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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.
- 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.
- 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.
So if you are looking for gravitational influences, there is nothing special about "massive" objects more than "non-massive" ones like the Earth.
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.
Quote from: evan_au- 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.
- In their last few milliseconds, we have seen orbiting black holes (initially just kilometers apart) convert the mass of the Sun into gravitational waves.
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.
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 imperceptibleI 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.
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?
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.
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
Quote from: HalcA 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.
given that the reach of gravity is governed by the speed of gravity as it traverses the space between all objects.
if it is within the reach of gravity it is part of the energy that constitutes the field.
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.
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 .
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!
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.
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.
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
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.
Just to put in my two centsAs 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.