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Is Spacetime Real?

forbes.com

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Re: Is Spacetime Real?

#11

Post by jakelazaroff »

thisiscorrect wrote: post #8
ncann wrote: post #6

Earlier quoted context omitted.

While not a perfect definition of "real", don't we already have images of atoms?

We do. Thinking a bit about what that means, we have photographs showing how the physical entity we model as atoms interact with light, and can confirm that the theory lines up with experiment. If we adopt that same definition for spacetime, we also have photographs of it, e.g. https://en.wikipedia.org/wiki/Solar_eclipse_of_May_29,_1919#... and https://en.wikipedia.org/wiki/Gravitational_lens#Gallery .

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.

Re: Is Spacetime Real?

#13

Post by enkid »

codeulike wrote: post #10
thisiscorrect wrote: post #5

“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 dont agree its a false dichotomy. Yes every theory is just a model to fit observations etc etc. But Atoms are conceivable - they work as a model, but we can also imagine how to fit into the reality that we experience. We can 'see' them to an extent with special instruments. And their abilities/behaviours are evident in all the physical world of compounds and elements around us. You can disolve salt in water, you ca…

Our ability to conceive of something should not be in the definition of reality. Quantum mechanics and relativity have just as much, if not more experimental evidence to support them as atomic theory, and make even better predictions. This has implications in the "real world." If we base our definition on what is "intuitive" instead of what is provable, we end up with things like humour theory in medicine.

Re: Is Spacetime Real?

#14

Post by thisiscorrect »

codeulike wrote: post #10
thisiscorrect wrote: post #5

“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 dont agree its a false dichotomy. Yes every theory is just a model to fit observations etc etc. But Atoms are conceivable - they work as a model, but we can also imagine how to fit into the reality that we experience. We can 'see' them to an extent with special instruments. And their abilities/behaviours are evident in all the physical world of compounds and elements around us. You can disolve salt in water, you ca…

"But Atoms are conceivable - they work as a model, but we can also imagine how to fit into the reality that we experience."

"Quantum Mechanics is a model that fits experiment results very well, but is very hard to conceive of."

These two statements stand in contradiction. Atoms only work as a model if quantum mechanics holds. In a non-quantum world, electrons collapse into a nucleus, shedding electromagnetic radiation and lowering their energy as they do so. That's also necessary to understand why neon signs have their colors.

More broadly, if you want to compare one scientific theory to another and contrast their "realness" you have to take quantum mechanics along with your atomic theory.

Re: Is Spacetime Real?

#15

Post by ordu »

ncann wrote: post #6
thisiscorrect wrote: post #5

“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…

While not a perfect definition of "real", don't we already have images of atoms?

Those images, as I understand, constructed by heavy calculations based on a theory of atoms. Isn't it? So it is arguable that images are not "real", they are visualizations of a data.

At the same time not every real image is real. We could sometimes see two Suns in the sky, or we can see a rainbow, but it doesn't mean that the second Sun and the rainbow are real.

Re: Is Spacetime Real?

#16

Post by enkid »

jakelazaroff wrote: post #11
thisiscorrect wrote: post #8

Earlier quoted context omitted.

We do. Thinking a bit about what that means, we have photographs showing how the physical entity we model as atoms interact with light, and can confirm that the theory lines up with experiment. If we adopt that same definition for spacetime, we also have photographs of it, e.g. https://en.wikipedia.org/wiki/Solar_eclipse_of_May_29,_1919#... and https://en.wikipedia.org/wiki/Gravitational_lens#Gallery .

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.

I don't see the distinction you're making between "sensing" and "measuring related phenomena." What's different from using a specialized microscope to take a picture of an atom and using a telescope to take a picture of black hole?

Re: Is Spacetime Real?

#17

Post by bobcostas55 »

jakelazaroff wrote: post #11
thisiscorrect wrote: post #8

Earlier quoted context omitted.

We do. Thinking a bit about what that means, we have photographs showing how the physical entity we model as atoms interact with light, and can confirm that the theory lines up with experiment. If we adopt that same definition for spacetime, we also have photographs of it, e.g. https://en.wikipedia.org/wiki/Solar_eclipse_of_May_29,_1919#... and https://en.wikipedia.org/wiki/Gravitational_lens#Gallery .

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.

Re: Is Spacetime Real?

#18

Post by mhh__ »

ncann wrote: post #6
thisiscorrect wrote: post #5

“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…

While not a perfect definition of "real", don't we already have images of atoms?

We have images of black holes merging too.

Re: Is Spacetime Real?

#19

Post by thisiscorrect »

jakelazaroff wrote: post #11
thisiscorrect wrote: post #8

Earlier quoted context omitted.

We do. Thinking a bit about what that means, we have photographs showing how the physical entity we model as atoms interact with light, and can confirm that the theory lines up with experiment. If we adopt that same definition for spacetime, we also have photographs of it, e.g. https://en.wikipedia.org/wiki/Solar_eclipse_of_May_29,_1919#... and https://en.wikipedia.org/wiki/Gravitational_lens#Gallery .

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.

You sense spacetime directly too. It's what holds you do this planet we inhabit.

I think atomic phenomena may feel somehow more familiar because it takes far less energy to make them dynamic than it does for gravitational phenomena. If we were somehow huge beings made of binary stars or something, gravity would probably be the very familiar force and atomic phenomena almost inconceivably small to you.

Re: Is Spacetime Real?

#20

Post by yes_man »

ncann wrote: post #6
thisiscorrect wrote: post #5

“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…

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 aggregations like the economy or game theory real as well. But they are just concepts
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