitational) force on one another (you'd think I'd catch this little discontinuity). I just named them wrong
The magnitude of the acceleration does, of course, vary with distance between the objects, but when dealing with basic situations that shoot projectiles through the air from earth's surface, the distance between the earth and the projectile will not make but the very slightest difference in the acceleration.

[/yapping]

Field, particle... Both would be easier to manipulate artificially than anything else. What ever it is, I hope it's something that can be affected with machines without the need of extensive real mass. Seems improbable, though...

I think Mort-Hog must be the only one who has done some sort of particle physics course here or read some physics journal, because otherwise a lot of you should have known about something called the "Standard Model" and how the Higgs boson fits in with it....

for those that don't have a clue go read here...

http://www.phy.uct.ac.za/courses/phy400w/particle/higgs.htm

for a few explanations, you shouldn't need any high level physics knowledge to understand those definations...

you all better hope that gravity is a particle, ie the Higg's because otherwise for the past 20 years physicists have been playing around with toys (particle accerators) that can create black holes on earth, basing how these things work on a model that, if gravity isn't caused by a particle, is fundamentally flawed....

of course you must include the graviton in this equation as well because its the thing that translates the force of the Higg's to other particles...

whats with all the formula guys? none of them actually explain what gravity is, just what is does to things, I can see that from outside my window.

and there is your answer, what is gravity, a particle, the other things are just effects of gravity.

course, it COULD all be wrong and it might turn out to be something different, but thats our best guess at the moment.

Actually, considering that most of Albie's theorems have been proven true when relating to gravity (i.e. Light bending around the moon in an eclipse, or Frame Dragging, or time slowing down), I'd say his is probably our BEST bet.

And how the hell could they create black holes--that's just infinite mass with no volume.

From what I understand about gravity (both through self-taught knowledge and an Intro to Superstrings class at Cambridge University, England), the larger the mass of an object, the more it "bends" spacetime, and then things going by on the spacetime plane are effected by that little dip, which causes it to move towards them. (Obviously this is the more laymens definition, I haven't had nearly enough sleep to remember the more technical explinations)

So the big problem with gravity in classical physics is that it was seen as a force that is exerted from one object to another, but this was flawed, seeing as gravity is instantanious, it can effect things before the light of them reaches it. (It would have to travel faster than light).

erg.. more later.

No, black holes have finite mass. It was first measured in September this year, when they observed some matter orbitting around the black hole and then going into it, from which they could calculate the mass of the black hole - between 10 and 50 million solar masses.

Black holes also have finite volume. It certainly isn't zero, it is very large. It is so large that you'd be forgiven for thinking it was infinite.
The 'size' of a black hole is generally given by the radius of its event horizon. The volume is not given by the usual 4/3 pi r^3, as relativity makes it more complicated than that. As you pass the event horizon, the spatial direction 'inwards' becomes 'towards the future'- you WILL reach the center. The direction an outside observer would think of as their 'future' becomes a spatial dimension once you are inside. The volume of a black hole, therefore, is its surface area times the length of time the hole exists (using the speed of light to convert from seconds to meters). Black holes last almost forever, so their volume is close to infinite.

Yeah, but I'm talking about the center (if I'm right) which has the only mass of the black hole. The rest is just the effect of the mass.

I hadn't heard about that report on Black Hole masses, but thanks for sharing. I'll remember that.