Time Explained v3.0

[Farsight]

TIME EXPLAINED

 

Time is very simple, once you get it. But “getting it” is so very difficult. That’s because your current concept of time is so deeply ingrained. You form a mental map of the world using your senses and your brain. You use this mental map to think, and you are so immersed in it that you can’t see things the way they really are. You are locked into an irrational conviction that clocks run, that days pass, that time flows, and that a journey takes a length of time.

 

It takes steely logic to break out of this conditioning. First of all we need to look at your senses and the things you experience. Let’s start with sight. Look at the picture below:

 

 

Squares A and B are the same colour. They’re the same shade of grey. The apparent difference in colour is an illusion. Look at it from a narrow angle and you'll realise I'm right. What this tells you is that colour is subjective. It isn’t a real property of things in the world. It’s perception, a quale, it’s in your head. A photon doesn’t actually have a colour. It has a wavelength, an oscillation, a frequency. What’s it’s got is a motion.

 

Let’s move on to sound. Imagine a super-evolved alien bat with a large number of ears, like a fly’s eye. This bat would “see” using sound, and if it was sufficiently advanced it might even see in colour. But we know that sound is pressure waves, and when we look beyond this at the air molecules, we know that sound relies on motion.

 

 

Pressure is related to sound, and to touch. You feel it in your ears on a plane, or on your chest if you dive. This pressure of air or water is not some property of the sub-atomic world. It’s a derived effect, and the Kinetic Theory of Gases tells us that pressure is derived from motion.

 

You can also feel kinetic energy. If a cannonball in space travelling at 1000m/s impacted your chest you would feel it for sure. But apologies, my mistake. It isn't the cannonball doing 1000m/s. It's you. So where's the kinetic energy now? Can you feel it coursing through your veins? No. Because what’s really there is mass, and relative motion.

 

You can also feel heat. Touch that stove and you feel that heat. We talk about heat exchangers and heat flow as if there’s some magical mysterious fluid in there. And yet we know there isn’t. We know that heat is another derived effect of motion.

 

 

 

Taste is chemical in nature, and somewhat primitive. Most of your sense of taste is in fact your sense of smell. Do you know how smell works? Look up olfaction and you’ll learn about molecular shape. But the latest theory from a man called Luca Turin says it’s all down to molecular vibration, because isomers smell the same. That’s motion again.

 

The point of all this is there’s a lot of motion out there, and most of your senses are motion detectors. But it probably never occurred to you because you’re accustomed to thinking about the world in terms of how you experience it, rather than the scientific, empirical, fundamental, ontological things that are there. And nowhere is this more so than with time.

 

So, what is time? Let’s start by looking up the definition of a second:

 

Under the International System of Units, the second is currently defined as the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom...

 

So, a second is nine billion periods of radiation. But what is a period? We know that radiation is electromagnetic in nature, the thing we commonly call light. We also know that light has a frequency. So let’s look at frequency:

 

Frequency = 1 / T and Frequency = v / λ

 

This says frequency is the reciprocal of the period T, and is also velocity v divided by wavelength λ . Combining the two, we can say T = λ / v, which means a period T is a wavelength λ divided by a velocity v. To try to find out more, we can drill down into wavelength and velocity. We know that a wavelength is a distance, a thing like a metre:

 

The metre is the length of the path travelled by light in vacuum during a time interval of 1/299792458 of a second...

 

And we know already that a velocity is a distance divided by a time. So if a period is a wavelength divided by a velocity, that means a period is a distance divided by a distance divided by a time. So let’s do some simple mathematics. Let’s work it through. We can combine T = λ / v and v = λ / t and write it down as:

 

T = λ / ( λ / t).

 

Then we can cancel out the λs to get:

 

T = 1/(1/t)

 

Then we cancel the double reciprocal to leave:

 

T = t

 

The answer we get is T = t. A period of time is a period of time. This mathematical definition of time is circular. What is its true nature? How do we dig down and get to the bottom of it? Let’s look at frequency some more. What’s the definition in English?

 

Frequency is the measurement of the number of times that a repeated event occurs per unit of time.

 

Our unit of time is the second. Frequency is the number of events per second. A second is nine billion periods of electromagnetic radiation. A period of radiation is an electromagnetic event, caused by an electromagnetic event happening inside an atom. For an event to happen, something has to move. Some component of the caesium atom has to travel some distance. A hyperfine transition is to do with magnetic dipole movement, a flip-flop interaction between the nucleus and an electron. It’s magnetic, so it’s electromagnetic in nature. Like the electron is electromagnetic in nature. Like the photon is electromagnetic in nature, because the photon is the “mediator“ of the electromagnetic force. So in some simple respect, we can consider some vital component of the atom to be electromagnetic just like light.

