Which theory of time is the most evidence-based?

[curiosity1]

TL;DR Summary

Which theory of time is the most evidence-based?

1. Presentism: This theory posits that only the present moment is real, and the past and future are simply constructs of human consciousness. According to presentism, the past no longer exists, and the future has not yet occurred.
2. Eternalism/Block Universe Theory: This theory suggests that all moments in time, past, present, and future, exist simultaneously. Time is viewed as a sort of block, where every event that has ever occurred or will occur already exists, similar to how all the frames of a movie exist on a film strip.
3. Growing Block Universe: This theory is similar to the block universe theory but adds the idea that time is "growing" or expanding as new events come into existence. The past and present exist, but the future does not yet exist.
4. The Block Time Theory: A variant of eternalism, this theory suggests that time is a dimension similar to space, and just as we can move through space in any direction, we can also move through time.
5. Transactional Interpretation: In quantum mechanics, this theory suggests that the past, present, and future are all interconnected, and events in the future can influence events in the past.

Which theory of time is the most evidence-based?

 

[Dale]

Those aren’t theories, they are interpretations. None of them make different experimental predictions for anything, so none of them are any more or less evidence based than the others

 

[curiosity1]

Those aren’t theories, they are interpretations. None of them make different experimental predictions for anything, so none of them are any more or less evidence based than the others

Is there any theory of time that makes experimental predictions?

 

[jbriggs444]

Is there any theory of time that makes experimental predictions?

The special theory of relativity makes some predictions about the speed of light and about the implications for at least one operational definition of simultaneity.

 

[PeterDonis]

theory of time

What is a "theory of time"?

 

[Dale]

Is there any theory of time that makes experimental predictions?

Every physics theory that I am aware of uses time as part of the theory. I don’t know if I would call any of them a theory “of time”.

 

[curiosity1]

What is a "theory of time"?

Well, there is a theory of gravity. Shouldn't there be a theory of time?

 

[Frabjous]

I wouldn’t call it a theory of time, but there is stuff like this
https://www.amazon.com/Physical-Origins-Time-Asymmetry-Halliwell/dp/0521568374/?tag=pfamazon01-20

TOC

 

[Vanadium 50]

Well, there is a theory of gravity. Shouldn't there be a theory of time?

That's just stringing words together.

People are being polite. It's nice that they are trying to help, but if you don't know what you are looking for, there is no way they know what you are looking for.

<reference to deleted post removed>

 

[Dale]

Well, there is a theory of gravity. Shouldn't there be a theory of time?

The current theory of gravity is a theory of spacetime. Time is part of the theory, but again, I wouldn’t call it a theory “of time”.

It is well supported by evidence. It is compatible with all of the interpretations you mentioned in the OP

 

[Bosko]

TL;DR Summary: Which theory of time is the most evidence-based?

Time and space as separate categories are a relic from the time before the theory of relativity.
These are philosophical questions from 120 years ago. Now they don't make sense because space and time are not basic concepts.

You should define more precisely what it means that something exists? For example time , space, point...?
A similar question is whether there is a coordinate system or is it "simply constructs of human consciousness". Everything is "simply constructs of human consciousness" if you look at it from that angle.
In my humble opinion, it is better to look at everything as a scientific model.

Walking around the city, you will never see the coordinate system. The coordinate system exists in the mathematical-physical model, but not in reality.
Is there a mathematical point (something that has neither length nor height nor width)? It is a question of the philosophy of science, not a question of science itself.

[*]Presentism: This theory posits that only the present moment is real, and the past and future are simply constructs of human consciousness. According to presentism, the past no longer exists, and the future has not yet occurred.

But also the present moment which alone exists has a duration of zero. Just like it doesn't exist :-)
So nothing of time exists.

[*]Eternalism/Block Universe Theory: This theory suggests that all moments in time, past, present, and future, exist simultaneously. Time is viewed as a sort of block, where every event that has ever occurred or will occur already exists, similar to how all the frames of a movie exist on a film strip.

"exist simultaneously" is defined over time. Circular thinking

[*]Growing Block Universe: This theory is similar to the block universe theory but adds the idea that time is "growing" or expanding as new events come into existence. The past and present exist, but the future does not yet exist.

"growing" or expanding in what?
Undefined ?

[*]The Block Time Theory: A variant of eternalism, this theory suggests that time is a dimension similar to space, and just as we can move through space in any direction, we can also move through time.

This is something true. We always move through time at the rate of one second per second :-)

[*]Transactional Interpretation: In quantum mechanics, this theory suggests that the past, present, and future are all interconnected, and events in the future can influence events in the past.

This is only one interpretation, but then even deeper philosophical questions are opened, what are the causes and what are the effects in physical experiments.
That is a question for the philosophy of quantum mechanics

Which theory of time is the most evidence-based?

The basic term is the speed of light (the speed of any electro-magnetic wave and also gravitational waves)
Experimental evidence began in 1887 with Michelson–Morley experiment
Theoretically with Maxwell's equations
Using the constant speed of light, space-time is defined as a unique coordinate system.

