greendoor wrote:Grimer - I have taken on board your comments about Force being Stress. I do believe you are right - very interesting. And your idea about 'destroying' the force of gravity to create an unbalance has really switched on a light ... bear with me ...
Force is an alias for strain, not stress.
Force producing a linear acceleration is an alias for linear compressive strain.
Centrifugal Force is an alias for biaxial strain, area compressive strain'
Hydrostatic force is an alias for triaxial compressive strains.
Tensile strains are negations, i.e. reductions in external compressive force.
My view of gravity (for practical terrestrial machines) is that it is an Acceleration (i.e. can simulated on a rocket sled or rotating space station).
It is an acceleration, certainly, but not the same kind of acceleration you are envisaging.
Take the rotating space station as an example. That acceleration is applied to the external layer of a body. You feel the same in a rotating space station as you would walking on the earth. I'm assuming that the diameter of the station is as large as the diameter of the moon, say, so that you wouldn't get any feeling of giddiness which you might on a very small station.
The acceleration of gravity acts at a vastly different level. It acts on the very smallest of material particles within our body. As such we don't feel it anymore than a deep sea free diver feels the pressure of the water around him - as I explained previously. What didn't you understand?
How it works or why it exists doesn't really matter
Of course it matters. If we don't understand at which level of structure gravity is acting how on earth do you expect to conquer it. You can't kill viruses with antibiotics. Their action is at a totally different scale.
The Acceleration of gravity is (for our purposes) unlimited, moves with the mass it is accelerating, and does not change significantly with height. (You need extremely sensitive equipment to measure the changes - not relevant for a man-sized wheel).
Agreed.
If we raise a 1 kg mass up 10 meters from the ground, we can calculate the PE - and let it fall to the ground. Once on the ground, we could say it has zero PE. But say the 'ground' turned out to be a manhole over an abandoned mine - which suddenly opened up a 100 meter drop - then suddenly our mass has an unexpected increase in PE.
PE is a negative concept (cf. debt) with an arbitrary datum (cf. minus ten degrees Fahrenheit).
In reality - nothing has changed with the mass or it's position in space. So PE is just an abstraction - it does not represent a real 'thing'.
Agreed. It's just bookkeeping.
The point I'm making is that the 'Force of Gravity' is always acting on a mass at all times - it does not go away, and it doesn't really change (for practical purposes).
Absolutely correct.
We know that the Force of Gravity can Accelerate a Mass (because that's it's formal definition). But what happens to this force the rest of the time (because we know it never goes away...)?[
Nothing happens to it. It is in equilibrium with the force on your feet. Gravity is accelerating you down and the floor strain is accelerating you up.
Let me give you an example from sailing. Boats are easy to understand because the two fluids are not co-spatial but separated by a surface.
If you go down to a seaside town like Littlehampton when the tide is ebbing and the river current is therefore very strong you will see boats trying to sail into the harbour. The wind acting weakly on a large surface area is blowing the boat in. The water acting strongly on a much small surface area is carrying the boat out. The boat is stationary relative to the observer but accelerating relative to the wind and to the water.
I don't think I can constructively comment on the rest of your post until you have exorcised the notion of stress (force per unit area) and replaced it with the concept of natural strain.