 

 

The answer comes with a rush. It’s basically light moving inside the atom, and it’s travelling a distance. It does it nine billion times, and we call that a second. Then we use this second to measure the speed of light. We measure the speed of light in terms of the speed of light. In caesium atoms, in hydrogen atoms, in our own atoms, in the atoms of everything. No wonder it never changes.

 

And so the penny drops: the mathematics is circular because time is circular. The interval between events is measured in terms of other events. And the interval between those events is measured in terms of other events. Until there are no events left, only intervals. And intervals are frozen timeless moments. But you need events, not frozen timeless intervals to mark out the time. The events aren’t in the time, the time is in the events. Because time is merely the measure of events, of change, measured against some other change. And for things to change, there has to be motion. You don’t need time to have motion. You need motion to have time.

 

You don’t need regular atomic motion to mark out time. Any regular motion will do. Yes, we counted nine billion oscillations and called it a second. One, two, three… nine billion. But you don’t have to count hyperfine transitions in a caesium atom. You could count beans in a bucket. Ping, ping, ping, chuck them in, regular as clockwork.

 

 

You’re sitting there counting beans into the bucket, ping, ping, ping, regular as clockwork. Now, what is the direction of time? The only direction that is actually there, is the direction of the beans you’re throwing. A fuller bucket is not the direction of time. More beans is not the direction of time. The direction of time is the direction of your counting, and I could have asked you to count the beans out of the bucket. There is no real direction. It’s as imaginary as the direction you take when you count along the set of integers.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 →

 

It’s imaginary, so you cannot actually point in this direction. Nor can an arrow. There is no Arrow of Beans, so there is no Arrow of Time. And since there’s no direction, there’s no direction you can possibly travel in. And since you can’t travel, you can’t travel a length, and a length can’t pass you by. It’s all abstraction, a false concept rooted in the language we use to think. Yet we never ever think about what the words actually mean. Instead we say the clock is running slow as if a clock is an athlete. We say the day went quickly but it didn’t go anywhere. We say years pass, but they don’t go by like buses.

 

 

The only directions that are there, are the directions of the spatial motions that make the events that we use to measure the intervals between the other events. What’s there is the motion of light, the motion of atoms, and the motion of clocks, buses, and rivers. What’s there is the motion of the earth, and the sun, moon, and stars. And these motions are being counted, incremented, added up. We count regular atomic motion to use as a ratio against some other motion, be it of light, clocks, or buses. All of these things have motion, both internal motion and travelling motion. And all those motions are real, with real directions in space. But the time direction isn't real. It's as imaginary as a trip to nine billion.

 

That's why the past is only in your head, in your memory, in your records. It isn’t a place you can travel to. It’s just the places where things were. All those places that are still here in the universe. And while the past is the sum of all nows, now lasts for no time at all. Because there’s no time like the present, and time needs events, and when you take away the events, you take away the time. A second isn’t some slice of spacetime. It’s just nine billion motions of a caesium atom. Accelerate to half the speed of light and a second is still nine billion motions of a caesium atom. But there's only half the local motion there used to be, because the other half is already doing the travelling motion through space. That’s why time dilates.

 

It’s easy to understand time dilation. Imagine yourself as a metronome. Each tick is a thought in your head, a beat in your heart, a second of your time. If you’re motionless with respect to me I see you ticking like this: |||. If you flash by in a spaceship, I see you ticking like this: /\/\/\. If you could reach c and we know you can’t, you wouldn’t tick at all. Your time would flatline like this ______ because any transverse motion would cause c to be exceeded. You wouldn’t tick for me, you wouldn’t tick for you, and you wouldn’t tick for anybody else in the universe.

 

That’s the thing we’re interested in. The universe. That’s the thing that’s out there, the thing we’re a part of, the thing we’re trying to understand. It’s full of motion, and this is what it’s like:

 

 

What can you see? What can you measure? You can measure the height. You can measure the width. And if it wasn't just a picture you could measure the depth. That's three Dimensions, with a capital D because we have freedom of movement in those dimensions. What else can you see? What else can you measure? You might imagine a fourth dimension, a time dimension. But the picture comes from the wikipedia temperature page. It’s a gif, a moving image, and in that image, those red and blue dots are moving. The thing you can measure is temperature.

