Mass Space & Infinity

@soothfast said
No, you do not understand.

Physics needs to start tackling the big questions: what exactly is space, and what exactly is time?

Right now, it's precisely the words "space" and "time" that are meaningless terms when used on the (quite literally) most universal scale. Typically they're the stage on which physics plays out, but stand oddly apart from physics itself. Th ...[text shortened]... honest scientific sensibilities in the quantum age. What's that "emptiness's" secret for doing so?

"empty space" creating a separation between objects somehow. Huh! Not good enough for honest scientific sensibilities in the quantum age. What's that "emptiness's" secret for doing so?"

If there was no separation between any 2 or more objects, 2 or more objects could not exist. 'They' would all be one object.
If there was no space how could we describe movement?
And if time is an illusion (not real) how could we recognize cause and effect?

Space and time are not physical objects, but both are real and can be defined.

@kilroy70 said

"empty space" creating a separation between objects somehow. Huh! Not good enough for honest scientific sensibilities in the quantum age. What's that "emptiness's" secret for doing so?"

If there was no separation between any 2 or more objects, 2 or more objects could not exist. 'They' would all be one object.
If there was no space how could we describe ...[text shortened]... cause and effect?

Space and time are not physical objects, but both are real and can be defined.

Some say "time is an illusion" but I don't exactly count myself among them, because I don't think we've entirely nailed down, scientifically, what time is -- or at least, what we perceive it to be.

As for "empty" space, this comes back to the idea about perception. What is empty space? For that matter, what exactly is an electron or quark? These are not trivial questions, nor do I think they can be waved off as "merely" philosophical or, at best, metaphysical.

While I do not expect that our science will ever be able to answer all such questions, I believe that better answers for the nature of space and time can be discovered -- if we ask the right questions.

The empty space in a room disappears with the closing of one eye. Now there's just a flat picture, and different sensory input -- such as extending a hand into the space -- is needed to perceive the emptiness. A crude example, but one which conveys the basic idea that much of what we sense of the physical world is a construct of mind. The mind is the ultimate model-maker, taking raw sensory input and arraying it into something we can navigate through and live in. This fact is relevant to physics to the extent that how we think and theorize about the physical is indelibly colored by our senses and minds.

Admittedly I'm driven to this way of thinking by Buddhist ideas about emptiness and contrast. Ol' Shallow Blue's link has a cartoon in it showing someone rambling about light and darkness. Indeed, all structure arises from contrasts. Shadow play. An electron can be defined just as well by all the things it isn't as all the things it is, but even still, it has no essence that admits complete explanation, because any essence of a thing is a thing in itself that would require in its turn a further explanation. "Turtles all the way down," as the saying goes.

Shallow Blue will scoff at all this, most likely, but it strikes to why I say physics cannot answer all the questions, and also why some questions remain stubbornly unanswered. I believe physics can go much deeper than heretofore, and part of the process will be to question all the answers we think we know about the nature of spacetime itself.

@kilroy70 said
If there was no separation between any 2 or more objects, 2 or more objects could not exist. 'They' would all be one object.
If there was no space how could we describe movement?
And if time is an illusion (not real) how could we recognize cause and effect?

Space and time are not physical objects, but both are real and can be defined.

Also, you bring up questions that are precisely the ones that motivate thinking of space and time as merely the stage upon which physics plays out, rather than part of physics itself.

Space and time are primarily treated as mathematical constructs suited to casting physical theories in the form of tidy mathematical equations. Ultimately they form a four-dimensional coordinate system which may be represented as a "space" consisting of ordered quadruples (x,y,z,t). That's fine for most occasions.

Once we turn to the problem of unifying gravity with quantum mechanics, we find that the spacetime stage itself seems somehow involved. We can't play things out on the stage in the manner that we have since Galileo's time, because the stage is one of the characters in the play. Oh. So we need a bigger stage that holds spacetime itself, or better yet, find a "coordinate-free" model of the universe that addresses the workings of physical reality without treating all things as chess pieces moving around over time on a board. This is something many theoretical physicists are working on, and that includes physicists who say time is an illusion as well as those who don't.

@Soothfast
I guess we just lump all the time theory into, it's another dimension. But isn't it correct to say there could be universes with only TWO dimensions? But you can't make up a universe with no time dimension if I understand it correctly.

@sonhouse said
@Soothfast
I guess we just lump all the time theory into, it's another dimension. But isn't it correct to say there could be universes with only TWO dimensions? But you can't make up a universe with no time dimension if I understand it correctly.

Because it would be a static universe in which nothing would happen.

@kilroy70 said
An infinitely large universe could not expand because (by definition) it's already as big as it can possibly be.

It's possible that the universe is not infinitely large but will keep expanding infinitely.