Gravity, when the feeling's gone and you can't go on, it's gravity

[itsmydamnation]

this thread delivers,

would read again

i love how everyone here takes themselves so seriously even when there out of thier depth. its like arguing with a woman, you can either be happy or right, not both

 

[Mintmaster]

There's no gravitational FORCE.

Grall, I was with your semantic argument of 'gravity' not being a force, but to say there is no gravitational force is just plain wrong.

Force is the gradient of any potential energy field. Gravity results in such a field, and hence you can use the adjective 'gravitational' to describe this force.

RudeCurve, you need a potential energy field to hold the planets in orbit, but you do not need to use any energy aside from conversion between gravitational and kinetic in elliptical orbits, where you cycle between positive and negative work being done on the planet. The merry go round has a kinetic energy field with respect to your body position, but you do not need to expend any energy to hold yourself in the same position. You may need to waste some heat to tense your muscles, depending on how you latched yourself on, but that's irrelevent.

As for the topic, he hasn't proven anything. Chances are he just doesn't know how to measure power (i.e. integral of V*I over time, not simple RMS V times RMS I). I don't know how the bike video is related, as he even extolls the recharging resistance as an exercise benefit.

 

[Grall]

but to say there is no gravitational force is just plain wrong.

There is gravitational attraction, or influence (whichever you want to call it) certainly. However it's not a force in the physics sense of the word force, as it would require work to exert a force, and there's nothing 'working' when gravity pulls on stuff. That's what I've been trying to say, I'm not a physicist so I've probably not expressed it in an optimal way, but hey... Nobody's perfect.

I don't know how the bike video is related, as he even extolls the recharging resistance as an exercise benefit.

It isn't related, because RC doesn't understand the difference of the (fictional) concept of regenerative acceleration, and that of the (real) concept of regenerative charging.

 

[_xxx_]

there's nothing 'working' when gravity pulls on stuff.

Then please tell us what pulls on stuff then? How is stuff being pulled with no work?

A little hint: when you heave something off the ground, you must insert work to do it (work = force x distance). Why, if there's no force working against that?

 

[Tahir2]

Then please tell us what pulls on stuff then? How is stuff being pulled with no work?

Magic. Everyone knows that!

 

[3dilettante]

If keeping something stuck to the surface via gravity requires work, then why hasn't everything burst into flames?
If it took an actual net expenditure of energy merely to keep something in a gravity well, then this constantly expended energy would eventually devolve into heat. (An unending, infinite source of heat...)

 

[Mize]

If keeping something stuck to the surface via gravity requires work, then why hasn't everything burst into flames?
If it took an actual net expenditure of energy merely to keep something in a gravity well, then this constantly expended energy would eventually devolve into heat. (An unending, infinite source of heat...)

Well, the force of the ground under my feet exactly equals the force of gravity on my mass. There is no "work" because work is the integral of F*dx and I don't move.

 

[3dilettante]

Well, the force of the ground under my feet exactly equals the force of gravity on my mass. There is no "work" because work is the integral of F*dx and I don't move.

That's why I am asking for clarity on the implications of the previous _xxx_ where the wording indicates that there should be work being done in that situation.

 

[Mize]

Look, in classical Physics gravity is a force. Classical Physics is all that should matter to the layman.

In modern Physics, large masses merely cause a curvature in the geodesic that makes the normal pathway of an object in motion curved instead of straight (classical Physics). Think of it as bowling balls and baseballs on a waterbed. The curvature from the mass of the objects affects the pathways that objects take as they move across the surface. This curvature of space is not a force.

So, yes, gravity is not considered a "force" that "does work" in modern physics, BUT that's highly non-intuitive and violates common sense (or classical Physics concepts).

To the layman or following classical Physics, gravity is a force.

 

[London Geezer]

Or just put a cat+toast in the middle of the rear axle

Not sure why i was going to this thread, and thanks for all the laughs, but i did laugh out loud the most at this...

 

[Grall]

Then please tell us what pulls on stuff then? How is stuff being pulled with no work?

Haven't we gone over this about 3000 times already in this thread? The pull comes from the deformation of space-time. I even linked to the appropriate Wiki page about this (and added a quotation), why's this issue still cropping up again and again?

A little hint: when you heave something off the ground, you must insert work to do it (work = force x distance). Why, if there's no force working against that?

You're doing work to lift...whatever. Emphasis: you're the one doing the work. There's no counter-work happening.

If you screw apart a standard ballpoint pen and remove the spring from the mechanism, then put the spring between your thumb and forefinger and compress it, what's going on right then and there?

Your muscles are working against the tension of the spring. But what's the spring doing? Has it suddenly become an infinite source of "push energy" just because you compressed it? Can you run engines off of its inexhaustible "push power"?

