Originally posted by Bosse de NageThis is a somewhat Kantian issue. Perhaps my less scientific and more philosophical approach will not be of any help to answer your question, but it might help in understanding why it is that we cannot know what gravity 'is'.
I'd like answers to all these questions, really, but I'll take what I can get.
I asked FabianFnas where mass comes from because as far as I can tell the answer is 'gravity' (see Ambrose Bierce quote above).
I was reading about Newton the other day and realized that I'd thought all my life that Newton 'discovered gravity' but in fact he did no suc ...[text shortened]... non fingo indeed.
Well, bring it on, if you please. How does energy do what it does?
Every system is composed of two key components.
1) The set of objects that exist within this system.
2) The set of rules that govern the interactions between them.
The thing is that we are objects within the system. Since our ability to understand these objects is limited by our ability to describe their phenomena, then all knowledge of them must come from observing and identifying patterns in the phenoma.
From identifiable and stable patterns we identify what we call 'rules' or 'laws' that are based on definable, but not identifiable 'forces'. Our component 2). But note that this is purely descriptive. We then characterize the objects by the way they interact with each other and identify what we call properties.
This means that we can never really 'know' (in a standard sense of the word) what these rules 'are' because they are not objects in themselves. At best, we can identify more patterns and improve our understanding of how they work, but not what they 'are'.
To my knowledge, all four forces that we know of suffer from the same issue as gravity:
- strong nuclear force
- weak nuclear force
- gravitational force
- electromagnetic force
Since our knowledge is still incomplete, we still search a 'Unified Field Theory' that may re-identify these 4 basic forces to a single one. But this single one would still suffer from the same issue that it is not an object in itself.
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Originally posted by PalynkaThis is all very well put by you. I'll just add the we can too take into account the different ideologies that one can have while doing science. I'll simplify a lot just for the sake of brevity here. We can be called realists, platonists, formalists, operationalists,... And this can change a little bit some things of waht you said. I consider myself to be a platonist/realist in the sense that I believe that there is a reality independent of us and the mathematical/physical laws are real. I think this is easier to explain in the mathematical field since in physics everything we have is always approximate. For instance that Pythagorean theorem was there before it was found and would still be there even if it hadn't been found. Or in another way all future theorems that will be found out will be found out. Not made up. So I just take heart with this notion of yours: what these rules 'are' because they are not objects in themselves.. For me they are ojects in themselves the thing is just that we don't have an immediate access to them. But of course I'm used to argue with a lot of people regarding this aspect of science and I don't expect to convert someone on this i just want to say what I think.
This is a somewhat Kantian issue. Perhaps my less scientific and more philosophical approach will not be of any help to answer your question, but it might help in understanding why it is that we cannot know what gravity 'is'.
Every system is composed of two key components.
1) The set of objects that exist within this system.
2) The set of rules that go e one would still suffer from the same issue that it is not an object in itself.
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Originally posted by adam warlockYes, I had many doubts of what word to use instead of 'objects' to avoid such comments. What I mean by 1) the elements of the system on which the rules of interaction apply. In that sense, there is a clear dichotomy between what I call 'objects' and what I've called 'rules'.
This is all very well put by you. I'll just add the we can too take into account the different ideologies that one can have while doing science. I'll simplify a lot just for the sake of brevity here. We can be called realists, platonists, formalists, operationalists,... And this can change a little bit some things of waht you said. I consider myself to f science and I don't expect to convert someone on this i just want to say what I think.
I wasn't implying that they are not real, just that they are fundamentally different.
Edit - Another way of looking at it is that 1) are the variables and 2) the equations that govern how those variables interact, change, etc.
Edit 3 - Where would you put the parameters? To me it seems they are a part of 2) but I'm having doubts now.
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Originally posted by PalynkaJust not to make a fool of myself let me first ask: What do you exactly mean by parameters?
Yes, I had many doubts of what word to use instead of 'objects' to avoid such comments. What I mean by 1) the elements of the system on which the rules of interaction apply. In that sense, there is a clear dichotomy between what I call 'objects' and what I've called 'rules'.
I wasn't implying that they are not real, just that they are fundamentally diffe ...[text shortened]... you put the parameters? To me it seems they are a part of 2) but I'm having doubts now.
And my comment was just a complement to yours. From what you write you seem to be something of a realist too. I just wanted to make more points of view available for whatever people are interested by these things.
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Originally posted by adam warlockAll such questions boil down to this: Is there a greater universe outside the one we are in now, that is to say, did the universe we all know and love come about because of something that went on in the larger universe, where maybe an infinite number of our kind of universes may exist, each with slightly differant laws, such as the fine constant or C. I think we are getting closer to answering that question with the deeper probes of the background radiation, right now we see the differances in temperature when the universe was about 380,000 years old, when it went transparent, we see that now with details somewhere about 1 part in one million. When we see details of it in parts per billion, we may see what the overall shape of the universe is and maybe imprints of other dimensions on that background. So the answer may come about in the next 25 years or so. It would be an interesting experiment if we could make matter dissapear star trek wise, because we could directly measure the speed of gravity, probably right at the speed of light, not sure if it is measurable directly with our level of technology yet. Anyone know of such measurements?
