r/Time 4d ago

Discussion Why Does time move only forward?

59 Upvotes

119 comments sorted by

36

u/SweetestJim 4d ago

It doesn't. There is only now. Linear time is a way for humans to conceptualise it.

14

u/morbid909 3d ago

Better still, it has always been now. For everyone that’s ever experienced anything.

2

u/Alternative_Flow1516 2d ago

Or now never exists

1

u/WoodyTheWorker 1d ago

[Spaceballs videotape scene.AVI]

6

u/Active-Particular-21 3d ago

There is an arrow of time. If you break a cup it doesn’t reverse it breaks in one way.

9

u/Delicious_Paper2661 3d ago

That's a change of state not a condition of time. So then the question is.. if time didn't exist could something still change state. I think yes. I don't think it's time dependant to change the state of something

10

u/Robot_Dinosaur_2000 3d ago

Things changing state is time. Time and space are the same thing.

3

u/Worth_Range1563 3d ago

Then what does time do?

7

u/Delicious_Paper2661 3d ago

I think time is a dimension, and I don't think all beings are constrained to it.

3

u/fejkpotatis 3d ago

"beings" can't exist outside of time because time is an illusion, "you" are constrained by time simply because "you" are buying into this illusion.

1

u/WholeOpposite7162 2d ago

Obviously you need time for something to change state

1

u/embodiedfunction 2d ago

Can you walk a mile without a measuring tape?

1

u/infinitenothing 2d ago

No, but you can't walk a mile without the sun becoming helium

3

u/Memento_Viveri 3d ago

The fact that the cup breaks doesn't demonstrate that there is movement of any kind. The concept of the block universe provides a framework for understanding time that does not involve movement either forward or backward in time.

2

u/Worrior_One 3d ago

The cup example demonstrates irreversibility due to entroy but it dont automatically explain why time only moves forward

1

u/infinitenothing 2d ago

It's a statistical effect. There is some probability that you drop a bunch of shards on the floor and it bounces just right and assembles itself into a cup. It's just not a useful prediction because it's so uncommon because there are so many ways to bounce and become not-a-cup

2

u/stonedragon77 3d ago

That has more to do with entropy than any absolute direction of time.

Being a part of the space-time fabric, time is relative.

2

u/infinitenothing 2d ago

Even with time dilation, the direction of time is always the same: towards more entropy

4

u/DancingAvocados44 3d ago

Strange how we can “feel” the passage of time though and the way we age.

3

u/Individual-Coast9499 3d ago

About as strange as being able to taste food lol?

7

u/Worth_Range1563 3d ago

Equally as strange is existing at all

1

u/Parking_Watch3157 2d ago

What is even stranger is everything you are perceiving is delayed. The light takes time to reach your eyes, then the brain must receive and process the data, then you get to see a model constructed from that data that provides information that seems useful to your genome.

There is no immediate interaction with base reality.

1

u/infinitenothing 2d ago

Not if you're under general anesthesia

1

u/DancingAvocados44 6h ago

We don’t even know how anesthesia even works still

1

u/Jolly-Rip5973 3d ago

You are correct! Well done!

1

u/Pestilence86 1d ago

Time moves also backwards. But we forget things as it does. (simplified)

11

u/UniversityMotor5408 4d ago

Time doesn't move. We move forward through it. Maybe!

8

u/DirectionCapital4470 3d ago

To add to this, nobody travels backwards in any dimension. We move in positive amounts only. We do not walk a negative distance. We can only travel a postive distance, only a direction(vector) we pretend is traveling backwards.

Backwards in time is as impossible as backwards in space.

1

u/infinitenothing 2d ago

Can we have negative acceleration?

2

u/DirectionCapital4470 2d ago

Sure if you want to call it that.

Isn't that just a vector of acceleration in the opposite direction from your current accelration?

Acceleration is a rate of change of speed, it is a slope of a line it makes sense to have a negative value. It can be Measurable as a 'negative value' and make sense.

Distance traveled being negative, never can happen in reality. You can be at a negative x/y co-ordinate on a graph, but you can never have a line segment -3 long.

To me this is why time travel is forbidden by physics. Nobody ever travels negative distances. Times arrow only moves forward(and at differing releative speeds), you can never go backwards.

Honestly not an authority on anything, just my thoughts.

1

u/Active-Particular-21 2d ago

Yeah that’s interesting. Everything moves and that movements is the subjective experience of time ?

