Iggy

I'm sorry... you're not making any sense. This is what you said before: ½[w (1-mR² /I)]² multiplies out to give ½w ² [(1-2mR² /I)+(mR² /I)² ]. The final term in the brackets is insignificant. ½w ² (1-2mR² /I) times I+mR² , multiplies out to give ½w ² [(I+mR² ) - 2mR² - (2m² R^4/I²)]. Again the final term in the brackets is insignificant. The rest is just addition/subtraction. All of the terms have m in them. The answer has an m in it. m2 is more significant as a term than m. Ignoring terms with m, or m2, is not what happened, nor could happen. It's like you're trying to figure out how this math was done and having quite a lot of trouble figuring it out. Calculating the change in speed is an extremely easy calculation. The method of approximating it is given in post 42.

Ok, I see what you were thinking, like in this link, http://www.funexhibits.com/magnetoscope.html how everything is inside the plastic bubble. I had missed that link. It definitely looks cool with a big tray of fluid like that. Perhaps another solution would be to use electromagnets and vary the current rather than moving the magnets. Nothing would have to move

Not sure how you mean. The jar would stay still and the magnet/s would move outside the jar (closer to and further from it). The magnets never touch the oil -- they're outside the jar -- and the volume of the container holding the fluid never changes. EDIT: Imagine filling this jar half full of ferrofluid oil: If you then held a strong magnet against the top of the jar it would pull a column and a good deal of the oil up to the top of the jar. If you then held another magnet against the bottom of the jar it would pull some of the oil back down and it would make a pretty pattern with multiple columns. Then you could move the two magnets (or you could just move one of them if it isn't a very elaborate setup) further from and closer to the top and bottom of the jar. You'd get a lot of cool changing patterns as the oil is more or less attracted to the bottom or top of the jar. Something larger like an aquarium could, I think, be cooler -- more like the video, but not as easy to set up. You'd have to seal a piece of glass over the top of the aquarium that could take a bit of force pushing up on it. The magnets would always be outside the sealed aquarium space though. Is that not the way you'd understand to do it?

To hold the oil I would think a glass jar would be easiest and cheapest. Something like a flour jar maybe: You'd definitely want something airtight so the oil doesn't leak out when it gets pulled up to the top. To hold the magnet I'd use a rotary drill press since they are cheap and it would be easy to hold a magnet instead of a dremel... $51.99 $81.99 It would mostly be a matter, I think, of having the size or strength of the magnet work with the size of the jar (or sealed up aquarium or fish bowl or whatever you end up using) and the size of the drill press stand.

Oh, yes, I certainly agree with that. Adding 'physical' things to the venn diagram I'd put like: so that some things are measurable and real, but not physical... like energy. I wouldn't say that gravitational potential energy is physical (or a physical thing), but I would say that it is real and can be measured. No, I didn't mean to imply otherwise... only that we'd have to be careful, or at least very specific, with what we mean by 'real' and 'observed'. I agree -- that would be the way I'd look at it I think it is an interesting question. I remember reading Einstein's very complicated thoughts about whether the coordinates of the gravitational field in general relativity could be considered 'real' or 'physical' in relation to their being measurable and that type of thing: Einstein -- November 1918. (about the 7th or 8th paragraph from the bottom. It is really a very complicated issue.

The edit I added to that post while you were posing yours works here to. Why assume "If God exists then believing in him will get you a reward"? If anything I'd guess that "if God exists then he is hiding from us". I don't know what other people's impressions are, but in my experience people who are hiding are not very happy about being found. We might as well assume "If God exists then believing in him will get you sent to hell". I think that would be a fine addendum to Pascal's blackmail, or whatever it was called.

good, yes, I agree I've always thought of something being real if it can be, at least in principle, measured. But, I have to admit the idea could get murky. Like you say with an illusion. Would the axe murderer in my nightmare be 'real' and 'observed'? Yeah, I think someone in the 1950's could say that the far side of the moon was real.

If there is a hell, and if you find yourself there... Don't make the mistake of getting mad at someone and yelling, "look, why don't you just piss off and go straight to..." It's terribly embarrassing. edit: I heard that once and thought it was funny. your post reminded me of it. Of course, I agree... "if god exists..." is the biggest 'what if' that people have ever collectively assumed, and it amazes me how many people are happy filling in "if God exists then _______". Like "if God exists then I can't wear a condom", or "if God exists then women have to wear burqas". It seems like people should, on the average, be quite a bit smarter than that.

Would a venn diagram like this work? 'Something' would have to be real to be measured, but there would be, and could be, real and unmeasured/unobserved things.

