[Bogie_smiles (OP)]

By "massive objects" in this context, we are talking about neutron stars and black holes.
- In their last few milliseconds, we have seen orbiting black holes (initially just kilometers apart) convert the mass of the Sun into gravitational waves.

Yes. That would explain what they refer to as “chirping” at the end of the recorded gravitational wave, and would be consistent with the gravitational waves record by LIGO.

- Howevever, even the Earth on it's orbit for billions of years has been continuously radiating about 200W of gravitational waves. The mass is much smaller, and the distance is much greater. But this radiation is too subtle for us to measure using any currently conceivable method.

Yes, that would be consistent with my acknowledgement in the OP that even very tiny events would emit gravitational waves that are unmeasurable.

- It is thought that the Big Bang would have created gravitational waves at very high frequencies, and a team in China is actually searching for these "relic" gravitational waves.

Yes, that is some of the exciting research that is going on.

So if you are looking for gravitational influences, there is nothing special about "massive" objects more than "non-massive" ones like the Earth.

Agreed, it might take a billion apples falling to the ground to make a measurable impact when it comes to the emission of a meaningful detectible gravitational wave.

But my reason for going into the “apple falling” scenario was to work my way to discussing the  “cause of gravity”. That is the reason I went on to say, “… but it seems logical that there is a “mechanism” involved, and the ever-changing dynamic of gravitational wave energy in space must be related to it. I would refer to that mechanism as the “cause of gravity” and equate it to the acceleration of objects caused by other objects in space with mass that are in relative motion.

[evan_au]

I would refer to that mechanism as the “cause of gravity” and equate it to the acceleration of objects caused by other objects in space with mass that are in relative motion.

There is gravity between you and the Earth, even when there is no relative motion between you and the Earth.
- This gravity is sufficient to cause lethal injuries if you fell from a height of just 10 meters.
- However, if you add up all the gravitational wave influences from all the sources, that would probably amount to less than the impact of air molecules on your body - completely imperceptible

I conclude that the chorus of gravitational waves permeating the universe cannot be the cause of gravity - by many orders of magnitude.

Of course, I would not recommend being in close proximity to colliding black holes, as that would be really spoil your day.

[Halc]

- In their last few milliseconds, we have seen orbiting black holes (initially just kilometers apart) convert the mass of the Sun into gravitational waves.

Yes. That would explain what they refer to as “chirping” at the end of the recorded gravitational wave, and would be consistent with the gravitational waves record by LIGO.

The chirp is the high frequency of waves being detected as the masses get closer and closer and the orbital period drops to a lower and lower value.  A coin put into one of those big funnel collectors does a similar 'chirp' right at the end that ends abruptly as the coin falls through the 'event horizon' at the bottom.

But my reason for going into the “apple falling” scenario was to work my way to discussing the  “cause of gravity”. That is the reason I went on to say, “… but it seems logical that there is a “mechanism” involved, and the ever-changing dynamic of gravitational wave energy in space must be related to it. I would refer to that mechanism as the “cause of gravity” and equate it to the acceleration of objects caused by other objects in space with mass that are in relative motion.

I don't think you can get a 'cause of gravity' from the waves.  A big object has a powerful gravitational field, yet doesn't emit any gravity waves at all unless accelerated by something.  It could have a pair of objects orbiting on opposite sides, thus totally cancelling any acceleration of the big object at all, so if gravity waves are caused by acceleration, the big object should have no effect at all on the orbiting things.

[Bogie_smiles (OP)]

There is gravity between you and the Earth, even when there is no relative motion between you and the Earth.
- This gravity is sufficient to cause lethal injuries if you fell from a height of just 10 meters.
- However, if you add up all the gravitational wave influences from all the sources, that would probably amount to less than the impact of air molecules on your body - completely imperceptible

I conclude that the chorus of gravitational waves permeating the universe cannot be the cause of gravity - by many orders of magnitude.

Of course, I would not recommend being in close proximity to colliding black holes, as that would be really spoil your day.

Gravity exists even if there is no place for objects to go because the density of the ground or the tension of the surface they are resting on exceeds the local gravitational force. Never-the-less all mass still produces gravitational waves.

Because the equations for gravity have all been worked out, and because they boil down to the relative proximity and motion of objects with mass in space, gravity follows the mass around in the form of either relative motion, or a potential to cause relative motion.

The force of gravity is in the proximity of the surrounding massive objects, in accord with the equations that have been developed to quantify it. So isn’t it safe to say that the cause of gravity is in the relative mass of objects, their relative motion, and the potential for their masses to cause relative motion?

[Colin2B]

The force of gravity is in the proximity of the surrounding massive objects, in accord with the equations that have been developed to quantify it. So isn’t it safe to say that the cause of gravity is in the relative mass of objects, their relative motion, and the potential for their masses to cause relative motion?