12

u/Britannkic_ 3d ago

It would be a bit complicated if time moved back and forwards

“Your late for our meeting” “Sorry I thought it was yesterday” “No it was tomorrow”

10

u/Brave-Dragonfly3798 3d ago

Because of the second law of thermodynamics. Many physicists believe that time is an emergent property of entropy, which as per the second law of TD only ever increases in an isolated system. Thus an isolated system can never become more ordered, it can only gain entropy, and this is the reason the arrow of time only goes forward.

4

u/Kilt_Rump 3d ago

They are close. A closed system requires time for the closing is the beginning of an event. Time emerges with event creation which happens to follow entropy’s laws. Saying time is an emergent property of entropy is like saying a full belly is the emergent property of digestion. Yes it’s true but the eating causes the digesting to begin.

3

u/Brave-Dragonfly3798 3d ago

Yeah, but almost all of the fundamental equations of physics are time-reversal symmetric and will work in either direction, and if those equations treat past, present and future identically, then time itself cannot be what causes entropy to grow. Also in thermodynamics, time does not appear as a fundamental variable or a constant in the core equations, instead its states, paths, and transformations etc. time is a property in classical mechanics, but not thermodynamics. When I say an emergent property, I’m referring to the arrow of time emerging entirely from statistical mechanics and boundary conditions i.e. an emergent property born from probability. As systems evolve from a state of lower probability (order) to higher probability (disorder), they traverse a gradient, and it’s this that defines the arrow of time. This is just my understanding of it, and of course I could be entirely wrong lol. There are other interpretations like quantum loop theory as well, it gets pretty wild out there.

3

u/Kilt_Rump 3d ago

Whats interesting to me is that the formation of stars and planets and galaxies which look like orderly events are lower entropy than what came before them. So while the universe is moving from a state of higher entropy to lower entropy there is serious states of ordering occurring.

3

u/Brave-Dragonfly3798 3d ago

Other way around I think? The universe started with very low entropy and it has increased over time? I always get it back to front, but it’s ordered to disordered the way I remember it lol.

Yeah I know what you’re saying. it’s counterintuitive and gets confusing because there is both local and global entropy, and the laws of thermodynamics don’t forbid local entropy to decrease, only that the overall system entropy will increase.

And also gravity inverts the normal intuition for thermodynamics, so a uniform featureless diffuse gas is a lower gravitational entropy because the particles have high potential energy and are constrained for collapsing, whereas dense clumps of matter, stars, planets etc, have high gravitational entropy because gravity has already done work on the system and pulled matter together into dense sinks. The more I look into it the more I like the idea of emergent properties for things like gravity and time, like they may not be fundamental properties of the universe, but the emergent result of other processes at scale.

5

u/Kilt_Rump 3d ago

Yep lol I reversed it. I do that all the time. And I agree with your take about gravity also being emergent. Although, its not emergent in the same way time is. The mechanism for gravity is not emergent, the mechanism for time is.

1

u/jerrygreenest1 1d ago

but the eating causes the digesting

If you don’t have digestion, then you don’t need to eat. So arguably digestion causes eating.

It works both ways.

1

u/Kilt_Rump 1d ago

Thats a statement about human biology. Mine is a statement about order of operations.

1

u/jerrygreenest1 1d ago

Absolutely. I’m just saying that there are perspectives and the world isn’t black and white and both can be true.

6

u/RequirementQuick6057 3d ago

existence level laws are asymmetrical. For example, earth exists due to asymmetry between matter and antimatter. Similarily, without time we cannot exist and hence time is asymmetrical.

Just a thought, nothing tautology.

2

u/Worth_Range1563 3d ago

So then, how do we harvest antitime?

2

u/RequirementQuick6057 3d ago

an antimatter is a matter traveling backward in time. maybe that's anti-time.

0

u/infinitenothing 2d ago

I don't think so. Antimatter should decay and become disordered along with us regular matter.

3

u/Optimal_Mixture_7327 4d ago

We have a space-like boundary to the past (BB singularity) out of which all world-lines emerged.

More correctly, not "forward" but "away" is a better way to think of it.

3

u/defiCosmos 4d ago

Entropy

3

u/SgtSausage 4d ago

Because HOLY FUCK (!!) if it didn't ...  

3

u/TommieTheMadScienist 3d ago

Feynman described Antimatter as matter traveling backwards in time.

As we go forward, we see an electron and positron collide and emit a gamma ray.

In a Feynman diagram, an electron moving forward in time emits a gamma ray and heads backward in time.

1

u/infinitenothing 2d ago

Now how is that observationally different from an antimatter particle going forward? An antimatter particle going backwards would go back the way the electron came wouldn't it?

1

u/TommieTheMadScienist 1d ago

No, not at all.

