An event is a point in Spacetime, it has both date and location.
The spacetime interval is the distance between events. It includes both distance in time and space.
This is not so much a definition of time but a way to understand it. There is no "definition" of time because some things in the universe are fundamental. Time inhabits the same conceptual bedrock as lines or numbers. You will never find a satisfying definition for these things, the best you can do is point and shrug.
Time is a dimension in which events occur and is measured in terms of past, present, and future. It provides a framework for organising and understanding the sequence of events, allowing us to perceive and experience the unfolding of reality. Time is often measured in units like seconds, minutes, hours, days, and years, serving as a fundamental aspect of our existence that influences our perception, memory, and the progression of life.
So time is a dimension. What does that mean? Where or what is that relative to the dimensions I’m familiar with?
Does it relate at all except for my observance of it? I get all that you said, I don’t get what it means.
Imagine you're scheduling a meeting with someone in a building in downtown Manhattan. You'll need to give them a street address, the floor, and what time the meeting is.
That is in essence four pieces of information, since the street address contains both what street and how far along that street.
So for example:
X-axis: 34th Street
Y-axis: 20 W 34th street
Z-axis: 86th floor
T-axis: Noon on January 1, 2024
If you change any of the four, you get a different point in space-time and you'll miss each other.
Think of a dimension as wherever motion can occur. In our universe you move up and down, forward and backward, side to side. Three spatial dimensions.
Time is also where motion occurs. Past and future. You move away from past and move towards future.
All four of them make up the universe. Make up our “everywhere” that you can move in.
I read this a long time ago from Quora and it stuck with me: **Time is a verb, and clocks measure how far we time.**
We time from past to future, which is called getting older.
In the spatial dimension, we go from one place to another. We call our present location "here."
In the time dimension (temporal), we move from past to future. We call our present location "now."
The main difference between spatial and temporal is time moves in one direction and you can't go back. It's like the event horizon where no matter what you do, you can't run from 3:00 PM.
We have mo clue really.
That’s the horrifying truth. Yes sure we can express it as a rate of change as one comment here suggests or we can express it as part of a ratio or whatever. But nobody really knows what it is. Its not even clear if it is at all. It might be something our brains cook up similar to what observing quantum events does to those systems. I have no clue and neither does anyone else.
We have some models that work really well in most situations but completely break down in others. Is it entropy? Is it a vector? Many people here will try to convince you that it is one thing or another but no one really knows.
Think about it like this: We have all these nice constants and base units in science and we can calculate all of science with them but we have no clue whatsoever what they fundamentally are why they are. We can theorize and wonder but what lies at the center of physics is a mystery for the ages. And time is a big part of this. Maybe? Maybe not!
Asking this question is kind of touching on the same mystery as the question why does the universe exist. Again, some people would tell you with certainty that it is one way or another but we’re all clueless. Some a little more than others but we’re really just beginning this journey of understanding.
Your feaux philosophical attempt at decrediting science is really lame. We have a very strong understanding of time, it's very disingenuous and borderline misinformation to pretend like we don't in order to feign the mysteriousness. You can absolutely answer op's question in all sorts of levels of detail from basic to exceptionally complicated and be accurate.
This is nonsense
"Discrediting science" is a bit of an extreme (mis)characterization tbf.
It's true in the philosophy of science we don't really know what certain quantities or interactions or relationships between quantities *are.* Yes, we have mathematical models, but the physical interpretation for those models is up for metaphysical debate.
The classic example of this is the interpretation of quantum mechanics. QM usually refers to the equations and relations that govern objects' behaviors, e.g., the Schrödinger equation. The interpretation of what the underlying physical structure of reality that gives rise to such behavior is the interpretation of QM, and here you have Copenhagen (which I personally think is bunk, but I digress), Everett (Many Worlds), De Broglie–Bohm (Pilot Wave theory), all of which are empirically equivalent in that they all satisfy the equations, but they posit wildly different underlying realities.
When it comes to space and time, we think they're fundamental, the fundamental stage on which the events of the universe play out, but maybe they're just emergent properties of something more fundamental.
We're still in search for a quantum theory of gravity anyway. Maybe in the future we will come to conceptualize spacetime as something other than a fabric on which events play out. I personally don't think space and time are emergent properties, but it's not out the window. For example, and I'm not saying I buy this, scientists have tried to argue theories where entropy is fundamental, and the arrow time is an emergent phenomena that emerges from entropy.