 

[curiosity1]

Using the constant speed of light, space-time is defined as a unique coordinate system.

Thank you very much for your detailed reply. I don't understand what space-time is. What is it made of? Isn't space just emptiness? As far as I know, at the speed of light, time stops. How does that work? I am sorry if my questions are silly - they reveal how little I understand!

 

[Dale]

I don't understand what space-time is. What is it made of? Isn't space just emptiness?

Spacetime is the geometry of the universe. There is no reason that geometry should be made of something. Geometry is part of both vacuum and non-vacuum regions of the universe.

The interesting part is that time is geometrical, and that the geometry of the universe is non-Euclidean. The universe is surprisingly complicated.

 

[Bosko]

Thank you very much for your detailed reply. I don't understand what space-time is.

Space-time is a coordinate system.
There are 4 numbers for each coordinate. Three for space and one for time.

What is it made of?

Some laconic answer would be that, like any coordinate system, it consists of points.
In the theory of relativity, these points (four numbers) are called events.
If you're looking for a meaningful deeper answer, I don't know one.

What is "space" in the mathematical axioms of geometry : "The set of all points"
Whereas set, point, straight line and plane are basic terms that satisfy the axioms of geometry and have no definitions

Isn't space just emptiness?

It is full of electromagnetic and gravitational waves.
For deep questions about what exists and what doesn't, I can only quote Nils Bohr :

“Everything we call real is made of things that cannot be regarded as real. If quantum mechanics hasn't profoundly shocked you, you haven't understood it yet.”
― Niels Bohr

As far as I know, at the speed of light, time stops.

Movement is a basic concept. If nothing moves at all, neither time nor distance(space) can be defined.
Also, everything is defined relative to a observer. Time and space are not absolute.
Nothing reaches the speed of light. As it approaches the speed of light, time slows down relative to our time as an observers.

How does that work?

I've been trying to figure it out for years and there are still details I don't quite understand.

I am sorry if my questions are silly - they reveal how little I understand!

Take a book, follow this forum...

 

[Mister T]

Well, there is a theory of gravity. Shouldn't there be a theory of time?

Theories help us to predict how objects behave. For example, theories of gravity tell us how to predict the behavior of objects influenced by gravity. Time is something we use to help us describe how objects behave. It's used in theories. It's not a theory in and of itself.

 

[phinds]

As far as I know, at the speed of light, time stops.

Not it any real sense, only in a co-ordinate sense. If you are traveling at very close to the speed of light, I see your clock as almost stopped. You, on the other hand, see nothing of the kind since from your frame of reference, you are not moving at all and *I* am traveling at nearly c.

 

[Vanadium 50]

As far as I know, at the speed of light, time stops.

It sounds like you are trying to come up with a coherent description of physics by stitching together sound bites from popularizations you have read. It would be nice if this worked, but it doesn't.

You either have to put in the effort to learn the subject properly, from classes and textbooks, or accept the fact that you have a superficial understanding that isn't 100% right, but might be close enough to give you a flavor of what is going on.

 

[curiosity1]

It sounds like you are trying to come up with a coherent description of physics by stitching together sound bites from popularizations you have read. It would be nice if this worked, but it doesn't.

You either have to put in the effort to learn the subject properly, from classes and textbooks, or accept the fact that you have a superficial understanding that isn't 100% right, but might be close enough to give you a flavor of what is going on.

I am just trying to understand how the universe works. I am not studying physics at the university level. I have read popular physics books that I didn't understand.

 

[Ibix]

I have read popular physics books that I didn't understand.

That's really a symptom of popularisation. They can't use the maths so they can't really say what they mean, and they come up with nice ways of vaguely describing some corners of the model. But the descriptions are not the model, and they're often unclear on how tiny a corner they are describing, and people take the description of one tiny corner and try to apply it to another corner - unsurprisingly, it doesn't work. If you want to actually understand you need the maths. And that means a textbook, and probably several more for the topics you really need to understand first.

You can get Special Relativity (within limits) with nothing more complex than Pythagoras' theorem. General Relativity requires calculus and vectors immediately.

 

[Ibix]

Space-time is a coordinate system.

Spacetime is a manifold with a metric and a connection. You can use a coordinate system to identify events within it, but it isn't obligatory. In fact, the mark of real physics, rather than coordinate based interpretation, is that it does not use coordinates.

 

[Vanadium 50]

I am just trying to understand how the universe works. I am not studying physics at the university level. I have read popular physics books that I didn't understand.

So, how many popularizations do you think it will take you to learn "how the universe works"? And if that were a good pathm why do you think people would spend many years in school to do the same thing?

 

[Dale]

I am just trying to understand how the universe works.

In that context I like the fact that you asked to compare the various interpretations in terms of experimental evidence. That is a good approach.

All of these interpretations are equally compatible with the evidence. The distinction between them and the desire to choose one over the others appears to be a human conceit, not a feature of nature.

 

[curiosity1]

So, how many popularizations do you think it will take you to learn "how the universe works"? And if that were a good pathm why do you think people would spend many years in school to do the same thing?