 

Temperature is an aspect of heat, an emergent property, a derived effect of atomic and molecular motion. When you measure the temperature, you are measuring an aggregate motion. If you were one of those dots, you would not talk of climbing to a “higher temperature”. There is no real height. You can’t literally climb to a higher temperature. Hence we don’t call temperature a dimension. But people did. Temperature used to be called a dimension, but the word has gradually changed from its original meaning of “measure”, and is now assumed to be something that offers a degree of freedom, something you can move through.

 

We are immersed in time like the dots are immersed in temperature. It’s a different measure, but just as we cannot travel in temperature because there is no real height, we cannot travel in time because there is no real length. Because time is a dimension with a small d. There is no degree of freedom. I can hop backwards a metre but not backwards a second. Because time is a measure of change rather than a measure of place, and it has no absolute units, because you can only measure one change of place against another. It’s a relative measure of motion. The units are relative, and that’s what Special Relativity was telling us all along.

 

Special Relativity tells us that your relative velocity alters your measurement of space and time compared to everybody else. You increase your relative velocity and space appears to contract while time dilates by a factor of √(1-v2/c2). If you travel at .99c, space appears to contract to one seventh of its former size. So your trip to a star seven light years away only takes you a year. But physics is about the universe, and in that universe it took you seven years. The star didn’t become a disc because you flashed by. The space in the universe didn’t really contract because you travelled through it. But your time did.

 

 

It’s difficult to be sure about the history. There are certainly some surprises for the general reader. Einstein started off by saying there is no absolute time, using the “Lorentz Invariance” postulate that says the the speed of light is always measured to be the same. He knew this didn’t explain why the speed of light is always measured to be the same, and this seems such an obvious next step. But then his former teacher Hermann Minkowski invented the idea of spacetime. This nailed down time as the fourth dimension and moved the goalposts in the wrong direction. Einstein was most unhappy about it and said:

 

“Since the mathematicians pounced on the relativity theory I no longer understand it myself”.

 

The consensus is that Einstein had come round to valuing the mathematical reformulation when General Relativity came out in 1916. But when you read the original translation, he doesn’t actually mention curved spacetime at all. And he seemed somewhat unconvincing with the Twins Paradox in 1918, using acceleration in an explanation which doesn’t account for passing clocks. Then in 1920 he gave an address at the University of Leyden:

 

According to the general theory of relativity, space is endowed with physical qualities; in this sense, therefore, there exists an ether. According to the general theory of relativity space without ether is unthinkable; for in such space there not only would be no propagation of light, but also no possibility of existence for standards of space and time (measuring-rods and clocks), nor therefore any space-time intervals in the physical sense. But this ether may not be thought of as endowed with the quality characteristic of ponderable inedia, as consisting of parts which may be tracked through time. The idea of motion may not be applied to it.

 

He doesn’t talk about spacetime, he talks about space. He even talks about aether, which is taboo. But we just don’t get to hear about this kind of stuff. It seems as if there’s been some rewriting of history going on, and we’re somehow steered away from what Einstein actually said, to what people say he said. I don’t know his innermost thoughts, but I read hints such as “time is suspect”, I look at that hangdog expression, and I wonder What do you know? I think Einstein worked it out at some point. I’m not sure when. Certainly by 1949:

 

In his response to Godel's paper in the Schilpp volume, Einstein acknowledged that "the problem here disturbed me at the time of the building up of the general theory of relativity." This problem he described as follows: "Is what remains of temporal connection between world-points in the theory of relativity an asymmetrical relation (like time, intuitively understood, and unlike space), or would one be just as much justified to assert A is before B as to assert that A is after B? The issue could also be put this way: is relativistic space-time in essence a space or a time." (Palle Yourgrau, A World Without Time: The Forgotten Legacy of Godel and Einstein).

 

I think he wanted to tell the truth, but people couldn’t handle the truth. And he was afraid to shout it in case people thought he was a crazy old fool. And so the misinterpretation carried on: Godel didn’t “find a way to time travel” with his rotating universe. He merely used this conjecture to demonstrate that time could not have passed if you could visit the past:

 

It is a widely known but insufficiently appreciated fact that Albert Einstein and Kurt Godel were best friends for the last decade and a half of Einstein's life. They walked home together from Princeton's Institute for Advanced Study every day; they shared ideas about physics, philosophy, politics, and the lost world of German-Austrian science in which they had grown up. What is not widely known is that in 1949 Godel made a remarkable discovery: there exist possible worlds described by the theory of relativity in which time, as we ordinarily understand it, does not exist. He added a philosophical argument that demonstrates, by Godel's lights, that as a consequence, time does not exist in our world either. If Godel is right, Einstein has not just explained time; he has explained it away.” (Palle Yourgrau, A World Without Time: The Forgotten Legacy of Godel and Einstein).

