Now I have no scientific knowhow apart from the very basics you learn in school. But recently I was discussing something of with a colleague and it brought up anti matter. And I started to wonder if there is such a thing as Anti Time. As I'm lead to believe everything in science appears to have an opposite or a pair. For example Matter and Anti Matter are opposites to each other is that the same for time.

Sorry if this is badly worded. :}

1 minute ago, CosmicDreamer said:

Now I have no scientific knowhow apart from the very basics you learn in school. But recently I was discussing something of with a colleague and it brought up anti matter. And I started to wonder if there is such a thing as Anti Time. As I'm lead to believe everything in science appears to have an opposite or a pair. For example Matter and Anti Matter are opposites to each other is that the same for time.

Sorry if this is badly worded. :}

Hard to envisage, I think, like asking if there is anti-space. What would that look like? Matter and antimatter are entities, whereas space and time are just dimensions. So not really comparable. You can speak of going forward or backward in either space or time. But anti? What could that mean? But maybe a physicist can add more.

Time is actually part of space time though yes? Malleable?

There is the Anti-de Sitter space but that needs an actual physicist to explain. @MigL

Edited September 3Sep 3 by pinball1970
Added Migl

1 hour ago, CosmicDreamer said:

Now I have no scientific knowhow apart from the very basics you learn in school. But recently I was discussing something of with a colleague and it brought up anti matter. And I started to wonder if there is such a thing as Anti Time. As I'm lead to believe everything in science appears to have an opposite or a pair. For example Matter and Anti Matter are opposites to each other is that the same for time.

Sorry if this is badly worded. :}

Time isn’t matter, or a particle.

Is there an antilength, that cancels out length?

1 hour ago, CosmicDreamer said:

As I'm lead to believe everything in science appears to have an opposite or a pair.

Yes many things come in pairs.

I have no proof that everything comes that way however.

Partly because for any X you can divide the universe into that which is X and that which is not X.

But elephants are not anti-dolphins, they are something else entirely.

The 'anti' bit is a special relationship.

11 minutes ago, studiot said:

Yes many things come in pairs.

I have no proof that everything comes that way however.

Partly because for any X you can divide the universe into that which is X and that which is not X.

But elephants are not anti-dolphins, they are something else entirely.

The 'anti' bit is a special relationship.

You can have antipopes though.

3 minutes ago, exchemist said:

You can have antipopes though.

And antigens and ..........

Yes the list is quite long.

6 hours ago, pinball1970 said:

There is the Anti-de Sitter space but that needs an actual physicist to explain.

Actual Physicist ??

Anti-deSitter space refers to the intrinsic curvature of space-time, absent matter and due to the energy density of the vacuum ( Cosmological Constant ? ), having the opposite sign of deSitter space, hence having hyperbolic curvature and negative Cosmological Constant.

I have never read or heard the term anti-time, and would not know what it means.
Although in Feynman diagrams, anti-particles can be treated as particles travelling backwards in time.

42 minutes ago, MigL said:

Actual Physicist ??

Or "someone who knows physics to a decent level who knows what they are talking about."

I know there a few mods and experts but Clint Eastwood is a bit easier to remember.

6 hours ago, MigL said:

Actual Physicist ??

Anti-deSitter space refers to the intrinsic curvature of space-time, absent matter and due to the energy density of the vacuum ( Cosmological Constant ? ), having the opposite sign of deSitter space, hence having hyperbolic curvature and negative Cosmological Constant.

I have never read or heard the term anti-time, and would not know what it means.
Although in Feynman diagrams, anti-particles can be treated as particles travelling backwards in time.

So two things. One, when we speak of opposites do we mean opposite is "Some" way or opposite in many or ALL ways?

I am not sure what Feynman might mean by a particle traveling backward in time. There seems to a causal arrow where one event causes another. How could something be uncaused? Once it has happened the arrangement of the Universe is different and there is, in my estimation NO way to set the universe up in the exact arrangement of the prior moment. So no time travel is possible. You cannot undo the universe, and you cannot put the entire universe into a future configuration.'

So anti time might be the reversal of the casual arrow, but what would that mean? How could an explosion become a bomb? It makes no sense. All those photons from the explosion would have to be retrieved and there is no even hypothetical way you could do that.

Which brings up another aspect of this and that is what can happen in one's mind cannot necessarily happen in reality. So even if YOU can think of the opposite of something, that does not mean reality can do it.

Regards, TAR

10 minutes ago, tar said:

I am not sure what Feynman might mean by a particle traveling backward in time. There seems to a causal arrow where one event causes another. How could something be uncaused? Once it has happened the arrangement of the Universe is different and there is, in my estimation NO way to set the universe up in the exact arrangement of the prior moment. So no time travel is possible. You cannot undo the universe, and you cannot put the entire universe into a future configuration.'

