Question about gravity

[UglyCasanova]

Ok, I am trying to understand this. Einstein's theory of general relativity tells us that spacetime is curved. Mass and energy curve spacetime so that objects fall towards one another. Is the curvature gravity? I mean, is gravity this pulling force or is it curves in spacetime? When I jump in the air, do I fall to the ground because the earth curves spacetime much more so than I do?

 

[zephyrprime]

Yes, this curvature is gravity.

As to why you fall when jumping, I believe you have some sort of misunderstanding about gravity. That the earth distorts spacetime more than you do is not why you fall. Anything that distorts spacetime at all attracts anything else regardless of how strong the distortion is. Of course, stronger distortions will yield stronger pulls.

 

[UglyCasanova]

I think that's what I meant, I'm not sure. So gravity is not a pulling force, but a falling between 2 objects?

 

[Elledan]

You can try posting this topic at Physics Forum for an in-depth answer

There are already some related topics as well.

 

[KIAman]

Gravity has nothing to do with "falling." It is just the attractive force of any object in the universe. When you jump, the earth gets pulled towards you and you get pulled towards the earth. There are attractive forces between you and your next door neighbor. The reason for your misconception is because of the minisculity of the forces of gravity. Lets just say it takes a HUGE amount of MASS to make enough gravitational force to even be felt.
The curvature of spacetime is mainly to help us understand gravity since we generally have no clue what it really is. It helps us understand that the deeper the curve, the faster an object is pulled in towards the mass, a black whole is theorized as a complete TEAR in space where things go in, but *edit for those quantum mechanics* visible light can never go out, unless the black hole dies in which it could radiate visible photons, of which we have never observed.

LOL you can learn alot from PBS.

 

[Elledan]

<< (..) a black whole is theorized as a complete TEAR in space where things go in, but can never go out, not even light. >>


*grin* How about Hawking radiation?

 

[Heisenberg]

<< *grin* How about Hawking radiation? >>



Oh you had to go and drag quantum mechanics into it, didn't you?

The problem arises when we try to conceive four (so far, anyway) dimensional space-time in our three-dimensional perceptions. The curvature caused by mass results in what we term gravity. A popular example is putting a heavy ball in the center of a trampoline and then placing another, lighter ball at the edge. The lighter ball will roll towards the heavier one (or be "attracted" to it) due to the stretching of the material of the trampoline. The effect of gravity is similar -- only seeing an object fall to earth is our 3-d view of the underlying 4-d effect.

 

[DRGrim]

So... did anyone else get The Universe In A Nutshell by Stephen Hawking this year?

 

[Kaosjester]

no i havn't gottenit yet i've thought about it but am wondering if i should... I read and enjoyed a brief history of time but am unsure if i have the time to read his new book. how is it?

 

[DRGrim]

The parts I have read are very good. It is also very well illustrated. You can hardly tell the pictures were done with Bryce
Anyway, its a good read, even if the ideas are hard to understand.

 

[bigshooter]

So if there was some way to use energy to controll mass (matter-energy conversion--hehe sounds like star trek) we could probably generate anti gravity by using a significant mass at x distance from the other one to cancel out each other?

 

[SsZERO]

That trampoline analogy is pretty good. But the next question would be...if I were to travel to the center of the earth, assuming it is hollow in this example, would there be a state of gravitational equilibrium, or would I fall "through" the earth?

I have my own thoughts about the universe and the things in it. There are 3 dimensions that make up our universe, and they occur in a certain order: space, energy + matter and time. Time is a control dimension...while our perception of time is minutes, seconds, etc, time is actually like a container. Space is not a container, but the area that is contained. Energy and matter both exist within space having the constraints of time. Energy and matter are also both interchangeable with each other; matter is an altered state of energy. Think of energy as water, and matter as ice...time would be temperature. Just like ice has more volume than water, matter has more volume than energy.

Therefore, for matter to exist, it must displace energy. By default, space is full of energy... Matter requires more space than energy does, per unit. So the more matter contained in an object, the more energy it is displacing. Now the opposing force of this displacement is pressure exerted from the surrounding energy, in all directions, onto the mass. Think of a neutrally buoyant sphere inside of a larger sphere, and the space between the inside of the larger sphere and the outside of the smaller sphere is filled with water. The water will be exerting a similar pressure on the smaller sphere, as gravity does to mass in space.

Another interesting topic is that by knowing this, making matter into energy isn't quite as complicated. Basically, matter WANTS to be energy, that is the "normal" state. To make matter into energy, it needs to move faster than time...now we need to think of time as an actual dimension, and not a concept of measure. To make energy into matter, one needs to put energy into stasis. I can't tell you how to do that, yet. If I could, I'd be on my starship right now. heh heh

-= SsZERO =-

 

[KIAman]

If the earth was a hollow sphere (ex only the crust) than the gravitational acceleration within the hollow earth is ZERO at all points within the hollow earth. Since it is not hollow, there is an equilibrium point in the center of the earth (not exactly center since the earth is not EXACTLY a perfect sphere and the mass is not exactly distributed).

As for matter into energy, its all about the laws of thermodynamics.
As for energy into matter, E=mc^2 it would take a HUGE amount of energy even to make small amounts of matter.

And by the way, ice has more volume than water because water expands when frozen because it turns to a structured lattice.

If you really wanted to get down to the nitty gritty, even energy if you look close enough is some sort of phsyical matter.

I can just imagine it now the universe as a slop of low level thermal radiation within space, how sad.

