Forces emit energy outward, in one level of strength, they don’t adjust their strength at all,
Nothing to do, so I'll try to clarify a point. Just one, so there will be some chance that turbonium will have the patience to read me thoroughly.
If I press a book against a wall, the book does NOT go through the wall, no matter how great my force. Because the wall DOES adjust the level of strength with which it reacts to mine.
But let's forget about this and suppose that gravity IS indeed the only kind of force which adjusts its level of strength.
Why this? Why do all objects fall at the same rate (in vacuum, in a certain location)?
This is a FULLY LEGITIMATE question, and physicists have posed it for centuries.
They did careful experiments to see whether this was true for substances with a different protons/neutrons ratio.
(then came Einstein who gave a nice answer, with GR, but let's forget about this for now)
But
(please read carefully, this is the main point)
we have a FACT: things fall at the same rate.
If we do NOT know WHY this happens, this does NOT make the fact go away.
People often think that science is about finding causes, and if it cannot do it, then it's a failure.
But physics, especially fundamental physics, is NOT about causes. It's about finding RULES.
The rules according to which things happen.
Newton's Law is such a rule. Once thought to be exact, now only approximate (a very good approximation though, except around black holes or such stuff)
It helps us to describe how the “rate of falling” varies slightly, on Earth, with latitude and altitude. And how it varies greatly from near Earth to Moon's distance to near Jupiter. And many other things.
turbonium is totally free to propose another set of rules, but they have to predict/describe the same range of phenomena (and possibly some more)
For now, his “density rule” can predict that denser bodies go down in a less dense medium, and less dense bodies go up. Really not much.
And HOW can we know that a body is denser or less dense? Why, from its going DOWN or UP!
That is, “things go the way they go because that's the way they have to go”!
Very zen, but hardly useful.
What we need is a set of rules according to which, if we put on a plate of a scale a cubic inch of lead and on the other plate a bottle with half a liter of water, the lead (denser) goes UP, and the water (less dense) DOWN. But if we make the arm of the 1st plate 4 times long as the 2nd, then it's the lead to go down!
We NEED such rules, to build cranes, bridges etc.
Can turbonium give such a rule, based only on density? No need to take the trouble, I can do it for him.
Rule (“density rule”): on every object near Earth's surface acts a downward force given by:
F = g*V(D – DM) (of course, if D < DM, F is < 0, that is, directed upwards)
where V is the volume of the object, D its density, DM the density of the surrounding medium (for vacuum, DM = 0), g a number whose average value is 9.81 and which, mysteriously, varies a little with latitude and altitude, and greatly in space. Unlike with Newton's Law, we have here no means to predict its variations.
And if we want the downward acceleration (the “rate of falling”) we must divide by V*D and get (in vacuum, with DM = 0) just g
And we have this mysterious, magical phenomenon. Given a certain quantity of matter, if we vary its density (e.g. water freezing or ice melting) the “rate of falling” stays the same. Objects of different D, or V, or both, all have the same “rate of falling” (in vacuum, in a certain location).
Conclusion: as to equality of the “rate of falling” Newton's Law or this “density rule” are equally mysterious. With Newton's Law having the advantage of predicting the variations of g.
Or maybe I haven't been smart enough in formulating this “density rule”?