Does relativity even exists?

[Edgard Neuman]

Hi,

I tried to explain relativity to somebody, and I thought of a newtonian situation where relativity would appear.
And strangly It seems to be enough to generate relativity effects (without any spacetime involved).. here is the exemple :

 

If we have a group of ships immobile on the ocean (far enough that they can see each others), and they have to communicate. So they use flying birds to carry messages from one ship to another. Birds are perfect they are never tired and always fly at the same speed according to the ocean.

If one ship want's to get an information about something, in every case, it have to send a bird, and wait for the bird carrying the answer to come back. So in every case, the path taken by the information is a closed path, and the integrale of the displacement of birds is null.

Now let's assume the group of ship is moving on the ocean (in the same direction at same speed, but slower than birds). If one ship wants an information, it just have to send a flying bird, and wait until it comes back. The ship would have to wait more, because, during the flight of the bird, the requesting ship have moved (in some kind of Zeno paradox), but after a time, the bird would come back.

Now let's imagine that the group of ships coordinate their relative distances by mesuring the time it take for birds to come back. Naturally, while moving, they would have to get closer along the global movement direction. But they would be able to adjust their relative distance so the bird come back in the same time as when they were immobile.

 

So if we observe trajectories of any information between ships, we have the very same effects for the ships than those given by special relativity : length contraction or time dilatation, simultaneity shift, and even more : if they try to mesure the speed of birds, because the group compensate their relatives distances, birds would take the same time to come back how ever they are moving on the ocean or not (if they use ship distance given by bird flight time as the unity of length, of course birds speed is invariant)

 

And all this, without involving any spacetime trick, only a newtonian ocean, with newtonian birds.

 

So is the special relativity just an illusion ?

Edited April 23, 2014 by Edgard Neuman

[SamBridge]

Normal relativity appears in Newtonian mechanics, but special relativity doesn't, because Newtonian physics assumes information travels instantaneously to all observers and that there's no speed limit to anything. It's not so much that all of relativity is an illusion as much as that anyone is correct to report what they observe from their own frame, I can't speak for everyone when I say it's 4:00pm, but that doesn't mean I'm wrong when I say my clock reads 4:00pm.

Edited April 23, 2014 by SamBridge

[Edgard Neuman]

I speak about special relativity. Newtonian physics doesn't assume anything about speed of light or information (yes at that time, light was believed to be instantenous.. but Newtonian physics would only assume any speed depends on the frame) , the special relativity only exist to explain the constant speed of light in any frame (which is contrary to Newtonian).

Here light and information are transported by birds : it is not assumed instantaneous. My point here is that relativity doesn't disproove the existence of aether since we mesure length using mater that depend on light (through atomic interactions) to maintain its own length (and length unit define speed).

Edited April 23, 2014 by Edgard Neuman

[Janus]

Hi,

I tried to explain relativity to somebody, and I thought of a newtonian situation where relativity would appear.

And strangly It seems to be enough to generate relativity effects (without any spacetime involved).. here is the exemple :

 

If we have a group of ships immobile on the ocean (far enough that they can see each others), and they have to communicate. So they use flying birds to carry messages from one ship to another. Birds are perfect they are never tired and always fly at the same speed according to the ocean.

If one ship want's to get an information about something, in every case, it have to send a bird, and wait for the bird carrying the answer to come back. So in every case, the path taken by the information is a closed path, and the integrale of the displacement of birds is null.

Now let's assume the group of ship is moving on the ocean (in the same direction at same speed, but slower than birds). If one ship wants an information, it just have to send a flying bird, and wait until it comes back. The ship would have to wait more, because, during the flight of the bird, the requesting ship have moved (in some kind of Zeno paradox), but after a time, the bird would come back.

Now let's imagine that the group of ships coordinate their relative distances by mesuring the time it take for birds to come back. Naturally, while moving, they would have to get closer along the global movement direction. But they would be able to adjust their relative distance so the bird come back in the same time as when they were immobile.