Again
You might educate yourself on Feynman diagrams before making blanket statements like the above.
The fact that in the model, you can consider anti-particles as travelling backwards in time to make calculations easier, has no implications on the real.
The fact that you don't understand something should lead you to ask questions, not assert unwarranted conclusions.

Understood, MIgL,

But that was my point. The particle going back in time was a mathematical device, it was not representative of anything real.

Regards, TAR

MigL, I understand the difference between reality and the model.

Swansont locked a thread of mine where I was suggesting models can be nonrepresentative of reality but reality is always correct. It is IMPORTANT to understand that you can correct a model but you cannot "correct" reality. Reality is already correct. It already fits together perfectly with no mistakes.

Sort of depressing really MigL. You guys chased me off of here before, and now you are doing it again. You are assuming I need to understand your model to understand reality. But understanding your model is NOT understanding reality. It is understanding your model. And by your own admission your model is not representative of anything real. Its a model. Not even a working model. Just a model. It cannot, in ANY case be more real than reality.

Regards, TAR

CosmicDreamer

I apologize for hijacking your thread to voice a grievance of mine.

But I think the point is important to consider in answering your question about anti-time and ANY speculative consideration. ALL models are analogue versions of reality, built in the synapses and folds of your brain. They are NOT the thing you are modeling, and what works in your brain does not HAVE TO work in reality.

Regards, TAR

1 hour ago, tar said:

Understood, MIgL,

But that was my point. The particle going back in time was a mathematical device, it was not representative of anything real.

Regards, TAR

MigL, I understand the difference between reality and the model.

Swansont locked a thread of mine where I was suggesting models can be nonrepresentative of reality but reality is always correct. It is IMPORTANT to understand that you can correct a model but you cannot "correct" reality. Reality is already correct. It already fits together perfectly with no mistakes.

Sort of depressing really MigL. You guys chased me off of here before, and now you are doing it again. You are assuming I need to understand your model to understand reality. But understanding your model is NOT understanding reality. It is understanding your model. And by your own admission your model is not representative of anything real. Its a model. Not even a working model. Just a model. It cannot, in ANY case be more real than reality.

Regards, TAR

CosmicDreamer

I apologize for hijacking your thread to voice a grievance of mine.

But I think the point is important to consider in answering your question about anti-time and ANY speculative consideration. ALL models are analogue versions of reality, built in the synapses and folds of your brain. They are NOT the thing you are modeling, and what works in your brain does not HAVE TO work in reality.

Regards, TAR

Why even think about a reality outside of what we can know because it is absolutely unknowable, Models describe parts of the behaviour of nature, which in itself is one seamless whole.

"A Feynman diagram is a graphical representation of a perturbative contribution to the transition amplitude or correlation function of a quantum mechanical or statistical field theory. Within the canonical formulation of quantum field theory, a Feynman diagram represents a term in the Wick's expansion of the perturbative S-matrix. Alternatively, the path integral formulation of quantum field theory represents the transition amplitude as a weighted sum of all possible histories of the system from the initial to the final state, in terms of either particles or fields. The transition amplitude is then given as the matrix element of the S-matrix between the initial and final states of the quantum system."

Drom Feynman diagram - Wikipedia

If you think I scolded you because I can do the path integrals QFT requires, you are mistaken; I use Feynman diagrams because they make life ( and understanding ) so much easier.
IOW, I'm giving advice, not chasing you away; you have always been welcome to stay and learn.

8 hours ago, tar said:

One, when we speak of opposites do we mean opposite is "Some" way or opposite in many or ALL ways?

Which echoes my point.

I can't think of anything that is opposite in every way.

Fundamental particles still obey the same laws of gravity., ie they don't have anti or negative mass.

Antiparticle have opposite properties in regard to CPT symmetry. So you have opposite charge. Neutrinos and antineutrinos have opposite spin orientations. Antiparticles behave like particles (and vice-versa) under time reversal.

Mass isn’t part of that symmetry.

And time is the symmetry, not a particle subject to the symmetry.

On 9/3/2025 at 10:23 PM, StringJunky said:

Why even think about a reality outside of what we can know because it is absolutely unknowable, Models describe parts of the behaviour of nature, which in itself is one seamless whole.

This is a continuing consideration of mine StringJunky. Why for instance predict how the Universe is going to end in 300 billion years. There is no way to verify your prediction.

