Philosopical criticisms of the Einstein thought experiment - do they exist?
I refer readers to the thought experiment described in Albert Einstein's book, now published online, at gutenberg.org.
Have there been any philosophical criticisms of this thought experiment and its conclusions? (The train experiment) At times it appears to follow inconsistent reasoning.
I refer specially to the reasoning contained in this paragraph:
Have there been any philosophical criticisms of this thought experiment and its conclusions? (The train experiment) At times it appears to follow inconsistent reasoning.
I refer specially to the reasoning contained in this paragraph:
Of course we must refer the process of the propagation of light (and indeed every other process) to a rigid reference-body (co-ordinate system). As such a system let us again choose our embankment. We shall imagine the air above it to have been removed. If a ray of light be sent along the embankment, we see from the above that the tip of the ray will be transmitted with the velocity c relative to the embankment. Now let us suppose that our railway carriage is again travelling along the railway lines with the velocity v, and that its direction is the same as that of the ray of light, but its velocity of course much less. Let us inquire about the velocity of propagation of the ray of light relative to the carriage. It is obvious that we can here apply the consideration of the previous section, since the ray of light plays the part of the man walking along relatively to the carriage. The velocity w of the man relative to the embankment is here replaced by the velocity of light relative to the embankment. w is the required velocity of light with respect to the carriage, and we have
w = c-v.
Comments (78)
In this instance
This is all well and good.
There are no laws of nature broken here. All measurements are taking place in the embankment frame of reference. What Einstein is referring to is the 'closing speed' that is, the calculated difference between the speed of light of the carriage and that of the ray of light.
Then he goes on to say:
What exactly comes into conflict with the principle of relativity? Subtraction? Remember that the speed of light is never observed from the carriage as being less than c.
Whenever the example is given that two beams of light are travelling relative to each other at more than the speed of light, this is always explained away as being 'closing speed'.
Yes, closing speed works via subtraction, and can yield values > c. Closing speed is not a velocity. Notice they don't call it closing velocity.
Of course for the observers riding in those objects, the theory says that they will see the other object closing at them at c or less.
About .96c, yes. Observers aside, the wording of the situation is: In the frame of either object, the other object would actually be approaching at .96c. It takes light time to travel between the objects, so the observers never see where the other object is, but a picture of the past when the other object was further away.
Thus there might be a star a light year away, and I can watch a really fast ship appear to pass it and arrive here a month later. That's not twelve times faster than light, it is just the ship getting here almost as fast as the image being observed. The trip still took 13 months in my own frame.
Quoting noAxioms
You are saying that you may see a spaceship passing a star a light year away, the spaceship travelling directly towards you, and see the ship arrive at your location a month later.
So after the ship actually arrives, images of the ship will continue to arrive at your eyes? Will there be 13 months of images?
The only way this can happen in real life is if the object is already travelling that fast and passes by checkpoints. Nothing can get an object up to a speed like that nor expect to stop it at the other end. OK, our particle accelerators do it. Maybe the distant star has a planet made of gold and somebody finds it economical to send the stuff here one atom at a time at .92c
The ship takes 13 months to travel here. That is not in question. What of the particles emitted from the ship? The first one will take 12 months or one year to reach us. The last one will take zero time to reach us.
1 year of travel is compressed into 1 month of images?
Yes, the first one has 12 light-months distance to go, and the last one has zero distance to go. All this is in the frame of the planets.
No, the image is as viewed by the observer on the destination side, who does not travel at all. He just observes the 13 month trip, and that observation takes only a month since he doesn't see the beginning until 12 months after the trip actually started and the ship is already almost at its destination.
Any time you see something, you are observing the past, not the present. The further away something is, the further back you are seeing. Things on Earth are so close that this effect doesn't matter, but even the sun actually sets 9 minutes before the image of it disappears.
Again, none of this is relativity or has relevance to Einstein's thought experiment. This stuff was known in the 18th century when they first started adjusting actual positions of planets due to measured light speed.
Does it mean that in inertial frames moving relative to each other, that mutual time dilation occurs? Is it just an illusion?
Sounds good. Frames don't move since they don't have a position, but they have velocity relative to each other and I think that's what you mean.
