Iggy

Without understanding science, at least at an elementary level, you cannot be good at philosophy of science. Thank you so much for answering! The ball, you say, is going 20 mph and the runner is going 10 miles per hour so the ball is moving away from the runner at 10 miles per hour. You find this by subtracting 10 from 20. Very good. I am very glad you answered this. Here you use a different method to answer the question (you didn't subtract anything from anything)... you actually used no method at all for this one. I'm sure you don't think it is a problem not having any method to answer the second question, so we need to ask another question. The key question is... The catcher throws the ball very fast. The runner is running half the speed of light (335 million miles per hour) away from the catcher. Right before the first baseman catches the ball, the runner figures out that the ball is moving away from himself at 0.9 times the speed of light (603 million miles per hour). How fast is the ball moving away from the catcher? How did you get the answer? The reason this is the critical question is that you will absolutely not be able to answer it. By trying, and failing, to answer it I believe you could discover the problem with your view of reality. Right now you obviously don't see why a constant speed of light is incompatible with classical mechanics. If you try to solve some classical mechanical problems while acknowledging that the speed of light is constant then you might discover the incompatibility and the problem with your view of reality. The examples are insulting or I'm being insulting? I can understand if you find my description of your misunderstanding insulting, but I don't know what about these examples would be insulting. They are just thought experiments involving velocity.

Yeah, general covariance, I agree. Good point. I think that is at the heart of the solution to any perceived paradoxes. Philosophy of science involves interpreting scientific theories. To interpret a theory, a working understanding of the theory is necessary. I believe you need someone to be brutally honest. You do not have even an elementary understanding of relativity. Your posts in this thread show that you would not be able to use the theory and that you don’t understand what makes the theory necessary or what purpose it serves. A few posts ago you said that the distance between objects is constant in relativity when expressed in light units because the speed of light is constant. In truth, a constant speed of light makes the opposite true. With that kind of misunderstanding of the purpose and application of the theory, you can’t expect a good philosophical interpretation. I won’t get into a philosophical debate, but special relativity really doesn’t suggest subjective idealism. A frame of reference is like a two dimensional slice through a three dimensional object. The three dimensional object is the same even if all the two dimensional slices are different. Imagine a three dimensional object like a tomato. Imagine all the different ways that you could slice it at different angles. The surface of the slices will all look different, but the tomato is still a tomato. In relativity, frames of reference are three dimensional slices through ‘four dimensional’ space-time. Space time is the same even if all the three dimensional slices, or frames of reference, are different. If you understood how and why that is true then you would also understand that relativity offers an objective reality independent of the various differing perceptions of reality that come with different frames of reference. You ask if it denies a cosmos independent of observational frames of reference and the answer is that it establishes exactly the opposite. This is what Dr. Rocket has been talking about. The speed of light is constant; which means that it is the same in all inertial frames of reference, while the duration between events and the distance between objects is relative to velocity. This was predicted by special relativity in 1905, but more important, it is confirmed experimentally to very high precision on a daily basis. It is a physical fact that can’t be argued against reasonably. Characterizing this fact by saying “there is no actual objective distance” doesn’t seem completely correct or useful to me. A direct answer is fine, but first--I asked you a question about baseball and I don’t think I got an answer. A player is running from home plate to first base after bunting the ball. He is halfway there going 10 miles per hour relative to the catcher. The catcher grabs the ball and throws it to the first baseman. The catcher who is standing on home plate finds that the ball is moving away from himself and toward the first baseman at 20 miles per hour. Just before the first baseman catches the ball and gets the out the runner asks the question, “how fast is that ball going relative to me?” If the runner measured the speed of the ball as compared to himself while he was running what would be the answer? How did you come up with the answer? A second version of the same thing -- The runner travels half the speed of light relative to the catcher (he is a very good runner). The catcher decides to shoot the first baseman with a laser rather than throwing him the ball (he is a very bad catcher). Just before the laser hits and kills the first baseman the runner asks “how fast is that laser beam going relative to me?” If the runner measured the speed of the laser beam as compared to himself while he was running what would be the answer? How did you come up with the answer? If you work through this problem recognizing, like you do, that the speed of light is constant for all observers then you should realize that there is a problem. If the runner in the second version of the game assumes that distance is constant and he uses the same method to answer the question as you used in the first version of the game then he cannot come up with the right answer. Oh Boy! After hitting "preview" I realize that this post ended up way longer than I meant it to. Sorry. A question for the site administrators if any are reading, is it OK to be so far off topic for so many posts? Should maybe the thread be split up into two threads if that is something you do, or maybe Owl or I should start another thread? I'm not familiar with the usual practice so just want to be sure we're not posting inappropriately.