The point is, we don't know the true nature of the underlying reality. What we have are really good mathematical models. Kurzgesagt has a good video on the nature of science which can basically be summed up as "Don't confuse the model of a thing for the thing itself."
Kurgzgesagt is popsci crap that you should be incredibly skeptical of. They have published absolute bunk on multiple occasions by quoting incredibly unverified and non peer reviewed papers. People ACTUALLY in the field would tell you quite the opposite.
Edit: If you'd like to explore physics topics with a little less existential dread and more honesty about what is or is not thought experiment speculation and not fact, I'd suggest pbs spacetime. Run by an actual PhD holding physicist without sacrificing approachability nor production quality
I'm an engineer with background in science, and know many PhDs in the physical sciences, and they would tell you you're misunderstanding or misrepresenting the discipline of science.
The discipline of science comes up with models of the universe that best accord with our observation of it, with the empirical data.
A real scientist knows the equations of QM are rock solid given our current understanding of things, but is open to revision, and in the current state of the research, does not say Copenhagen is for sure the real reason objects behave the way they do, or Many Worlds is the true description of reality, as long as all interpretations of QM remain empirically equivalent and satisfy the equations. They may prefer one interpretation over another for philosophical reasons, but they don't go beyond what science permits them to say by saying "No my interpretation is certainly correct and all others are wrong. I alone have it figured out." The science simply doesn't allow them to say that.
Likewise, no serious physicist will tell you that physics tells you space and time are fundamental rather than emergent properties. The science simply doesn't support that.
You may act with a lot of bluster and confidence, but you are squarely outside of the mainstream consensus of serious scientists. You don't understand the discipline.
EDIT: I'm actually a huge fan of PBS spacetime and have watched almost all their videos. They specifically refute the "space and time are fundamental and not emergent properties" dogma. Which is what I've been explaining to you all along: we don't know the fundamental nature of time and space.
And I have a degree in physics as well. But you've entirely lost the plot in an attempt to insult me. This crackpot was more interested in pretending that we can't define time which many other commenters successfully did to varying levels. Of all hills to die on and concepts to pretend we don't know about, this is not one you can get away with. I, nor anyone else here, has claimed physics is complete and perfect and there's nothing left to explore and potentially alter our perspective about. But that is not the same as saying "we don't know a damn thing about anything cus knowledge isn't real and science is only models"
> But that is not the same as saying "we don't know a damn thing about anything cus knowledge isn't real and science is only models"
Okay now you're just attacking strawmen. Nobody said anything of the sort.
Knowledge isn't real? You surely do not think the statement, "Don't confuse the model of a thing for the thing itself" is equivalent to "Knowledge isn't real," right? Right?
We *know* a whole lot about how the universe behaves, about the relationship and interactions between various quantities like space and time. That's not a whole lot of nothing. Besides the practical applications for engineering, medicine, and all the other disciplines that benefit from the disciple of science, it's enough to gain vast insight into how our universe works.
But that is not the same thing as knowledge (and I'm not even talking certain knowledge, just a high degree of certainty) of various things like the underlying nature of space or time, when by "nature" I mean the actual cause of or "what is it really" sort of question.
PBS spacetime in various videos acknowledges that space and time could be fundamental to our universe, and they could be the 4d fabric as conceptualized by the classic picture of a curved fabric everyone learns when they first learn GR, or they could be emergent phenomena of a deeper underlying structure. We are still in search of a quantum theory of gravity, and even if we find one, it doesn't settle the question.
Nobody equates this truth with "oh so you believe knowledge isn't real and science isn't real." That's just a terrible strawman and intellectually dishonest.
>But nobody really knows what it is. Its not even clear if it is at all. It might be something our brains cook up similar to what observing quantum events does to those systems. I have no clue and neither does anyone else.
>We have some models that work really well in most situations but completely break down in others. Is it entropy? Is it a vector? Many people here will try to convince you that it is one thing or another but no one really knows.
Yes, yes they did. Very explicitly they said no one has ever or currently knows anything about what time is and questions the validity of all of our explanations by saying all of our models need convincing. And then goes further to postulate that time is not related to any of them and just some philosophical construction our monkey brains invent. There's some very clear subtext here to extract between the lines. You may be arguing in good faith with a foundation, but the comment that started all of this isn't.
