md65536

Do you have a reference for that? http://en.wikipedia.org/wiki/Lorentz_ether_theory says the opposite: "However, in LET the existence of an undetectable ether is assumed and the validity of the relativity principle seems to be only coincidental, which is one reason why SR is commonly preferred over LET." The preceding sentence is, "Because of the same mathematical formalism it is not possible to distinguish between LET and SR by experiment." So it is metaphysics to speak of one being real while the other is not. Wouldn't a reasonable scientist let evidence falsify a theory? What does it mean to say that one theory is correct while an equivalent theory, with equivalent evidence, is wrong?

I think you have to introduce the topic differently, so that people who don't know anything about SR don't mistakenly think there's no speed limit, and those who know a thing or two about SR but don't understand it don't mistakenly think that that's what you're trying to say. -- Edit: Which should be expected since you do mistakenly say "and there's no speed limit"... In this case, the length contraction argument is good but I don't think throwing in time dilation helps. Considering only length contraction, you use the moon's contracted ruler and the traveler's clock, and you can reach the moon in arbitrarily small local time. You break no speed limit; you don't get a valid measure of speed using your clock and someone else's ruler anyway. Considering also time dilation, the mixing of reference frames becomes a problem. If you say "you have longer to do it" you're implying using the moon's clock. If you do this it's not complete unless you include relative simultaneity as well as length contraction and time dilation. And you would have to do this, because you say "just accelerate"... so there will be a change in relative simultaneity. And as with the twin paradox, it's inescapable that the moon (in this case like the "stay at home twin") will age relative to you in a change to relative simultaneity, negating your "you have longer to do it" advantage. -- These problems are not there if you just stick to using your local clock, which doesn't experience time dilation or change in simultaneity relative to you. You can get places in arbitrarily small local times, but anywhere you get to will effectively age at an advanced rate. If you say you get there "fast", it implies might be confused with velocity, which is relative to your destination. It would be better to phrase it so that it's clear you're using only a local clock, because relative to any other clock you're not moving arbitrarily fast at all.

So first is the postulates. Then the transformations. Then the relatively simple derivables. If you haven't yet got around to figuring out the simple derivables, you don't know anything about SR. "To competently discuss the LHC experiment described in post #17, in terms of SR, you should at least be able to apply the composition of velocities formula." If you know about the postulates of relativity you already know more than the average person about SR. I don't think people should feel they know nothing until they're able to pass your initiation test, but on the other hand I don't think it's helpful to believe that one knows enough about SR and doesn't need to figure out something like composition of velocities. +1 for provoking me to try to derive it. Personally I don't think it's simple, it's certainly mind-boggling to figure out on your own, but the math isn't bad (high school level?). But yes, it is definitely not a complicated matter to set out learning about the postulates, about the transformations and how they're derived and what they mean, and the composition of velocities and how it's derived.

So the velocity composition formula is the very first thing one typically knows about SR? Did you really mean to emphasize the word anything? Perhaps it was a mistype of "quite a bit"?

But what does such a device count? Is it 100% certain to correctly count particles? If there's a physical, inherently uncertain chance that a given particle emission will hit the detector vs. going somewhere else, then does the precision of the count have any real meaning? As for the coins examples, how many individual measurements would it take to determine the number of coins in your pocket with 100% certainty. Eg. if you put them on a table and took a picture of them with a digital camera, that showed the count with absolute certainty, then the individual pixel sensors would each count as a measurement, or perhaps each photon detected might be a measurement. What would be the minimal number of measurements, using any method? Would you be able to reach 100% certainty by some method other than by taking enough measurements to achieve statistical certainty? Your post is like a lesson in how to describe scientific ideas properly, and how not to, respectively. Not that I understand the first sentence, but it's preferable to know what I don't understand and be able to look it up, than to have it explained in a simple way, and mistakenly think that I get it. Worse is when those simple explanations are passed on by other people who don't know what they're talking about, and you get "science" documentaries about QM that include the words "It doesn't make any sense, but..." It's sad that with a popular understanding of QM, people can believe that they understand it AND that it doesn't make sense.

I've been thinking about this some more and want to repeat what I said except hopefully more clearly. Cox explains his point by saying that when he rubs a diamond, heating up the atoms, all the other atoms in the universe shift in order to allow the diamond's atoms to change states. But this is misleading, because there's no causal relationship. I could instead claim that some atoms in the universe want to be in the state currently occupied by some of the atoms in the diamond, and so the atoms in the diamond are forced to change energy state, and they do that by having Cox rub it. Of course, this is an absurd explanation, as is the implication that the desire of some atoms somewhere are the cause of Cox's rubbing. And rightly so... there is no causal relationship between the different atoms changing energy state. That doesn't mean that Pauli's exclusion principle doesn't hold, it's just not causation. And that's a problem with the way Cox explains it. My causal example is absurd, but Cox's is equally wrong, yet it is plausible enough to imply a classical "common sense" connection (ie. causation) between his actions and all the atoms in the universe.