 

 

That’s the true meaning of Special Relativity. Time exists like heat exists. It’s real because it does things to us. But just like heat it’s an emergent property, a derived effect of motion. Time isn’t absolute, it isn’t fundamental. It isn’t a dimension like the dimensions of space. We don’t see four dimensional spacetime. We see three dimensions of space, and we see motion through it. It isn’t a 4-dimensional world, it’s 3+1 at best.

 

The speed of light was always the problem, and time was always the answer. Because at the speed of light there’s no time left for anything else to happen. It’s why c isn’t really a speed, because you run out of time trying to get there. And if there’s no time, there’s no speed, because speed is distance divided by time. The thing called c is in reality a conversion factor, between the measure of distance and the measure we call time. It’s the motion that’s king, the velocity of light that defines your very metres and your seconds. Your velocity shouldn’t be measured by the things it defines. It should be measured as a fraction of c, in “natural units”. Because it’s motion we see, and c is the ultimate motion, how fast things happen, the inescapable property of photons and those electromagnetic things from which we’re made. From which the universe is made.

 

The universe is not a block universe, it is a world in motion. The worldlines are only in mathematical space, and in your head. There’s no place that’s the future, and no place that’s the past. There’s only this place, and the time is always now. We don’t travel in time at one second per second. We don't travel in time at all. Relativistic clocks don’t travel in time at different rates, they travel through the universe at fractions of c. When they collide, they collide at the same location at the same “time”, whatever their faces say is local time. To travel backwards in time we'd need to unevent events, we’d need negative motion. But motion is motion whichever way it goes. You can’t have negative motion, just as you can’t have negative distance. Just as you can’t have negative carpets. So you can’t travel in time. There are no time travel paradoxes, because there is no time travel, and there is no time travel because time is just a relative measure of motion. And motion is travel. You can’t travel through travel.

 

So those celebrity physicists who talk earnestly of time machines are wrong. Dead wrong. Not even wrong. You wonder how they can get it so wrong. And all those folk who puzzle about the beginning of time are chasing a dream. There never was any beginning of time. Time didn’t start thirteen point seven billion years ago. Because time didn’t start in the first place. It was motion that started in the first place. It was a place, not a time. And it’s this place, the place we call the universe, marked out by every light path you can track through timeless space. That’s how far we’ve come. A long long way, in no time at all.

 

But now we can move on. Because now we’ve got the key, Einstein’s key, the key that unlocks all the doors in physics: spacetime is a space.

 

[FastTrack]

A point in Time is like a point in Space.

 

If you moved from one point in Space and at a later date returned to that point, it does not mean that other objects that were in that area before, will have to be there now.

 

Thus if you moved from one point in Time and at a later date returned to that point, it does not mean that other objects that were in that area before, will have to be there now. You would simply be at the same point location in the dimension and depth of Time, and that is all.

[Farsight]

The concept of time that you find here is nothing new. Maybe five years ago I read Julian Barbour’s 1999 book The End of Time. It didn’t sink in much. It was just another fairly interesting book that I read on my Saturday afternoons on the sofa. A couple of years later I also read About Time by Paul Davies, dating from 1995, but again it was just one book amongst many. I didn’t pay too much attention. I was sleepwalking. But thank you Julian and Paul because something along the lines of time is change became lodged in my mind, and it made me query the speed of light. In August 2006 I got myself into an argument about it on the internet. I remember looking up at my bookshelf and pulling down those books on time, weighing them in my hand, pondering. I resolved to get it down so darn straight that nobody could argue any more. I knew it wasn’t a brand new idea, because it goes back to Aristotle, who was born 2391 years ago and counting. But I could put a fresh slant on it, using catchy conversational language and a tight delivery that would be crystal clear even to the layman.

 

 

So I wrote a little essay called TIME EXPLAINED and posted it on an internet forum. Even the first version referred to the optical illusions, because I already knew that we take things too much for granted, and seeing is not always believing. Hence I’m very grateful to “echalk” Online Resources For Teachers, and to R Beau Lotto and Edward H Adelson, see http://www.echalk.co.uk/amusements/OpticalIllusions/illusions.htm. That was October 2006.

