Is Spacetime Real?

[Nakosis]

But despite all the things that spacetime enables us to predict and know, it isn’t real in the same way that an atom is real. There’s nothing you can do to “detect” spacetime directly; you can only detect the individual quanta of matter and energy that exist within your spacetime. We’ve found a description of spacetime in the form of Einstein’s General Relativity that can successfully predict and explain every physical phenomenon we’ve ever observed or measured, but as far as exactly what it is — and whether it’s “real” or not — that’s not a question that science has yet discovered the answer to.
Spacetime: is it real and physical, or just a calculational tool?

I tend to think of it a simply a "calculation tool". We can use it to successfully predict the behavior of physical objects but we can't actually detect/measure spacetime independently of physical objects. For example what is space except a distance measure between to objects?

Do you believe spacetime is real? And, what makes it real?

 

[Clizby Wampuscat]

But despite all the things that spacetime enables us to predict and know, it isn’t real in the same way that an atom is real. There’s nothing you can do to “detect” spacetime directly; you can only detect the individual quanta of matter and energy that exist within your spacetime. We’ve found a description of spacetime in the form of Einstein’s General Relativity that can successfully predict and explain every physical phenomenon we’ve ever observed or measured, but as far as exactly what it is — and whether it’s “real” or not — that’s not a question that science has yet discovered the answer to.
Spacetime: is it real and physical, or just a calculational tool?

I tend to think of it a simply a "calculation tool". We can use it to successfully predict the behavior of physical objects but we can't actually detect/measure spacetime independently of physical objects. For example what is space except a distance measure between to objects?

Do you believe spacetime is real? And, what makes it real?

I think it is real in a sense that it explains our universe. Without space and time wrapped together gravity would not exist or the speed of light would not be constant etc. It describes real phenomena that we can measure. I read that some have hypothesized that spacetime comes in small packets, there is a quantity of spacetime that cannot be broken up into smaller amounts. I don't know why they think that may be the case.

 

[Nakosis]

I think it is real in a sense that it explains our universe. Without space and time wrapped together gravity would not exist or the speed of light would not be constant etc. It describes real phenomena that we can measure. I read that some have hypothesized that spacetime comes in small packets, there is a quantity of spacetime that cannot be broken up into smaller amounts. I don't know why they think that may be the case.

I've read something about fragmenting spacetime. Beyond my understanding atm.
Currently, spacetime doesn't fit my definition of real. Maybe that will change if/when I understand it better.

 

[Clizby Wampuscat]

I've read something about fragmenting spacetime. Beyond my understanding atm.
Currently, spacetime doesn't fit my definition of real. Maybe that will change if/when I understand it better.

Yeah, I just read stuff and try to understand. Gravity fascinates me, trying to understand it.

 

[beenherebeforeagain]

Isn't space-time where the quantum foam exists?

From Wikipedia:

Quantum foam or spacetime foam is a theoretical quantum fluctuation of spacetime on very small scales due to quantum mechanics. The theory predicts that at these small scales, particles of matter and antimatter are constantly created and destroyed. These subatomic objects are called virtual particles.[1] The idea was devised by John Wheeler in 1955.[2][3]

Background​

With an incomplete theory of quantum gravity, it is impossible to be certain what spacetime would look like at small scales. However, there is no definitive reason that spacetime needs to be fundamentally smooth. It is possible that instead, in a quantum theory of gravity, spacetime would consist of many small, ever-changing regions in which space and time are not definite, but fluctuate in a foam-like manner.[4]

Wheeler suggested that the uncertainty principle might imply that over sufficiently small distances and sufficiently brief intervals of time, the "very geometry of spacetime fluctuates".[5] These fluctuations could be large enough to cause significant departures from the smooth spacetime seen at macroscopic scales, giving spacetime a "foamy" character.

 

[The Sum of Awe]

But despite all the things that spacetime enables us to predict and know, it isn’t real in the same way that an atom is real. There’s nothing you can do to “detect” spacetime directly; you can only detect the individual quanta of matter and energy that exist within your spacetime. We’ve found a description of spacetime in the form of Einstein’s General Relativity that can successfully predict and explain every physical phenomenon we’ve ever observed or measured, but as far as exactly what it is — and whether it’s “real” or not — that’s not a question that science has yet discovered the answer to.
Spacetime: is it real and physical, or just a calculational tool?

I tend to think of it a simply a "calculation tool". We can use it to successfully predict the behavior of physical objects but we can't actually detect/measure spacetime independently of physical objects. For example what is space except a distance measure between to objects?

