# Farsight

Senior Members

616

1. ## Time Explained

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.
2. ## Time Explained

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".
3. ## Take a look at this paper about General Relativity

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

Thanks 5164. Of course, I forgot the weight of the chair. Duh.
5. ## Relative Motion Question

Noted. I'll look elsewhere.
6. ## Time Explained

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

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.
8. ## Time Explained

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.
9. ## Relative Motion Question

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

11. ## Speed of sound

Sorry Evo, I was in a hurry.
12. ## Relative Motion Question

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.
13. ## Speed of sound

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.
14. ## Time Explained

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.
15. ## Time Explained

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.
16. ## Time Explained

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.

18. ## Quantum Gravity and the elusive "Event Horizon Gate"

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.
19. ## Transparent aluminum

I think it'll turn out to be "transparent" to microwaves or something, woelen.
20. ## Relative Motion Question

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?
21. ## Relative Motion Question

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.
23. ## Relative Motion Question

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.
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