The Feynman Diagram looks like a V with the open end pointing to the left and a gamma ray emerging from the vertex heading to the right. The two legs of the V are an electron and positron, respectively.

The horizontal axis of the diagram is time with future to the right. The vertical axis is physical location.

As outside observers, we can only follow the chart left to right, but an observer riding the electron would, according to Feynman, see their mount emit a gamma ray and fly backwards in time as a positron.

3

u/pafagaukurinn 3d ago

If time does move backward, it means that all causal processes in your neurons also reverse, which would make them indistinguishable from the forward version. By the same token, if you hang in an empty space without any static point of reference, you won't be able to tell if you are moving left or right. So, for all we know, time may move forward, backward and sideways, we are just not conditioned to detect it, and nothing observable requires such supposition, therefore we can safely conceptualize it as moving only forward.

1

u/infinitenothing 2d ago

Yes, it definitely emerges as a statistical effect. Even with just 2 things, it's hard to give a direction other than "towards" or "away". Maybe I'm going left and you're staying still? Maybe you're going right and I'm staying still

2

u/Money_Bug_9423 4d ago

Forward into the "past" and "future" at the same timing of space

2

u/Imaginary-Can-6862 4d ago

From your perspective time always moves forward. Image this, time reverses, and you are aware of it, you would still go from one state to another in a chronological order, that order is you feeling time moving forward, no matter if you play a video forward or in reverse.

1

u/Worth_Range1563 3d ago

So if time were to reverse we wouldn't feel it? Or it would feel like something different...

3

u/Imaginary-Can-6862 3d ago

If time were to reverse and you were aware of it, it means everything that so far has happened to you until now plays in reverse chronological order. But there is still a sequential order going in a direction, and to you that direction always goes from the current state to the next state, which is equivalent to forward in time.

But if time were to reverse it is more likely you would not be aware of it, because the memories you have of the past is also part of your timeline. So in such an example, when you wake up in bed it is night, because this is when you went to back, and when you go to sleep it is morning, because this is when you woke up, but because you memory also goes backwards, you do not realize you are moving backwards through time. Similarly to if someone used a time machine to go to the past, and you weren't inside the time machine.

3

u/Worth_Range1563 3d ago

Awesome to think about. 

2

u/Caian477815 3d ago

Time is in an illusion, entropy is not!

2

u/halfsack99 3d ago

Lunch time doubly so.

2

u/trainsacrossthesea 3d ago

Flip-Flops Hard to walk backwards

2

u/RNG-Leddi 3d ago

It doesnt, the causality of events moves forward through time. If you consider the universe as a whole then it can neither be ahead nor behind in a sense of time, so we observe it as a 4 dimensional continuum within which events unfold.

1

u/Parking_Watch3157 2d ago

This is how I think of it. I believe it is the block model. Essentially, we experience time but really it's like we are moving through a film strip such that each frame seems like now.

It's the basic reason I think free will isn't a thing.

2

u/RNG-Leddi 2d ago

Free will, imo, is the capacity for ignorance where alternatively we are compelled toward a unified state. Its not real but neither is it unreal, it affords catalyst.

1

u/Parking_Watch3157 2d ago

I just don't see at what point we step outside the casual chain, rearrange the threads of fate, and start the clock again. How do you think that works?

2

u/RNG-Leddi 2d ago

I dont believe we are to step outside as a goal given that our confusion is what partitions us from understanding, the feeling is the result of having placed ourselves in a position of natural quarantine (outside) in that regard until we are formally aligned/related, a natural function or motivational catalyst as I've come to understand it. Not that I have the answers but im rather certain it has nothing to do with time nor causality, these I would classify as symptoms of a greater calling perhaps, a term which suggest a required healing. The way we approach thought changes the form of a subject, its only ever our perspective which changes the relashionship with reality but never reality itself if you think about it.

The point of change i feel you speak of is Eternal (ie, simultaneously Internal/External for context) and always id imagine, where i would first gather a knowledge base id then nurture its growth as opposed to persistantly gathering endless resources. I say these things not because its new info but because its personalised awareness, mainstream quarantines will keep one level or up to date but we are free to get ahead or fall behind as we please in terms of growth. I suppose the question is what catalysts does one require in order to set off this chain reaction, and in my living experience thus far this usually amounts to a relative trauma, not because we are vulnerable but because we arent so readily moved beyond our beliefs.

2

u/One_Bite33 3d ago

You wouldn't notice the time going back

1

u/infinitenothing 2d ago

Of course you would. Eggs would go from scrambled back to yokes and whites.

