If all we perceive is the present, what are the proofs to affirm that time exists?

Question

I know this seems like a very trivial question and I don't know if there are methods to prove the existence of time. But even if there were, the fact that you can't perceive time as something continuous but as dots doesn't sound strange enough?

This is the thought experiment I imagined:

Imagine a series of points on a 2d graph, the y axis is position and the x axis is time. Suppose that each value in y corresponds to one photo, and each value of x corresponds to one second, that is FPS.

Since we do not see continuous time and we only see points (instants of times where there are very large spaces between the intervals) then we do not know how radically the object changes position (even to infinity), to make this more visible, Imagine you have glasses in which you can adjust your vision between 60 and approximately 0 fps, that means that at less fps your vision will be reduced even more without being able to predict the fluidity of the movement, this means that if you would choose an abysmal fraction of fps like 1/28800 fps that would be something like 1 frame every 8 hours, what you would see would change radically every moment. So if time existed we could not perceive time as something continuous either, even seeing at 60fps or 144fps, even more, you do not know how many frames really exist in a second, and since we assume that time is continuous that figure rises to infinity.

So the only way to see a continuous time would be to see an infinite number of frames per second

Therefore an object could in a certain position at a certain instant of time and radically change its position in a very short interval (what we perceive as very short).

So even if you could prove it exists, how can you trust the coherence of time?

EDIT 1.1: I ask these questions from complete ignorance, I am not versed in science so any correction is more than welcome. I tried to think about it from an ontological point of view.

EDIT 1.2: I would like to add to my questions: how can you ensure that the future exists? If the future has not happened and there are infinite possibilities (indeterminism) then the fact that there is a 4D block is impossible, since that would mean that the future happened and the universe is deterministic.

EDIT 2: When I ask if time is coherent, I mean: how can we be sure that there is something like past and future? I try to summarize by asking: what are the proofs to affirm that time exists? And if this can be proven (I don't know) then how can you trust the coherence in relation to the present? If we can only perceive and live in 3D that means that we cannot live in the past or in the future, by not being able to "feel" time we can only infer that time exists, but we cannot feel it (or can we?). The example of the fps serves to make this question visible, if the time were continuous (using intuition, since it could be discrete but this is less intuitive) we would not be able to notice all the changes, I did not notice that the speed of movement is limited by c, even so, I'm not sure if the fact that we cannot perceive time as something continuous in some way could generate huge distortions that we cannot notice as objects that move faster than light or something like that. Again I'm just speaking from ignorance.

Answer 1

We don't know time is continuous at small scales. But I don't think anyone claims it is.

You have asked several questions. But Is time real? does not seem to be one of them

(1) Is time continuous at small scales?

Experience tells us time seems to be continuous at large scales, but that might just be a consequence of it being divided into very small frames too small to measure with current instruments.

For example matter seems continuous at large scales -- like you can keep chopping a block of cheese in half forever -- but on closer inspection the cheese is not continuous. It is broken into atoms and there is a smallest possible amount of cheese you can have.

General relativity relies on time being continuous (at large scales) and gives accurate predictions. This however says nothing about the small scale physics where GR stops being useful. In my experience most mathematicians and scientist only see the continuousness as a useful mathematical tool and not a 100% accurate desciption of reality.

At small scales the properties of space behave strangely. The uncertainty principle from Quantum Mechanics tells us that the exact position of an object has no physical meaning. There are just degrees of certainty. Another problem is it sometimes becomes meaningless to say which of two atoms is which.

So it would not surprise me if the small scale structure of time also behaves strangely. Maybe not discrete, but probably not continuous. Say once you zoom in close enough it becomes meaningless to give the exact moment an event happened.

(2) If time is continuous can we prove it?

Probably not. Any experimental setup will only have finite precision. One might verify time does not behave as though it is broken into 0.0000001 nanosecond chunks, simply by designing a camera that can take that many frames per second, and filming a light beam as it travels across the room. But then what about 0.0000000001 nanosecond chunks?

Suppose there are Doctor Who aliens who, once per minute, appear all over the planet. They give everyone on the planet strange looks and then vanish one micro-nano-attosecond later. With the correct instruments you could prove whether these aliens are real or not. But that says nothing about the aliens that only last one micro-nano-atto-PICOsecond.

Of course this raises the cosmic speed limit problem. Nothing travels faster than the speed of light c and location stops being meaningful at the so-called planck length p. So a universe with frames smaller than c/p might have no physical meaning, since that's too short for anything meaningful to happen.

In this case you ask a question and, rather than have an answer for you to discover, the universe sticks out it's tongue and blows you a big raspberry.

There is also the foundational issue of what you should compare to in order to establish a temporally continuous universe. We set up the experiment such that if the universe is temporally continuous we get outcome X and otherwise we get outcome Y. It's unclear (and perhaps meaningless) how you would predict the behaviour of an experiment in a universe that by definition does not exist.

(3) Is time coherent?