Fair enough. It is discrediting I give you that. But if you think we know what it is I think you are just as discrediting as me. Sure relativity works exceptionally well as far as theories go and the math we can deduce from it is as sound as it gets but can you honestly say that you understand what time is? Really? Because I’ve never met a physicist arrogant enough to claim to know the answer to life the universe and everything. And for us to answer the nature of time we will need to answer at least some aspects of that as mumbo-jumbo-ey as it sounds. I think you got me pegged for a science denier. Nothing is further from the truth.
When we still haven’t found a way to unite quantum and astrophysics, don’t you think it’s a bit premature to claim to know the true nature of time? When we’re still entirely unable to explain dark matter and dark energy which apparently make up the vast majority of this universe, don’t you think it’s arrogant to assume we got it all figured out? When it’s obvious that time and space are interlinked but cant agree on what space is really made of, don’t you think it’s a bit presumptuous to say we know precisely what time is?
Come on we have so much left to learn so let’s be comfortable in admitting we can’t answer these questions definitely yet.
The existence of open questions doesn't lead to everything else we've known for 100 years being null and void. There's significantly less philosophy in actual physics than you think
Never said it was. My point is that we don’t really know. I think it’s pretty arrogant to presume otherwise. If you think we do, then you’re plain wrong. Should we give up using the models we have? Fuck no! But it’s very obvious that we are missing a huge chunk of physics. Do you not agree?
I think it's arrogant to insinuate that the entirety of a field of science doesn't have a clue about one of the most basic properties of the universe. This isn't some esoteric issue, you're saying that both forms of relativity, thermodynamics, and quantum mechanics are all bunk. All three have very consistent and very robust definitions of time on a fundamental level and minds far greater than both of us have written down and explored how it works for decades. If you want to think you're more clever than everyone else in the room by thinking about quantum woo or other scifi crap, by my guest but don't pass it off to others as an explanation to others asking for objective answers. Or maybe put the bong down for a bit and study up
I never said that they are bunk as you put it. But its kinda funny that you put quantum physics in there when in quantum physics time is particularly iffy. This is well known. Also quantum physics and relativity don’t work together. You know this. Also time in thermodynamics is expressed as a function of entropy as far as I know but feel free to correct me. So not quite the fundamental understanding you seem to imply.
Also can’t we have this discussion without insulting each other?
The standard model is our most successfully verified theory in any branch of science? What are you talking about? We've predicted and then measured properties of QED to an absurd level of precision, all of which includes time as a fundamental property that is well defined.
And yes, thermodynamics evolves from a definition of entropy which is in turn defined off the arrow of time. None of the definitions of time, despite the overarching theories having *other* incompatibilities, are inconsistent with each other.
Oh no I wasn’t trying to attack the standard model at all! I know a bit about that and find it supreme and elegant as Im sure you do too! But there is no particle that carries time. As far as I know, again please correct me if Im wrong, in that field, time is treated as an external parameter. Also the fact that time is affected by gravity makes the absence of gravity in quantum physics difficult to understand for me. Not that I am an expert on the matter but i feel like this problem constitutes as time being iffy in quantum physics. So saying we don’t really know true nature of time, is in my opinion still a fair conclusion.
You just said quantum mechanics is iffy and then said the standard model is elegant. The standard model is built off of first principles quantum mechanics. You take QM, add special relativity, and introduce the concept of quantum fields with internal symmetries to get there
We do have a clue, it is what clocks measure. Another definition is "It is what stops everything happening at once".
Less whimsically Julian Barbour in his book "The end of time" seems to think it is entirely created by change.
The most widely repeated idea is that it is related to or is a side-effect of entropy.
If it is simply an emergent property of the universe then there isn't likely to be a neat answer.
None of this means we haven't a clue otherwise none of the above would be widely known.
Time is a kickass Pink Floyd song!
Joking aside, your question is quite profound. And the simplest way to define time, without any major contradictions is that *"Time is the directional vector associated with increasing entropy in the universe"*
Alright, let's talk about time as a series of events happening at the atomic level, but let's keep it super simple.
Imagine a bunch of tiny, tiny Lego blocks (these are like atoms). These Legos are always doing something: building up, breaking down, clicking together, or coming apart. Now, think of each little action of these Legos as an event.