I'm not sure what you mean there... After reading it a second time I think I know what you mean. The distance between events in space time (the space time interval) is invariant. If that is what you mean then I agree.

Indeed. That is at least one issue. Owl is saying that length is invariant. I'm not sure what you mean there. I consider anything I can measure both physical and real. Length and time are physical, but not invariant. My point to Michel is that their relative nature does not make them non-physical or unreal any more than kinetic energy's relative nature in classical mechanics makes it unreal.

I can't assure that every (or any) publication would insert that fine print, but it is true. I think you are mixing frames. The rocket takes just over 2.5 million years to reach the Andromeda galaxy as measured by us here on earth. Light takes 2.5 million years to reach the Andromeda galaxy as measured by us here on earth. They spend more time traveling between galaxies (as measured by us) than it takes light. The rocket takes just over 35,354.5 years to reach the Andromeda galaxy as measured by those on the rocket. Light takes 35,354.5 years to reach the Andromeda galaxy as measured by the people on the rocket. It takes them (as measured by them) longer to reach the galaxy than it takes light (as measured by them) to travel the distance. In both frames of reference light spends less time traveling the distance than the rocket does. When you say "by some magic" I think you mean that it is paradoxical. That is not the case. Nothing that I'm saying is beyond an explanation. Time and distance must be relative for the speed of light to be fixed between observers of differing velocity. How else could you explain that the velocity of light is constant? How could the person on the rocket and the person on earth agree about the distance between galaxies and the time spent traveling and measure the speed of the same ray of light and say "it is receding from me at one light year per year"? The first step is understanding why that is impossible.

That's what I'm saying. The same thing should be considered true in regards to distance or length. Length (of an object or any other kind) is a function of two points and the frame of reference that those points are taken with respect to. It is not only a static property, but is itself relative to velocity just as much as kinetic energy and velocity are. "the distance of the object is two meters" is not a complete statement any more than "the velocity of the object is two meters per second". Distance and velocity are relative, so we must say "the distance of the object is two meters relative to a specific FOR" and "the velocity of the object is two meters per second relative to a specific FOR" Actually, the term relativistic mass is avoided exactly because it implies what you think it implies. John Taylor and Archibald Wheeler write in their book, "Spacetime physics -- Introduction to special relativity": "The concept of "relativistic mass" is subject to misunderstanding. That's why we don't use it. First, it applies the name mass - belonging to the magnitude of a 4-vector - to a very different concept, the time component of a 4-vector. Second, it makes increase of energy of an object with velocity or momentum appear to be connected with some change in internal structure of the object. In reality, the increase of energy with velocity originates not in the object but in the geometric properties of spacetime itself."

To say "c is constant" means that every observer will measure the speed of light as c. In the thought experiment with the Andromeda galaxy the earthlings measure light traveling 2.5 million light years in 2.5 million years. The speed of light as we measure it is 2.5 / 2.5 or 1c. The rocket traveling .9999c relative to us measures the same light traveling 35,354.5 light years in 35,354.5 years. They measure the speed of light as 35,354.5 / 35,354.5 or 1c. In special relativity, the speed of light is constant. The distance between the two galaxies is not constant. Right. If you think of length in the same way then length contraction makes sense. If you think of either length or kinetic energy as properties of the bus then their relative nature does not make sense.