I am not sure what this means. But I will point out that even if there was discrete time, it does not rule out coherence in the sense that each moment influences the next. It's just the influence looks different. For example video game time is discrete but the time is still coherent, in the sense that inputs from the player at one moment influence the world at subsequent moments.

Answer 2

In physics, time is part of a four-dimensional spacetime. Loosely, you can think of it as the name we give to the gaps between colocated events. Spacetime definitely exists for physicists, and I cannot imagine how you can doubt its existence given that it is a central part of everyone's day to day experience. We don't yet know whether spacetime is continuous or granular in some way, although there is a lot of research based on the assumption that it is granular at a scale far beyond reach of current experiments, which can measure intervals of time as short as 0.0000000000000000003 seconds, or thereabouts. Odd- to us- things might happen over very short timescales, but if they do then their effects must average out to yield what we consider to be normal physical behaviour at a macro scale.

You ask whether the future and the past exist. That is a matter of conflicting opinions among philosophers, and doesn't arise in physics, which instead takes the view that events happen over time, so a past event did happen at some point in spacetime and a future event will happen at some other point in spacetime. When an event happens, it does so in the present locally. There is no simple way of defining a universal 'present' in physics.

Your conscious experience of now is governed by the rate at which chemical process take place in your brain. Human perception cannot differentiate between events that are less than milliseconds apart, which is why a movie seems to be continuous when in fact it is not.

Answer 3

Imagine that time is nothing more than difference or change. If every single particle kept its location, there would be no time. This falls within how B-series proponents look at time.

Well what if some particles just moves so quick our brains can't see the changes? Nothing moves infinitely quick. There is a speed limit given by SR and GR. Each snapshot can only change so much in a certain duration. Each snapshot can only be so different from one to the next. Yes our conscious thoughts cant keep up with what the max speed limit allows to occur (picture a photon can circle the earth in the time a neuronal signal can travel 1026 feet), but we know from SR and GR what those limits are, and we can devise technology to really test that.

The laws of physics as we know them don't allow for just anything to happen between snapshot1 and snapshot2, there are restrictions. Each snapshot of the universe is just all the particles and their relative positions. For this example say a snapshot is 1/10 seconds long. Then the maximum distance a particle could go, is 30,000,000 meters (photon at c) from one snapshot to the next. As you make the snapshots quicker, the differences between snapshots become less.

Notice I did not need to invoke discrete vs continuous time. It could be either case at the deepest level, both are compatible with above.

Besides the speed limit laws/theorems, there are other laws like the conservation laws. These all put restrictions what particles can do from one snapshot to the next. I do not need infinite shutter to see without jump-cuts. But, maybe you say there is still an infinite continuum to space, so a free photon traveling at finite speed c, still must jump infinite infinitesimal distances, and we don't see that. Right, we don't witness that, as humans who can only process thoughts on much slower time scales, and our best experiments don't either.

Now we're just rehashing the old discreteness vs continuous nature of reality endless argument. Physics can work with both. There is math to handle both cases. Perceptually, I've already said why humans without aids don't experience jump-cuts as our biology is too slow to witness even non-infinite speed certain process can take place at (photons move at c, etc).

Answer 4

This is something St. Augustine wrestled with in Book 11 of his Confessions. He concluded that the only time we really perceive is the present. I'm not sure what would count as a proof that the past exists. Our own memories about the past are often flawed and incomplete. We all often forget or misremember our own pasts. Think of The Mandela Effect.

I don't believe this is a question of science. If you want a scientific answer you could measure the entropy of any system. If the entropy increases then time has definitely passed.

Answer 5

Sure. There's a philosophical argument that goes like this: Evolutionists claim the world is billions of years old and creationists claim it is only thousands of years old. But how can we know for sure that it is more than, say, 10 minutes old? Perhaps whoever or whatever created the universe created it to look older. They carefully made objects that appear old and rusted. They made rocks that look worn and weathered. Etc. But you say that's impossible because your memory goes back more than 10 minutes? But what is memory? If memory is just electrochemical impulses in your brain, perhaps the "maker" made you with impulses that are indistinguishable from true memories. Or if you have some more metaphysical theory about the mind and memory, makes no difference: perhaps the "maker" did whatever he needed to do to plant these false memories in your mind.

Science can only tell us about the present. Every experiment must be performed in the present. You say that you did a Carbon 14 test proving that this object is 5000 years old? But you weren't there 5,000 years ago to see it made. All you can really say is that you performed a chemical test in the present and found the relative concentrations of C14 and C12, and based on those measurements and a theory about decay rates etc, you conclude that the artifact is 5000 years old.

I've had many conversations where someone has said that science is the ONLY reliable way to gain knowledge. IF that's true, then we would have to conclude that we know absolutely nothing about history (and other subjects, but that's the relevant one here). It is impossible to test scientifically whether, say, Julius Caesar led an army that conquered Gaul, because no one claims that that war is going on now. It is a claim about the past, and -- unless someone invents a time machine -- there is no way we can perform an experiment in the past.

You then go on to what I think is a very different question about whether time is continuous or quantized, but this answer is already long enough so I won't even get into that.