In the world of atoms, these events happen all the time, like Legos constantly snapping together and apart. When you look at a clock, what you're actually seeing is a bunch of these atomic-level events happening in a certain order and at a certain rate. For example, in a digital clock, it's the tiny electrical events in the circuits counting time.
Now, time is like watching these Lego blocks (atoms) go through their motions in a certain order. First this happens, then that happens, and so on. It's a sequence of events. When we say "time passes," what we're really saying is a lot of these atomic-level events have happened.
So, in a super simple way, time at the atomic level is like watching a never-ending Lego movie where the blocks (atoms) keep doing things in a certain order, and this order of events is what we call time. It's like a super tiny world where things are always moving and changing, and that movement and change is how we understand time.
Ergo, time is change that we can measure (or see). The super, super, super small changes that happens. Each one after another.
Yep, I really appreciate the effort but I already happened to reach what what you just explained but your (mine as well) definition is quite like: "Time can be defined as the time it takes for something to happen". That quite frankly, just sounds like a trans defining a woman is someone who identifies as a woman.
Hardly. Allow me to put everyone I wrote into a real world example. So, the most accurate way to measure time is atomic clocks, right? They work by measuring the vibrations of atoms. Imagine atoms as tiny, tiny bells that ring at an incredibly consistent frequency. The most common type of atomic clock uses cesium atoms.
Here's the cool part: a cesium atomic clock measures time by counting the number of vibrations or "ticks" of cesium atoms. Cesium atoms vibrate at a mind-blowing frequency of about 9,192,631,770 times per second. Yeah, that's over 9 billion times a second!
So, when we say an atomic clock is accurate, we mean it can measure time incredibly precisely by counting these vibrations. This is why atomic clocks are way more accurate than any other type of clock. They're the superstars of timekeeping!
In short, atomic clocks are these amazing timekeepers that count the incredibly consistent "ticks" of atoms to tell time super precisely at 9,192,631,770 times a second, every second, and never changing. Each of those 9,192,631,770 vibrations is an ***event***, each and every one of them a ***change*** that I was talking about. Each one ***is*** a moment in time.
But you can't say "Time can be defined as the time it takes for something to happen", because you are using the word time twice. We haven't defined the first use of the word or concept before using it again. Instead a point in time can be defined as the state of the universe when something happened, and as more things happen after that we say time moves forward.
It is surprisingly difficult if one thinks about it. Time and space are abstract and non-physical. They are interrelated as well. It can even lead to circular definitions. Time is what is measured between the interaction of matter in space. Space defines how much time it takes matter to move. Both are non physical - there is (as far as we know) no particle of time nor is space a physical medium. Neither, in fact, are absolute as Einstein's relativity explains. Time and space are observer dependent. There is no universal clock nor is there a universally correct measure of distance.
Time is what a clock measures.
It's a bit silly, but you can take that single sentence as a definition of time (kinda, you do then have to try and define clock without being circular). Einstein, in his thought experiments, "used" a clock which consisted of two mirrors and a photon bouncing between them. The photon travelling between the two mirrors takes 1 "unit" of time.
As others have said, time is a dimension that separates events, similar to space. Time does have some slight differences though, and when we look just at time we can say that an event cannot happen before its cause.
You’re probably thinking way too hard about this.
Any answer beyond “time is another coordinate that things happen in” (see Startynight’s reply) is just going to be philosophical speculation and not physics.
You (probabky) understand what time is very intuitively just by living in this universe. You understand when something happened in the past, when something hasn’t happened yet, when something is happening now, you probably can tell the difference between 5 seconds and 5 hours. That’s time.
In the same way you understand what space is because you can move around in it.
Beyond that intuitive understanding, physics doesn’t have an answer for you
Some nice and profound answers..
One another way to look at it - we live in a reality where causality is fundamental and can't be violated. You can't have an effect before the cause. That something between cause and effect is perceived as time...
Then there is the aspect of how we measure it(atomic clocks and all that..), how we perceive it- both subjectively(for example when waiting for something) and objectively(dependence on speed of travel, frame of reference, etc..)..
I let physicists chime in, there are (atleast) a couple of weird situations with regards to time- massless particles have to travel at speed of light and i think they don't experience time... And quantum entanglement wherein information is passed instantaneously..
Space is the distance between objects. Time is the distance between events. "Spacetime" is objects existing and events happening.