It's quite real. Not sure what you would consider an illusion, but none of it is fake and the clocks are not being inaccurate. It really is possible to get to a place 1000 light years away and not die of old age en-route or require cryonics. But alas, my car seems to be a bit underpowered for the task.
There are fast particles that get created in the upper atmosphere (60000 m up) that have a lifespan long enough for light to travel about 600 meters before decaying. Almost none should reach the ground, but a vast percentage of them do because their decay is delayed by the time dilation from moving at about 99.5% of light. They age slow enough to reach a destination well beyond their life expectancy of about 2 microseconds. They could not do this if the dilation was but an illusion.
Take the statement
Quoting noAxioms
"There are fast particles that get created in the upper atmosphere (60000 m up) "
Fast as measured in our frame
"that have a lifespan long enough"
A lifespan in our frame of reference
" for light to travel about 600 meters "
in which reference frame?
"before decaying. Almost none should reach the ground, but a vast percentage of them do because their decay is delayed"
When measured in our FoR
" by the time dilation from moving at about 99.5% of light."
" They age slow enough to reach a destination well beyond their life expectancy of about 2 microseconds. They could not do this if the dilation was but an illusion."
Could there be any other explanation for this? I accept it as is, but just wondering.
Well, at no point does it look like any laws are being violated. The laws would be wrong if that was observed. That's how ToR came about: The laws appeared to be violated, so they knew they needed better ones. I think I see what you mean though. The muons in the atmosphere appear to violate half-life laws (under Newtonian physics) until the transformation is used to yield the actual age of the typical particle measured here near sea level.
Yes. Those particlues (muons I think) are stationary in their own frame, and Earth is what moves fast.
No, in its own. I have a halflife of 72 years in my own frame, and an arbitrarily large one in other frames, which is why I can get to places more distant than 72 light years away.
2.2?s half life multiplied by c. In its own frame I guess, since duration is otherwise ambiguous.
Yes, only in our frame. In its own frame, it doesn't travel at all, but Earth moves and hits the particle before it dies.
No other theory competes at this time. If you want, you can interpret the data as one 'correct' inertial frame, and none of the clocks or tape measures are accurate unless stationary in that frame. In that sense, time and space dilation would be an illusion born of not having accurate measuring tools, but then we would have no tools to measure actual time and space at all, so we're not really measuring anything accurately. That's a pretty useless interpretation.
Quoting noAxioms
Imagine, if there was a God, or an "Intelligence" that knew everything, and whose knowledge is not limited by the speed of light. Would this allow the possibility of an absolute centre of the universe, or an absolute frame of reference? Could God know if one 'correct' inertial frame exists, or not?
There is a center of the universe, but it doesn't suggest a frame. Most people deny it for the same reason the center of the Earth appears on no map. If it did (Paris??), it would define the correct time zone, no? Look at the entire Earth and the center is obvious. Look at the entire universe, not just one surface of it, and the center becomes obvious.
Not sure I am getting the connection between things that expand from us at a speed faster than light and them not existing. Sure they won't ever interact with us given the light speed limit and all, but that does not imply that they would cease to exist for us.
I am on record for saying that the distance between any two events (points in spacetime) can be expressed by pure spatial separation or by pure temporal separation, or if right on the edge between the two, then undefined singularity. That assertion contradicts my denial of existence of things not in our reference frame.
So consider the event of you making that post, and Mr Cee on some other forum on some seriously distant planet making a similar post. Mr Cee does not exist in the frame in which Mr Bee is at rest, but that just means the wrong frame was chosen. Consider the frame where some spot about halfway is at rest. In that frame, the universe is now about a trillion years old and Mr Bee and Mr Cee are very near opposite edges of the expanding universe where time is dilated about 70x. Mr Cee is moving at about .9999c one way and Mr Bee the same speed in the opposite direction. Nobody is going faster than light. The separation is about 2 trillion light years and they both exist in that frame.
Words eaten. Thank you for the correction.
So which one are you rejecting here? Seems like the former, but if that is the case, then I still don't understand where the assertion that some things don't exist in some reference frames if they are moving away faster than light. Your response still amounts to this assumption that they do, but I am afraid I don't see how or why.
Also, since we are on the topic of absolute frames, I don't think that GR allows for the notion of a reference frame, due to the curvature of space-time. Instead the idea of an absolute frame is replaced with a preferred global foliation, which though technically not a frame of reference, defines a global time like the correct inertial frame should under SR. I am not sure if your statements above apply there, but I think I should throw that out since GR is the theory we are currently using.
