md65536

I agree. The expected proportion of girls to total children on the island is Assuming that answer is accepted, is my original "erroneous" question essentially the same question? To repeat: Are you more likely to find that a) the number of girls is greater than or equal to the number of boys, or that b) the number of boys is greater than or equal to the number of girls, or that c) neither case is more likely than the other? You are given no further information (how many couples there are, how long this has been going on, how many children a couple can realistically have, etc).

How do you mean, like, can you cut open the paper and take the time out?

I think the forums are littered with examples of the Dunning–Kruger effect. http://en.wikipedia.org/wiki/Dunning%E2%80%93Kruger_effect I know I'm guilty of it myself... When people think they know what they're talking about, they tend to get offended when others point out that they're not making sense. But if they don't even know what is commonly accepted as making sense (say in a specialized field), they don't recognize either their own nonsense or the sense of what others say. Over and over I see people mistaking their inability to comprehend an expert reply, with a belief that the reply must not make sense. I think it's a waste of time trying to explain something to someone who is not even willing or able to accept answers. Recently all of the 3 active topics I was following, involved repetition of the same questions, the same objections to answers (even accepted science), with a clear dismissal of any replies as "you're not getting it; let me repeat" or whatever. The D-K effect suggests that not being able to understand something can be easily twisted into confidence that the thing is wrong.

Derivation? Difference? You can describe the differences between distinct analogous things. You can also consider it in different ways so that it *does* involve a change in time, for example: - "The state of the paper with one equation written on it, vs. the state with two equations written." These states don't exist simultaneously. The contents of the paper changes as stuff is written on it (but the equations as objects themselves don't change). - "The act of contemplating the first equation, and then the second." Use of the word then implies different times. There are many ways to look at it and many opportunities to confuse an idea for a physical object it represents, or a word for its manifestation in writing, etc.

Yes... I didn't quite specify the frame of reference. In Earth's frame, the object's length is contracted. In the object's frame, its own length (or local ruler) remains "normal" and the distance to Earth (as well as the depth of Earth, etc) contracts.

Yes, not applicable: Light does not "experience" proper time. There's no clock or reference frame for light, such that the timing of the trip is meaningful "from light's perspective". If an object is making the same trip, approaching c relative to Earth, then the Lorentz factor diverges to infinity, the length-contracted distance to the Earth approaches 0, and the locally measured time it takes to cross that small distance approaches 0.

Well, keep at it, you'll get it eventually! Even if you have to shun every single answer given to you. This is difficult stuff, even for geniuses. I remember I didn't get it either, when I was first taught it in high school. The earliest explanation of these concepts that I remember being taught involves Einstein's thought experiment of emitting photons from one side of a box and absorbing them at the other side. http://www.adamauton.com/warp/emc2.html In that experiment, you see that it is accepted that both the emission and absorption of photons involves a "push" on the box.

By what definition of change can you describe a "change between" two distinct things? If you put A=B and then you put 2A=2B Try this if you can, to type "2A=2B" while keeping your eyes on the "A=B". Does it change???? Or is it still there after you type the next line? The new line is something different based on the first line. The first line doesn't change. If there is some meaning that you can extract from "the change between two distinct lines of text", then, since the two lines exist simultaneously, that is not a change due to time. Now you're wasting people's time with your "astonishing" clever reasoning about things that don't even make sense.

Nothing that happens will violate physical laws. If something does, then they weren't laws. Better? What would happen if physical laws were violated? Make up an answer! If there's a law that says your answer isn't so or is impossible, just consider the law violated. Though, a more reasonable answer comes from considering the limits of what is physically possible, for example not considering something moving at c but rather what happens in the limit as v approaches c. This is what Einstein did in some of the examples. But to get back on track... owl, what is missing is a basic understanding of special relativity. I apologize, as having an incomplete understanding of things pointed out by someone seems to be considered offensive around here. Why not start with a simple example of SR found elsewhere on the web and ask about what doesn't make sense to you, rather than devising your own complicated thought experiment that doesn't help you see how it works?

Nothing.

