Farsight

You misunderstood something there Edtharan. I'm not disputing Special Relativity, or any of the experiments that have vindicated it. I know about the atomic clock experiments. My trip to Saturn was an illustration of the same. Let my clarify the point I'm trying to make using your post above: Yes, the two clocks will show different times. But if one of them had travelled forwards through time, how come it's here now? Not the middle of next week? The answer is that it hasn't travelled forwards in time. The clock on the plane hasn't travelled anywhere in time, either forwards or backwards. It experienced less time, or "underwent less time" if you prefer, because it experienced more space.

Yep. But when we get back to the spaceport bar to compare notes, we look up through the glass roof at Saturn and we do agree that it is a billion miles away. And we agree that I did travel two billion miles. We also agree that our wristwatches show different elapsed times, and relativity is real. And we also agree that we're both here now. It doesn't matter how fast or slow I travel to Saturn, or anywhere. It doesn't matter if I find some massive rotating cylinder. I can never escape now. I can never "travel in time". Time is a measure, a dimension in the generic sense, not a dimension you can travel through. Spyman: if you can tell me where you started to get confused, I'd appreciate it. Why do I get the feeling you're going to say "on line one".

Hi Zanket. If you've clarified any portions of your article I'd be happy to go through it again.

Thanks 5164. Of course, I forgot the weight of the chair. Duh.

Noted. I'll look elsewhere.

http://www.google.co.uk/search?hl=en&q=%22mass+dimension%22&btnG=Search&meta= Yep, and they're both here now.

If I ignore friction and think about how many Newtons it would take to accelerate the chair to 1m/s/s we're talking about 335 / .722 = 464 Newtons and so 464kg. The coefficient of friction of .33 means the chair ain't as heavy as that, but to be honest, hands up, I don't know about friction and 464 * .67 = 311kg sounds too easy.

But you could say that about anything Ed. You could pick any axiom you want and defend it by saying it is what you say it is. There's a big difference between distance and time. I can hold up my hands a metre apart like I was telling you about a fish I caught. I can say this distance is a metre. Then I can take a step sideways and travel a metre. It's there, in the world, it's empirical, fundamental, we can see it, and we can move through it. Whilst I can hold up my wrist theatrically looking at my watch and do nothing for a second, that doesn't show you a second. I'm doing nothing. I'm not showing you something. All that's happening is that you're counting the events in your atoms and photons and wristwatch until you declare that a second has elapsed. I can't take a step forward or backwards or sideways by a second. I could be standing there talking to you at what we both agree is right now, then jet off to Saturn and back at close to the speed of light. Then when I'm back we resume our conversation, and I'm still talking to you right now. OK our wristwatches are out of synch by an hour or two. I travelled a very real two billion miles, that much we can both agree upon. But I didn't travel any time. Because time is just a subjective experience that depends on my motion. Let me put it another way: I can examine the fundamental properties of some subatomic particle and determine its mass, spin, charge, wavelength, etc. I can measure its momentum. But I can't measure its time. Because time isn't fundamental.

It makes perfect sense ParanoiA, but when you work it through there's a big and somewhat nasty surprise waiting for you. At least that's my take on it. Swansont, I'd be grateful if you could point out if this is wrong: http://www.scienceforums.net/showthread.php?t=23348

I got your PM ParanoiA. The important thing to remember that is you move fast you experience less time. It's like you're a metronome, where each tick is a thought in your head or a beat of your heart. If you're moving forward at c the metronome can't tick, because any transverse motion would cause c to be exceeded. Everything looks motionless, and you experience no time. If you're moving forward at just under c you can tick, but not very fast, so you experience time but not much. If you're not moving forward at all, the metronome is free to tick with a transverse motion of c, and you experience lots of time. This is what Special Relativity tells us. You can look this up and check it out. The simple way to look at it is that your time experience depends on how the motion of your photons/electrons/atoms is "cut" into the forward and transverse elements. OK. You're moving apart from your twin, and you each have a different time experience. / But you don't know if it's you moving or your twin moving, so there's that symmetry when you look at each other's time experience. It's like you're a couple of bricklayers with an angled perspective. Your bricks look shorter to him and his bricks look shorter to you. Only they're not bricks they're ticks. Time. When you turn round and start heading back you still have an angled perspective. But when you meet you can now compare your respective time experience. The thing to remember is you're the guy on the bottom. Your twin was receding from you, and after you turned around, he wasn't. Anyhow. You find that you experienced less time than him. /\ There was never any paradox. It can all be explained very simply. But there is a stunning consequence.

Sorry Evo, I was in a hurry.