Well, in our frame, Mr Cee is in the future and does not currently exist, so is not moving faster than light. Similarly, we don't exist in Mr Cee's frame. The frame is not a valid one for us since it would have us moving at about 140c, far beyond light speed.
Yes, it says that SR laws only work locally. They break down over any significant distance, and my example far exceeded that. Does it make it invalid? I was just trying to counter my prior assertion.
Messages could in principle reach distant places if the expansion of the universe was constant, but it isn't. Hence the event horizon, which delimits events that can never have a causal effect here on Earth.
But coordinate systems exist that map really distant events like Mr Cee's post. Mr Cee has a proper-distance from us (length of a tape measure that curves with space), and a proper velocity (how much that measurement grows per second) and that value can be greater than light speed without violation of GR.
Yes, there is an obvious global foliation (comoving coordinates), and I was unaware that GR rules (with space and velocity expressed in actual distance, not proper distance) would be valid at all in that coordinate system. Yes, that's where 'proper-distance' comes from. It essentially paints 4D spacetime in polar coordinates instead of the rectangular coordinates that yield inertial frames. The math to do Lorentz calculations in polar coordinates would be an interesting exercise, perhaps beyond my capabilities.
The trick works for fairly distant places, but my example put these events a couple trillion light years apart, too far.
So that brings us down to one's definition of existence to ask if Mr Cee exists.
Once we say God knows something, then it forces it into the realm of existence since God cannot know something that does not exist?
It would have no effect on us if such an arbitrary definition was made.
It is known to me even, so I hope God is aware of it. Didn't you see my post about that? The centre of the universe does not define a frame, even if it does suggest an origin for a non-orthogonal coordinate system.
Don't know what you mean by that. All parts of the universe of which I am aware (including the ones undetectable from here) are temporal and lit up, even if only dimly. Perhaps you define the universe as more than just what came from the big bang.
Not sure if that qualifies as a circular definition. What if God knows that something doesn't exist? Probably not a valid example since I seem to be playing epistemological meta-language games in making that statement. The nonexistent thing doesn't exist, but the fact that God is aware of its nonexistence does exist. But it must exist, having been referenced...
I'm not sure of your definition of 'exists' either. Does 2+2=4 exist? Surely God knows it, so it must exist.
I find existence to be a relation, not a property, so there is no 'exists', there is only 'exists in'. Your definition may vary, but I cannot comment clearly without knowing it.
Probably the most demonstrative and damaging philosophical critiques of Relativity derive from Bergson's approach to the issues raised.
http://m.nautil.us/issue/35/boundaries/this-philosopher-helped-ensure-there-was-no-nobel-for-relativity
Bergson had no problem with the scientific issue of determining simultaneity via use of clocks. His objections were giving Relativity and Relativity's definition of time, ontological status, which he thought was absurd (I agree). The time (duration) is the one that we experience, clocks and simultaneity are only products of this duration and the mind that is experiencing it.
Stephen Robbins provides his own Bergsonian critique of Relativity here:
https://www.amazon.com/review/R17WTYWUM6881A
I think what I am really getting at is: is a purely Newtonian universe possible, with all relativity being Galilean Relativity. Could God create such an universe which neither violated Newtonian physics nor Relativity as an illusion due to the limits of the speed of light, meaning limiting the speed of information transfer?
One can imagine that information transfer is limited by the speed of light, reality is not. For example, is God's knowledge of an event is delayed by the time it takes light from the event to reach Him? Surely this is an absurd statement? (Asimov hinted at this, that the speed of light was slowing the second coming of Christ).
Thank you. What about Herbert Dingle's critiques?
Despite criticisms, the theory, or at least the popular thought experiments and popular conception of the theory is still widely accepted. Is this changing? And how can an inconsistent theory be confirmed by experiments?
Probably the best discussion of the philosophical issues appear in these two videos by Stephen Robbins:
https://youtu.be/mcMnn5TpqT0
https://youtu.be/RjQg8on4yS0
Ontologically, Relativity is quite a mess especially if one tries to bounce between time as used in Special vs. General and then attempting to use both interchangeably. For those who are interested in the"experience" of life, this subject is well worth studying.