We know that any form of energy bends spacetime and causes the effect we can measure as a gravitational field.
Mass is a very, very concentrated form of energy - there is a lot of energy locked up in it - so it bends spacetime more than any other form of energy. But it is the absolute masses  not the relative masses that determines the field.
Yes, the gravitational field at any point is the sum of the effects of all the masses and will change with their motion.
Short version 

[jeffreyH]

It has to be remembered that acceleration can be a change in speed, a change in direction or both. Both orbital and radial free fall cause acceleration and yet within a falling frame you would detect no gravitational radiation

[Bogie_smiles (OP)]

I don't think you can get a 'cause of gravity' from the waves.

What else is there in space occupied by a gravitational field besides the mass of the objects that are generating the field, and the gravitational waves emitted by the object/objects in the space that are within the reach of gravity of the object in question?

 
A big object has a powerful gravitational field, yet doesn't emit any gravity waves at all unless accelerated by something.

Let’s take that thought further. What constitutes the volume of space that the gravitational field occupies. It is the reach of gravity, from the massive object that is generating the gravitational field, and encompasses the full extent of the reach of the field in space, which evolves and expands at the speed of gravity and light, as the object moves relative to every other object in space. So every object in space is subject to acceleration caused by every other object in space; no matter how insignificant, and no matter how undetectable, no matter how far away, if it is within the reach of gravity it is part of the energy that constitutes the field. 

It could have a pair of objects orbiting on opposite sides, thus totally cancelling any acceleration of the big object at all, so if gravity waves are caused by acceleration, the big object should have no effect at all on the orbiting things.

I don’t want to agree to the cancelling of gravity on opposite sides because each to the objects on opposite sides have a different gravitational wave energy profile and by that I mean that the proximity of the all the mass surrounding each of the opposite objects is established by a different configuration of massive objects and so the fields will not be exactly the same.


We can say that they approximately cancel each other, but in science I think they want to be more precise, and they do not precisely cancel each other.

[Bogie_smiles (OP)]

It has to be remembered that acceleration can be a change in speed, a change in direction or both. Both orbital and radial free fall cause acceleration and yet within a falling frame you would detect no gravitational radiation

All frames are ultimately within the reach of all surrounding massive objects, given that the reach of gravity is governed by the speed of gravity as it traverses the space between all objects.

[Halc]

A big object has a powerful gravitational field, yet doesn't emit any gravity waves at all unless accelerated by something.

Let’s take that thought further. What constitutes the volume of space that the gravitational field occupies.

There is no edge to the field, so there is no meaningful volume to it.

It is the reach of gravity, from the massive object that is generating the gravitational field, and encompasses the full extent of the reach of the field in space, which evolves and expands at the speed of gravity and light, as the object moves relative to every other object in space.

given that the reach of gravity is governed by the speed of gravity as it traverses the space between all objects.

The field does not expand and there is no speed to it, and it doesn't evolve since the object in the example was just a stationary one.
An expanding field suggests that it is meaningful for this object to have suddenly 'switched-on' its gravity.  Conservation of mass would be violated by such a thing happening.

if it is within the reach of gravity it is part of the energy that constitutes the field.

A field by itself is not energy.  A rock in a field has (negative) potential energy since that sort of energy is a function of mass and depth of the field.  But no energy is represented by just the field itself.

It could have a pair of objects orbiting on opposite sides, thus totally cancelling any acceleration of the big object at all, so if gravity waves are caused by acceleration, the big object should have no effect at all on the orbiting things.

I don’t want to agree to the cancelling of gravity on opposite sides[/quote]I said cancelling the acceleration of the central object, not cancelling gravity of anything.

We can say that they approximately cancel each other, but in science I think they want to be more precise, and they do not precisely cancel each other.

They would precisely cancel the acceleration of the middle object.  Net force would be zero.

[Bogie_smiles (OP)]

Your response shows adequate disagreement between our definitions of various words and phrases to cause the thread to be moved to the Lighter Side, where it might be more appropriate to explore the precise definitions involved?

[jeffreyH]

All points in a gravitational field have a gravitational potential associated with them. This is not energy and the units for this potential are J/kg (joules per kilogram). The unit for energy is just the Joule. This is the same as the unit for work.

So the potential represents the amount of work required to get an object to a particular point in the gravitational field. This is why it is stated that an object gains potential energy by being moved to the point in the field. That is raised off the ground for instance.

This is an important distinction to remember .

[Bogie_smiles (OP)]

All points in a gravitational field have a gravitational potential associated with them. This is not energy and the units for this potential are J/kg (joules per kilogram). The unit for energy is just the Joule. This is the same as the unit for work.

So the potential represents the amount of work required to get an object to a particular point in the gravitational field. This is why it is stated that an object gains potential energy by being moved to the point in the field. That is raised off the ground for instance.

This is an important distinction to remember .

Perhaps the simplest definition of a gravitational filed would be this definition from a search for the term,
Gravitational field:
1) the field produced by the gravitational force of mass
2) a field of force surrounding a body of finite mass

----------------

The gravitational force of matter surrounds the finite mass that produces it. Matter is a very compact form energy that produces gravitational waves based on the fact that all matter in space is producing a gravitational force.