You're right on both counts there ParanoiA. I think. You wouldn't be able to move your arm, and you wouldn't be able to travel at c anyway. The point is, if you could travel at c, you'd experience no time. See my post 10 re the bricks and ticks. I didn't quite like the explanation in the link so tried to rephrase it. I don't think "reference frames" gets to the bottom of it or really explains what's going on. It's to do with how much time you experience. If you're travelling at c you experience none. If you're travelling at 0 you experience lots. At c/2 you experience less. Uh, work calls, gotta go.

S = (.5 * 9.8 * T1 * T1) = (340 * T2) (4.9 * T1 * T1) = (340 * T2) (T1 * T1) = (69.387 * T2) (T1 * T1) / 69.387 = T2 Also T1 + T2 = 1.89 T1 + (T1 * T1 / 69.387) = 1.89 69.387T1 + (T1 * T1) = 131.14 Shuffle terms and drop the 1 from T1 T² + 69.387T - 131.34 = 0 Using quadratic T = (-69.387 +- sqrt(69.387² - 4 * -131.34)) / 2 T = (-69.387 +- sqrt(4814.55 + 525.36)) / 2 T = (-69.387 +- sqrt(5339.91)) / 2 T = (-69.387 +- 73.074) / 2 T = 3.7687 / 2 T = 1.84 T is T1 S = 4.9 * 1.84 * 1.84 * = 16.58m Uh. I just couldn't let it go.

Edtharan: don't have a problem with the counting and measuring, but I think you're upholding your assumption of time using your assumption of time and nothing else. Look at arbitrary timer period and the assumption that they occur regularly in time. There's an axiom here that you haven't examined. What is this time that events occur in? Imagine yourself as a metronome. Each tick is a thought in your head, a beat of your heart. If you're travelling with a forward motion of c you can't tick, because any transverse motion would cause c to be exceeded. If however your forward velocity is zero you can tick with a transverse motion of c. Your time experience is different, but it depends on how your motion is cut rather than on a real fundamental thing called time. That's what Goedel worked out.

Thanks for the response Edtharan. In reply: IMHO using count instead of period strengthens the argument rather than breaks it. Counting 9 million peak/trough events passing us by is, like you said, a 0-dimensional count. If we forget the count and say a second is the duration it takes for light to pass us by 300,000 metres, it leaves us hanging when we also say a metres is how far light travels in 1/300,000th of a second. The "second" is a very slippery thing indeed. You just can't get hold of it. It isn't fundamental. Special relativity tells us it's variable subject to your motion. It's all rather like a video tape recorder making a record of a series of events. Only the recording is another series of events, and the only thing you can measure the tape against is some other series of events. Then whilst you can rewind the tape and review the history, you can't travel down the tape or visit the history recorded upon it. Yes, colour is how we interpret electromagnetic radiation, but a photon has a wavelength, not a colour. All the colour you see is in effect a "false colour". There's no reason why some other wave phenomena couldn't be perceived as a colour. Did you try the link where two identical colours look totally different? You have to see it to believe it. So if I count the number of centimetres in a metre, that means that a metre does not exist? I didn't say that. But when you count those wavelengths you're effectively counting the number of centimetres passing you, and calling it a second. Yes, my argument does centre on the way we use the convention of "distance" when talking about time. It's the wrong convention, but we don't realise where it leads us. It takes us from a situation where events happen and are counted, to one where we imagine this count yields an extra dimension that we can physically visit. It makes us think we've got world lines, a block universe, time travel, paradoxes. Weird stuff.

If anybody can point out any serious problem in the above, I'd be sincerely grateful to find out now before I spread it more widely.