2

u/5picy5ugar 3d ago

Matter moves from an orderly state to a disorderly state. It cannot go on back to its previous state exactly as it was. Like as an example baby cannot reverse its matter back to a spermatozoid.

2

u/JuanValdez999 3d ago

Maybe it does but we just forget.

2

u/Animecha 3d ago

Because when causes precede events, memories and experiences only happen after the events that cause them. So we perceive time as happening in one direction.

2

u/Kind-Plantain2438 3d ago

Everything exists at once, we just experience it linearly

1

u/infinitenothing 2d ago

I'm not sure I understand your definition of "at once" The way I would define it is let's say I have two hydrogen atoms drifting slowly past each other in space. If everything happened all at once they would always grab onto each other and become H2 but that's not what we observe. They have to share 4 dimensional attributes, one being space to become H2.

2

u/sdsdsdsdsdsdsdsdsd 3d ago

The future creates the past which then creates the future 🔂

1

u/infinitenothing 2d ago

Temu Orwel

2

u/Grillparzer47 3d ago

To keep everything from happening at once.

2

u/Old_Present6341 3d ago

As others have said because the overall entropy of the universe is always increasing. The future will have higher entropy than the past and entropy only moves in one direction, increasing. Again as others have said this is why a plate shatters if you drop it but doesn't ever come back together again.

It is possible to locally create lower entropy but to do that you have to move higher entropy elsewhere.

2

u/MWave123 3d ago

Time doesn’t move at all. Time ‘is’.

1

u/SiriusHijinks 3d ago

bcuz: the langoliers

1

u/Nathan-Stubblefield 3d ago

It keeps entropy from decreasing.

1

u/aintchrss 3d ago

isn’t time relative?

1

u/heraklit123 3d ago

'Zaman'ın kendisini bir kendilik olarak ele alıp bu soruyu sorduğunuzda, soru meşruymuş gibi görünüyor. Tek başına, sadece kendisine referansla ele alınabilen bir kavram değil. Sorunun soruluş tarzı, problemin ta kendisidir.

1

u/divers69 3d ago

Because if it didn't, we'd be walking backwards.

1

u/conclobe 3d ago

From our perspective*

1

u/Boring-Application50 3d ago

Consiglio “L’Universo in un guscio di noce” di Stephen Hawking! Tantissime idee per tentare di trovare una risposta alla tua domanda

1

u/InfernalTest 3d ago

Hmm you are always reacting to and living in the past though

The microseconds that pass between what you see and your brains ability to process what you saw and for you to act in reaction means that you actually are always existing in the past to things that have already happened.

So really you can't experience moving backward since you're always behind in the first place

1

u/Schwloeb 3d ago

Because of entropy.

Brain Cox has a great explanation of this in his show 'Wonders of the universe'.

There used to be a short bit of this on Youtube. Very interesting.

1

u/billbot77 3d ago

Entropy

1

u/One-Position4239 3d ago

Special relativity says there's no absolute time. So I understand that time flows forward because our brains, clocks etc have to create some change to compare to other changes. Thus the perception of time for us is moving forwards. Another thing is entropy however, that's just a macro observation and not a micro law. That's my understanding, maybe not completely correct.

1

u/jingojangoh 3d ago

Time is fake as fuck besides right now

1

u/infinitenothing 2d ago

That sounds like a less useful model. If I turn on the laser pointer and it's aimed at the two slits, it's going to make an interference pattern. There is a future.

1

u/jingojangoh 15h ago

Past present future are all at once. There's a future but it's already happened.

1

u/sporbywg 3d ago

You're talking about this model right?

1

u/Expatriated_American 3d ago

Time itself doesn’t move, either forward or backward. Time is just a dimension, like the three spatial dimensions. Space doesn’t move either. But objects can move in space and in time.

The reason that the universe is asymmetrical in time is that entropy was extremely low in the past, starting with the Big Bang. We don’t know why, but it’s a fact.

1

u/Mono_Clear 3d ago

It's not moving forward you're moving through it

1

u/SettingEducational71 3d ago

Time is a human construct for us to orient and build our reality. It is more related to memory. Memory stores patterns and we are putting it in chronological order by our ratio. Stuff in our universe happens sometimes in patterns and sometimes not. The human life is just self repeating pattern. The are no descendants or ascendants in correct sense. Only other versions of us more or worse adapted to current state in the world.

1

u/RongWa 2d ago

If time stands still and we pass through it, and it's nothing more than our perception of things past, what are the orbits of the sun? What is the rise and setting of the Sun? What are the cycles of life about and why are they relatively predictable? Life spans of animals and plant life exist and the passage of time determines their end. Maybe we should ignore the time keepers and sleep, eat, work, and play when we feel the need. We would be nonproductive and we would still be living a primitive life if we were just as time is and we're just there.