But they do match. All existing evidence is in favor of consistent realities agreed upon by any set of observers. Using some multi-world or alternate existences interpretation, a pair of entities who do not expect their realities to match should also never expect to meet and be able to compare notes (or have any other measurement of each other's existence). Equivalently, if they expect to be able to meet, they should expect their realities to match. It sounds like you're defining existence by a single observer's experience, as in your neutrino example. So anything that I don't know about doesn't exist. That's not the common definition of existence. The point of consistency is that if any two observers compared notes on what events they knew happened (or for that matter what they know didn't happen), then those lists would match be mutually consistent. No observer can say that one event certainly happened while another (who is "meeting and comparing notes" with the first, meaning that they're at the same place and time) says that it certainly didn't happen. There would likely be a lot of events that one observer knows about and the other doesn't, but let all pairs of observers meet and they'll all be consistent. If what I say isn't true, there's no known evidence of it. There has never been evidence of an inconsistent universe. Its consistency implies that existence is empirically agreed upon by all observers. If there are theoretical alternate realities, they should not be measurable from our reality.

I didn't read all of it but I don't think this addresses the consistency with which different observers see the universe. A given event either happens or it doesn't, and all observers agree (though not generally agreeing on the timing). You may theorize the existence of observers who measure a universe inconsistent with what we measure, but there is no experimental evidence of such (nor should there possibly be, in any way that is consistent with our reality). Or does that fit your point? -- That if there is some existence beyond what we can theoretically detect, it doesn't matter because it makes no difference in anything we will ever measure.

So do it. Everyone else can get rid of GR when you have a superior replacement (equal or better in ability to make predictions, precision, practicality etc). Spatially uniform acceleration is equivalent to a uniform gravitational field. A uniform gravitational field is not something typically found in nature as far as I know, but that's not a problem because natural gravitational fields* are locally uniform ("local spacetime is flat"*). I don't see anything wrong with that, unless you presuppose that spacetime is globally flat and what applies locally must apply globally. So the equivalence principle works, either locally with acceleration at a single point equivalent to a uniform gravitational field, or over a larger area but using different acceleration at different points and a non-uniform gravitational field with tidal forces. * Ignoring singularities, which are I guess an unresolved issue with GR, and a genuine opportunity for improvement (or even replacement)... but you improve something by building a replacement, not by first destroying the only thing you've got and saying "We needed something better anyway!"

Sorry to butt in as an uneducated slob, but... I don't see the difference. It is a postulate either way. It is known that the reasoning or clue behind Einstein's postulate comes from Maxwell's equations (and is backed by experimental evidence), so it's not like it would have made a revolutionary difference in SR. And it's not like replacing one postulate with another would reduce the number of assumptions made. If Einstein chose to use Maxwell's equations as a postulate, he would then have had to explain why that implies an invariant speed of light ---- which was what is important to SR. Why not skip right to what is important? Using Maxwell's equations would be just an extra step, and not really useful if he never referred to them again.

Well at least he admits "I don’t know why they don’t do that," rather than saying something like "WE NEED TO GET OXYGEN TO THESE FIRES!" Giving him the benefit of the doubt, perhaps "It’s a real problem," refers to him not knowing why airplane windows "don't do that." Perhaps "So it’s very dangerous...." refers to a presidential candidate not knowing about these things. To many in the GOP, reality is defined by one's understanding of it. Especially(?) true of climate, economics, sex, ethics, theology. "I'm an elected representative, and that makes me an appointed expert. If it doesn't make sense to me, it's because it doesn't make sense."

To quote someone famous, "Brian Cox is Full of **it" Meanwhile, this Guardian article seems to concede there's some truth to the interconnectedness of all things. It explains that the effect is non-local, so effectively instantaneous across distance "(whatever than might mean)", so I guess relativity of simultaneity would not apply??? I wouldn't bother trying to resolve the apparent paradox of it, because as it's mentioned, it can't be used to transfer information and so there's no violation of SR. However I agree with the first link above. Brian Cox is either wrong or he's explaining it wrong, because his explanation (that distant electrons shift their state in response to his example actions) implies a causative effect, which requires information transfer. The electrons across the universe don't change as an effect of his rubbing of a crystal. I don't know the answer to your question. I suspect it's based on BS from Cox. However if it's true that there's some mechanism that ensures all atoms in the universe are instantaneously each in unique states, I suppose it would apply to all possible instants. Because there's no information transfer, it would have to be an automatic property of the atoms, not a causal "response" to other atoms. They would not have to be "changed retroactively", because they would already have been satisfying all applicable physical laws.