But it takes an effort on the ships' part to maintain the equal round trip flight time, The ships also could measure that the distance between them is shorter when they are moving than standing still. For example they could stretch ropes of equal lengths between them while sanding still. When they move together, the ropes would go slack. The difference between this and SR is that it that the ships themselves would not measure any difference in in their respective distances, but other ships to which they are moving with respect to would.

So if we observe trajectories of any information between ships, we have the very same effects for the ships than those given by special relativity : length contraction or time dilatation, simultaneity shift, and even more : if they try to mesure the speed of birds, because the group compensate their relatives distances, birds would take the same time to come back how ever they are moving on the ocean or not (if they use ship distance given by bird flight time as the unity of length, of course birds speed is invariant)

 

And all this, without involving any spacetime trick, only a newtonian ocean, with newtonian birds.

 

So is the special relativity just an illusion ?

Again, the ships have to actively alter their respective distances in order to maintain equal round trip times. With SR the ships don't have to do anything.

 

The closest thing your example relates to is Lorentz Ether Theory. In which there is an undetectable ether, and that nature just conspires to cause clocks to run slow and objects to contract when they move relative to it. In other words, it is basically just a coincidence that this effect happens give the measured result of an invariant speed for light. There is no reason given as why this effect is just the right amount, it is just an ad-hoc requirement to make it work.

[ajb]

Here light and information are transported by birds : it is not assumed instantaneous.

This sounds more like a good analogy than real physics. You kind of have a maximum speed defined by how fast the birds can fly, and so you will have some effects similar to special relativity. Observers won't agree on simultaneity and so on...

 

But this is an analogy and you will have to be careful how much you try to extract from it.

 

My point here is that relativity doesn't disproove the existence of aether since we mesure length using mater that depend on light (through atomic interactions) to maintain its own length (and length unit define speed).

Relativity does not require an aether to explain the propagation of light. As this aether is undetectable and plays no role in anything, how can it be considered real in any sense?

[Edgard Neuman]

In my story, it is important that the only interaction boats can have is by birds : they can't see each other, can't mesure any distance using ropes (it's part of the hypotheses of the story).

They use birds to mesure distance because it's their only way. In real life space isn't defined by itself : we observe it as a property of existing objects (they seems to have intertial movement and positions).

I suppose ships and birds have no other properties what so ever that being objects in newtonian physics, and boats don't observe bird newtonian relative speed when they arrive (just the moment they arrive)

As I'm speaking about relativity, I don't study the period of adjustement of distances, I just consider time when speed of the group is constant and equal to each other's.

The only difference with SR is that ships could adjust the distances to maintain the time birds takes to come back, or just don't (and it would be just like time of the group is slown for the observer).

If time spans are defined by the birds (ships don't have clocks) we can imagine that information only according to birds flow would produce something like SR.

I thought of an other difference : to be like SR, boats would have to depend on bird to define energy to emit an other boat faster than them.

I know it's an analogy, but it disturb me that boats couldn't disprove any thing about the ocean. I agree that if something is not detectable, it should be considered as inexistent, but i'm disturbed by the idea that if definition of space time is somehow strictly based on photons, it seems to me that we wouldn't be able to tell if photon are or not simply moving in an eather..

Edited April 24, 2014 by Edgard Neuman

[swansont]

 

So is the special relativity just an illusion ?

 

No. As you say, if the round trip time of the signal stays the same in any frame, the distance has to change: IOW, the distance between the ships depends on which frame you use to measure it.

 

Your scenario doesn't work in the reality of Newtonian physics, because length is absolute and the ships can't have two distances between them, as would be required for two observers in different frames. You must have a system where length and time are actually relative to the frame used to measure them.

[Edgard Neuman]

 

No. As you say, if the round trip time of the signal stays the same in any frame, the distance has to change: IOW, the distance between the ships depends on which frame you use to measure it.