Bergson's claim was religious based, claiming that the immaterial mind somehow can detect what no clock or other physical device can: The rate of advancement of the present.
There is an empirical test against that claim (do the twin experiment with a human instead of a clock), but such an expenditure of resources would only prove that people detect time, not the advancement of the present. It would not conclusively be evidence of the ontological status of time.
Wayfarer, I've yet to read your article on the subject
Not a religious argument, but more an experiential and intuitive one based upon Bergson's studies of biology, mathematics, and education. Time (durée), as it is experienced, is heterogeneous and continuous. This is the opposite of scientific time which is homogenous and discontinuous. These differences provide a completely different view if the nature of experience and the mind that is experiencing. Bergson's series of books and papers on this subject provide a steady development of this point of view and metaphysics. The key components of the metaphysics are Durée, Memory (the experience of mind), and Elan vital (the creative impetus).
Sound works like that. It has a speed limit (that varies with the medium), but if I'm in a supersonic jet, I can hear the person behind me talking. Outside, nobody hears the jet approaching. Sound obeys Galilean Relativity only because we can carry its aether with us.
Your God has a location, and light travels there? Indeed, that's absurd. God is outside and does not gain knowledge the way we do: by waiting for physical photons and such to reach us. God has access to all states, and thus can meaningfully be said to be everywhere.
Intuitive yes, but if we went by that, the world would still be flat with the sun being carried overhead each day. Very few scientific advancements in the last couple centuries would qualify as intuitive findings.
???? So we should experience a series of stationary images while watching a 60fps movie.
No idea how this relates to ontology of time, or what you mean by 'scientific time'.
Indeed, explicit within Relativity, two observers are experiencing events differently. To Bergson, time (duree), is precisely what we experience as life. Memory is continuously evolving and sometimes it feels as time is moving very slowly and sometimes very quickly depending upon what we are experiencing. This is the duree of life, what Bergson called real time. Thomas Mann (and other modernist writers) attempted to express this experience in their novels, such as Mann's Magic Mountain.
What Bergson, in his critique, attempted to express was that life as experienced is different than life as science views it, science addressing the issue of determining simultaneity of events.
Quoting noAxioms
Our way of looking at things change as we share actual experiences, and in almost all cases, some creative intuition is involved whether it be ocean travel around the Earth or in a laboratory. It is in the laboratory, where creative experiments are first designed and implemented, that new discoveries are found. I would like to emphasize that it is the creative mind of the applied scientist in the laboratory that encourages evolutionary change. Theorists most frequently react to surprising new developments (Kuhn) that disrupt. Bohm writes quite eloquently about the nature of creative intuition in the advancement of scientific understanding.
On another front, Daoists, Greeks, and Muslims, developed a very concrete and effective view of health and medicine based upon experience and intuition. Creative intuition is the heart of evolution, not natural selection
So does this mean that the Relativity of Simultaneity does not apply to God? I would think he knows the Universe the way we would know fish in a fishbowl - we know were each one is, the limits, the center of the fishbowl ( I note your comments) , and the position and velocity of each fish in real time (since fish move at very much less than the speed of light, there are no detectable relativistic effects for us). He would know whether a fish is absolutely at rest or at motion with regard to the edges of the fishbowl, for example, or the water (ether?) or an arbitrarily chosen set of water molecules which happen to be in the same inertial frame?
Does Relativity apply to God?
Does Special Relativity apply only to 'real time' events? That is, events where information is communicated only by the speed of light and at the speed of light? No examining of historical traces or event logs, Einstein's train thought experiment seems to only illustrate real time effects.
Now if you put time outside the universe (as Rich does), then it can be said that God existed before the universe and eventually caused it to begin, and it is a thing that continues to 'happen'. Then I guess the question of relativity at least has some bearing. Anyway, in this interpretation, time is not part of the universe and thus would seem utterly undetectable. Clocks don't measure it (as relativity shows), but people are special and apparently do detect it, but not well enough to say what is going on elsewhere right now, so I find this claim completely dubious. This is probably not a fair description, since it is a view I don't hold. Ask the question of its adherents.
Relativity says there is no outside boundary, the bowl grows over time, and there is no possible designation of something stationary that gives a sub-light velocity to most of the fish.