I say the spring's doing absolutely fuck-all during all of this. It's an inert piece of metal, that's all. What do YOU say?

Gravity's the same thing; you get (at best) no more out of it than you put in. Typically much less. That means any energy coming out of the system is energy YOU ADDED in the first place; gravity actually isn't doing anything at all; it's a zero-contributer. You can't tap power out of it, because it has no power to tap. It's a spatial curvature, not a motor force...

 

[_xxx_]

Have you ever seen any proof of deformation in space-time? How does that deformation make bodies attract? How "right"/valid is Wiki?

Hint: noone knows how it works or what happens there. It's all just guesswork so far, and until there is a sound foundation to one of those theories, I'm sticking to the classic definition, see Mize post above.

As for work, when you lift something you're doing work or applying force against the opposing force. If there was none, you wouldn't need to use force or invest work to accomplish that.

Do you know the experiment with two balls, one spinning with 20000+ rpm and one steady, then you kick them up a bit and let them both fall freely? The spinning one will go higher and fall faster, quite visibly. Nothing in our current science can explain that. You can do it yourself, use a drill or a router to rotate the spinning ball.

Tthere is currently a e-motor doing 50000+ rpm which is specified "weight: 1kg; 0.1 kg when running". If it had the appropriate air flow through the middle, you might as well see it lift off eventually Same case as above, noone knows why except that its obvious that spin has something to do with gravity.

So I'd strongly assume that neither the classic theory nor the space-time warping nails it, we're still missing something there.

 

[dskneo]

Way out of my league but aren't there 4 known proper forces, as in, they have an effect on the residues from the universe formation (all visible matter which is ~1% of the universe, being ~30% dark matter and ~70% dark energy) ?




But none if these forces produces work, it just transfers potential energy from one state to another. I guess this is correct?




gravity
electromagnetic
strong nuclear
weak nuclear




So these forces are not forces but instead are inherent qualities of what makes the universe.
This makes all matter have potential energy when displaced "against" whatever affects it, but the displacement it self consumed energy from other source of potential energy. So energy just keeps converting to equals of another "force".




all in all, in my understanding the true perpetual machine is the universe it self, meaning, all the energy it can ever produce is already there, its just that it keeps changing to an equivalent but different state and we use it.




Perpetual implies infinite but I guess in this context it means it can produce more energy than it consumes? is this the discussion?
well, I don't think it can happen that way then. How can we introduce energy to a universe that has zero energy? I mean, its a flat universe, everything is balanced between the 4 "forces" and whatever we Cant see but know its there. So it has zero energy, you can't add energy to zero energy, right?




sorry if this was dumb but it was my understanding from reading Lawrence krauss michio kaku etc



A nice 1hour discussion on what we know so far.
http://www.youtube.com/watch?v=7ImvlS8PLIo

 

[Davros]

You missed out the force of "The" as in may "The" force be with you
and of course Gaming Goodness the most powerful force in the known universe

 

[nutball]

Have you ever seen any proof of deformation in space-time? How does that deformation make bodies attract? How "right"/valid is Wiki?

Hint: noone knows how it works or what happens there. It's all just guesswork so far, and until there is a sound foundation to one of those theories, I'm sticking to the classic definition, see Mize post above.

http://en.wikipedia.org/wiki/Gravitational_lens

 

[dskneo]

yea sorry about my post Davros. I know it falls apart in contrast to the knowledge already exhibited here...

Its just my notion that the universe already has all the energy it can have distributed between different forms and if any energy is to be added (creating more energy than the one being wasted) it has to come from outside this universe.

looking forward to the rest of the discussions, sorry about my input.

 

[dskneo]

http://en.wikipedia.org/wiki/Gravitational_lens

well you have yet another more complicated concept than that.... The famous picture of a galaxy behind a galaxy, in which the galaxy in front only has 30% of the mass necessary to warp light. So the rest of the energy must be dark matter (the code work for = we don't know what it is).

something like that. I forgot.

 

[Davros]

No idea why your apologizing to me dskneo

 

[London Geezer]

Gravity was discovered by Sir Isaac Newton. It is chiefly noticeable in the autumn, when the apples are falling off the trees.

 

[Albuquerque]

... in which the galaxy in front only has 30% of the mass necessary to warp light.

Gravity affects light, to what degree depends on how much gravity and how accurately you can measure. There's no specific mass required to bend light, planets can do it, even our moon can do it with measuring tools we currently have.

As for the question of deforming space -- everything works in theory Gravity is as much a force as it is a deformation, insomuch as they're both plausible explanations that both fit the observable world effects and neither have yet to be proven false. Is it a force? Is it a deformation of spacetime? Maybe that's the same damned thing for all we know.

Howabout less of the "zomg you can't prove that" and more of the topic at hand -- which is the absurdity of the initial claim