TIME EXPLAINED Time is very simple, once you get it. But “getting it” is very very difficult. That’s because your current of time is so deeply ingrained. You think of time as a length: Q: How long will it take to get to London? A: What do you mean long? We form a mental map of the world using our senses and our brains. But the map is not the territory. We use time to think, but we’ve grown so accustomed to thinking the way we do, that we don't think about time any more. We don't see time for what it is. But let’s start with something easier. Let’s start with colour. Follow the link below to conduct an experiment: http://www.echalk.co.uk/amusements/OpticalIllusions/colourPerception/colourPerception.html This demonstrates something important about colour perception. What you thought was yellow is in fact grey. It really is. It isn’t a trick. Tear a small hole in a piece of paper to make your own mask to remove context. Hold it up to one image after the other, and you realise that the effect is genuine. It comes as a shock, but genuine it is. Yellow is grey. What does this tell you? It tells you that colour is perception rather than reality. 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 would see in colour. This should be a reminder that in the subatomic world there is no such thing as colour. A photon has a wavelength, an electromagnetic oscillation, a motion. Next let’s take a look at heat. Put your hand on the griddle and sizzle, you know heat is real. But 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, because junior-level physics tells us that heat is atomic or molecular motion. It’s a “derived effect”, or a macro effect if you prefer. Sure, heat is a real thing. But you know it's motion. Pressure is similar. You can’t measure the pressure of an atom, because pressure isn’t a fundamental property of the sub-atomic world. It’s another ”derived effect”, and the Kinetic Theory of Gases tells us it’s derived from motion. How about Kinetic Energy? A cannonball in space travelling at 1000m/s has Kinetic Energy. Oh sorry. I made a mistake. It isn't the cannonball doing 1000m/s. It's me. So where's the kinetic energy now? Nowhere. Because it's just a mathematical expression of stopping distance. There isn't any. All there is is motion. We’re all familiar with Sound. It’s like light because it’s waves, and like pressure because they’re pressure waves. And when you look beyond this at the molecules that make up the air around us, you see that sound is motion. Did you know that smell is really shape? Nevermind, because you should be getting the drift by now. We are accustomed to thinking about the world in terms of how we experience it, rather than the scientific, empirical, fundamental, underlying things that are there. And nowhere is this more so than with Time. 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. This definition refers to a caesium atom at rest at a temperature of 0 K…” OK, a second is nine billion periods of radiation, of light. Now, what’s a period? We mentioned light, so let’s have a look at frequency: Frequency = 1 / T and Frequency = v / λ Flipping things around, I see that period T is wavelength λ divided by velocity v. 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 1/299 792 458 of a second...” And a velocity is a distance divided by a time. So: A period T is a distance divided by a distance divided by a time. That’s a another period, another time. OK, so that definition of time is circular. We can’t see the empirical fundamental definition. The axiom warning light is flashing, so let’s look at frequency again: Frequency is the measurement of the number of times that a repeated event occurs per unit of time. And the penny drops. We measured nine billion oscillation events and then we defined that as a second. We counted events. We counted motions. That’s what time is. It’s counting. One two three four five… nine billion. Mark that down as a second. One two three four five… nine billion. Another second. And you don’t have to count the motion in an atomic clock. You could count the motion of beans in a a bucket. Ping, ping ping, chuck them in, regular as clockwork. But now you should notice something: the only direction that is actually there, is the direction of the beans' motion. "More beans" is not a direction. There is no direction for the “Arrow of Beans” to point to. It’s just a mathematical notion, as imaginary as the direction you take when you count along the set of integers. So why on earth do we say things like Clocks slow down as if a clock is something that moves like a car? It isn't travelling. There's no slow or fast or up or down to it. We say The day went quickly but it didn’t go anywhere, and it didn’t go quickly at any speed at all. It isn’t travelling and there is no direction. The only directions that are there are the directions of the internal cyclic motion. And they’re being counted, incremented, added up. We count this regular motion to use as a ratio against some other motion, be it of light, atoms, buses, or brains. All of these things have motion. Some have more of it than others. And all those motions are real, with real directions in space. But the time direction isn't real. It's as imaginary as that direction you take when you count along that set of integers. That's why the past is only in your head and your records. It's the places where things were. All those places are still here, now. It isn’t a place where you can go. The past is the sum of all nows, and now lasts for zero seconds because there is no time. Only motion. A second is 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 motion through space. Look again at the definition of the second and the metre, and you will understand Special Relativity. Time didn’t begin fifteen billion years ago. Because it never started in the first place. It was motion that started in the first place. And it was fifteen billion light years a go-go. Let’s go over it again. Motion is a change of place in space. We measure this by comparing it with some other motion, and use the term "time" in our measuring. It's a measure, so by definition it's a dimension in the proper sense. But that only makes it a parameter, not a spatial, linear dimension that we can move along. So why do we say how long when we're thinking about time? We imagine a length of time. We imagine that we travel along this imaginary length at a speed of one second per second. When you "get" time, you realise just how ridiculous this is. We don't travel anywhere. Our atoms and everything else are in motion, but there's no travelling through the measure of this motion. To travel backwards in time we'd need negative motion. Motion is motion whichever way it goes. You can’t have negative motion. So What do we do with SpaceTime? Ah, Einstein. He knew all right. He found his Hole. Einstein’s Hole. Look it up. Talking of Einstein, let’s look at Simultaneity, and a little thought experiment called the “Cylinder and the Nail”. The cylinder is the same length as the body of the nail. At the far end of the cylinder there's a sheet of paper stretched across it like a drumskin. If you were to slide the nail into the cylinder, the pointy end of the nail just touches the paper, but it doesn't penetrate because the head of the nail is too wide to fit into the cylinder. You mount collision detector A on the head end of the cylinder, and collision detector B on the paper end of the cylinder. Now with a very special gun, you can fire the nail at the cylinder, or the cylinder at the nail, and monitor your collision detectors. From the cylinder's perspective, the nail is a shortened spike. So the first detector to fire is A at the front end of the cylinder. The nail doesn't stop (in reality we're talking gamma-ray plasma jets here) so detector B at the paper end fires later. From the nail's perspective, the cylinder is a flattened doughnut. The first detector to fire is B at the paper end. Detector A at the front end of the cylinder fires later. From the cylinder's perspective A "happens before" B, whilst from the nail's perspective B "happens before" A. The time experience is therefore subjective to each object and its motion, and is not an objective experience independent of motion. Ergo our experience of time is a subjective experience that is the product of motion, and our treatment of time as a length and a travel direction is incorrect. The correct concept of time has to defer to velocity. Velocity is not distance over time. Instead velocity determines your measure of time and space, because spacetime is fundamental, not space, and not time. Velocity is motion, more absolute than distance, more absolute than time. We measure the motion of the molecules of a gas using temperature. There is no time in temperature. And while we talk of a “high temperature”, we cannot travel a “height of temperature”, because there is no height. And we cannot travel a “length of time”, because there is no length. I’ll show you a picture: What can you measure? OK you can measure height. And width. And if it wasn't just a picture you could also measure depth. That's three Dimensions, with a capital D because we can move in those dimensions. What else can I measure? What is the fourth dimension? Well, the picture comes from the Wikipedia Temperature page, so I can also measure the temperature. The motion. The velocity. It's a measure of change of place 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 fourth dimension, but you can't move in this dimension so it's a dimension with a small d. And because there are no absolute units, the units are relative, which is what Special Relativity is trying to tell us. And Special Relativity is also trying to tell us something about the speed of light. Speed is distance over time. But light experiences no time, so talking about speed doesn’t make sense. Light doesn’t travel at any speed. It is a constant, because it is constant. And that constant c has its own units of velocity that we should liken to temperature. Velocity should be defined by degrees, not by metres and seconds, because it defines metres and seconds. And because it defines metres and seconds it but a short step from there to telling the children that the speed of light is the speed of time. Strange but true. Because when you get down to the subatomic nitty-gritty, there is no colour. There is no heat. There is no sound. There is no pressure. There is no time, not the way you think. Now try to imagine a particle, without a surface please. And you see why the quantum world, the real world of physics, is oh so very strange. If you don't believe me, if you think I'm wrong, show me the maths. But make sure you kick t out of all of your equations. And note that there are physicists who think like me. Julian Barbour. Carlo Rovelli. And more. Ever heard of a book called A World Without Time: The Forgotten Legacy of Godel and Einstein, by Palle Yourgrau? "It is a widely known but insufficiently appreciated fact that Albert Einstein and Kurt Goedel 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 Goedel 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 Goedel's lights, that as a consequence, time does not exist in our world either. If Goedel is right, Einstein has not just explained time; he has explained it away..." Time Travel is bunk. Sleep tight.