The center has no position and no duration, so it does not define such a reference. It is an event, not a frame. Where on this map is the center of Earth? "Not on the map." OK, but which spot is directly over the center? "All of them".
Einstein's experiments involve implications of frame-independent constant light-speed, so yes, there's going to be discussion of light in them. Not sure how that makes it more 'real time'.
Quoting FreeEmotionBeen on that, and yes, it seems a place for people who know their stuff to make fun of people who don't. Some are worse that way than others.
Not sure where in any of the descriptions that prediction is made.
So you're saying that the round Earth model is just a convenience for scientific problems, not corresponding the real flat world as we experience it in life.
Not absurd, but pretty idealist. Not sure if FreeEmotion is asking about this.
Not what I said or meant.
Could we define an arbitrary boundary based on a set of stars that move very slowly relative to each other? Within this frame of reference, we can define absolute motion, does this make sense? How large does the frame of reference have to be to become useful?
Take for example the train and lightning strikes thought experiment. I have always thought that one could tell which lightning strike occurred first by stopping the train, and taking readings with measuring rods and clocks.
At the time the train is moving, however, it may not be possible to do this, due to the impossibility of using variations in light speed to determine simultaneity of events. This is an 'as it happens' view. Science also consists of taking measurements of past events using not speeds but displacements and locally recorded times.
Frames don't have a size.
Only in the frame of the platform
The experiment presumes a fixed light speed, as has always been measured. If the speed was variable, empirical measurements would vary depending on the frame in which the experiment took place. This has been done, and it is always a constant.
In the train example, there are two observers taking the measurements, each spatially centered between the two events. So the events are simultaneous if they're detected at the same time, even though it takes time for the light from the events to reach the measurer.
The Lumiferous Ether when it was thought to exist, was to serve the purpose of an universal frame of reference. A local volume of the Ether would then serve the same purpose.
I don't understand, can the same be said of the Ether? The Ether being the particular thing?
So there is no philosophical objection to light, or light waves or photons or whatever, being measured at the same speed no matter how fast the emitter and receiver are moving relative to each other?
None?
Can the concept of an object whose speed always is your speed + its natural speed raise any alarm bells?
That's the intuition, and intuition is wrong here. All measurements (light in a vacuum) always yield the same number. Light is slowed if it goes through water, glass, etc.
E >>>>>>>>>>>>>>>>>D1>>>>>>>D2>>>>>>>
It makes no difference if the emitter is moving towards or away from the detecting apparatus, the speed of light they measure will always be the same. Is that correct?
One explanation is that E, D1 and D2 all are immersed in an invisible medium just like air is to sound, that transmits light by first responding to the disturbance at E and then transmitting the light at the natural speed that the ether transmits light to D1 and D2.
I suppose no alarm bells need to be raised here, this is the explanation involving ether.
What I think I meant was, in the absence of ether, what other explanation is possible? The ballistic theory will be ruled out by the independence of the speed of the emitter.
The wave theory would work, but it needs a medium.
How would you describe the way in which light is transmitted, without using either the ether, waves in ether or the ballistic theory? What is this concept and can it be put into words?
That said, if the experiment is expressed as three events instead of three potentially moving objects which are not events, then the measurement can be taken in any frame and it will always result in the same speed of light.
This explanation has been falsified long ago. You persist in a model that predicts different results than those that are empirically observed.
Relativity is not a statement about the mechanism of light getting from here to there. It is about the geometric implications that directly follow from a fixed light speed.
This does clarify things somewhat, however questions remain:
What is the underlying method of light transmission that relativity ultimately describes? With Newton, you had a mechanism - photons, if relativity is a description of reality, then what is the underlying reality?
OK, but the distance and time to D1 is not needed, just take the event consisting of light reaching D1 and the event of light reaching event D2, and measure the speed in between.
It is called the photoelectric effect. But it's not well understood, and that's why there is quantum uncertainty, the creation of conceptual fields, and wave functions. The inadequacy of which demonstrates that there is no underlying reality for this conceptual structure.
Quoting Metaphysician UndercoverThe photoelectric effect concerns emission of electrons when light shines on a surface and has nothing to do with light transmission mechanism or relativity.