I'm not sure. I think it depends on how you define length, or the radial distance. The Schwarzschild r coordinate, for example, is not the same as a shell observer's r coordinate. Section 4 of this lecture talks about it: http://www.uio.no/studier/emner/matnat/astro/AST1100/h10/undervisningsmateriale/lecture15.pdf Someone could object, "which is it? There is only one reality". You don't have to choose one. They are all real. Relative to the person on the bus, it has no kinetic energy. Relative to the person on the street, it has kinetic energy. Kinetic energy is real even though it is relative to velocity. Frame dependence does not imply non-realness. If frame dependence does not imply non-realness then that is not a reason to reject length contraction as non-real or "only an optical distortion".

I see. No, an object is never longer than in its rest frame. Why do you ask? Must the largest length be the realest? What is the kinetic energy of a plane? Does the plane have only one "real" value of kinetic energy and many other "apparent" values?

Let me put it another way: both you and the rod you are holding are expanding in a coordinate system in which the velocity is approaching your velocity. What is the kinetic energy of a plane? Does the plane have only one "real" value of kinetic energy and many other "apparent" values? Edited to add: I'm sorry, you asked for an example and I forgot to answer. An example is that the space shuttle expands as it lands from our perspective. In orbit it is about 37.189999987484 meters long and on the ground it is about 37.19 meters long. It expands about 0.0000000125 meters relative to the ground. From the shuttle's perspective the united states expands by about .16 centimeters.

Those with a good understanding of relativity have no conceptual problem with the reality of length contraction. My post was intended to give you a better understanding. That is what I said. I said "I agree that your understanding is common--even among those studying physics." The paper reports on how common misconceptions are in those learning relativity. It would be helpful to discuss more than one frame dependent quantity. What is the kinetic energy of a plane? Does the plane have only one "real" value of kinetic energy and many other "apparent" values? Both you and the rod in your hand are expanding in a coordinate system which is decelerating relative to your coordinate system. Length contraction will not make sense as a physically real process until you stop thinking of length as an inherent property of objects. Length depends on velocity. The distance to the Andromeda galaxy depends on velocity. From our perspective the length is 2.5 million light years. From the perspective of someone traveling between galaxies at near the speed of light the distance is only a few thousand light years. Neither perspective is any more physically meaningful than the other.

I agree that your understanding is common--even among those studying physics. Studies show: Villani and Pacca have demonstrated that university students’ reasoning in relativistic contexts is similar to that observed by Saltiel and Malgrange in Galilean contexts. A case study by Hewson with a physics graduate student illustrated the importance of “metaphysical beliefs” (e.g., time is absolute) to his understanding of special relativity The student in the study classified certain relativistic effects (including length contraction) as distortions of perception. Posner et al. report similar results in interviews with introductory students and their instructors. O’Brien-Pride has conducted interviews and administered early versions of some of the research tasks described here in which university students appear to believe that the order of events depends on observer location. Her preliminary results provided impetus for the investigation detailed in this paper. http://arxiv.org/ftp/physics/papers/0207/0207109.pdf Can I please ask--how much kinetic energy does an airplane have? If there is only one reality does that mean there is only one real value of kinetic energy? Since kinetic energy depends on velocity, I don't think it has to mean that. Two observers who are 1,000 lightyears apart will make the same measurement for the length of something if they have the same velocity. I think a lot of people have the same view. The problem with that view that I have is the distance to the Andromeda galaxy. If a person travels the distance with a velocity 0.9999c relative to the galaxy then it will take them 35,357.99 years. Distance is speed times time. The distance to the Andromeda galaxy is therefore 0.9999 lightyears / year times 35,357.99 years = 35,354.5 light years. We on earth measure the distance at 2.5 million light years. The person actually making the trip measures the distance at about 35 thousand lightyears. Who are we to tell them that their distance isn't real if they are the ones traveling the distance? I believe that you are correct that there is only one reality. But, that reality is four dimensional. There are many different 3 dimensional versions or perspectives of the four dimensional reality. Spatial distance is a 3 dimensional property and there are many different equally correct and equally real spatial lengths of a four dimensional thing--just like there are many different equally correct and equally real lengths of a 2D cross section of a 3D object. Distances in space are relative to reference frame. Distances in space time are invariant--they do not change from reference frame to reference frame.