But if God were real and manifest then he could be proved, don't you think? I mean, if the story of Elijah's altar in 1 Kings 18 were true and reproducible then God could be, as the story suggests he was, proved. With disproving God, I agree.

Yet my posts that you find insulting are the only ones to which you reply. There is noting insulting in my previous post. It might have been helpful to consider and reply, but it fulfills no censorious and masochistic need to cry before you've been hurt -- so, of course, you didn't. Then you missed my point already. I said the very nice, very non-hostile, and very repetitive explanations are stultifying the thread -- they aren't going to work. Sometimes paying the price of ill-concealed laughter that Sam Harris explains in the following clip is an improvement. http://www.youtube.com/watch?v=WwG9pDNSAXA

You have none to withhold. Get over it and we can be done with this stultifying thread.

that high pitched screeching sound is a horde of millions of angry adolescent girls declaring jihad

What your belief deserves is debatable. What I'm telling you it doesn't deserve is exemption and protection from ridicule. Are you clear on that now?

How peaceful a belief is has nothing to do with how intellectually honest it is. That's a red herring. Because there is no objective theistic evidence, theistic beliefs require cognitive bias... so, of course, they are intellectually dishonest no matter how peaceful you want to make them. Plus, your religious beliefs may be benign, but when you start demanding that other people not be allowed to ridicule them -- *that* is not benign. You're looking and hoping for some kind of rule against impiety, and you could look up the death of Socrates or the exile of Anaxagoras to see what a bad idea that is.

So... Some Christians are crazy for their faith, but it isn't right to ridicule faith that looks more like yours. I'm sure there's nothing intellectually dishonest about that. How about "God hates fags"? Is that so stupid that we can all laugh at it, or is it like "God created the big bang"... something that is too special not to be protected from INow's viscous tongue? The real crime here is that you think you get to decide. How natural it must feel to call some Christians crazy for believing the former and telling INow that he has no right to ridicule the latter. and people who think like that are happy +ing your posts to oblivion...

Special relativity is kinematic. It deals with the distance and time between events, and the velocity of objects. If you're matching up numbers with real stuff the numbers would concern time, distance, and velocity. The only things -- or somethings -- proposed by special relativity are measuring rods, clocks, and light. Those were the things used in Einstein's 1905 derivation. here is a quote by Einstein: Just as in Euclidean geometry the space-concept refers to the position-possibilities of rigid bodies, so in the general theory of relativity the space-time-concept refers to the behavior of rigid bodies and clocks. -Space-Time by Albert Einstein Those are the "real referents". in general relativity the gravitational field provides inertia to the twins so that the one that turns around feels acceleration Yeah, the gravitational field in GR can be loosely thought of in that way.

Either. If I, for example, recede away from you at 0.99c (our relative speed is .99c) then every second you will find (using your ruler) that I get 296,794,533 meters further away. I would find (using mine) the same about you -- your velocity away from me is 296,794,533 meters per second. This post explains. All inertial observers (non-accelerating observers) should measure the speed of light at c. In other words, anyone traveling at a constant velocity should measure light to travel one lightyear per year (or whichever units you like) with their own clock and ruler. For example, imagine you are here on earth measuring the speed of light rays that go from the sun to the earth. With your ruler the distance to the sun is 8.3 light-minutes. With your clock it takes light 8.3 minutes to go from the sun to the earth. The speed of light, you will find, is 8.3 light-minutes divided by 8.3 minutes, or 1c. If I, on the other hand, am approaching the sun at .6c in a spaceship (my velocity relative to it is .6c) I would measure the distance between the sun and earth as 6.64 light-minutes with my ruler. This is shorter than you found because of length contraction. From the rocket I would measure the time it takes light to travel the distance at 6.64 minutes. This is again shorter than your time because of time dilation. I would calculate the speed of light as 6.64/6.64=1c. It is because of length contraction and time dilation that c is invariant. The short answer is that the homebody didn't change reference frames so the thought experiment isn't symmetrical. Because of the relativity of simultaneity this makes a big difference. If both twins accelerated away from each other, then toward each other, equally then they would cancel out. Have you tried reading any online publications on relativity? I think you might enjoy, for example, Special Relativity