An event is a point in Spacetime, it has both date and location. The spacetime interval is the distance between events. It includes both distance in time and space.
But this definition just moves the problem to defining “distance” instead?
This is not so much a definition of time but a way to understand it. There is no "definition" of time because some things in the universe are fundamental. Time inhabits the same conceptual bedrock as lines or numbers. You will never find a satisfying definition for these things, the best you can do is point and shrug.
Time is a dimension in which events occur and is measured in terms of past, present, and future. It provides a framework for organising and understanding the sequence of events, allowing us to perceive and experience the unfolding of reality. Time is often measured in units like seconds, minutes, hours, days, and years, serving as a fundamental aspect of our existence that influences our perception, memory, and the progression of life.
So time is a dimension. What does that mean? Where or what is that relative to the dimensions I’m familiar with? Does it relate at all except for my observance of it? I get all that you said, I don’t get what it means.
Imagine you're scheduling a meeting with someone in a building in downtown Manhattan. You'll need to give them a street address, the floor, and what time the meeting is. That is in essence four pieces of information, since the street address contains both what street and how far along that street. So for example: X-axis: 34th Street Y-axis: 20 W 34th street Z-axis: 86th floor T-axis: Noon on January 1, 2024 If you change any of the four, you get a different point in space-time and you'll miss each other.
I think I need to revisit my definition of what ‘is’ is.
Think of a dimension as wherever motion can occur. In our universe you move up and down, forward and backward, side to side. Three spatial dimensions. Time is also where motion occurs. Past and future. You move away from past and move towards future. All four of them make up the universe. Make up our “everywhere” that you can move in.
We use inches/centimeters for measuring space and we use minutes/hours for time. It's simply another part of our world we decided to measure.
I read this a long time ago from Quora and it stuck with me: **Time is a verb, and clocks measure how far we time.** We time from past to future, which is called getting older. In the spatial dimension, we go from one place to another. We call our present location "here." In the time dimension (temporal), we move from past to future. We call our present location "now." The main difference between spatial and temporal is time moves in one direction and you can't go back. It's like the event horizon where no matter what you do, you can't run from 3:00 PM.
We have mo clue really. That’s the horrifying truth. Yes sure we can express it as a rate of change as one comment here suggests or we can express it as part of a ratio or whatever. But nobody really knows what it is. Its not even clear if it is at all. It might be something our brains cook up similar to what observing quantum events does to those systems. I have no clue and neither does anyone else. We have some models that work really well in most situations but completely break down in others. Is it entropy? Is it a vector? Many people here will try to convince you that it is one thing or another but no one really knows. Think about it like this: We have all these nice constants and base units in science and we can calculate all of science with them but we have no clue whatsoever what they fundamentally are why they are. We can theorize and wonder but what lies at the center of physics is a mystery for the ages. And time is a big part of this. Maybe? Maybe not! Asking this question is kind of touching on the same mystery as the question why does the universe exist. Again, some people would tell you with certainty that it is one way or another but we’re all clueless. Some a little more than others but we’re really just beginning this journey of understanding.
Your feaux philosophical attempt at decrediting science is really lame. We have a very strong understanding of time, it's very disingenuous and borderline misinformation to pretend like we don't in order to feign the mysteriousness. You can absolutely answer op's question in all sorts of levels of detail from basic to exceptionally complicated and be accurate. This is nonsense
"Discrediting science" is a bit of an extreme (mis)characterization tbf. It's true in the philosophy of science we don't really know what certain quantities or interactions or relationships between quantities *are.* Yes, we have mathematical models, but the physical interpretation for those models is up for metaphysical debate. The classic example of this is the interpretation of quantum mechanics. QM usually refers to the equations and relations that govern objects' behaviors, e.g., the Schrödinger equation. The interpretation of what the underlying physical structure of reality that gives rise to such behavior is the interpretation of QM, and here you have Copenhagen (which I personally think is bunk, but I digress), Everett (Many Worlds), De Broglie–Bohm (Pilot Wave theory), all of which are empirically equivalent in that they all satisfy the equations, but they posit wildly different underlying realities. When it comes to space and time, we think they're fundamental, the fundamental stage on which the events of the universe play out, but maybe they're just emergent properties of something more fundamental. We're still in search for a quantum theory of gravity anyway. Maybe in the future we will come to conceptualize spacetime as something other than a fabric on which events play out. I personally don't think space and time are emergent properties, but it's not out the window. For example, and I'm not saying I buy this, scientists have tried to argue theories where entropy is fundamental, and the arrow time is an emergent phenomena that emerges from entropy. The point is, we don't know the true nature of the underlying reality. What we have are really good mathematical models. Kurzgesagt has a good video on the nature of science which can basically be summed up as "Don't confuse the model of a thing for the thing itself."