...This description corresponds to perspective, or optical deformation: the book intrisically does not change because someone somewhere is observing it. It looks like I used a not-too-helpful analogy. The front of the book is wider than the spine. It isn't an optical deformation. It really is wider. If, for example, you had a hole in the wall just a few cm wide and you want to fit a book through that hole then you might have to rotate the book just right to fit it through. The idea is that rotating a book in three dimensions changes its two dimensional width, or length. In the same way, rotating an object in 4 dimensional space time (which is the same thing as giving it velocity or changing its frame of reference) changes its length in three dimensional space. If something rotates relative to me (or I rotate relative to it) in space time then I should expect its spatial property of length to change. This may not be a very helpful analogy, it's just what helps me when thinking about the reality of length contraction. Probably more helpful is to realize that length is not an inherent property of an object. The way that an object's momentum or kinetic energy depends on velocity is like how its length depends on velocity. Momentum, kinetic energy, and length are all three dimensional, frame dependent, things. You could probably see how saying "that object has a lot of kinetic energy" only makes sense if you're really saying "that object has a lot of kinetic energy relative to our frame of reference (or relative to some other specified frame of reference)". Spatial length is the same way. It really does not make complete sense to say "the distance between those things is very large" unless you're really saying "the distance between those things is very large relative to our frame of reference (or some specific frame of reference" If you leave off the "relative to" part of the description then you don't have a meaningful description--it's incomplete.

I think an easy way to consider that length really changes with frame of reference is to compare it to other things that change with frame of reference. Momentum, for example. No one would doubt that momentum is real or that it is different depending on the speed of the observer. The most satisfying consideration for me personally is that length is a 3D property in a 4D space time, or, it might be more exact to say that it is a spatial property in a space time world. If you look at the a book so that the face of it is toward the front it could be 15 cm wide. The 3D book has a certain 2D width. Rotating the book in 3D so that the spine is facing front will give it less 2D width. It isn't as wide when looking at the spine. The 2D width depends on how the book is positioned in 3D. Changing the velocity of something in 3D amounts to rotating it in 4D space time, so it makes sense that the 3D property of length changes depending on its velocity, or its angle of rotation in space time. Just like all of the 2D images one could take of a 3D object from whatever angle are real and none are preferred, so too are all the possible 3D lengths of something in space time real and not preferred. Living in a 4-Dimensional World

It's always the same length in its own frame. It is different lengths in different frames.

A lot of people that don't have a background in science or math find the balloon analogy confusing. The surface of a balloon is two dimensional. It represents a 2-manifold that is not embedded in a higher dimensional space. It has what is called intrinsic curvature. In one dimensional space there is one set of directions that you can move--forward/backward. In two dimensional space there are 2 sets--forward/backward and left/right. In three dimensional space there are three--forward/backward, left/right, and up/down. Because the surface of the balloon represents a 2-manifold there are only two sets of meaningful directions--forward/backward and left/right. There is no third spatial dimension either filled with nothing or filled with empty space. The same analogy can be made with a 1-manifold. A string that stretches would represent one dimension of expanding space. A circle that expands also represents one dimension of expanding space. A line and a circle are both one-dimensional manifolds. Unfortunately, it looks like you don't understand relativity. The distance measured in light minutes or any other units depends on the reference frame. The speed of light is constant. If two reference frames have different velocities and they both agree on the speed of the same photon then they won't be able to agree on the distance the photon travels or the time it takes to travel. A good example of this is to think of the photon as something slow like a baseball. The catcher is at home plate and he isn't moving. The batter is running at 5 miles per hour toward first base after bunting the ball. The catcher grabs the ball and throws it toward first base--it flies through the air past the runner. If the speed of the baseball is constant then both the runner and the catcher need to agree on the speed of the ball. The runner should figure that the ball is moving away from himself at 10 miles per hour and the catcher should look at the ball and say that it is moving away from himself at 10 miles per hour. A couple quick questions then--if the baseball is moving away from the catcher at 10 miles per hour and the runner is moving away from the catcher at 5 miles per hour then how fast does the runner think that the baseball is moving away from himself? If the runner is going half the speed of light and the baseball is instead a laser then how fast does each think the laser is going? Understanding the solution to this thought experiment is the first step in understanding relativity. It can give a lot of people trouble.

