Recent content by bcl

I don't disagree with this. I just have a hard time with what it means, it's kind of abstract.

I often hear that a certain behavior of an animal is "hard wired". I get the analogy, but what does that really mean in the brain? What two things are "wired" together and what is the actual "wire"? If a dog runs after a squirrel (dogs are of course "hard wired" to chase squirrels), are his eyes...

Sorry I'm being tedious. I did not realize that you had to read and respond to all these.

Your right. Gronks would not help either. What helps me from this discussion is that spacetime is something fundamental. We don't necessarily know what it is, but it's something, and not nothing (like someone might think of the vacuum of space as). Therefore, I don't have to reconcile nothing...

Ooh, that's a very good point and very enlightening. At the most fundamental level, we don't know what matter or energy are, so why should we know what spacetime is? At the same time though, I'm thinking "that sucks, we actually don't know what anything is."

But Newtons theory is wrong, it's useful but not perfect. For example, it can't predict the orbit or Mercury. Newtons theory does not try to explain what gravity is. It just makes an approximation (usually a good one) of gravity. General relativity explains gravity more accurately and also "why"...

Okay, I actually do ask what matter and energy are. Matter can be described by its mass, which is E/c^2 (so mass is just a form energy). Energy is the ability to do work. I can picture an energy field and the work it does on some mass moving through it. But, your point is well taken. Perhaps...

That's a good point. I will have to contemplate the universe for a bit on that one.

I agree that it has a broader definition in mathematics. But its not just limited to a mathematical description. Its curvature has direct impacts on us, on reality (e.g., gravity).

Not necessarily. If it was made of something, it would be easier to envision it having some kind of form. Do physicists agree that it is made of something then? If not, I struggle with how we can assign shape (or curvature or flatness) to nothing.

jbrigg2444, Thanks, that's a great explanation of intrinsic and extrinsic curvature. The conceptual difficulty I have is that these explanations require matter to assign the geometry to. But the space I envision around, say a ball in deep space, is not matter, but still has shape, how? Even if I...

If spacetime isn't nothing, are there theories as to what it could be? It doesn't seem to be matter or anti-matter. It is some kind of energy or dark energy? If we create a deep vacuum we can watch sub atomic particles suddenly appear and disappear. Is that a clue at to what space can be, since...

So I understand that mass creates curvature in space-time. But what I struggle with is how nothing has a shape. I picture the space around say a planet, but how does the space (nothing) actual have form? Does anyone have a good intuitive explanation for that?

I’m studying large strain and deformation solid mechanics and I have a (seemingly) basic question on solution approaches. Is my interpretation below correct? The governing equation of momentum for solid mechanics can be solved using a total or updated Lagrangian approach. The updated...

Bathe (reference below) outlines the updated Lagrangian (UL) and total Lagrangian (TL) approaches using the second Piola Kirchhoff (PK2) stress. Others (i.e., Ji, et al. and Abaqus) define the UL and TL formulations in terms of the Kirchhoff or the Cauchy stress in rate form. This form requires...