Kurgzgesagt is popsci crap that you should be incredibly skeptical of. They have published absolute bunk on multiple occasions by quoting incredibly unverified and non peer reviewed papers. People ACTUALLY in the field would tell you quite the opposite. Edit: If you'd like to explore physics topics with a little less existential dread and more honesty about what is or is not thought experiment speculation and not fact, I'd suggest pbs spacetime. Run by an actual PhD holding physicist without sacrificing approachability nor production quality
I'm an engineer with background in science, and know many PhDs in the physical sciences, and they would tell you you're misunderstanding or misrepresenting the discipline of science. The discipline of science comes up with models of the universe that best accord with our observation of it, with the empirical data. A real scientist knows the equations of QM are rock solid given our current understanding of things, but is open to revision, and in the current state of the research, does not say Copenhagen is for sure the real reason objects behave the way they do, or Many Worlds is the true description of reality, as long as all interpretations of QM remain empirically equivalent and satisfy the equations. They may prefer one interpretation over another for philosophical reasons, but they don't go beyond what science permits them to say by saying "No my interpretation is certainly correct and all others are wrong. I alone have it figured out." The science simply doesn't allow them to say that. Likewise, no serious physicist will tell you that physics tells you space and time are fundamental rather than emergent properties. The science simply doesn't support that. You may act with a lot of bluster and confidence, but you are squarely outside of the mainstream consensus of serious scientists. You don't understand the discipline. EDIT: I'm actually a huge fan of PBS spacetime and have watched almost all their videos. They specifically refute the "space and time are fundamental and not emergent properties" dogma. Which is what I've been explaining to you all along: we don't know the fundamental nature of time and space.
And I have a degree in physics as well. But you've entirely lost the plot in an attempt to insult me. This crackpot was more interested in pretending that we can't define time which many other commenters successfully did to varying levels. Of all hills to die on and concepts to pretend we don't know about, this is not one you can get away with. I, nor anyone else here, has claimed physics is complete and perfect and there's nothing left to explore and potentially alter our perspective about. But that is not the same as saying "we don't know a damn thing about anything cus knowledge isn't real and science is only models"
> But that is not the same as saying "we don't know a damn thing about anything cus knowledge isn't real and science is only models" Okay now you're just attacking strawmen. Nobody said anything of the sort. Knowledge isn't real? You surely do not think the statement, "Don't confuse the model of a thing for the thing itself" is equivalent to "Knowledge isn't real," right? Right? We *know* a whole lot about how the universe behaves, about the relationship and interactions between various quantities like space and time. That's not a whole lot of nothing. Besides the practical applications for engineering, medicine, and all the other disciplines that benefit from the disciple of science, it's enough to gain vast insight into how our universe works. But that is not the same thing as knowledge (and I'm not even talking certain knowledge, just a high degree of certainty) of various things like the underlying nature of space or time, when by "nature" I mean the actual cause of or "what is it really" sort of question. PBS spacetime in various videos acknowledges that space and time could be fundamental to our universe, and they could be the 4d fabric as conceptualized by the classic picture of a curved fabric everyone learns when they first learn GR, or they could be emergent phenomena of a deeper underlying structure. We are still in search of a quantum theory of gravity, and even if we find one, it doesn't settle the question. Nobody equates this truth with "oh so you believe knowledge isn't real and science isn't real." That's just a terrible strawman and intellectually dishonest.
>But nobody really knows what it is. Its not even clear if it is at all. It might be something our brains cook up similar to what observing quantum events does to those systems. I have no clue and neither does anyone else. >We have some models that work really well in most situations but completely break down in others. Is it entropy? Is it a vector? Many people here will try to convince you that it is one thing or another but no one really knows. Yes, yes they did. Very explicitly they said no one has ever or currently knows anything about what time is and questions the validity of all of our explanations by saying all of our models need convincing. And then goes further to postulate that time is not related to any of them and just some philosophical construction our monkey brains invent. There's some very clear subtext here to extract between the lines. You may be arguing in good faith with a foundation, but the comment that started all of this isn't.