 

The feedback was interesting. I learned a lot. I learned about Presentism, a philosophical concept introduced by John McTaggart in 1908 in an essay called The Unreality of Time, see http://www.ditext.com/mctaggart/time.html. I found myself siding with Presentism rather than Eternalism, an opposing philosophy that involves the block universe and big problems for free will.

 

 

A fellow forummer called mganderson flagged up A Hole at the Heart of Physics; A Matter of Time; Special Editions; by George Musser. It was in the September 2002 issue of Scientific American, and I was too mean to buy it. But I read the synopsis. Sorry George, but thanks, and thanks mg. And thanks THoR for vital encouragement when I was flagging. Ditto to amrit, real name Amrit Srecko Šorli, who was ahead of the game but language was a barrier. And thank you yquantum. On 29th October 2006 you recommended a book called “A World Without Time: the forgotten legacy of Godel and Einstein” by Palle Yourgrau, professor of philosophy at the Brandeis University in Massachusetts. This book was published in 2005, and I bought the last copy Amazon had in stock at the.. time. It’s historical and philosophical, and pure gold dust. I was amazed to discover that Einstein thought of time this way too. Not in 1905, but in 1949, when he was at Princeton with Godel. Thanks Palle.

 

I also came across a 1999 paper Quantum Spacetime: what do we know? by Carlo Rovelli, see http://arxiv.org/abs/gr-qc/9903045, who said “At the fundamental level we should, simply, forget time”. Thanks Carlo. There’s also Process Physics by Reginald T Cahill, see http://www.scieng.flinders.edu.au/cpes/people/cahill_r/HPS13.pdf dating from 2003. Whilst I didn’t find myself empathising with all aspects, I did find myself empathising strongly with the basic premise that time is process. Thanks Reg.

 

Much of what I learned went into a new improved version of TIME EXPLAINED, which is pretty much what you’ve read here. It’s all just a rehash of an old idea, and isn’t particularly original at all. As to why it’s news to anybody I’m not quite sure.

 

 

Understanding time seemed to be the key that would open all the doors in physics. It was enough to convince me that I could make a difference. I could break the impasse. And then the fun began.

[Billy Ray]

Well written, thank you. I disagree when you say space is fundamental while time is not, I think they are both non-fundamental.

 

IMO the basic concept is an event (not necessarily motion as you seem to have). Two events may happen at the same time or one may happen after another and they may happen at the same point or they may happen separately. These are fundamental things while everything else, including space and time, are invented by man. One uses time to deal with events that happen one after another and space to classify events that do not occur at the same place.

 

Are space and time different? Sure. Is it 3+1 not 4? Yes. But is space any more fundamental than time? No, I don't think so. They are equally non-fundamental.

[Klaynos]

I will admit only reading a short bit... (infact about 5 words)... because I'm tired and don't feel it fair to read it when I'm this tired... but...

 

What is often "clear" to the layman is often just plain wrong. Nature doesn't have to be clear, or intuitive... This is an important lesson that all should learn at an early age.

[Reaper]

I will admit only reading a short bit... (infact about 5 words)... because I'm tired and don't feel it fair to read it when I'm this tired... but...

 

What is often "clear" to the layman is often just plain wrong. Nature doesn't have to be clear, or intuitive... This is an important lesson that all should learn at an early age.

 

And its something that K-12 teachers consistently ignore, or don't want to inconvenience themselves with. There is nothing like coming into college and learning that most of the things you learned in high school physics is wrong.

[Farsight]

Well written, thank you. I disagree when you say space is fundamental while time is not, I think they are both non-fundamental.

 

IMO the basic concept is an event (not necessarily motion as you seem to have). Two events may happen at the same time or one may happen after another and they may happen at the same point or they may happen separately. These are fundamental things while everything else, including space and time, are invented by man. One uses time to deal with events that happen one after another and space to classify events that do not occur at the same place.

 

Are space and time different? Sure. Is it 3+1 not 4? Yes. But is space any more fundamental than time? No, I don't think so. They are equally non-fundamental.

 

Thanks for the feedback Billy. It's good to talk, and if we all agreed about everything life would be dull. But here's a potted version why I think space is fundamental while time is not:

 

If the universe consisted of no objects whatsoever, we could not say the universe even existed. We could hold no concept of time, and no concept of space. If the universe consisted of one object and that object alone, we could hold no concept of space, for that object is the whole universe. If the universe consisted of two objects and two objects alone, separated by some distance, we could then hold a concept of space. But if those objects do not move, we can hold no concept of time. When those objects do move, then and only then can we conceive of time, for it is not time and space that are cofounded, it is time and motion that are cofounded.