I suppose we may never know, then... I've been thinking about this earlier comment of yours. You're wrong. You don't lack the grey matter to understand this (I'm assuming no brain damage or anything like that), but perhaps you lack a proper attitude? It's a good excuse though, if you don't want to learn about this, to say you're incapable. But I've seen examples of people who've overcome greater challenges than perhaps any of us here will ever know, including those who've taken online courses for no reason besides self-improvement, and excelled against the odds. I doubt many who learn something difficult begin by believing they're unable to. I doubt many who believe they're incapable ever try. I've been thinking about this in terms of an analogy (even though my last one didn't work I'll try again). Imagine that cosmology is like a cruise ship, which is designed by many people, and no one person can focus on every single detail of the entire ship. So you may study some particular aspects of it, and end up with a particular combination of knowledge that no one else has, which may perhaps even make you an expert on that. And you may find a small flaw in the ship, something like "Deck 10-forward is not wheelchair accessible", perhaps a detail missed by someone looking at only the big picture. You may even discover something big that was overlooked by everyone else, such as "If this collided with an iceberg, it would likely rip through the hull!" By analogy, what you're doing in this thread is like saying "The cruise ship can't float, because it's made of metal." And then it's explained that it can, and you say "Well even so, there are so many details to a cruise ship that something must have been overlooked, so I still think it can't float." Anyway, back to cosmology... experts on this don't get that way just by thinking about it. They learn about it. What is your source for the information you're posting in this thread? Perhaps you can request a better resource (a book or web site) to learn about it. Yes, Krauss is assuming that information will be lost. For example, we don't know what a particular dinosaur might have observed when looking up at night. We have no way of accessing that information... it is lost. It's a fairly safe assumption too, because even if say 100 billion years from now all of our information was somehow still preserved, there will still be other places, and other times, where that information is not possibly accessible. Krauss is making a very coarse prediction.

How are photons detected, in such a case?

It's not just the cost of bringing it down that's the problem, but of getting to it and mining it in the first place. It's not worth it to get something from space, when the same thing can be obtained here on Earth for much cheaper. There's no resource needed, at least not yet, that would make this cost effective. However, if you need the material to be in space anyway, then the cost of mining it on Earth and also then sending it up into space can become great enough to outweigh the extra cost of mining it in space. It's not just the value of the materials that we're talking about, nor just the differing costs of mining it from different places, nor just the cost of transporting it to where it's needed, but a combination of factors that will be different for different situations or locations.

The voice of god in that video speaks volumes of nonsense: "Quantum theory works... even though it shouldn't." --- Says who it shouldn't? "This could only happen if the particles go through both slits at the same time." --- Did you not watch to the end of the video, ie. "All this kind of language is not applicable"? "Does this mean that reality itself... is not real?" --- Reality is real by definition. This disproves that "there are no stupid questions." It's all so much claptrap trying sadly to express the idea that "reality 'should' be only what classical common sense says about it." The scientist at the end expresses a useful way of looking at it, but they ignore it in the narration and throw in sensationalist "science is spooky and doesn't make sense!" crap. --- I don't think you even have to say that the results of a given photon's behavior is "affected" by the detector, because you don't know where that particular photon would end up. It's not as if there is a "typical path" a single photon would take in absence of the detector, and a modified path in its presence. Trying to avoid "this kind of language that is not applicable", I'd say that it just means that a photon's behavior depends on its measurement. The behavior of the photon before it is observed, is not applicable or defined.

Yes, and I think that in the future more of our daily experience will involve relativistic effects compared to now, and kids will learn about relativity when they first learn about time and distance (rather than having the first 11 years of education treating length and time as universal, as was the case for me), and eventually it will be a commonly understood thing that few rarely think about enough to question.

That seems appropriate. 1. Condemning one thing doesn't mean that nothing else is condemned. They don't have to list everything that's condemned, lest they imply that everything else is sanctioned. 2. They wouldn't be immature and say "Well I guess inciting violence is not as bad as the violence itself, therefore we won't condemn those who incite violence because then we're taking sides..." 3. Condemning incitement of violence is pretty clear-cut. Condemning attackers needs finesse. If you don't do so, for example with a tough but tactless stance, saying things like "Bring it on," then people can get killed. Things are not the same as they were 10 years ago. If there's an ongoing effort to avoid condemning attacks, that's something else, but a single instance of condemning something besides the attacks isn't "inept".

tar, an "object as it exists throughout all of time" doesn't disappear behind an event horizon. Events that already have been observed can be taken as fact. They won't be "erased" from one's past knowledge. Scientists avoid this type of confusion by talking about "events" and "event horizons", not about eternal objects. As Iggy pointed out, a galaxy that disappears behind an event horizon was not even always a galaxy. When speaking of events and whether they'll "ever" be visible, there is no confusion between events related to the state of an object after it crosses an event horizon, and events related to past states of the object. It is the events that occur after it crosses an event horizon that will never be visible. Several times in this thread you mention something that is a misunderstanding of what Krauss is saying, and appear on the verge of understanding it. But then you re-assert your belief that Krauss must be wrong anyway, and the opportunity is lost. Krauss could be wrong. The Big Bang model could be wrong. Inflation theory could be wrong. Gravity theory could be wrong. If you already know something is wrong, there's no need to bother understanding it.