Do you believe spacetime is real? And, what makes it real?

It's very real, in the same way that gravity is real, and the same way that 'width or length or height' are real, or numbers. Spacetime is a physical law and constant, its effects on matter and energy are what make it real.

EDIT: Just to clarify, I think matter and energy have an effect on spacetime more than vice versa. But regardless the effects are measurable. Space is distance and time is duration.

 

[Nakosis]

It's very real, in the same way that gravity is real, and the same way that 'width or length or height' are real, or numbers. Spacetime is a physical law and constant, its effects on matter and energy are what make it real.

EDIT: Just to clarify, I think matter and energy have an effect on spacetime more than vice versa. But regardless the effects are measurable. Space is distance and time is duration.

If it effects physical objects it is real of course. How do we know though it is actually affecting physical objects vs simply predicting their behavior?

 

[The Sum of Awe]

If it effects physical objects it is real of course. How do we know though it is actually affecting physical objects vs simply predicting their behavior?

By predicting their behavior does that include measuring their behavior? I think spacetime mostly does that. I don't see why that makes it any less real though.

 

[Stevicus]

But despite all the things that spacetime enables us to predict and know, it isn’t real in the same way that an atom is real. There’s nothing you can do to “detect” spacetime directly; you can only detect the individual quanta of matter and energy that exist within your spacetime. We’ve found a description of spacetime in the form of Einstein’s General Relativity that can successfully predict and explain every physical phenomenon we’ve ever observed or measured, but as far as exactly what it is — and whether it’s “real” or not — that’s not a question that science has yet discovered the answer to.
Spacetime: is it real and physical, or just a calculational tool?

I tend to think of it a simply a "calculation tool". We can use it to successfully predict the behavior of physical objects but we can't actually detect/measure spacetime independently of physical objects. For example what is space except a distance measure between to objects?

Do you believe spacetime is real? And, what makes it real?

The article made an interesting analogy in comparing spacetime to a stage, with the "actors" being the observable universe. The universe itself is real, and if spacetime is the place in which the universe exists and continues to move, then I suppose it's as "real" as anything.

 

[RestlessSoul]

If space and time themselves are quantised, and the consensus appears to be that they are, then they are as real as any material phenomena. But how real is that?

A more productive question might be, are space and time fundamental or emergent?

 

[Twilight Hue]

But despite all the things that spacetime enables us to predict and know, it isn’t real in the same way that an atom is real. There’s nothing you can do to “detect” spacetime directly; you can only detect the individual quanta of matter and energy that exist within your spacetime. We’ve found a description of spacetime in the form of Einstein’s General Relativity that can successfully predict and explain every physical phenomenon we’ve ever observed or measured, but as far as exactly what it is — and whether it’s “real” or not — that’s not a question that science has yet discovered the answer to.
Spacetime: is it real and physical, or just a calculational tool?

I tend to think of it a simply a "calculation tool". We can use it to successfully predict the behavior of physical objects but we can't actually detect/measure spacetime independently of physical objects. For example what is space except a distance measure between to objects?

Do you believe spacetime is real? And, what makes it real?

It's only real if it can be demonstrated.

 

[ChristineM]

Do you believe spacetime is real?

No. It doesn't claim to be real

But, without it we'd be in a hell of mess.

 

[RestlessSoul]

The article made an interesting analogy in comparing spacetime to a stage, with the "actors" being the observable universe. The universe itself is real, and if spacetime is the place in which the universe exists and continues to move, then I suppose it's as "real" as anything.

The concept of spacetime as the dimensions of the stage on which objects and forces enact their dramas, belongs to classical Newtonian physics. In redefining gravity as the distortion of spacetime in proximity to massive objects, General Relativity superseded that concept. Whether the fabric of spacetime is physically real, or a geometric abstraction which nevertheless allows accurate predictions, is as yet undecided.

 

[Bear Wild]

But despite all the things that spacetime enables us to predict and know, it isn’t real in the same way that an atom is real. There’s nothing you can do to “detect” spacetime directly; you can only detect the individual quanta of matter and energy that exist within your spacetime. We’ve found a description of spacetime in the form of Einstein’s General Relativity that can successfully predict and explain every physical phenomenon we’ve ever observed or measured, but as far as exactly what it is — and whether it’s “real” or not — that’s not a question that science has yet discovered the answer to.
Spacetime: is it real and physical, or just a calculational tool?