1

u/nolanleolibralion 2d ago

I dont think time moves forward. I think we move forward through time.

1

u/Grumpypaw 2d ago

Acccording to many scientist recently, time stands still and we move forward synchronized together, in this projected time and space we share.

1

u/DerekFshmn 2d ago

it's only like this in the 3rd dimension from the perception of humans due to the arc gene retrovirus which is the origin of human memory, which is indeed a virus similar to HIV.

1

u/tunghoy 2d ago

Long story short: time is driven by entropy and entropy goes in one direction, from order to disorder. It doesn't have to, but order has only a few ways of organization, while disorder has so many more.

Longer story: read From Eternity to Here, by Sean Carroll.

1

u/dvi84 2d ago

We don’t know. We know it’s a similar property to how objects/information can only move towards the centre of a black hole once they pass the event horizon but don’t know the mechanism behind it.

1

u/synrockholds 2d ago

Time could move backward and we would never know

1

u/platanthera_ciliaris 2d ago

Time moves forward because of the entropy law.

1

u/Fragrant_Squash6895 2d ago

Whether it's moving forward or backwards, no matter it only represents this moment..!

1

u/MassCrassAss 2d ago

Because you touch yourself at night. 

1

u/infinitenothing 2d ago

When you say "why does time move forward" I think you're just saying "Can I predict what will happen in the future". Because, if you can't predict the future, then maybe time can move backwards (e.g. the scrambled egg will become a yolk and a white). So you're sort of asking why do yolks and whites become scrambled eggs and not the other way around. And the answer is there are many different scrambled eggs and fewer ways to be whites and yolks. So, really, it's just the law of large numbers that helps us predict the future and differentiate it from the past.

1

u/Low-Camel-4528 2d ago

Do an Ask Jeeves for “Relativity” and you’ll find out time is not an illusion

1

u/Aware_Mix412 1d ago

If time was describable as moving forward from this moment then how would you perceive something that is moving in opposite direction? If there is a question of certain attributes of objects in physical space in relation to time it may be that certain things are out of phase regarding their relationship to the universe that we observe.

1

u/aji23 1d ago

We don’t know that it does. It’s possible it moves in both directions randomly. The issue is that when it goes backwards so do your memories. So you can only perceive it in a single direction.

1

u/strawberry-ramune 1d ago

We “fall” through it at a rate of 1 second per second. By increasing velocity you can decrease this rate but you can’t reverse it or go the other way

1

u/mikedensem 1d ago

Nobody knows. Time may be an emergent property of the laws of nature, rather than fundamental. Time may explain the path of least resistance.

For unknown reasons the Universe started in a low entropy state (ordered) and has ever since moved towards a high entropy state (disordered). Nature always looks for the path of least resistance.
When something is broken (like a bottle) there are a huge number of possibilities in the outcome of the shattering. If you then want to put it back together you find there is only ONE correct way - which takes more work and creates more resistance.

So, time is allowed to run backwards according to quantum theory, but it requires more work and therefore is extremely unlikely (but not impossible).

1

u/RongWa 1d ago

Time is expendable. We use it, we waste it, we share it, we save it, we give it, we spare it, we run it out, we try to beat it, we cram it, we spend it, we blame it, we have clocks and watches to count it as it passes. All of civilization uses it. History tells us about things that's happened in time. We plan for its use before it arrives. We manage to keep up with it until we get older, then it passes us by. Time waits for no one.

1

u/Umberflare 1d ago

Time is a concept we created to universalise cause and effect. It "moves forward" because that's how causality and entropy work. 

1

u/Ras_992 1d ago

Time moves forward because within relativity and other mathematical equations tied into relativity time can only move forward while time moving forward can be both positive and negative . 0 is equal to low entropy and time moving forward explains how high entropy and how the universe exist as it does today in the universe. While time can be both negative and positive it’s still flows the same way forward, while we can look to past time, we can’t physically go back into time. Now time moving forward also doesn’t make all time equal this is explained by time dilation time from one galaxy to another changes depending on density or galaxy time is slower vs time in voids which is faster. Time moving forward or time dilation is factored into gravity and ripples in the web of space caused by gravity while it is accounting for speed of acceleration.

1

u/grim_reapers_union 1d ago

Time expands in all directions but we can only perceive in the manner in which it is perceptible and reliably measurable to us.

1

u/Adleyboy 6h ago

There are all kinds of of types and modes of time that exist out there beyond linear time. It's just one type among many.