I just heard a commentator on CNN accusing Israel of piracy and it had me thinking--maritime law must allow for at least some situations where warships are allowed to legally board vessels in international waters even if the ship is flying a legitimate flag. I figured that suspicion of arms smuggling might be that type of exception, but after looking at the United Nations Convention on the Law of the Sea article 110, I see it isn't. Article 110 Right of visit Except where acts of interference derive from powers conferred by treaty, a warship which encounters on the high seas a foreign ship, other than a ship entitled to complete immunity in accordance with articles 95 and 96, is not justified in boarding it unless there is reasonable ground for suspecting that: the ship is engaged in piracy; the ship is engaged in the slave trade; the ship is engaged in unauthorized broadcasting and the flag State of the warship has jurisdiction under article 109; the ship is without nationality; or though flying a foreign flag or refusing to show its flag, the ship is, in reality, of the same nationality as the warship. [*]In the cases provided for in paragraph 1, the warship may proceed to verify the ship's right to fly its flag. To this end, it may send a boat under the command of an officer to the suspected ship. If suspicion remains after the documents have been checked, it may proceed to a further examination on board the ship, which must be carried out with all possible consideration. [*]If the suspicions prove to be unfounded, and provided that the ship boarded has not committed any act justifying them, it shall be compensated for any loss or damage that may have been sustained. [*]These provisions apply mutatis mutandis to military aircraft. [*]These provisions also apply to any other duly authorized ships or aircraft clearly marked and identifiable as being on government service. It appears the boarding would have been legal, or could have been construed as legal, if the Turkish ship were suspected of engaged in piracy, the slave trade, or broadcasting a pirate radio station. Being suspected of supporting terrorism or smuggling arms is apparently not cause enough--which is not to say that I think the suspicion itself would have been valid. Very odd it seems for the Israeli navy not to wait for the crossing.

I see. I would just again say that you present "slavery and obedience is good" and "you should be like a good slave" as if they are mutually exclusive. They are not and I believe the passage does both. I see no reason to exacerbate any differences in interpretation in this thread or another.

But, I used the word "like". I don't understand your point.

The point is a matter of interpretation, but I should say that I don't like that you put quotes around that. If you're trying to restate something that I said, I'd rather you didn't use quotes. And again, reinterpreting what Jesus said might not deserve quotes either. I'm really not interested in word play. I have no reason to understand the parable as anything other than it says: Blessed are those slaves whom the master finds alert when he comes; truly I tell you, he will fasten his belt and have them sit down to eat, and he will come and serve them. If he comes during the middle of the night, or near dawn, and finds them so, blessed are those slaves... Blessed is that slave whom his master will find at work when he arrives... Jesus is blessing slaves who do their master’s bidding and asking for people to be like his slaves. True, but I would argue that those things are not mutually exclusive. The passage seems to do both.

