I'll give it a go James ... see if this makes sense !primemignonite wrote:Something is wrong with my understanding of part of what "M" has allowed, compliments of Fletcher.
He instructs us that gravity is an ". . . acceleration field (NOT a force) . . ." !
As I understand it, when mass is not under the influence of gravity, it possesses 'inertial mass' of a certain quantity, this depending upon the quantity atoms of the material present. When that, the 'inertial mass', comes under the influence of gravity, it then possesses 'gravitational mass' which is added to the inertial. The first is absolutely constant when not in motion; the second varies according to the amount of pull applied to the mass by gravity when motionless.
With that understood and accepted as accurate (if so), I then ask, how can gravity not be 'a force' with respect to a mass, accelerated or not???
Could someone knowledgeable point out my error and address the question? Thank you.
James
Gravity is a gradient or field - it causes objects with mass to have motion towards each other, if unrestrained & free to do so - this motion translates to increased kinetic energy [energy of motion] as the separation distance closes & reduced gravitational potential energy - the sum of the two types of energy is always the same at any distance between start & finish.
A force is just something we can feel or measure that pushes or pulls something & it requires a mass x acceleration given to that mass - because we live in largely a material world then objects all have some mass so its intrinsic, inescapable & a common denominator common to everything - but we can theoretically escape the acceleration component of the dualopoly depending where the mass is located - so if a mass is way out in space it will have inertial mass but no acceleration acting on it [acceleration = change in velocity or direction] therefore the manifest force is zero [seems like an oxymoron statement] - so the force [the push or pull we feel or measure] is not dependant on the mass, intrinsic to everything material, but to the acceleration, in this case supplied by the field or gradient.
Further argument to gravity being a field lies with your description of inertial effects & I'll try to elucidate by example.
Move any object perpendicular to the earths surface [right angles to gravity acting vertically] & you need to apply a force or energy to that object to change its state of motion - but that object has inertial mass to overcome - so in order to move it sideways [without changing its gravitational potential] you have to be cognisant of the amount of its inertial mass N.B. inertia being its resistance to a change in its state of motion - so a larger mass to move sideways [forgetting about other frictional losses] requires more energy input or force to move a certain distance because that force has to overcome the inherent resistance to change in motion which is proportional to the mass of the object - in simple terms, larger mass requires more force or energy.
Now take the gravity example - we now have two unequal masses tethered in space but affected by the gravity field - we release them & they fall to earth - although their masses are different they both experience the exact same rate of acceleration - this is strange because it seems the field can automatically compensate for the right amount of acceleration required, even though two unequal masses are side by side etc - where it becomes even more interesting is that no extra force is required to overcome inertia of the different masses when falling in the gravity field [i.e. vertically] - but were you to introduce a sideways component of movement then suddenly the force required to move them laterally equally must be different for both of them [to allow for inertia when not moving with the field].
In summary bodies falling vertically in a gravity field experience no inertial effects in that the field automatically adjusts itself to guarantee the same rate of acceleration regardless of mass or inertia which is quite different from supplying a force to move something sideways or outside a gravitational field.
What can I conclude ? - that the gravitational force is the physical manifestation we measure or feel but because all things accelerate at the same rate [all else being equal] then gravity is an unusual field or gradient rather than a applied force per se.
P.S. the gravity field exists whether an object has mass or not - its just that there aren't too many examples of objects without mass & by definition if they don't have mass then they will not have any force associated with their motion - it may seem like a circular argument & perhaps it is - perhaps someone else can give another perspective that is clearer.