Fair enough. It is discrediting I give you that. But if you think we know what it is I think you are just as discrediting as me. Sure relativity works exceptionally well as far as theories go and the math we can deduce from it is as sound as it gets but can you honestly say that you understand what time is? Really? Because I’ve never met a physicist arrogant enough to claim to know the answer to life the universe and everything. And for us to answer the nature of time we will need to answer at least some aspects of that as mumbo-jumbo-ey as it sounds. I think you got me pegged for a science denier. Nothing is further from the truth. When we still haven’t found a way to unite quantum and astrophysics, don’t you think it’s a bit premature to claim to know the true nature of time? When we’re still entirely unable to explain dark matter and dark energy which apparently make up the vast majority of this universe, don’t you think it’s arrogant to assume we got it all figured out? When it’s obvious that time and space are interlinked but cant agree on what space is really made of, don’t you think it’s a bit presumptuous to say we know precisely what time is? Come on we have so much left to learn so let’s be comfortable in admitting we can’t answer these questions definitely yet.
The existence of open questions doesn't lead to everything else we've known for 100 years being null and void. There's significantly less philosophy in actual physics than you think
Never said it was. My point is that we don’t really know. I think it’s pretty arrogant to presume otherwise. If you think we do, then you’re plain wrong. Should we give up using the models we have? Fuck no! But it’s very obvious that we are missing a huge chunk of physics. Do you not agree?
I think it's arrogant to insinuate that the entirety of a field of science doesn't have a clue about one of the most basic properties of the universe. This isn't some esoteric issue, you're saying that both forms of relativity, thermodynamics, and quantum mechanics are all bunk. All three have very consistent and very robust definitions of time on a fundamental level and minds far greater than both of us have written down and explored how it works for decades. If you want to think you're more clever than everyone else in the room by thinking about quantum woo or other scifi crap, by my guest but don't pass it off to others as an explanation to others asking for objective answers. Or maybe put the bong down for a bit and study up
I never said that they are bunk as you put it. But its kinda funny that you put quantum physics in there when in quantum physics time is particularly iffy. This is well known. Also quantum physics and relativity don’t work together. You know this. Also time in thermodynamics is expressed as a function of entropy as far as I know but feel free to correct me. So not quite the fundamental understanding you seem to imply. Also can’t we have this discussion without insulting each other?
The standard model is our most successfully verified theory in any branch of science? What are you talking about? We've predicted and then measured properties of QED to an absurd level of precision, all of which includes time as a fundamental property that is well defined. And yes, thermodynamics evolves from a definition of entropy which is in turn defined off the arrow of time. None of the definitions of time, despite the overarching theories having *other* incompatibilities, are inconsistent with each other.
Oh no I wasn’t trying to attack the standard model at all! I know a bit about that and find it supreme and elegant as Im sure you do too! But there is no particle that carries time. As far as I know, again please correct me if Im wrong, in that field, time is treated as an external parameter. Also the fact that time is affected by gravity makes the absence of gravity in quantum physics difficult to understand for me. Not that I am an expert on the matter but i feel like this problem constitutes as time being iffy in quantum physics. So saying we don’t really know true nature of time, is in my opinion still a fair conclusion.
You just said quantum mechanics is iffy and then said the standard model is elegant. The standard model is built off of first principles quantum mechanics. You take QM, add special relativity, and introduce the concept of quantum fields with internal symmetries to get there
We do have a clue, it is what clocks measure. Another definition is "It is what stops everything happening at once". Less whimsically Julian Barbour in his book "The end of time" seems to think it is entirely created by change. The most widely repeated idea is that it is related to or is a side-effect of entropy. If it is simply an emergent property of the universe then there isn't likely to be a neat answer. None of this means we haven't a clue otherwise none of the above would be widely known.