In the recipe example, you listed environmental conditions, but you'd also have to list "bake while traveling at low speed relative to The Clock, while in a low gravitational potential relative to The Clock." Those last two aren't environmental conditions. A local environment doesn't depend on its speed etc. relative to some remote point. For example, consider the environmental conditions here on Earth. Imagine putting a master clock deep space somewhere. A cake may take 20 minutes or say 1,000,000 UTU. Now imagine moving the master clock into a black hole. Does that change the environment on Earth? (No) A cake still takes 20 minutes to bake, but now it may take only 10 UTU... and now 9... 8... as the master clock appears to slow relative to local clocks. Moving your clock wouldn't affect the environment on Earth. Yes, the master clock still ticks consistently at 1 UTU per UTU, but now the timing of everything else is changed. If you can't "go to the black hole to bake your cake" then to use a recipe you must adjust for the gravitational differential between you and the clock. Or just use a local clock that is not synchronized to the master clock. Yes, and in a sense we adhere to a master clock (the rotation of the earth for days, and the orbit of the earth for years) for practical purposes, but that no longer is a sufficient definition of time. The Earth slows its rotation due to friction of the tides. Occasionally our main atomic "local clocks" are adjusted to sync with the Earth's rotation. This is exactly what you're suggesting is the right thing to do. However the Earth's rotation doesn't make a sufficient definition for time. If we still defined a second by the Earth's rotation, then we'd find that the tides do not slow the Earth but instead they increase the speed of light.

I feel that anyone who says "I don't believe in prayer" without qualifying it might be dangerously closed-minded. What is prayer? Why do people associate it with a wish-list hot-line to God? Imagine you call aunt Gertrude and ask for a train set. She doesn't get you one. Conclusion 1: Telephones don't work. Conclusion 2: Telephones are just a means of communication. Imagine you walk up to an ATM and ask it for a million dollars. The ATM looks at you kinda funny. Conclusion 1: ATMs don't work. Conclusion 2: ATMs are a means of accessing only what you already have. Whether you're an atheist or fundamentalist, you can define "god" in such a way that prayer has "power". Even if it's just a means of communicating with yourself, or perhaps even parts of your subconscious, but using words and higher brain function, it can be useful. Believing that prayer has "no power" because it doesn't directly lead to physical manifestation of your requests, is not far from believing that meditation is of no use because it doesn't have a direct effect on physical reality, and that's not far from believing that thinking has no value because thoughts do not directly affect the outside world. Imagine growing up with parents who encouraged you to believe "Thinking has no power" without qualifying it? The power of prayer need not be more than the mental power of words and thought. Anyway to answer the question, nothing goes through my mind when I see an atheist pray. How do I know what they're thinking, and whether or not it's rational?

How is a "steady beam" different from a stream of individual photons? From the perspective of the ship, the ship is at rest, and not traveling into the beam. That's one explanation for how it can't be so. If the light were traveling through some "ether frame" then you could describe an absolute velocity of the ship relative to that frame, but that isn't so. When discussing the movement of light relative to the ship, the frame in which the ship is at rest is as valid as any other frame.

The local speed of light expressed in terms of UTU will depend on your frame of reference. As it is now, the local speed of light is invariant and universally equal to c. There's a law that is affected, and doesn't become "more universal". Yes, relative to local time. Say that at P2, each P1 pulse takes 2 local P2-seconds. P2 sends out a pulse every 100,000 P1-pulses, so it sends out a pulse every 200,000 P2-seconds, or once every 100,000 UTU. Say at Earth each P1 pulse takes 4 local Earth-seconds. Each P2 pulse takes 400,000 Earth-seconds, or 100,000 UTU. (This assumes that P1 and P2 share a frame of reference, so that a "P1 second" is the same as a "P2 second". Ie. it assumes that P1 and P2 clocks are synchronized. As long as they're synchronized, they can be considered to be a single clock?)

From an "interested but limited knowledge" perspective: Uncertainty is the physical impossibility of measuring both of certain pairs of aspects to arbitrary precision. The key point being that it is not that it is difficult to the point of impossibility to measure both precisely, but perhaps meaningless? I would say that the reality of a thing is different depending on how you look at it, and if you look at it in a way that for example position can be very precisely known, then from that point of view, very precise momentum becomes physically meaningless?, and vice versa. Also something about a wave When I first accepted the idea that knowing one thing can prevent knowing another, I think it was explained in terms of a wave.

Yes, but it's measured in "UTU", which would have a period that is time-dilated by the same (I'm assuming) factor as the P2 period. It's useless as a local measure of time (baking cakes etc), but it's true that everyone would agree on the proper timing of events that happen at P1 or P2 (or anywhere). It's true that everyone who came together to compare notes would agree on the total number of pulses counted. Everyone everywhere would agree on what P2 sees (which is 100000 P1 pulses per P2 pulse, or whatever). Any clock arbitrarily called a "master clock" will tell proper time consistently according to everyone, but will fail depending on reference frame to sync with local clocks (and processes like baking cakes etc). OP is concentrating on arguing that proper time is consistent (true), mistakenly thinking that that means that relativity must be wrong.