Just not to make a fool of myself let me first ask: What do you exactly mean by parameters?
And my comment was just a complement to yours. From what you write you seem to be something of a realist too. I just wanted to make more points of view available for whatever people are interested by these things.
I can see one way: If you had a quantity of matter and an equal quantity of antimatter, bringing them together would turn the whole thing into radiation. Wouldn't that make a change in the bend of spacetime around the explosion? So if it went at the speed of light, you might see the the now missing mass, having been converted to massless photons, it should effect a change in spacetime. What do you think?
Originally posted by Bosse de NageUnless I am mistaken, mass not dependent on gravity. Mass is a measure of inertia and can be measured without taking gravity into account.
I asked FabianFnas where mass comes from because as far as I can tell the answer is 'gravity' (see Ambrose Bierce quote above).
In fact, the masses of atomic particles etc are measured by seeing how their trajectories are deflected by a magnetic field not gravity. It is interesting though that an objects mass is directly proportional to the amount of gravitational pull it has on other objects whereas it is not related to the other fundamental forces of nature.
It must also be noted that mass bends spacetime.
Originally posted by twhiteheadMass CAN be measured by seeing how far they are deflected by magnetic fields. That is my field, ion implanters use mass analyzers to bend a particular ion to an exact angle, usually 60 or 90 degrees to form an ion beam. But that does not work with neutral particles, any neutral, whether its a hydrogen atom with its electron or a neutron, you can't measure mass that way with neutrals.
Unless I am mistaken, mass not dependent on gravity. Mass is a measure of inertia and can be measured without taking gravity into account.
In fact, the masses of atomic particles etc are measured by seeing how their trajectories are deflected by a magnetic field not gravity. It is interesting though that an objects mass is directly proportional to the am ...[text shortened]... d to the other fundamental forces of nature.
It must also be noted that mass bends spacetime.
Originally posted by FabianFnasInertia mass being the energy carried by EM waves? Photons? I know they IMPART mometum even though they are massless. Is that what you mean by inertia mass?
We have to remember that the mass property is in fact two properties at the same time:
The gravitational mass and the inertia mass.
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Originally posted by sonhouseNo. Inertia mass is the one tha relates how a body resists to a change of movement. Gravitational mass is the one that is related to how a body creates and reacts to a gravitational field. Obviously there must be some kind of proportionality between them and Newton took the easy way out and said that the proportionality constant is in fact one so that inertial mass equals gravitational mass. Eotvos (or whatever way his name is spelled) made a lot of experiments later and confirmed what Newton supposed theoretically in an experimental way. But the thing is that in the context of newtonian theory there is no apparent reason for that to be so. Untill Einstein made his theory of GR this fact was just a very deep coincidence but then everything was made clear.
Inertia mass being the energy carried by EM waves? Photons? I know they IMPART mometum even though they are massless. Is that what you mean by inertia mass?
Originally posted by sonhouseInertia is covered by Newtons first law:
Inertia mass being the energy carried by EM waves? Photons? I know they IMPART mometum even though they are massless. Is that what you mean by inertia mass?
"An object at rest tends to stay at rest and an object in motion tends to stay in motion with the same speed and in the same direction unless acted upon by an unbalanced force."
You can measure a inertia mass by accelerate a body with a certain force, and the acceleration you get is a measure of its mass.
It's gravitational mass, however, is measured by the force needed to counteract gravitation.
Originally posted by FabianFnaswell more like split from the universal force. like electromagnetism, weak nuclear force and strong nuclear force.
Gravity is one of the basic forces of the universe. It came into being at the same time universe came into being, some 14 billion years ago.
Originally posted by Bosse de NageCoult it instead be stead that gravity, like vacuum, arises not from
I've read that the origin of gravity has yet to be discovered, but I'm not so sure. Does anybody know where gravity comes from?
GRAVITATION, n. The tendency of all bodies to approach one another with a strength proportion to the quantity of matter they contain -- the quantity of matter they contain being ascertained by the strength of their tenden ...[text shortened]... of of B, makes B the proof of A. Ambrose Bierce (1842-1914), 'The Devil's Dictionary', 1911
something but from the absence of something?
Originally posted by PalynkaAll right. Gravity is empirical knowledge derived from experience, but cannot be known as a thing-in-itself. Gotcha.
This means that we can never really 'know' (in a standard sense of the word) what these rules 'are' because they are not objects in themselves. At best, we can identify more patterns and improve our understanding of how they work, but not what they 'are'.
That kind of destroys my line of enquiry. Unless gravity is a formal characteristic of the empirical world? I know it's meant to be space, time and the Categories, but gravity seems to be implicated in time, so ...