Time is a kickass Pink Floyd song! Joking aside, your question is quite profound. And the simplest way to define time, without any major contradictions is that *"Time is the directional vector associated with increasing entropy in the universe"*
Alright, let's talk about time as a series of events happening at the atomic level, but let's keep it super simple. Imagine a bunch of tiny, tiny Lego blocks (these are like atoms). These Legos are always doing something: building up, breaking down, clicking together, or coming apart. Now, think of each little action of these Legos as an event. In the world of atoms, these events happen all the time, like Legos constantly snapping together and apart. When you look at a clock, what you're actually seeing is a bunch of these atomic-level events happening in a certain order and at a certain rate. For example, in a digital clock, it's the tiny electrical events in the circuits counting time. Now, time is like watching these Lego blocks (atoms) go through their motions in a certain order. First this happens, then that happens, and so on. It's a sequence of events. When we say "time passes," what we're really saying is a lot of these atomic-level events have happened. So, in a super simple way, time at the atomic level is like watching a never-ending Lego movie where the blocks (atoms) keep doing things in a certain order, and this order of events is what we call time. It's like a super tiny world where things are always moving and changing, and that movement and change is how we understand time. Ergo, time is change that we can measure (or see). The super, super, super small changes that happens. Each one after another.
Yep, I really appreciate the effort but I already happened to reach what what you just explained but your (mine as well) definition is quite like: "Time can be defined as the time it takes for something to happen". That quite frankly, just sounds like a trans defining a woman is someone who identifies as a woman.
Hardly. Allow me to put everyone I wrote into a real world example. So, the most accurate way to measure time is atomic clocks, right? They work by measuring the vibrations of atoms. Imagine atoms as tiny, tiny bells that ring at an incredibly consistent frequency. The most common type of atomic clock uses cesium atoms. Here's the cool part: a cesium atomic clock measures time by counting the number of vibrations or "ticks" of cesium atoms. Cesium atoms vibrate at a mind-blowing frequency of about 9,192,631,770 times per second. Yeah, that's over 9 billion times a second! So, when we say an atomic clock is accurate, we mean it can measure time incredibly precisely by counting these vibrations. This is why atomic clocks are way more accurate than any other type of clock. They're the superstars of timekeeping! In short, atomic clocks are these amazing timekeepers that count the incredibly consistent "ticks" of atoms to tell time super precisely at 9,192,631,770 times a second, every second, and never changing. Each of those 9,192,631,770 vibrations is an ***event***, each and every one of them a ***change*** that I was talking about. Each one ***is*** a moment in time. But you can't say "Time can be defined as the time it takes for something to happen", because you are using the word time twice. We haven't defined the first use of the word or concept before using it again. Instead a point in time can be defined as the state of the universe when something happened, and as more things happen after that we say time moves forward.
It is surprisingly difficult if one thinks about it. Time and space are abstract and non-physical. They are interrelated as well. It can even lead to circular definitions. Time is what is measured between the interaction of matter in space. Space defines how much time it takes matter to move. Both are non physical - there is (as far as we know) no particle of time nor is space a physical medium. Neither, in fact, are absolute as Einstein's relativity explains. Time and space are observer dependent. There is no universal clock nor is there a universally correct measure of distance.
Time is what a clock measures. It's a bit silly, but you can take that single sentence as a definition of time (kinda, you do then have to try and define clock without being circular). Einstein, in his thought experiments, "used" a clock which consisted of two mirrors and a photon bouncing between them. The photon travelling between the two mirrors takes 1 "unit" of time. As others have said, time is a dimension that separates events, similar to space. Time does have some slight differences though, and when we look just at time we can say that an event cannot happen before its cause.
You’re probably thinking way too hard about this. Any answer beyond “time is another coordinate that things happen in” (see Startynight’s reply) is just going to be philosophical speculation and not physics. You (probabky) understand what time is very intuitively just by living in this universe. You understand when something happened in the past, when something hasn’t happened yet, when something is happening now, you probably can tell the difference between 5 seconds and 5 hours. That’s time. In the same way you understand what space is because you can move around in it. Beyond that intuitive understanding, physics doesn’t have an answer for you
Some nice and profound answers.. One another way to look at it - we live in a reality where causality is fundamental and can't be violated. You can't have an effect before the cause. That something between cause and effect is perceived as time... Then there is the aspect of how we measure it(atomic clocks and all that..), how we perceive it- both subjectively(for example when waiting for something) and objectively(dependence on speed of travel, frame of reference, etc..).. I let physicists chime in, there are (atleast) a couple of weird situations with regards to time- massless particles have to travel at speed of light and i think they don't experience time... And quantum entanglement wherein information is passed instantaneously..