It's not a question of practicality or functional simplicity, but theoretical simplicity. Having one useless clock is simpler than having an infinite number of independent useful clocks. Practical problems can be solved, for example every local clock can compute a prediction of what the occluded pulsar is doing (then you have a simple clock definition with overly complex implementation). Gravitational lensing should not be an issue. No observer will record that the pulsar ticked one billion times when viewed in one direction, but one and a half billion times when viewed in another. Even if the record of ticks gets out of sync, there should be an "official" relative time for any observer. For a single observer, it is never "two different times at once" at any given remote clock, so choosing a particular clock as a "master" clock isn't a problem. The time at the pulsar should be well defined according to any observer, with GR --- I think.

No, I don't think that's right. He's asking how many ticks of one pulsar do you measure relative to the other pulsar. From what I read he didn't explain the difference in location/gravity/velocity between the pulsars... we can assume for the sake of his argument that they're essentially collocated, acting like different hands of a clock. Everyone will agree on the number of P2 ticks per P1 tick, just like everyone will agree that a minute hand does 12 full rotations per rotation of an hour hand --- no matter how fast or slow those hands are observed to be turning. What Bart seems to fail to realize is that 1) Such results are completely consistent with relativity. Specifically, what any observer measures is consistent with what any other observer measures, ie. reality is consistent, even with time dilation. 2) Such results are not good enough to define a clock. Choosing a universal clock would be arbitrary, and it would not be universally applicable, so calling it "universal" would be a mistake. Yes Bart, your universal clock would is simpler, but it wouldn't suffice. Relativity (or this thread) doesn't disagree with all of your premises or evidence, only the conclusions that you're drawing from them.

I think another way to say what G.H said is that essentially those sound waves would quickly be lost in the relatively overwhelming "noise" of particle movement. Another idea is if the sound waves are encoded into something more permanent. For example, there is the idea that sound waves might be "recorded" into clay... If you drag a brush over wet clay, the brush may vibrate from sound and act like a needle does when recording a vinyl record. A few years ago someone tried to extract sound out of the brush strokes on old clay pots, hoping that they'd be able to hear the potters chatting. What a mind-blowing possibility! Unfortunately they didn't get any signal. (I assume even if it could work, the brush itself would be noisy enough to drown out any additional vibrations it picks up.) There might be some other way in which sound waves were naturally recorded?

Those are some interesting points to deepen the discussion. I think that superposition does not apply here, because even if you could say that the system was in two states at once (in some instant), you wouldn't describe it "changing" between those superposed states in that instant, would you? The words "at once" may or may not imply timing, and it's hard to phrase this to avoid loading the question. What prevents the possibility of some system that always is in a distinct state, and yet can have two such states share a single instant? I can't think of any real example, only an analogy: It's like if you pause a VHS tape and there's a line of noise at the bottom of the screen, and the pixels of the noise can be changing, and they're always a distinct color, yet each state maps to only one time on the tape. This is not the best example because while "VHS time" is stopped, our time continues, and the pixels are changing in our time. Another way to think of such an example is to borrow from Schrodinger's cat: Imagine determining the "instant" of death in a given reference frame, and having many observers in that frame all "measure" the cat at that particular instant, and suppose it is either alive or dead but that some of them find it's alive at that instant and others find it is dead --- there must be some subatomic phenomena that behaves like this??? But do you need a different time tag for different states in such a case? As another analogy, consider the real number line from -1 to +1, and "the change" from negative to positive numbers. What is the distance between the negative and positive numbers? Why can't the duration between time tags of two different states be zero? Edit: If time is discrete, and you can meaningfully describe a minimum duration between two instants, and the state of some system must be in exactly one distinct state at each instant, and the state is different for some such pair of instants, then the answer to the question is "No", because the difference in the two states is associated with the duration between the two instants. If any of those conditions are not true, then I think the answer might be "Yes", because... - If there is no difference in states there is no change, - If the state can be two different distinct states in a single instant then you can describe a change in 0 time (though superposition might throw a wrench in here) - otherwise, if you describe the change between different distinct states A and B over some small duration ε, then consider the state C halfway through ε. Either C != A or C != B. Since there is no minimum duration, you can keep repeating this. For the same reason that there is no smallest number greater than 0, there must be no smallest duration between different states with continuous time, and so the duration between different states must be possibly 0. (This argument might fail though, as the duration becomes 0 only after halving it an infinite number of times, and A/B/C would become identical if the states of the system were also continuous). So perhaps the question can be rephrased in terms of whether or not time is quantized and/or whether possible states are quantized?