Many things in science are done within the mathematical model, which you can imagine and share and work with. You can know how something you can never actually see might be behaving if it behaves how the model is predicting it will behave. But the Universe is immense and long lived beyond our comprehension. We will not even know what is happening now on Alpha Proxima for 4.24 years. We have NO way of knowing what is happening even on the other side of the Galaxy right now. We won't know for 10K years, at which point we will have forgotten why we cared. We can never know what is happening at the far reaches of our Universe. the light from the Universe outside the observable Universe will NEVER get here. So it is literally, as you say unknowable, yet we still imagine what it might be doing at the moment. Our brains can imagine containing the universe, when applying all the proper transforms to our analog model of the Universe.

Regards TAR

16 minutes ago, tar said:

This is a continuing consideration of mine StringJunky. Why for instance predict how the Universe is going to end in 300 billion years. There is no way to verify your prediction.

Many things in science are done within the mathematical model, which you can imagine and share and work with. You can know how something you can never actually see might be behaving if it behaves how the model is predicting it will behave. But the Universe is immense and long lived beyond our comprehension. We will not even know what is happening now on Alpha Proxima for 4.24 years. We have NO way of knowing what is happening even on the other side of the Galaxy right now. We won't know for 10K years, at which point we will have forgotten why we cared. We can never know what is happening at the far reaches of our Universe. the light from the Universe outside the observable Universe will NEVER get here. So it is literally, as you say unknowable, yet we still imagine what it might be doing at the moment. Our brains can imagine containing the universe, when applying all the proper transforms to our analog model of the Universe.

Regards TAR

I’m not sure what point you are making here. Are you saying we should not indulge our imagination? Or is it just that we should not present the fruits of our imagination as settled science, perhaps?

On 9/3/2025 at 5:38 AM, pinball1970 said:

Time is actually part of space time though yes? Malleable?

But spacetime isn't a tangible thing that can be shaped, is it? I thought spacetime was simply a model used to better understand things like Relativity.

10 minutes ago, zapatos said:

But spacetime isn't a tangible thing that can be shaped, is it? I thought spacetime was simply a model used to better understand things like Relativity.

We know it can be bent by a massive object but let's assume you are correct.

Just an abstraction to do calculations.

My point was they should be considered together as changing the conditions in a particular reference frame alters space and time.

As an example particle decay in a particle accelerator, at near light speed particles, last longer and travel further according to special Relativity. At those velocities space and time are altered.

33 minutes ago, zapatos said:

I thought spacetime was simply a model used to better understand things like Relativity.

Yes, the space-time of the model acts exactly like the reality ( in most situations ) and has been confirmed to a very high degree.

In the model space-time can be curved and is malleable; whether reality is also, is a question for Philosophers to debate.

7 hours ago, MigL said:

In the model space-time can be curved and is malleable; whether reality is also, is a question for Philosophers to debate.

The curvature of spacetime is as real as anything else.

1 hour ago, KJW said:

The curvature of spacetime is as real as anything else.

The effect we call gravity seems real (to me at least) as it appears to act consistently, but our description of it changes based on something we make up. We used to call gravity a force, then we called it spacetime, and if we can come up with a better model that describes it as a sort of blowing aether and it additionally addresses quantum gravity, then we'll call it blowing aether. All of the descriptions are invented by us as a way to describe the effect we see. Isn't the effect we call gravity more 'real' than a description we invented just because it is the best predictive model at the time?

4 hours ago, zapatos said:

but our description of it changes based on something we make up.

Science changes over time as new data comes in and theories are developed yes.

4 hours ago, zapatos said:

All of the descriptions are invented by us as a way to describe the effect we see

Yes physics is the attempt to understand the universe.

4 hours ago, zapatos said:

Isn't the effect we call gravity more 'real' than a description we invented

Yes there is the thing we want to work out, gravity and the attempt to understand it, the Theory of gravity.

5 hours ago, zapatos said:

The effect we call gravity seems real (to me at least) as it appears to act consistently, but our description of it changes based on something we make up. We used to call gravity a force, then we called it spacetime, and if we can come up with a better model that describes it as a sort of blowing aether and it additionally addresses quantum gravity, then we'll call it blowing aether. All of the descriptions are invented by us as a way to describe the effect we see. Isn't the effect we call gravity more 'real' than a description we invented just because it is the best predictive model at the time?

No, spacetime curvature is not merely an abstract theoretical notion. It is a measurable physical quantity. I've said on a number of occasions that the gravity with which we are familiar, including artificial gravity, is caused by time dilation. Time dilation is a measurable physical quantity, and by measuring how time dilation varies over the space surrounding the earth, one can prove that the spacetime surrounding the earth is curved. Thus, a correct theory of gravity must account for spacetime curvature.

Edited September 6Sep 6 by KJW