What is time??

[OnlyMe]

I think you agreed with the fact that , gravity ( or force-field ) exists around a mass .

While gravity is modeled as a field and does represent a force between two objects, it is not accurate to call it a "force field". To do so you would first have to describe the mechanism through which gravity acts between two objects.

GR is currently our best explaintion of gravity and even GR does not really explain how mass and space interact such that space is curved, resulting in what we experience as gravity. It only says that they do and predicts the effect of the force between two objects.

While we can say that given two objects there is some gravitational force that exists between them, we cannot say that there is any "force" of gravity where only a single object is involved. We must have two objects whether they are galaxies, stars, planets or even particles. We cannot describe gravity as we currently experience it as a force field.

 

[hansda]

You mean the fictional device?
No mention.
The physics version?
I think you'll find that the velocity-dependence refers to fluid friction, which is covered in your "air-drag" comment.
From Wiki on Friction:

See the site : http://en.wikipedia.org/wiki/Force_field_(physics) .

I quote from the site :

" Some forces, including friction, air drag, and the magnetic force on a charged particle, depend on the particle's velocity as well as its position."

 

[hansda]

While gravity is modeled as a field and does represent a force between two objects, it is not accurate to call it a "force field". To do so you would first have to describe the mechanism through which gravity acts between two objects.

GR is currently our best explaintion of gravity and even GR does not really explain how mass and space interact such that space is curved, resulting in what we experience as gravity. It only says that they do and predicts the effect of the force between two objects.

While we can say that given two objects there is some gravitational force that exists between them, we cannot say that there is any "force" of gravity where only a single object is involved. We must have two objects whether they are galaxies, stars, planets or even particles. We cannot describe gravity as we currently experience it as a force field.

I have time-constraint now. I will explain it later .

 

[OnlyMe]

Consider it simply : force = mass * acceleration ; or force = inertia * acceleration . Doesnt inertia vary with rpm or speed ?

In the first case F=ma, the force would be the objects momentum. (Where you use acceleration instead of velocity the momentum would be increasing along with the object's velocity, proportionally to its rate of acceleration.) This is why I mentioned that momentum could be thought of as force and does involve a component of velocity. (It is confusing sometimes to continue to use speed rather than velocity. Velocity involves both a "speed" and a direction. Speed says noting about direction. Speed alone also says nothing about acceleration or the rate of acceleration.)

The second case does not make sense. F= inertia * acceleration, does not make sense, to me. Inertia is the object's resistance to a change in motion which can be called accelleration. I don't see how you can multiply an object's inertia by acceleration. Though an object's rate of acceleration is certainly affected by its inertia.

 

[Dywyddyr]

See the site : http://en.wikipedia.org/wiki/Force_field_(physics) .

I quote from the site :

" Some forces, including friction, air drag, and the magnetic force on a charged particle, depend on the particle's velocity as well as its position."

Yes, and I covered that.

 

[AlexG]

Hansda misuses terms and concepts.

 

[OnlyMe]

Hansda misuses terms and concepts.

Yes. So do I, but I don't think I do as often as he seems to.

 

[origin]

Hansda, am I correct in assuming that you have never taken a physics course?

You seem to be having trouble understanding some extremely fundamental physics concepts. If you find physics interesting I would suggest taking a course in it.

 

[hansda]

The resistive force you refer to relative to precession, is inertia or momentum?

This resistive-force will depend on the rotational-inertia or moment-of-inertia . Moment-of-inertia depends upon the speed or rpm of the gyro . Thus , the speed or rpm of the gyro has some contribution to the resistive force for gyro-precession .

 

[hansda]

The second case does not make sense. F= inertia * acceleration, does not make sense, to me. Inertia is the object's resistance to a change in motion which can be called accelleration. I don't see how you can multiply an object's inertia by acceleration. Though an object's rate of acceleration is certainly affected by its inertia.

The rotaional-inertia of the object is dependant upon its speed of rotaion or rpm .

 

[James R]

No it isn't.

Try google.

 

[wellwisher]

Space and time are mental constructs. We often use x,y,z,t coordinates, but we can also use a spherical coordinate system composed of r, angle, angle, t. If space-time is curved the spherical coordinate system makes more sense since it too is curved.

Say we did use the spherical coordinate system, what special significance would the angles have in relativity? It is all mental construct, so we would eventually see and define a special significance that we would try to institute as though it was real.

If we were to travel into a black hole only r will change with time. The two angles would only change if we started to spiral or orbit. Does that means the angles have an orbital significance in space-time?

This is not really anything, but we could make a mental construct thst adds secial significance. I think it important to separate construct from reality, with space-time a construct in x,y,z,t.

T explain time in terms of reality and not construct of the imagination, we need to take all the tangible physics phenomena. Next we stop time so see what changes. Times is the potential that makes up the difference. This is solid and as has less imaginary construct to make other things work like we wish. It does not matter which coordinate system you use at this point.