I don't know. I can't afford to study physics at university level as I have neither the time, nor the money.

 

[Frabjous]

You might try “Relativity and Common Sense” by Bondi. It’s cheap.
If you are a little more ambitious, you might try “Spacetime Physics” by Taylor and Wheeler.
https://www.eftaylor.com/spacetimephysics/

 

[Vanadium 50]

I can't afford to study physics at university level as I have neither the time, nor the money.

That's fair, but I think we need to manage expectations here. "I want to be a concert pianist but I don't have time for school or lessons" is going to be a problem. Same here.

Popularizations will, at best, give you some flavor for "how the universe works", but it will be incomplete and to a degree wrong. If you're OK with that, great. But if you want a detailed, accurate and self-consistent picture, well, that takes work.

As was said more than a few years ago "there is no royal road to mathematics".

 

[Nugatory]

That's fair, but I think we need to manage expectations here. "I want to be a concert pianist but I don't have time for school or lessons" is going to be a problem. Same here.

Achieving a decent undergraduate-level understanding of special relativity through self-study is not necessarily unrealistic - more realistic than becoming a professional pianist or maybe even a competent home player without training.
However...

I have read popular physics books that I didn't understand.

Popular physics books are the wrong starting point and the time spent on them will prove to have been wasted. Several good textbooks are legally free on line (I like @Frabjous's recommendation of Taylor and Wheeler) and don't require that much background - just elementary differential and integral calculus and Newtonian physics.

 

[Renato Iraldi]

These are conceptions of the universe and there are no experimental demonstrations that allow us to reject one in favor of the other.
but I can give two indications in favor of the eternalist model.
1.- It is possible to formulate special relativity in an eternalist model assuming only reasonable methods to indicate the coordinates and assuming Epstein's postulate, the model has implicit Lorentz transformations, and these transformations imply that one can have a reference system in that events exist in the present, in the past and in the future for observers of another system who are all in the common present of that system.
The other clue is Bell's demonstration of the non-locality of measure theory in quantum mechanics.
one clue is circumstantial, two clues are a reasonable doubt, three clues are proof. Look for the third clue.

 

[phinds]

three clues are proof

No, clues are not proof

 

[Dale]

These are conceptions of the universe and there are no experimental demonstrations that allow us to reject one in favor of the other.
but I can give two indications in favor of the eternalist model.
1.- It is possible to formulate special relativity in an eternalist model assuming only reasonable methods to indicate the coordinates and assuming Epstein's postulate, the model has implicit Lorentz transformations, and these transformations imply that one can have a reference system in that events exist in the present, in the past and in the future for observers of another system who are all in the common present of that system.

That is not a clue, it is a personal preference. In particular "reasonable methods" indicates a personal value judgement.

The other clue is Bell's demonstration of the non-locality of measure theory in quantum mechanics.

This isn't a clue either. All of the interpretations of time are compatible with the data, including Bell-related tests.

 

[PeterDonis]

one can have a reference system in that events exist in the present, in the past and in the future for observers of another system who are all in the common present of that system.

Which is irrelevant for any actual physics, because the definitions of "present", "past", and "future" you are using are frame dependent, and frame dependent things have no physical meaning. The physical meaning is in invariants.

Basically you are repeating an argument that has already appeared, and been refuted, in the literature. See the Insights article referenced here:

https://www.physicsforums.com/threads/the-block-universe-refuting-a-common-argument-comments.843000/

 

[PeterDonis]

Thread closed for moderation.

 

[PeterDonis]

After moderator review, the thread will remain closed.

 

[bhobba]

Thank you very much for your detailed reply. I don't understand what space-time is. What is it made of? Isn't space just emptiness? As far as I know, at the speed of light, time stops. How does that work? I am sorry if my questions are silly - they reveal how little I understand!

The thread is shut.

Here's a comparison that might help. Remember geometry from school? Points have position but no size and a line length but no width. Such do not exist. They are abstractions. It talks about points and lines that exist in theory but not in the physical world. They're the building blocks of geometry, abstractions that help us understand the real world. Similarly, space-time is a theoretical construct that helps us make sense of the universe.

Every theory, every single one, is like that. They contain abstractions used in the theory. If you succeed in finding something deeper that either explains those concepts or somehow replaces them, in a sense, you have not got anywhere because what you replace it with has the same problem. Absolute knowledge is beyond science's grasp.

For time, like point and line, we all have an intuitive idea of what it is. To make it more precise, we need what is called an inertial frame. A frame is simply a standard of rest on which experiments can be conducted. An inertial frame has a special property - the laws of physics (again, an abstraction) are the same in any direction, at any point, or at any time. The earth is an approximate inertial frame. Suppose we have some repetitive process and count the number of times it occurs. Repetitive process is a fundamental abstraction. But since the laws of physics are the same at any point, time, or direction, we have a way to assign a number to the time it is anywhere in the frame. The count of the repetitive process measures time and is called a clock. This is the idea time is what a clock measures.

I will mention I am reading a book now that explains time at a deeper level, but it is advanced and needs as background what I wrote above:



Thanks
Bill