Quoting FreeEmotionOK, those are events, but how do you measure speed between events? There is no frame-independent definition of that in physics. So you've not specified a frame for these two events. Essentially you need to tell me the spatial separation between events E1 and E2, and given that we know light speed, we can compute (not measure) the time it takes for light to make the trip in the frame you've specified. This is obviously not a measurement of light speed since we're assuming a constant for it in our calculation.
Most (all??) light speed measurements are done via round trip so the emission and detection events are in the same place and the duration can be measured by a clock. That doesn't work if the events are spatially separated. Most of the thought experiments you reference in your early posts assume an already known light speed and from there find geometric implications about the ordering of events and the distance between them.
I believe that when light is transmitted through a substance, there is an interaction between the electrons of the material, and the light energy.
What does any of this have to do with relativity thought experiments that F-E is asking about?
Yes, that's what I meant by "photoelectric effect", the interaction between photons and electrons (maybe I misused the terminology), such as when photons are absorbed and reemitted when light passes through a medium like glass.
Quoting noAxioms
It concerns the speed at which light is transmitted. It's known that the speed of light is different in different mediums, and this involves refraction. I believe the classical way of understanding this, understanding light as waves, involves the wavelength of the light. The quantum understanding of this difference in speed involves the light photons being absorbed and reemitted by the atoms of the material.
Any further reference on this? Feynman's lectures are quite insightful, it seems.
If we have the spatial separation between events E1 and E2, and know the times at E1 and E2, we can calculate the light speed. (not measure?). Why assume it a constant when we are trying to measure it in the first place? Now I know that the clocks need to be synchronized, or the other option is slowly moved apart. If we are able to have control over how fast the clocks are moved apart, we can establish the error bounds due to non-synchronization and take this into account.
I believe there have been some studies done in this area.
Why "compute" and not "measure"?
Slowly moving apart doesn't necessarily work. You start at a midpoint and move the two clocks symmetrically in opposite directions. That defines a frame, but the two clocks stay synchronized despite the speed at which this might be done. Now you can measure your light speed. Painful way to do it, but valid.
Quoting FreeEmotionIf you use synchronized clocks, it is a measurement. If I know light speed, I can compute the time and don't need the clocks. But synchronization is frame dependent.
All the thought experiments you reference assume as a postulate that light speed is constant. None of the thought experiments involve the measurement of it. I have performed a light-speed measurement in a lab exercise using the length of a hallway and only an RPM meter as my clock. We got about one digit of accuracy with that setup.
The fundamental issue that you are inquiring into is whether STR should be elevated to an ontology. The answer is no, though some science fiction writers wish to do so. STR is simply a mathematical transformation between two frames of references. That is all.
At the superficial level, how can STR explain anything, e.g. time dilation and contraction between two frames if references, when all frames if references are reciprocal. It can't.
Now, GTR tried to address these issues, but the meaning of time is not the same in both theories (looking at the equations) and for sure there is no reciprocity since one frame of reference under GTR is considered to be accelerating! (They both can't be accelerating). Bergson and Robbins do the best at addressing these issues head on.
STR and GTR are best left as tools for scientific calculations and measurements and discarded as a means for arriving at any ontological meaning, which is why it cannot and should not be brought into any philosophical questions. To do so creates a mess.
Absorbed by the lattice? Doesn't "lattice' just refer to the discrete model, as an alternative to the space-time continuum model? It is my understanding that since they can't tell which atoms actually absorb the light, they have to model it as if all the atoms are potentially absorbing the light.
I'm curious what percentage accuracy?
So in the above example, it is possible to synchronize clocks, and it is possible to measure the one way speed of light?
How widely accepted is the above view? When we hear that a certain experiment 'proves relativity' we get the impression that scientists are one step closer to establishing relativity as absolute reality. Is this generally the popular view, what do you think?
Given a different frame choice, the chock synchronization would be different and therefore the time between the same two events E1 and E2 would be different, but the spatial distance between them would be different as well, so the measurement of light speed would still come out the same each time.
It sounds like a philosophical assertion, and you're hearing one person's asserted interpretation of some particular finding, and not what the experiment actually demonstrates.
It was all the rave in the media when gravitational waves were detected, this proves GR.
I am not alone in questioning the many ways scientists have figured out how to arrive at desired results. The whole world has been turned into one giant scam. Too bad. My belief in that people will do anything for easy money remains unshakeable.
http://www.everythingselectric.com/gravitational-waves/