 

Your scenario doesn't work in the reality of Newtonian physics, because length is absolute and the ships can't have two distances between them, as would be required for two observers in different frames. You must have a system where length and time are actually relative to the frame used to measure them.

You don't understand : distance exists only as properties you mesure from objects : energy you have to deploy to reach them (and / or mass that fit in). In my example, ship are always far from each and totaly blind to ocean distance (in fact : you really don't have no way to mesure distance in the ocean without GPS or looking at the sky)

 

For the ship : bird time is defining the distance. And without clock, bird trip frequency (like some kind of fine structure constant) may also define time itself for the ship.

 

We know newtonian distance exists here but they don't. So we may just be in fact as the ship : we don't sea ocean/eather because we only use photon/birds to mesure it.

Edited April 24, 2014 by Edgard Neuman

[swansont]

You talk about measuring the time it takes the birds to travel and then say there are no clocks. With no clocks, your scenario limits us to one frame of reference only.

[Edgard Neuman]

In fact, there is two option :

- with clocks, they can have an idea of newtonian time and adjust distance (there's a compression effect)

- without clocks, they can't adjust distance (no compression) but they can't communicate as fast as before because birds take more time to come back (for any maneuver, there time is slown)

 

both seems to me similar to SR

Edited April 24, 2014 by Edgard Neuman

[swansont]

Except that in SR, and even in Newtonian physics, there is more than one reference frame. Your scenario doesn't allow you to actually test other frames. If you could (with clocks), as I pointed out, you'd have the physical impossibility of contradicting results. Special relativity is mathematically consistent. That's a very, very dissimilar feature.

[Edgard Neuman]

Except that in SR, and even in Newtonian physics, there is more than one reference frame. Your scenario doesn't allow you to actually test other frames. If you could (with clocks), as I pointed out, you'd have the physical impossibility of contradicting results. Special relativity is mathematically consistent. That's a very, very dissimilar feature.

You still don't understand that "reference frame" exist only in the mind, constructed according to mesurements.

Boats would mesure time/distance using birds, and their "reference frame" is indeed different for any maneuver they would try to make.

They would have to say "this one is 10 bird flight hour away" for distance, or "this event will occure in 10 birds arrival", because they don't have any other information.

For anything they would try to do between boats, they have to count birds and their relative flight durations. That the only information they get about space or time.

For instance imagine 3 of them try to position themself into an equilateral triangle : they used birds to mesure length and they can triangulate using flight duration to put themself into what seems to them to be equilateral lengths. But if they are still globaly moving into the ocean, the triangle would indeed be compressed from an observer point of view.

 

Because of that, even their relative speed mesurment would depend on birds flight time (and you have here speed addivity in SR)

 

If you add an other hypothesis : birds are available in finite number, so they can still send several but they have to wait for some to come back to fill their bird stocks. It means that without clock, they can mesure relative flight time using average flight arrival count (and we have both SR effect).

 

It's important because in real matter, lengths and times are mainly the effect of electromagnetic forces (it defines the size of atoms and distance between them, by a dynamic equilibrium), information which is entirely carried by photons..

Edited April 25, 2014 by Edgard Neuman

[Klaynos]

It seems to me you have an absolute frame in your situation, the ocean, this does not exist for the universe all speeds are relative. Any comparisons are thus flawed.

[Edgard Neuman]

It seems to me you have an absolute frame in your situation, the ocean, this does not exist for the universe all speeds are relative. Any comparisons are thus flawed.

Speed for them is mesured by birds, just as all the information we get from univers is carried by particles.

In my story, if they mesure speed, even only with bird, their mesurement would still be relative.

Indeed, newtonian physics (so my example) suppose relative speeds.

Here ocean is absolute only for the birds. My point is just that we don't know if eather exist or not because speed mesured by constant speed particules would still be relative in it.

[Klaynos]

You used the ocean as a reference to make your point which isn't valid.

