What is time?

[Univalence]

But space has no attributes and we do not measure it.

Of course we measure space!

In computational complexity theory "space" means "memory". The unit for measuring memory is bit (classically) or qubit (quantum).

https://en.wikipedia.org/wiki/Space_complexity
In computer science, the space complexity of an algorithm or a computer program is the amount of memory space required to solve an instance of the computational problem as a function of the size of the input. It is the memory required by an algorithm to execute a program and produce output

Which is why all algorithms (mental models of reality) are subject to the space-time trade-off

Some algorithms take long time to execute (but require little memory)
Some algorithms take short time to execute (but require a lot of memory)

https://en.wikipedia.org/wiki/Space%E2% ... ff#History
Biological usage of time–memory tradeoffs can be seen in the earlier stages of animal behavior. Using stored knowledge or encoding stimuli reactions as "instincts" in the DNA avoids the need for "calculation" in time-critical situations.

[jayjacobus]

Scientists have changed the meaning of certain terms but the original meaning remains. We speak about space and everyone knows what is meant but if a scientist or a philosopher changes the meaning of space, the meaning gets confused. In part this is a flaw of language where there are more than one connotation of a word. The writer can change connotation and we might follow but only if we know that he has changed connotation. If we think he is being is being consistent, we understand that two or more connotations are actually the same meaning which is not true.

[Univalence]

We speak about space and everyone knows what is meant.

That's not true. Different people conceptualise things differently.

I know what I mean by space.
You know what you mean by space.

We don't know that our meanings coincide.
We could ASSUME it, but it needs not be true.

but if a scientist or a philosopher changes the meaning of space, the meaning gets confused.

They don't 'change' the meaning - they use the word differently, so the word acquires new meaning.

The writer can change connotation and we might follow but only if we know that he has changed connotation.

And the writer might tell you that he 'changed the connotation' if the writer thought of his own actions as 'changing the meaning of a word', rather than just 'using the word the way I learned to use the word'.

You are operating under the assumption of a universal/default language. It does not exist.

It's also difficult to grasp this point if you only speak one language, because you are unable to observe the process of 'translation' taking place in your own mind. You are unable to separate the concepts from the language you use to talk about them.

[jayjacobus]

I didn't understand space-time so I bought a book entitled "space-time". The authors initially spent a number chapters explaining relativity and then in the fifth chapter they said "Space-Time!" without explaining space-time's connection to relativity. Some people might think that the authors had explained space-time but they hadn't. Other texts say that Einstein used space-time to develop his theory on relativity. So understanding space-time would seem to be a requirement to understanding relativity. So the authors of "Space-time" should have explained Space-time before they explained relativity. But they never actually explained space-time at all leaving me confused.

Moreover, the naive person doesn't experience space-time at all so the term has no meaning to most people. The meaning of space-time is confused by the different connotations used by different writers.

[jayjacobus]

To construct space-time a mathematician used the frame of reference for space and combined it with the frame of reference for time. Frames of reference are abstractions. So the combination of two abstractions creates a new abstraction. Some writers recognize that space-time is an abstraction but many don't. Some writers seem to think that the abstraction creates a natural phenomenon. That is not true.

[jayjacobus]

It's also difficult to grasp this point if you only speak one language, because you are unable to observe the process of 'translation' taking place in your own mind. You are unable to separate the concepts from the language you use to talk about them.

Take as an example "artificial intelligence". Artificial intelligence is not natural intelligence because natural intelligence comes from the brain along with consciousness. Artificial intelligence is a substitute for intelligence but artificial intelligence does not use consciousness. Yet I have never read that artificial intelligence is not intelligence but a substitute for intelligence.

I cannot rely on authors to point out there own connotations. But I can understand their confusing explanations and reject their conclusions.

So I am able to separate the concepts from the language that people use. But I suspect that many people can't.

[RCSaunders]

But space has no attributes and we do not measure it.

Of course we measure space!

In computational complexity theory "space" means "memory". The unit for measuring memory is bit (classically) or qubit (quantum).