I disagree. If it's about time then probably (and certainly in this case) it's about the ordering of events. Since you're using a non-standard, personal definition of time, the meaning you assign to the phrase "change in time" is different from what others mean. The phrase might be left up to interpretation as is, but I don't think anyone else thinks it means the difference between how long it takes you to pee at different ages (though I can't speak for everyone and may be wrong). The ordering of events is maybe the essential aspect of time. The metric is perhaps just one of its properties. Having studied special relativity, you know that the "duration of a physical process" isn't constant, let's say. Knowing that, how can you prove that there must be a duration between any pair of connected events (connected via some process of "change")? You say "No." Please explain. Here are some examples to get into: 1) If you think of the first conceivable moment, say t=0 of the Big Bang. Can you say that involved the result of some change? And if so, was there any duration ending in that moment? Or if not, what might be the duration of the very first possible change? --- This proves nothing and I don't know the answers or if the questions even make sense, but it's something to think about instead of thinking that what applies to 2012 vs 2002 applies to all possible events. 2) If you consider a change in some point-like particle, is there a definite ordering to it, and is there a duration for that change to happen? Consider a muon decay http://en.wikipedia....Muon#Muon_decay In the diagram in the link (or see below), consider the change between the muon and the muon-neutrino. How long does that change take? Say it takes a duration of ε. What happens during that time? Is the particle in some sort of intermediate state? Is the ordering of all the transitions shown certain? My limited understanding of quantum mechanics is that they are not. My guess is that these transitions cannot be said to take time. Perhaps someone with a good understanding of QM can weigh in on that???? Anyway, I may be wrong. I've given an explanation of why the answer "No" may be wrong. Please show your reasoning for why the answer is "No", not just in a given example, but in all cases. Edit: Sorry I missed your earlier explanation, plus another definition, that "Change is movement". In that case what is the movement involved in the transitions between the particles? Thanks.

Duration addresses the "metric" of time... the measure of the temporal "distance" between events, but it throws away the "ordering" of time. If one pair of events has a duration of 1 s and another has a duration of 1 s, that doesn't tell you anything about what time the events happened. Did the former start before the latter, or vice versa, or were they simultaneous? If we say v = d / t, the t there is a duration. It is like saying v = x / t, where x = 0 when t = 0. Or, v = delta x / delta t. So, yes, you can consider any instant t as a duration from time's "origin" of 0, just like a location x can be considered the distance from a spatial origin. You can choose an origin in space and time (eg. let's call midnight t=0 and then any given time today is a duration since midnight). How did you conclude that change can only happen in time? Time's not an object... if you imagine an infinite number of imaginary clocks at the same location ticking at the same rate, is that any different from a single imaginary clock marking the same time as all the others? What you're talking about is like asking: What is the change in distance from the end of a ruler relative to the number of tick marks? The distance changes at a rate of 1 m per meter tick on the ruler. You don't need to have "emerge" another measure of distance on a ruler... you use the ruler's measure of distance.

Acceleration is the derivative of velocity with respect to time... dv/dt. dt/dt would be always 1... ie. proper time of functioning clocks always passes at a rate of 1 second per second. All higher derivatives would be 0. You could speak of [math]dt/d\tau[/math], I guess the change in one clock's time with respect to another's... At least in special relativity: ...that's the Lorentz factor... it tells you how many times a local clock (t) ticks per tick of another clock (proper time [math]\tau[/math]). http://en.wikipedia..../Lorentz_factor The derivative of that would be the change in Lorentz factor. It would correspond to a change in velocity, with a change in relative simultaneity. (In GR it would correspond to a change in relative gravitational potential.) I don't know if it has special meaning (as velocity, acceleration, jerk etc do) or what higher derivatives might mean. They're useful, eg. http://www.sciencech...php?f=84&t=8584 So, "the change in my time relative to (a change or period in) your time" refers to time dilation, ie. the value of the Lorentz factor. A change in that over your time, is the rate of change of the Lorentz factor. With a non-zero acceleration (and non-0 v), it would be non-zero. A change in that over your time, would be... ??? I dunno. But note that with a fixed positive acceleration (and positive v), this value (the rate at which the rate of change of the Lorentz factor changes -- ugh, confusing) increases as v increases...

I don't agree. Your reasoning applies equally well whether f is continuous at a or not.

I always find it strange when a puzzle is solved but the rest of the thread carries on obliviously. As well, "nm" is texting slang for nothing much, or nevermind. ...but next time I see someone reply with "nm", I'll be impressed with their Latin!