Well to quote Adams, Time is an illusion. Lunchtime doubly so.
Is Spacetime Real?
31–40 of 103 posts
Re: Is Spacetime Real?
#32Yes but you can warp space time with gravity according to Einstein. https://en.wikipedia.org/wiki/Spacetime But you need to warp space as in curve it. If you would fly close to a black hole space might be warped. https://www.space.com/1976-black-hole-puts-dent-space-time.h... You probably need to think of space in higher dimensions than three for example four dimensions.
I believe it's the other way around. Objects with mass warp spacetime, and the resulting curvature results in gravity. Everything not accelerating travels in straight lines, where straight lines are geodesics through spacetime. This is why gravity is not a real force, but the result of objects traveling through the curvature spacetime.
Re: Is Spacetime Real?
#33Earlier quoted context omitted.
While not a perfect definition of "real", don't we already have images of atoms?
We have devices that register electromagnetic radiation spectrum emitted (by ”atoms”) which can be visualized as an image. But this is at the heart of the parent comment: does the atom exist, or is it just a concept that describes the end result when strong interaction, electromagnetic force and gravity make particles stick together in a (usually) consistent way? If we call the atom real, we can call other aggregatio…
It isn't much of an argument. Everything we think of as "real" in the sense that you describe it is actually just a conceptual model we have for how certain patterns of energy in the universe behave. The universe has no special rules for apples, floors, wifi access points, cars, or basketballs.
Re: Is Spacetime Real?
#34Spacetime is a vector in Hilbert space.
Entanglement yields locality. Space emerges. I'm not convinced time is emergent, though (I give the idea low credence).
I'm not a scientist, I just listen to Sean Carroll's podcasts.
Re: Is Spacetime Real?
#35“What exactly is spacetime? Is it a real thing like an atom, or just a mathematical construct that is used to describe how mass 'generates' gravity?” This is a false dichotomy. Atoms too are "just" a mathematical construct used to describe how certain observable, physical systems behave. It's even called the atomic _theory_, and like all other good theories it knows its limits. At low enough energies, it's too fine a…
I disagree with you. Your argument could be made about anything, there is no such thing as a "human" either, it's just a big bunch of wave-particles that does not have some clear limits. Yet when we talk about a human, we all know what that is, and when a human is seating on a chair we don't think the chair is part of it. The same applies to atoms, we all agree on what they are, and we can show pictures of them etc.…
> The question here is whether spacetime is something like that, or if it is a proxy concept with no grounding whatsoever in the universe, but with good predictive powers?
I'd add: is it something one can develop an intuition for?
I don't think there is anyone who says gluons or general relativity are intuitive. You have to do the calculations (or memorize heuristics) to get something useful. Atoms, on the other hand, or electromagnetic radiation as another example, can be visualized (and mentally simulated) more or less correctly. (Note: atoms. Not nuclear mechanics.)
Re: Is Spacetime Real?
#36Earlier quoted context omitted.
I disagree with you. Your argument could be made about anything, there is no such thing as a "human" either, it's just a big bunch of wave-particles that does not have some clear limits. Yet when we talk about a human, we all know what that is, and when a human is seating on a chair we don't think the chair is part of it. The same applies to atoms, we all agree on what they are, and we can show pictures of them etc.…
"The same applies to atoms, we all agree on what they are, and we can show pictures of them etc." This is where you bury the lede. It's clear if you read many of the comments here that there is no such agreement. Some people _think_ of an atom as something you can reach out and touch, or grok in some deep sense distinct from performing specific experiments. Others take an approach that's more in line with theory in t…
> It's clear if you read many of the comments here that there is no such agreement
I guess I should have said "all experts agree" instead? Lack of knowledge about something by some people doesn't change the definition of that thing. I would add however, that you can reach out and touch an atom with a certain definition of touch (as touch is mostly a macroscopic concept).
> I'm certainly not claiming that atomic theory is a wild speculative guess which you seem to imply I've done.
You will have to explain this one to me then. You said "it's *even* called a theory" to reinforce your point that it was just a mathematical tool (and hence not real following your definition). This point is valid only if theory means guess, which it does not.
Re: Is Spacetime Real?
#37Earlier quoted context omitted.
> The question here is whether spacetime is something like that, or if it is a proxy concept with no grounding whatsoever in the universe, but with good predictive powers? Consider that "human", "chair", and "atom" are also just concepts are minds apply to certain patters of energy. We all "know what that is" because it is advantageous for our minds to place things in these categories for the purpose of modeling. You…
Right, and that was the point I was trying to make with the human analogy. So the question is whether spacetime is one of those patterns we can point to, like a "human" a "chair" or an "atom", which is what we call "real" in our everyday language, or whether it is only a useful modelization tool, like the Aether. There are no pattern anywhere in the universe matching the Aether. It is a valid question.
I'm saying the differentiation is meaningless. We have a model of space time that makes accurate and measurable predictions and that is as real as real gets.
Re: Is Spacetime Real?
#38Earlier quoted context omitted.
I disagree with you. Your argument could be made about anything, there is no such thing as a "human" either, it's just a big bunch of wave-particles that does not have some clear limits. Yet when we talk about a human, we all know what that is, and when a human is seating on a chair we don't think the chair is part of it. The same applies to atoms, we all agree on what they are, and we can show pictures of them etc.…
"The same applies to atoms, we all agree on what they are, and we can show pictures of them etc." This is where you bury the lede. It's clear if you read many of the comments here that there is no such agreement. Some people _think_ of an atom as something you can reach out and touch, or grok in some deep sense distinct from performing specific experiments. Others take an approach that's more in line with theory in t…
Theory is indeed separated into several disciplines, speaking about mathematization: Phenomenology, Model building, Mathematical Physics. FWIW I think Phenomenology is where a lot is going on, it's about looking what is there and how it compares to the models.
The fully formalized ("axiomatic") mathematical descriptions oftentimes lag behind the theoretical models ("postulated") in use that are used to compare with real data for instance.
That said, I would say Atoms are as real as it can get. There are so many experiments about them and applications as well, for instant nuclear fission. How can they not be real? :-) Speaking about Spacetime, of course it is real. There is such a crazy amount of predictions based on Special Relativity.
Re: Is Spacetime Real?
#39Spacetime is a vector in Hilbert space. Entanglement yields locality. Space emerges. I'm not convinced time is emergent, though (I give the idea low credence). I'm not a scientist, I just listen to Sean Carroll's podcasts.
> Entanglement yields locality
Could you please expand on that?
Re: Is Spacetime Real?
#40Earlier quoted context omitted.
Atoms aren’t just something we’ve modeled — they’re a physical thing , i.e. matter. We can sense them directly, not just infer their existence by measuring related phenomena. I realize when you get into theoretical physics the “thingness” of concepts becomes more and more abstract, but atoms don’t fall into that bucket.
>We can sense them directly What does this even mean? Unless you're talking about some supernatural "atomic sense", there's obviously no way to "sense them directly" - we sense them through their interaction with other things combined with our model of those things and the interaction.
Okay, that's fair. But taken to its extreme, we sense everything through its interaction with other things. But obviously, things exist; not everything can be just a mathematical model.