Call me cynic, but I read that article and formed a mental image of a tottering tower of conjecture, built out of negative carpets. A negative carpet is what you buy for a room measuring 4m by -3m, and the shop pays you.

I think it'll turn out to be "transparent" to microwaves or something, woelen.

That one's too complicated ParanoiA. I'd leave it if I were you. Just concentrate on the bricklaying twins. The thing with all this is that people make it too complicated when really it's very simple: When you've got a feel for the bricklaying twins, imagine you're spreadeagled out flying through space at a velocity of c. Now, can you move your arm?

ParanoiA: Yes. A change of direction is acceleration. And your question is what's called the "Twins Paradox". Like I said, acceleration is the answer, but doesn't explain it. You need to understand spacetime and velocity to get a grasp of what's going on. It's shockingly easy when you do understand, but there's a conceptual hurdle to overcome, and that's quite difficult.

ParanoiA: take a look at your first paragraph and compare it with 5614's last paragraph. There is a subtle but crucial difference between saying light travels at the speed of light and light travels at c.

Paranoia: The issue here is pretty deep, and whilst acceleration is the answer, it doesn't get to the bottom of it or explain it properly. I won't go into the details, but I can illustrate what's going on with "bricks and ticks". http://sheol.org/throopw/sr-ticks-n-bricks.html Imagine you're in a spaceship heading away from earth, whilst I stay on earth. Also imagine that we're each laying a line of bricks, but because of our different velocities, we're laying bricks at an angle to one another: / When you look sidelong at my bricks, the angle makes them look shorter than yours. And when I look sidelong at your bricks, they look shorter than mine. Now you change direction and start coming back to earth. You keep laying your bricks, so as far as you're concerned they make a straight line. And when you look sidelong at my bricks, they still look shorter than your bricks. But now instead of heading away from you, my bricks now look as if they're coming towards you. /\ When you get back to earth you find that the total length of my bricks is longer than the total length of your bricks. I aged more than you, even though all the while my bricks (or my seconds), looked shorter than yours to you, and your bricks (or your seconds) looked shorter than mine to me.