Edit: I erased what I wrote, because I've decided to abandon this conversation. My opinion remains that for things to look the way they do to us does NOT require such a viewpoint, because all our observations are consistent with light traveling at a speed of c.

Here's another example: A six-sided die with six unique sides, in a room with no mirrors, implies the existence of a god-like view, because without such a view, only 3 sides can be seen at a time, so a normal observer could never be sure that all 6 sides are unique at any single time, and so such an object couldn't exist. Correct? We have a model of the universe, or of a die, based on a combination of observations and predictions of where stuff goes when we're not seeing it. In the case of the universe, the model is a prediction and it's not precise enough for anyone to claim that the universe *is* exactly that, with 100% confidence. The make-up of the whole universe does not need to be known by any particular observer, in order to exist. Nor do our best models of it need to have any particular degree of accuracy, in order for it to exist. Which you've just repeated several times: No one does. Perhaps if you think that a description of the universe is "the way it is" as in a perfect, precise model of every detail of the universe, then yes I suppose that suggests impossible god-like perfect instantaneous knowledge of the universe. Well, guess what, the models aren't that precise! --- they're only as precise as can be made by ordinary reality-like observers, because no evidence obtained by a god-like observer is incorporated into any of them. And so, I think, does not imply the existence of such an observer. Our models basically assume that the side of the die that has one dot remains that way when it is turned away, and that the expansion of space is continuing consistent with all evidence so far, and that gravity continues to affect things after the last time we saw them, etc etc. But isn't it exactly true??? Because we ARE constrained by the speed of light, and we DO see it, as we see it. Is that not enough?

You're speaking now of an apparent horizon [http://en.wikipedia....pparent_horizon], which is different depending on the observer's point of view. From what little I understand, you (in a ship crossing the BH's absolute event horizon) would be able to see things (photons) that we on Earth couldn't see because they're inside the apparent horizon separating us from the BH. You would also have your own apparent horizon so the black hole singularity still looks like a (less massive) black hole to you. Then if your ship sends out a probe to enter what to you is the apparent horizon, the probe will be able to see light that you're not able to see, and it will have its own apparent horizon as well. This can be repeated ad infinitum? Ie. if you were heading toward the singularity, it would always look like a black hole though you would continually be able to see more of it?

Maybe you're missing the first and main point about Krauss's argument, which is that something which has crossed an event horizon from the observable universe to the unobservable will never be seen (assuming expansion continues). Nobody holds an image of this unobservable thing. It is not possible to receive an image of this unobservable thing. Predicting it, or imagining it (mentally generating an image of it but not receiving actual information from it) is not the same as observing it. Remembering an image of a past state of an object is not the same as observing it in its later states. Having information about something and then permanently losing access to that information is not AT ALL the same as having supernatural access to information. It's the opposite. We are able to see a past state of distant objects. Future observers will be able to see a past state of those distant objects. Far future observers will have less and less ability to observe a past state of those objects, until the objects are no longer detectable at all. SO WHO IS IT HERE THAT HAS A GOD-LIKE VIEW? Where ever is there the mention of someone observing something that can't be observed?

That's not correct. I don't even fully understand your concept of a god's-eye view, but in all your descriptions of it it sounds like you're setting it up to be something that is not physically possible. Krauss's view certainly doesn't imply that such a thing exists! I don't see how his view implies any super-observer characteristics at *all*. It's essentially about the opposite: A permanent loss of observable information. In such a universe, there is no need for a god-like being, because there is no possibility of universal observable knowledge. The universe continues to function without any part of it needing to know what all the rest of it is doing.

There's no continuous stream. Imagine shooting bullets out the side of an accelerating car (a Yardie Lobo, say). If you "connect the dots" of the bullets, it will make a curve, even though each of the bullets is moving in a straight line (ignoring gravity and wind drag). Similarly, even in flat space, your "stream of photons" can be curved because the photon source is moving. However each photon is moving in a straight line. There is no physically meaningful "stream"; it is only what you get when you consider all the photons together. However, there is nothing connecting one photon to another. They all behave independently, in their own individual null-geodesic "stream". I take back what I said about geodesics being "straight lines in curved space", because I guess that's taking the idea of geodesics far too literally, and is a misconception of mine, and I also think that my belief that a null geodesic is straight for an observer is not shared by mainstream science. I guess you would say: the path of a photon is only curved where space is curved.