[Edtharan]

Hi Farsight. I've haven't been on this site for some time and have missed our discussions.

 

If the universe consisted of no objects whatsoever, we could not say the universe even existed. We could hold no concept of time, and no concept of space. If the universe consisted of one object and that object alone, we could hold no concept of space, for that object is the whole universe. If the universe consisted of two objects and two objects alone, separated by some distance, we could then hold a concept of space. But if those objects do not move, we can hold no concept of time. When those objects do move, then and only then can we conceive of time, for it is not time and space that are cofounded, it is time and motion that are cofounded.

But a single object can change. For example a Neutrino can change into another type of Neutrino. So if we had a universe that consisted of just that single Neutrino, then we could measure time.

 

This, by your argument makes time more fundamental than space as with just 1 object you state that we could have no concept of space, but because that object can change, we can have a concept of time.

 

The answer we get is T = t. A period of time is a period of time. This mathematical definition of time is circular. What is its true nature? How do we dig down and get to the bottom of it? Let’s look at frequency some more. What’s the definition in English?

Here is the fundamental mistake that you keep making.

 

When we use the caesium atom to define a second, we are not using the electromagnetic pulses to define a second, but we are using the gaps between the pulses to define a second. It is just that we use the electromagnetic pulses to mark out the periods between them (because they are regular) to mark out what we mean by 1 second.

 

So a period of time is a period of time. But how long is a piece of string (or a period of time). Well, we use that regular pulse from that caesium atom to mark out what we mean by "a period" of time. Just like the marks on a ruler do not define what distance is, but only mark out what we mean by 1 centimetre.

 

This means that your article is actually based on a strawman. You have set up the argument that the current definition of time is circular, and then use that to "prove" your argument. However, what you have stated as the current definition of time, is not what the definition of time is. Therefore this is a strawman.

 

Our unit of time is the second. Frequency is the number of events per second. A second is nine billion periods of electromagnetic radiation. A period of radiation is an electromagnetic event, caused by an electromagnetic event happening inside an atom. For an event to happen, something has to move. Some component of the caesium atom has to travel some distance. A hyperfine transition is to do with magnetic dipole movement, a flip-flop interaction between the nucleus and an electron. It’s magnetic, so it’s electromagnetic in nature. Like the electron is electromagnetic in nature. Like the photon is electromagnetic in nature, because the photon is the “mediator“ of the electromagnetic force. So in some simple respect, we can consider some vital component of the atom to be electromagnetic just like light.

That 9 billion periods of radiation is not the definition of time, but the definition of a second. The term "Second" is what we use to measure time. And, as I have stated before: What you use to measure something, is not the thing you are measuring.

 

If I use a metre ruler to measure my room, the distance across my room is not that metre ruler, but I can describe the distance across my room in a ratio compared to that metre ruler (which is 3 ruler lengths : 1 room length - which we usually express as 3 metres).

 

Thus a second is defined by the cumulative periods of time separated by a series of regular events (that radiation). The second is definitely not the radiation it's self, nor is it dependant on the fact that it is electromagnetic (if we could detect gravity waves - which are not electromagnetic nor do they interact with electromagnetism - then we could use a regular source of those to define what a second is).

 

The events we use to mark out a period of time is not important, nor are what those events consist of. What is important is the gaps between those events. The periods of time that separate the events.

 

If there was no time, then there would be no separation between those events, just as if there was no such thing as distance there would be no separation between objects. The fact that there exists any separation between the events means that time is real, as real as the separation between objects proves that distance is real (because distance is defined as the separation between objects).

[Mr Skeptic]

The events we use to mark out a period of time is not important, nor are what those events consist of. What is important is the gaps between those events. The periods of time that separate the events.

 

As Edtharan said, we use the distance between the events (which are points in spacetime) in the same manner as we use our meterstick to measure distance in space. This is exactly like choosing our unit vector in a coordinate system. It should also be noted that all observers must agree as to the order that events occur in, even if they do not agree on the spacing between events (that is, how fast they occur).

 

Farsight, consider that space and time are linked through motion, such that if you understand any two of these terms, you understand all three:

velocity is the derivative of distance with respect to time

distance is the integral of velocity with respect to time

time is the integral of 1/velocity with respect to distance

 

For my part, I will not pretend to understand anything except the link between them.