[Colin2B]

Matter is a very compact form energy that produces gravitational waves based on the fact that all matter in space is producing a gravitational force.

Mass/matter does not always produce gravitational waves, only when it is accelerating.

Not sure what you are trying to do here!

[Bogie_smiles (OP)]

Mass/matter does not always produce gravitational waves, only when it is accelerating.


Not sure what you are trying to do here!

It is easy to structure a “what if” like in Halc’s example of two masses on opposite sides of a central mass. He points out that if we had a universe composed only of one central mass and two orbiting masses on opposite sides of that central mass we could postulate that the accelerations of the opposite masses are equal but opposite.

 I want to distinguish between “what ifs” and what I view as reality. The acceleration of the opposite masses in that specific “what if” example would mathematically off set and could be said to cancel each other, but that specific “what if” deviates from reality. The greater universe is full of other massive objects, near and far, that all have an influence, to a greater or lesser extent, on all other masses. So the circumstance where mass/matter does not always produce gravitational waves is never true in reality, if we consider reality to involve the entire greater universe.

[Colin2B]

The greater universe is full of other massive objects, near and far, that all have an influence, to a greater or lesser extent, on all other masses. So the circumstance where mass/matter does not always produce gravitational waves is never true in reality, if we consider reality to involve the entire greater universe.

the key words here are “greater or lesser extent“.
The reality is that some masses are not going to contribute much to an effect which is already infinitesimal compared to the gravitational field. Even the effect of 2 accelerating pulsars is extremely hard to detect - not exactly a mover and shaker 

[Halc]

I want to distinguish between “what ifs” and what I view as reality. The acceleration of the opposite masses in that specific “what if” example would mathematically off set and could be said to cancel each other, but that specific “what if” deviates from reality. The greater universe is full of other massive objects, near and far, that all have an influence, to a greater or lesser extent, on all other masses. So the circumstance where mass/matter does not always produce gravitational waves is never true in reality, if we consider reality to involve the entire greater universe.

True.  I cannot think of a non-accelerating mass anywhere.  Earth for instance continuousluy puts out about 200 watts of energy in the form of gravity waves due to its acceleration.  The gravitational field due to Earth's mass on the other hand produces a force on the nearby moon, is 2e20 Newtons. Earth also exerts about 1800 times that force on the sun despite the sun being so much further away. I can't say that's a lot more than 200 watts since there is no comparing numbers in different units.  Power can be measured.  Gravity waves can be measured (such as is done by LIGO).  Gravity cannot be directly measured (there is no gravitometer), but a non-uniform gravitational field can be directly measured.

[Bogie_smiles (OP)]

The key words here are “greater or lesser extent“.


The reality is that some masses are not going to contribute much to an effect which is already infinitesimal compared to the gravitational field. Even the effect of 2 accelerating pulsars is extremely hard to detect - not exactly a mover and shaker 

When being practical, the fact is well taken that not all accelerations qualify as movers and shakers. But I am trying to ask, is all space filled with gravitational wave energy at all times? Aren’t there greater and lesser gravitational waves everywhere, coming and going in all directions, from a perpetual history of the relative motion of massive objects?

I want to say that space is filled with gravitational wave energy, and that would include the meaningful gravitational waves like those produced by in-swirling blackholes, as well as the infinitesimal, insignificant waves produced when an apple falls from the tree.

[Bogie_smiles (OP)]

True.  I cannot think of a non-accelerating mass anywhere.  Earth for instance continuously puts out about 200 watts of energy in the form of gravity waves due to its acceleration.  The gravitational field due to Earth's mass on the other hand produces a force on the nearby moon, is 2e20 Newtons. Earth also exerts about 1800 times that force on the sun despite the sun being so much further away. I can't say that's a lot more than 200 watts since there is no comparing numbers in different units.  Power can be measured.  Gravity waves can be measured (such as is done by LIGO).  Gravity cannot be directly measured (there is no gravimeter), but a non-uniform gravitational field can be directly measured.

True, and if we conclude, as I proposed in my last reply, that space is filled with gravitational wave energy, to a greater or lesser extent everywhere, from a perpetual history of the relative motion of massive objects, then that begins to explain why my philosophy supports the possibility of an infinite and eternal universe?

[yor_on]

Just to put in my two cents
As far as I remember both Newton and Einstein agreed on that anything moving at at tangent (aka in a circle) is 'accelerating' even when having a constant speed. So yes, Earth is constantly accelerating if we define it as orbiting the sun.

[Bogie_smiles (OP)]

Just to put in my two cents
As far as I remember both Newton and Einstein agreed on that anything moving at at tangent (aka in a circle) is 'accelerating' even when having a constant speed. So yes, Earth is constantly accelerating if we define it as orbiting the sun.

My impression is that the Earth is falling toward the sun at a constant rate of acceleration, but fortunately the Sun is also in motion, so by the time the Earth gets there, the sun has moved out of the way, lol. The result is that the Earth falls into orbit around the sun until something comes along to mess things up.