If I understand you, clocks really do slow down when velocity changes, but meter sticks don't really shrink -- they just appear to from the mistaken perspective of others. If you have a clock and a meter stick you can measure how long it takes light to travel the distance of the meter stick (it's 0.3 billionths of a second). Then if you change speed, according to you; your clock would slow down and the meter stick will stay the same size. How far does light get in .3 billionths of a second on the now slower clock? An example: If the clock on the ship really did slow down, as you say, then maybe it measured a year from the start to the end of the trip. If the people on that ship measured how long it took light to get from earth to Alpha Centauri -- with their own clock -- they would find it went 4.3 lightyears in about a year... 4.3 lightyears per year. The astronauts would measure light moving 4.3 times the value earthlings measure it with their clock. If clocks really slowed down, but meter sticks didn't really shrink, people going different velocities would get different experimental values for the speed of light. The speed of light has been tested from different velocities and it is invariant. Another thing you may not have considered: you are happy thinking that the ship clock slows down with velocity (it goes slower than earth clocks), does this mean earth clocks run faster than the clocks on the ship? That being the case, any clock on a probe sent speeding from the ship towards Alpha Centauri would slow down, while a clock sent on a probe in earth's direction would speed up. People could find a state of absolute rest by sending clocks in different directions and seeing which slow down and which speed up. We don't see that sort of anisotropy experimentally. You could also compare a couple different assessments you've made: that earth rotates at the same speed regardless of frame of reference. It doesn't slow down or speed up with velocity. Clocks, on the other hand, you say do slow down with velocity. If the minute hand of a stopwatch really does slow down (rotate slower) when it has a velocity of 30 km/s relative to us, then what about Alpha Centauri which has the same velocity? Does it rotate slower? How could you hold that clocks tick with less frequency at greater velocity, but stars and planets don't rotate slower with velocity. Perhaps it's easy to imagine clocks slowing down because they are small, but hard to imagine planets slowing down because they are so big. Nonetheless, observation shows that the duration of a process as large as supernova depends on velocity just like the duration of a process as small as an atomic clock. So it clearly wouldn't be consistent to say that the process of a clock ticking really does slow with velocity, but the process of a planet rotating or a star exploding doesn't.

what?

I don't think it's childish. Another property by which you could inquire would be velocity, Why are velocity and direction relative while length and duration not? When it finally boils down to 'my unsupported worldview wants it to be that way despite what measurement, logic, science, and philosophy tell me'... well... I think that's usually when people stop leading the horse to the water it refuses to drink.

I'm not a scientist. One squared means one times one and it does equal one. When I said "moving to your right at .6c", that may have not been the best way to say that. I should have said "moving to your right at 0.6 lightyears per year". The speed of light is one lightyear per year. That may explain why I set v=0.6 and c=1. The equations I wrote don't need anything to be expressed in fractions of the speed of light. You can use any units -- just as long as c and v are both expressed in the same units. I'll rewrite it and see if it makes more sense: An event happens one lightyear to your right at t=0. Sally is in your location moving to your right at 0.6 lighyears per year. As she passes, her clock also says t=0. According to her clock the event happens at: [latex]t' = \left( \frac{1}{ \sqrt{ 1-v^2/c^2}} \right) \left( t - v x/c^2 \right)[/latex] [latex]= \left( \frac{1}{ \sqrt{ 1-(0.6 \ ly/yr)^2/(1 \ ly/yr)^2}} \right) \left( 0 \ yr - 0.6 \ ly/yr \cdot 1 \ ly/(1 \ ly/yr)^2 \right)[/latex] [latex]= -0.75 \ years[/latex] and according to her ruler it happens at: [latex]x' = \left( \frac{1}{ \sqrt{ 1-v^2/c^2}} \right) \left( x - v t \right)[/latex] [latex]= \left( \frac{1}{ \sqrt{ 1-(0.6 \ ly/yr)^2/(1 \ ly/yr)^2}} \right) \left(1 \ ly - 0.6 \ ly/yr \cdot 0 \ yr \right)[/latex] [latex]= 1.25 \ lightyears[/latex] You can do the same thing with any units. If you do, however, want to know what fraction of the speed of light a velocity is... just divide the velocity by the speed of light. For example, 100 million meters per second is one third of the speed of light because 100 million divided by 300 million is one third. The speed of light in m/s is 300 million.

I trust your command of English if you feel like you need to explain things better. The picture in the opening post shows up fine.

+1 Newts, I think the term you ignored, 2m2 R4/I2 should have been 2m2 R4/I. That term is larger than mr2/I, so you could, by your reasoning, just eliminate mr2/I from: [math] \frac{1}{2}I \omega^2 - \frac{1}{2} \left(\omega(1-mr^2/I) \right)^2 (I+mr^2) [/math] as insignificant. But, that should I think lead to the same bad result we had a couple posts ago. if you multiplied that by I/I+mr^2 you should get the exact answer I'd expect

It would make sense if the disk magnet pointed at the ring magnet when it was done. As it rotates out of that position it encounters stronger repulsion. It doesn't? So... the magnets may not be interacting with each other at all? It may just be the elastic potential of the string wiggling it back and forth with negligible influence from the magnets?