Appeal to authority

[polymath257]

At work.

In transports of delight.

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Newton was not formulating his works aout 'Something outside' of anything.

Right -- I hope my spatial metaphor wasn't misleading. He certainly didn't go to work thinking his goal was to find something outside of the real world, or outside of science. 

It's just that his work ended up re-drawing the boundaries as to what science addresses, and what it considers to be a success.

Another analogy might be an ancient Greek scholar giving a dissertation about the winds and predictive, developmental theorys pertaining to hurricanes.

This is an excellent analogy, because it points up the differences between Aristotelian metaphysics and what came later. 

Weather happens through more or less materialist/mechanical causes. Masses of air push each other, and the movement of air has force enough to send the leaves flying when it bumps into them. It was axiomatic for pre-Newtonian science that for something to impart motion to something else, it required physical contact. The leaves needed a push from the wind. Although alchemists posited no-contact influence called "action at a distance," Galileo and other serious scientists rejected the idea. Spooky no-contact influence was too counterintuitive. 

Newton's success was to quantify the behavior of gravity in the complete absence of understanding how it did what it did. The Aristotelians would have considered this a failure, since it left out the part they wanted to explain -- why the affected object has motion imparted to it in the absence of contact. This is still unexplained. (But see my response to polymath, below.)

More specifically, Aristotle claimed that *every* change required a force. So, motion required a continuing force to keep the object moving. One of the BIG splits once Galileo and Newton came on the scene is that motion itself (uniformn, that is) didn't require a force. it was *change* in motion that requires a force.

I'd point out that the more modern view has gone away from the Newtonian 'action at a distance' formulation. Now, all forces are carried by 'fields' that interact with object to affect their motion.

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In part, I *define* it [the real world] by what can be verified through the scientific method.

Good. This is a bold and clear metaphysical statement. It seems problematic to me, but certainly it's sufficient for getting through the day, and getting your car to start. 

I'd point out that Einstein described gravity as a curvature of spacetime, which is a dynamical entity in his viewpoint. So, in that sense, we *do* have a description of what gravity is. But, I will also say that any *fundamental* description of the real world (or anything else for that matter) *has* to be 'just so': anything other than that would be a deeper description.

Now I am no expert on this, so I hope you'll fill me in if I'm missing something big. 

But it seems to me that the concept of curved space is a way to explain better the behavior and trajectories of objects under the influence of gravity. It shows why a moon being pulled by gravity won't necessarily proceed in a line that is straight from the observer's point of view.

However, it still doesn't explain why the moon is attracted by the body with greater mass in the first place. And this is the question, to me. 

Curved space explains the curved trajectory of the moon, but not why the moon is pulled in the first place. Why doesn't it stand still, or move away from the object with greater mass? Is there some way in which the concept of curved space explains this?

Well, there is another aspect of Einstein's equations. This relates the amount of matter and energy is a region to the degree of curvature of spacetime in that region. So, mass curves spacetime and the curvature of spacetime affects the motion of other things in the region: that is gravity.


The details are probably irrelevant here, but the basic equation relates, on one side, an expression concerning the curvature of spactime and on the other side an expression describing the density of mass, energy, momentum, and stress. The geometry of spacetime, in turn, provides the notion of  a geodesic, which is the type of path that things move along if there are no other forces on them (like electromagnetism).

At best, it helps us to formulate our *opinions* (unjustified beliefs) and gives us things to investigate.

I'd say that good philosophy provides lots of justification for our opinions, even when they are not ultimately provable one way or another. In fact I think that you could write down a number of philosophical justifications for your metaphysical opinion that the real world is disclosed to us through the scientific method. Surely you don't want to say you have NO justifications for that belief.

Well, if solipsism is true, then all of my sensory information is false. Which is why I *define* the real world via the scientific method applied to sense data. It means that even in the cse of solipsism I can still look for patterns in my sense data, make predictions, and test to see if those patterns continue to hold.

And, of course, because of the basic problem of induction, I cannot know that the patterns I have seen up to now will continue to hold. But they do allow me to drive my car to work.
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