 

[Dywyddyr]

Space and time are mental constructs.

No they aren't.

If space-time is curved the spherical coordinate system makes more sense since it too is curved.

Nonsense.
We can use whatever coordinate system is easier or most practical to use. And it's not curved on human scale.

Say we did use the spherical coordinate system, what special significance would the angles have in relativity? It is all mental construct, so we would eventually see and define a special significance that we would try to institute as though it was real.

If we were to travel into a black hole only r will change with time. The two angles would only change if we started to spiral or orbit. Does that means the angles have an orbital significance in space-time?

This is not really anything, but we could make a mental construct thst adds secial significance. I think it important to separate construct from reality, with space-time a construct in x,y,z,t.

T explain time in terms of reality and not construct of the imagination, we need to take all the tangible physics phenomena. Next we stop time so see what changes. Times is the potential that makes up the difference. This is solid and as has less imaginary construct to make other things work like we wish. It does not matter which coordinate system you use at this point.

More word salad.

 

[wellwisher]

That was intelligent. Dyridder can't rise above to show his smarts. Instead he tries to put the other person in the hole of his own creation to create an illusion of rising. If you believe in relative reference this will fool you. But if you do an energy balance insults are cheap and have little energy value. It takes away from the discussion so he can dig his hole.

 

[Dywyddyr]

More intelligent than your posts. Any of them.
Still incapable of doing anything but make unsupported statements?

There is no "discussion" until you start supplying reasoning as opposed to (false) pronunciations.

 

[hansda]

While gravity is modeled as a field and does represent a force between two objects, it is not accurate to call it a "force field". To do so you would first have to describe the mechanism through which gravity acts between two objects.

Newton discovered gravity . As per Newton , two mass attracts each other . If a question is asked as to ; " why two mass attracts each other ? " What can be the answer for this question .

GR is currently our best explaintion of gravity

I am not denying this .

and even GR does not really explain how mass and space interact such that space is curved, resulting in what we experience as gravity.

So, GR has some limitaions .

It only says that they do and predicts the effect of the force between two objects.

Actually a mass does not interact with space to cause, curvature of space to generate force . BUT , the mass interacts with space-time , to cause curvature of space-time . This curvature of space-time generates force .

While we can say that given two objects there is some gravitational force that exists between them, we cannot say that there is any "force" of gravity where only a single object is involved.

when there is single object , there is no 'force' but 'force-field' .

We must have two objects whether they are galaxies, stars, planets or even particles.

It is true , for a 'force' to exists ; at least two objects are required .

We cannot describe gravity as we currently experience it as a force field.

Gravity is not exactly the force-field ; but 'gravity' can be explained in terms of 'force-field .

 

[hansda]

No it isn't.

Try google.

Rotational-inertia has some factors . RPM is one of them .

 

[James R]

hansda:

You continue to insist on something that is false, even after being corrected.

Please provide at least ONE link to a reputable site that supports your claim that rotational inertia has "some factors", one of which is "RPM".

Or else, retract your false claim.

P.S. Did you actually try googling "rotational inertia"? If not, you should. It will save you some time.

 

[hansda]

hansda:

You continue to insist on something that is false, even after being corrected.

Please provide at least ONE link to a reputable site that supports your claim that rotational inertia has "some factors", one of which is "RPM".

Or else, retract your false claim.

P.S. Did you actually try googling "rotational inertia"? If not, you should. It will save you some time.

OK. You are right . Technically , you are right in the sense that ; torque = rotational-inertia * angular-acceleration . Here rotaional-inertia depends upon mass and geometry of the object and not upon rpm . So, you are right .

But, what i am trying to explain is that ; consider a case , where a mass is spinning at some rpm and a linear force is applied to the mass . In this case , the spinning mass will offer some resistance for change to the applied force . This resistance for change , of the spinning mass will depend upon its rpm .

 

[Pincho Paxton]

OK. You are right . Technically , you are right in the sense that ; torque = rotational-inertia * angular-acceleration . Here rotaional-inertia depends upon mass and geometry of the object and not upon rpm . So, you are right .

But, what i am trying to explain is that ; consider a case , where a mass is spinning at some rpm and a linear force is applied to the mass . In this case , the spinning mass will offer some resistance for change to the applied force . This resistance for change , of the spinning mass will depend upon its rpm .

You are thinking at our scale. At the quantum scale rotational inertia works differently. For example, when two things at our scale bump together, at the quantum scale there is a gap between the two objects. This is explained in science by the electromagnetic resistance that bumps the two objects apart (I only partly agree with this, there is more to it). Unfortunately I can't explain further in a science forum. Having said that, you have some of the correct ideas, just slightly the wrong mechanical interactions. What you have to remember is that time is the cause of the rpm, and not the effect of it.