What is Space?

Physics is not my strong suit but I love reading about science that challenges traditional mechanistic worldviews. So I am fascinated by Quantum Physics and Relativity but my fascination is limited to popular science books which outline the concepts but do not attempt to explain the mathematics behind the theories. I am hopeless with maths.

Even these superficial descriptions of concepts can be mind-bending though. A couple of days ago I watched a YouTube video about gravity. It described the Einstein theory by which spacetime is distorted by massive objects (such as the earth) rather than the traditional, Newtonian version which posits an attractive force. I have been familiar with the Einstein theory since my teens but have never questioned it even in my own mind. The idea of something in free-fall merely following the contours of distorted space made perfect sense when it was demonstrated using the common rubber sheet analogy.

However, while watching the video, it occurred to me that what we are talking about with space (or spacetime, to be more precise) is not something tangible like a rubber sheet. That has a surface and the rolling ball is limited by that surface. That's why it follows the trajectory across the surface.  Space doesn't have a surface - or does it? I am not talking aout the difference between the 2D analogy and the 3D reality of space (or the 4D reality of spacetime). That is always pointed out when these analogies are used anyway.

So while, on the one hand I accepted, without question, the Einstein explanation of gravity, on the other hand I also accepted that space is mere nothingness in which massive bodies such as starts and planets exist. We take it for granted that space is mostly a vacuum and that it offers zero resistance to objects moving through it. So how does it have contours which can be distorted my those massive objects? What gets distorted? If space is nothingness, surely it doesn't make sense that it can be distorted? Or am I missing something?

So how does it have contours which can be distorted my those massive objects? What gets distorted? If space is nothingness, surely it doesn't make sense that it can be distorted? Or am I missing something?

Very thought provoking Dave.  I honestly don't like to think about it too much, it makes me feel peculiar. What is nothing? I suppose one might say a vacuum is nothing but it still sucks you in.

What keeps space empty?

...three things we could never remove according to Dr. Genz: (1) vacuum energy, (2) the Higgs field, and (3) spacetime curvature.

Lastly, spacetime curvature is an innate property of space itself, according to Einstein's General Theory of Relativity. Masses act on space by giving it curvature, and space acts back on masses by having them travel in its curved shape. The phenomenon of masses traveling in straight lines in a curved spacetime is known as gravity. The curved trajectory of a satellite in orbit is really a straight line in a curved space. A space devoid of masses still has a shape (it still has Einstein's metric field). That shape can even be curved, even without any masses, according to the equations. There is no way to suck gravity or block gravity out of a region of space because gravity is just the shape of space itself. As a result, even the most empty of physical vacuums will always have a curvature field.

I have to say that the text quoted there is what I had always accepted without question. Then the question arose, as I explained, how can nothing be shaped?

I have to say that the text quoted there is what I had always accepted without question. Then the question arose, as I explained, how can nothing be shaped?

I have always asked myself the same question.  Maybe information science can answer.  I'm just waiting for @stephenw  to see this.  I suspect that reality is an information field rather than nothing with stuff in it.

I have to say that the text quoted there is what I had always accepted without question. Then the question arose, as I explained, how can nothing be shaped?

I am very sceptical about huge swathes of science by now - partly by the way it manages to ignore great swathes of evidence for paranormal phenomena. This book explores the development of modern physics from a sort of sociological perspective. The author makes a reasonable argument (I think) that the difference in approach between European and US physicists meant that physicists became obsessed with producing complex models rather than really solving the key problems.

https://www.amazon.co.uk/Make-Physics-Gr...B0BS47CCNK

I do think he has a point, I'll be interested to hear what others think.

I have to say that the text quoted there is what I had always accepted without question. Then the question arose, as I explained, how can nothing be shaped?

I have the distinct feeling I'm missing something so apologies if I'm being daft......

I don't think describing empty space as "nothing" is accurate.  Reminds me of when we were all taught that null and zero aren't the same thing.  I think the concept is just so esoteric as to not fit neatly into the something/nothing dichotomy.  Does "empty" feel better (vs "nothing")?  Empty, in terms of physical matter and energy, but not nothing in terms of fields?

I have the distinct feeling I'm missing something so apologies if I'm being daft......

I don't think describing empty space as "nothing" is accurate.  Reminds me of when we were all taught that null and zero aren't the same thing.  I think the concept is just so esoteric as to not fit neatly into the something/nothing dichotomy.  Does "empty" feel better (vs "nothing")?  Empty, in terms of physical matter and energy, but not nothing in terms of fields?

Well that's basically the question I'm asking: am I wrong to assume space is "nothingness". I know that space is not empty - we occupy space as does the whole physical universe so it is certainly not empty. But does space have form? Does it have a surface? Or is this all sematic confusion? Words are clearly not adequate even to explain what I'm really asking but I can't think of any other way to put it: is space another word for nothingness? If not, what is space made of? How does it have shape which can be distorted by massive objects?

Here's an article that seems to be asking the same question that I am here:

https://www.abc.net.au/news/science/2018...d/10078824

But it then goes on to explain, not what space is made of but what it contains. That's not an answer to the question they are asking.

So after a bit more Google searching I found a few articles asking the same question but didn't find a definitive answer. Most seem to default back to the same non-answer as the article linked above - they describe what can be found in space, not what space itself is.

It seems that Einstein himself struggled with the same question and came up with a theory. I found an article but it is way above my head for the most part. Anyhow, here's a quote that seems to address what we are talking about.

Einstein called the new term that he added to the equations for gravity the “cosmological term.” ...
The cosmological term can be viewed in two ways. One way, the way Einstein viewed it, is as a modification of the law of gravity. Alternatively, the term can also be viewed as the effect of having a constant density of mass and also a constant pressure everywhere in space and for all time. Since this mass-density and pressure have the same value everywhere, they can be regarded as intrinsic properties of space itself. That’s the Grid viewpoint. If we take it as given that space has these properties, and focus exclusively on the gravitational consequences, we arrive back at Einstein’s viewpoint.

So, if I understand correctly, Einstein theorised that space has physical propeties: "mass-density and pressure". Thus it is not nothingness, it is a substance. As the article states in summary:

Summing Up: Space Today, Space Tomorrow

Space is effervescent, substantial, weighty, and elastic. Each of these properties equates to specific, observable phenomena; they are not whimsical metaphors. Space has a life of its own, and exists independent of any matter that might occupy it. Indeed, in our most fundamental equations particles—the building blocks of are described as disturbances in the activity of space-filling fields, or in other words of space itself.

Well that's basically the question I'm asking: am I wrong to assume space is "nothingness". I know that space is not empty - we occupy space as does the whole physical universe so it is certainly not empty. But does space have form? Does it have a surface? Or is this all sematic confusion? Words are clearly not adequate even to explain what I'm really asking but I can't think of any other way to put it: is space another word for nothingness? If not, what is space made of? How does it have shape which can be distorted by massive objects?

Here's an article that seems to be asking the same question that I am here:

https://www.abc.net.au/news/science/2018...d/10078824

But it then goes on to explain, not what space is made of but what it contains. That's not an answer to the question they are asking.

If you take 2 permanent ferrite magnets, and bring them together in repulsion, you can experience a field shape for yourself, and this phenomenon can only be most accurately understood in terms of quantum mechanics. It’s probably the closest you’ll get to experiencing the strangeness of our reality, analogous to the strangeness of spacetime (ie your worthwhile search to understand the nature of space).