It's the parable of the 'servant'. I pulled the quoted off of: http://en.wikipedia.org/wiki/Parable_of_the_Faithful_Servant and accidentally cited Mark where I should have cited Luke. Anyone familiar with the parable should, nonetheless, see that I quoted it accurately. My point stands. "It was as dark as night" doesn't mean that night is not dark, even though it's metaphorical, so your point is lost on me. I assure you, it doesn't say what I would want it to say. I would have it advocate peaceful noncompliance and advocate freedom, but it clearly calls for the opposite which only makes sense. It is a very good metaphor. I'm sure you've heard the anti-religious types make the metaphor before: [Religious belief] is a totalitarian belief. It is the wish to be a slave. It is the desire that there be an unalterable, unchallengeable, tyrannical authority who can convict you of thought crime while you are asleep, who can subject you - who must, indeed, subject you - to total surveillance around the clock every waking and sleeping minute of your life - I say, of your life - before you're born and, even worse and where the real fun begins, after you're dead. A celestial North Korea. Who wants this to be true? Who but a slave desires such a ghastly fate? http://en.wikiquote.org/wiki/Christopher_Hitchens I don't think that holds true for all religious belief, but it does seem to in the semitic religions. Nonetheless, I think we've strayed way off topic. I don't want to detract from the thread. I certainly have. I grew up in a denomination with a very heavy emphasis on scripture. I can still recite whole chapters. I've taken nothing out of context.

The greek, δοῦλος is slave. http://www.blueletterbible.org/lang/lexicon/lexicon.cfm?Strongs=G1401&t=KJV http://en.wikipedia.org/wiki/Doulos It comes from the root δeω meaning to tie or bond and ΔΕΑΩ meaning to ensnare or capture. Culturally speaking, the White House is a fine example as Herod had hundreds of slaves. I don't think there is any room for interpretation. When Jesus said "Blessed are those slaves whom the master finds alert when he comes; truly I tell you, he will fasten his belt and have them sit down to eat, and he will come and serve them. If he comes during the middle of the night, or near dawn, and finds them so, blessed are those slaves" (Mark 13) he is telling the enslaved to submit to slavery and endorsing the idea of slavery--which only makes sense. Slavery and submission to it is a major theme in the Bible.

The difference between one slice of time and another is time. Asking what connects slices of time or what it consists of is making time into a physical thing, something tangible, which I don't think is useful. One could say that the laws of physics describe the difference in slices of time. If you knew everything about one slice of time then you could probably describe the next slice completely.

Both. I was meaning to compare the two. In both classical and quantum mechanics there is a very precise sense in which information is never lost from a closed isolated system. http://books.google.com/books?id=cxJCBRUNmVYC&pg=PA69&lpg=PA69&dq=%22information+conservation%22+%22in+both+classical+and+quantum+mechanics%22&source=bl&ots=liI3-3H-3w&sig=3jijcmInBVvZ7oSMQOh05BJPN2U&hl=en&ei=YhLgS6L6CI_iNYHWwM8J&sa=X&oi=book_result&ct=result&resnum=1&ved=0CAYQ6AEwAA#v=onepage&q=%22information%20conservation%22%20%22in%20both%20classical%20and%20quantum%20mechanics%22&f=false

Information, like an object, does not 'move' through time. With conservation of energy we can prove that the energy making up the universe today will be here tomorrow. By conservation of phase space (or the conservation of information entropy) we can prove that the information here today will be here tomorrow. In spacetime it doesn't 'move' from one time slice to the next. It simply exists in both. To have information move from one instant of time to another would indeed require another dimension of time as 'movement' is, by definition, change in location over change in time. see: http://books.google.com/books?id=cxJCBRUNmVYC&pg=PA69&lpg=PA69&dq=%22information+conservation%22+%22in+both+classical+and+quantum+mechanics%22&source=bl&ots=liI3-3H-3w&sig=3jijcmInBVvZ7oSMQOh05BJPN2U&hl=en&ei=YhLgS6L6CI_iNYHWwM8J&sa=X&oi=book_result&ct=result&resnum=1&ved=0CAYQ6AEwAA I haven't read the other thread, but I might point out that relativity disagrees with your conclusion. The speed at which no time is needed to traverse a space is the speed of light. If you traveled very, very near the speed of light it would take you very, very close to zero seconds to get to the Andromeda galaxy.