I tend to think of it a simply a "calculation tool". We can use it to successfully predict the behavior of physical objects but we can't actually detect/measure spacetime independently of physical objects. For example what is space except a distance measure between to objects?

Do you believe spacetime is real? And, what makes it real?

Can space and time be truly separated in the real world? Do they actually exist independently?

 

[Stevicus]

The concept of spacetime as the dimensions of the stage on which objects and forces enact their dramas, belongs to classical Newtonian physics. In redefining gravity as the distortion of spacetime in proximity to massive objects, General Relativity superseded that concept. Whether the fabric of spacetime is physically real, or a geometric abstraction which nevertheless allows accurate predictions, is as yet undecided.

It's sometimes hard to get my head around the concept, since everything is in motion. Everything is going somewhere, taking up space and a measurable duration to get from point A to point B. I never could understand the concept of space having a "fabric," though. It seems to me that it would have to be empty, otherwise there'd be no place for all these galaxies and star systems in motion to actually go. And it's hard to make any real objective measurements since we're also part of the process, just going along for the ride, at 67,000 mph. And time...well, time just keeps slippin', slippin', slippin' into the future.

 

[RestlessSoul]

Can space and time be truly separated in the real world? Do they actually exist independently?

If we take a holistic view of the universe, we can ask, does anything exist independently of anything, or indeed everything else? In a sense, all distinctions are arbitrary; between space and time, mass and energy, object and observer, past, present and future, etc.

 

[RestlessSoul]

It's sometimes hard to get my head around the concept, since everything is in motion. Everything is going somewhere, taking up space and a measurable duration to get from point A to point B. I never could understand the concept of space having a "fabric," though. It seems to me that it would have to be empty, otherwise there'd be no place for all these galaxies and star systems in motion to actually go. And it's hard to make any real objective measurements since we're also part of the process, just going along for the ride, at 67,000 mph. And time...well, time just keeps slippin', slippin', slippin' into the future.

Yep, everything is relative. There is no privileged, fixed point, from which to observe neutrally, the restless shifting of the universe. Facts about time and space are never absolute, they depend upon a frame of reference which is unique to each observer. That time passes slower the closer we are to massive objects, is something that GR predicts, and which has now been tested and observed.

 

[Pete in Panama]

Yep, everything is relative. There is no privileged, fixed point, from which to observe neutrally, the restless shifting of the universe. Facts about time and space are never absolute, they depend upon a frame of reference which is unique to each observer. That time passes slower the closer we are to massive objects, is something that GR predicts, and which has now been tested and observed.

--and we have yet to reconcile some of the particulars of general relativity w/ those of quantum mechanics, but that's ok because both QM and GR are handy models until something better comes along. Meanwhile my thinking is that there IS in fact a "privileged, fixed point, from which to observe" and that's ourselves. I know that I'm observing because whenever I wonder if I exist I just ask for whoever is doing the wondering: me.

So once I know that I exist I can then go on to intuitively grasp that others exist (albeit somewhat shake ground there) but when we get into particulars like "spacetime" we're dealing (perhaps completely) w/ mere models of what appears to be happening. OK, so the models may be wrong somehow but they work for now. We can live w/ that can't we?

 

[RestlessSoul]

--and we have yet to reconcile some of the particulars of general relativity w/ those of quantum mechanics, but that's ok because both QM and GR are handy models until something better comes along. Meanwhile my thinking is that there IS in fact a "privileged, fixed point, from which to observe" and that's ourselves. I know that I'm observing because whenever I wonder if I exist I just ask for whoever is doing the wondering: me.

So once I know that I exist I can then go on to intuitively grasp that others exist (albeit somewhat shake ground there) but when we get into particulars like "spacetime" we're dealing (perhaps completely) w/ mere models of what appears to be happening. OK, so the models may be wrong somehow but they work for now. We can live w/ that can't we?

An interesting perspective, which chimes with Thomas Hertog’s account of his and Stephen Hawking’s conversations, towards the end of Hawking’s life when the latter was almost completely locked in.

Hawking apparently told Hertog that, in trying to conceptualise the universe as if from some hypothetical, Archimedean Point on the outside looking in, astronomers had been looking at it all wrong. And that a new, bottom up approach whereby we not only accept but embrace our human perspective, within the universe looking out, would yield significant results.

One implication of this perspective is that any “theory of everything” must, in order to be complete, give a full account of the consciousness of the observer: But where do physicists, or even neuroscientists, go with that?