 

[Heisenberg]

<< That trampoline analogy is pretty good. But the next question would be...if I were to travel to the center of the earth, assuming it is hollow in this example, would there be a state of gravitational equilibrium, or would I fall "through" the earth? >>



It would depend on your velocity as you passed through the earth. If you were going fast enough, you would keep going and escape the earth's gravity all together. If not, you would eventually stay in one spot after a period of oscillations.

I'm not sure I quite understand the rest of your post, but I'll give it a shot. Time is a dimension, just like the 3 space dimensions. Again, the problem is that we don't have a way to visualize 4 dimensions -- this makes understanding things like space-time curvature really hard. This is where the mathematics really come in to it, because the math doesn't care about the number of dimensions.

As for the energy/matter equivalence part, that's basically right. Very small amounts of matter (mass) contain huge amounts of energy. The key concept here is entropy. The entropy of the universe is increasing. Since matter is more 'organized' than energy, eventually all the matter will be converted to energy (mostly as infrared radiation). This is called the heat-death of the universe. It is possible to convert energy back into matter, but you always have to increase the entropy somewhere else to do it, so overall the entropy still increases.

Of course, this is just my understanding after a few years of school. Your mileage may vary.

 

[BraeBrae]

<<

<< (..) a black whole is theorized as a complete TEAR in space where things go in, but can never go out, not even light. >>


*grin* How about Hawking radiation? >>



How about my wife? Physics has still been unable to explain her, or even the smallest portion of her. She is why I got out of Physics!

 

[SsZERO]

<<

<< That trampoline analogy is pretty good. But the next question would be...if I were to travel to the center of the earth, assuming it is hollow in this example, would there be a state of gravitational equilibrium, or would I fall "through" the earth? >>



It would depend on your velocity as you passed through the earth. If you were going fast enough, you would keep going and escape the earth's gravity all together. If not, you would eventually stay in one spot after a period of oscillations. >>



Well, let's say that there is a hole directly through earth, and it passes through the center, and that I am not moving faster than 17 miles/sec or whatever is needed to escape the gravity of earth. Once at the center point, you agree that I would be suspended in a state of gravitational equilibrium.



<<
I'm not sure I quite understand the rest of your post, but I'll give it a shot. Time is a dimension, just like the 3 space dimensions. Again, the problem is that we don't have a way to visualize 4 dimensions -- this makes understanding things like space-time curvature really hard. This is where the mathematics really come in to it, because the math doesn't care about the number of dimensions. >>



Yes, I know that time is a dimension, but there are only 2 more...space and energy -- matter is a state of energy. When talking about energy as a dimension, it is not particles of any kind. It is not photons, radiation, etc. Energy is a component of the universe, which is what fills the dimesional component of space. Time provides the container for space, as well as determining the properties of energy. Basically, by gaining control of the dimesion of time, you will have complete and total control of this universe. The structure of this universe is remarkably simple, yet the possibilites of what can exist within it are infinite.

TIME
SPACE
ENERGY-TIME
SPACE
TIME

The thing that people might find confusing or hard to understand is the answer to "What IS a dimensional component?" Think about it, what IS space. We perceive it as area to exist, but what IS it? What IS energy? We perceive it as a force that allows something to happen, but what IS it? And most importantly, what IS time?



<< As for the energy/matter equivalence part, that's basically right. Very small amounts of matter (mass) contain huge amounts of energy. The key concept here is entropy. The entropy of the universe is increasing. Since matter is more 'organized' than energy, eventually all the matter will be converted to energy (mostly as infrared radiation). This is called the heat-death of the universe. It is possible to convert energy back into matter, but you always have to increase the entropy somewhere else to do it, so overall the entropy still increases.

Of course, this is just my understanding after a few years of school. Your mileage may vary. >>



Matter is state of energy...to understand how energy and matter relate, time has to become part of the equation, because time is what allows energy to have its many properties within the dimension of space. Time allows the contigious energy within space flow at a given velocity within the dimension -- not a velocity within space, we are talking on a dimensional level here (what we cannot perceive). When the velocity of energy at a point or section of space drops below that set universal velocity of time, it becomes some form of matter. The lower the velocity, the greater the volume of space occupied on a universal level (what we could perceive). Suffice it to say that this process happens more than trillions of times per moment, and each result is different.

-= SsZERO =-

 

[SsZERO]

Matter is a state of energy. And just like ice has more volume than water because it turns into a structured lattice, when energy becomes matter, it too goes from being a contigious unit in space to a structured unit. Even atoms, subatomic particles, particles we don't know about...they are all "matter", since energy is not a particle of any kind. Energy is energy, just like space is space and time is time. They are not anything else, they are only one thing. Conceptualizing a pure dimensional component is about as difficult as understanding concepts like infinity, absolute nothing (not even color...most people would think of blackness as nothing), and existence beyond our universe.

-= SsZERO =-



<< If the earth was a hollow sphere (ex only the crust) than the gravitational acceleration within the hollow earth is ZERO at all points within the hollow earth. Since it is not hollow, there is an equilibrium point in the center of the earth (not exactly center since the earth is not EXACTLY a perfect sphere and the mass is not exactly distributed).

As for matter into energy, its all about the laws of thermodynamics.
As for energy into matter, E=mc^2 it would take a HUGE amount of energy even to make small amounts of matter.

And by the way, ice has more volume than water because water expands when frozen because it turns to a structured lattice.

If you really wanted to get down to the nitty gritty, even energy if you look close enough is some sort of phsyical matter.

I can just imagine it now the universe as a slop of low level thermal radiation within space, how sad. >>