The word space is used to designate many different things, including "room," e.g. "is there enough space left in the closet for one more box?" In computers it may mean, "memory," but I think that is actually memory capacity. I'm sure you know this discussion has not been about any of those other meanings of the word space but of the hypothetical view that there some kind of metaphysical space with independent existence.

I'm sorry but what you are talking about has nothing to do with metaphysical space or time.

[Univalence]

The word space is used to designate many different things, including "room," e.g. "is there enough space left in the closet for one more box?"

So you are using 'space' to mean the same thing as volume. The remaining volume in the closet is X. The volume of the box is Y.
And you are asking: Does the box fit?

In computers it may mean, "memory," but I think that is actually memory capacity.

Capacity. Volume. Memory. Different language to speak about the same thing.

It's such a popular problem in computer science it even has a wiki page: Bin packing problem

I'm sure you know this discussion has not been about any of those other meanings of the word space but of the hypothetical view that there some kind of metaphysical space with independent existence. I'm sorry but what you are talking about has nothing to do with metaphysical space or time.

Really? All those meanings are functionally identical.
How many objects of volume 1 can you fit in your 'metaphysical space"?

[jayjacobus]

I knew a man who had written his thesis about packing tetrahedra in infinite space. Yet understanding space does not require understanding topology which is what his thesis was based on. In fact topology can confuse the average person who thinks he understands space. Simplifying space seems to be the best approach to the metaphysical discussion.

[RCSaunders]

Really? All those meanings are functionally identical.
How many objects of volume 1 can you fit in your 'metaphysical space"?

If you choose to think all those uses of the word space are only examples of some independent metaphysical existence, it probably does not harm. It is the way most people think about space.

The problem with that view of space (which I believe is mistaken) is that it easily becomes something mystical--a something without any properties that just exists. But space is actually a concept for what is not. If there is something, nothing else can be in that same position or place. Space is where there is nothing, but there is never nothing. Even what we imagine as "outer space," is absolutely full of radiation and particles. There is no space in the sense of nothingness. There is only everything there is and all the relationships between existents. I'm not attempting to convince you this view is correct, only explaining one of myriad reasons I know there is no metaphysical space.

[Univalence]

But space is actually a concept for what is not. If there is something, nothing else can be in that same position or place.

There's a word for things with with limited/constrained availability. resource.

And we have logics which deal with the availability of resources

Space is where there is nothing, but there is never nothing. Even what we imagine as "outer space," is absolutely full of radiation and particles. There is no space in the sense of nothingness.

Then why bother talking about that conception of space?

There is only everything there is and all the relationships between existents. I'm not attempting to convince you this view is correct, only explaining one of myriad reasons I know there is no metaphysical space.

OK. And you are still talking about quantities. How much of "everything" is there?

[jayjacobus]

Someone can say that space is only defined by what is in space. But it is not the matter and energy in space that gives space its characteristics. Space has very minimal characteristics by itself but it does have characteristics by itself. The characteristics are connections and separations and I know this because of space travel and separation of matter. The characteristic of space still exists without space travel and separation of matter, I suggest and, if that is right, then space characteristics are independent of matter and travel.

[Belinda]

Someone can say that space is only defined by what is in space. But it is not the matter and energy in space that gives space its characteristics. Space has very minimal characteristics by itself but it does have characteristics by itself. The characteristics are connections and separations and I know this because of space travel and separation of matter. The characteristic of space still exists without space travel and separation of matter, I suggest and, if that is right, then space characteristics are independent of matter and travel.

How could you measure space if there was nothing in it? How could you even detect space if there was nothing in it?

[jayjacobus]

I wasn't talking about measuring. I was talking about characteristics and I concluded that the characteristics of space when matter is present are the same characteristics when matter is not present. In fact I don't think that someone can conclude that space only has characteristics when matter is present.

My attempt to simplify the discussion is not meant to be argumentative but clarifying. Some posts on this thread go off on tangents that don't reveal the characteristics of space but instead over complicate the discussion.

The discussion about time also goes off on tangents that over complicate the discussion of time (in my opinion.)

[Belinda]

Since Einstein time , space, and force became conceived of in a way that is strange to most of us . Relativity is not so much "complicated" as
counter intuitive.