 

Whilst you might say that of you are moving in an ether you will not be able to measure it's effects with a single measurement of you measure two systems which are original you can tell if there is anything you are moving through which is altering the speed of what you are measuring. The mm experiment did this for light.

[Edgard Neuman]

You used the ocean as a reference to make your point which isn't valid.

 

Whilst you might say that of you are moving in an ether you will not be able to measure it's effects with a single measurement of you measure two systems which are original you can tell if there is anything you are moving through which is altering the speed of what you are measuring. The mm experiment did this for light.

My point is just that we don't know if eather exist or not because speed mesured by constant speed particules would still be relative in it. My point is not that aether exists, its that we can't disprove it only because of constant speed of light.

Here I place myself in the case where bird number is finite, and bird swap frequency define time.

 

I explain it again : if birds are defining space and time mesurements, you can't tell speed of birds eventhaugh they are actually moving in a Newtonian way in a newtonian space.

 

If one of the boats try to mesure birds speed, it while always have the same speed (if they uses birds arrival frequency has a clock). So you could do the Michelson Morlay experiment with newtonian birds and always have the same speed.

In the story, boats don't have access to newtonian relative speed of birds, they can only try to mesure time they take to come back using other birds arrival count to mesure time (which depend on the same structure of speed variation)

 

What's important here, is that if birds travel is the very definition of mesurement of space time, you will always gets the same speed (it will only depend of the ratio of boat and birds), and it wont tell you anything about the real nature of the space..

My other point is that we can make special relativity inside a newtonian space, if information vectors have a constant speed.

 

I think I should do some computer simulation to really proove it.

 

I will try to explain it an other way.

 

If the interaction structure in the system is defining space/time mesurement (information relative travel length between nodes) , then you can apply any 4D linear matrix to it, all mesurement would be the same. Because global speed (any equaly directional change in information travel in all links) is itself a linear matrix applyied to interactions, any group of node where is added a global speed would still be the same as before.

 

In other words : relative information permeability (which is what we call speed of light ) is only defined by the average number of links by node in the graph.

Edited April 25, 2014 by Edgard Neuman

[Klaynos]

But my point is orthogonal observations would show a difference as moving with or orthogonal to the background would provide a variation. If the background never has an observable effect then it is of no consequence and cannot be shown to exist.

[Edgard Neuman]

Orthogonal mesurment would be impacted by the same distortion that the speed of birds. If they send bird orthogonaly to their speed :

- they still move forward while the bird is flying

- if they are compressed along the direction : time stretch would be as asymetric as their contraction compensate.

- if they use birds to mesure time, average birds frequency would be impacted by the global speed.

It would be compensated by contraction of the group of ship along their moving direction.

 

I didn't spoke about it, but I assume birds are perfect and can do trajectory interception.

 

Sorry but I had an other idea, I don't know if it's true but it blown my mind so much I really have to write it..

 

I wondered what happens if the boats go faster than birds..

In any direction they send bird, relativly to them, every birds end up in a cone behind them. And they still could reach another boat, but only in that cone (relativly to the group). In other word, information in the moving group could only go into a cone, in the back of the sender.

Just like the futur cone in space time diagramme. It can't be a coincidence. It defines an arrow of time in the group.

(It's also related to my other post when particule go inside the black hole, faster than light from our point of view, photons they emit can only reach particules behind them. If we you those cone to define space time, it would create a inner univers around the center, the time line of the inner would be radiuses, the past is at the center, futur all around, because new emited photon can only reach the matter behind the matter movement)

Edited April 25, 2014 by Edgard Neuman

[Dekan]

Considering Edgard's boat and bird analogy, don't we note this: that a resistive medium is involved.

 

The resistive medium in the case of the boat, is the water. The water won't let the boat exceed a certain speed. And in the case of the bird, the air won't let the bird exceed a certain speed. Thus although the speed of both boat and bird, could in theory, be infinite - in practice their actual speed is limited, because they encounter the resistance of water and air.

 

Now consider the case of the photon. It could also, in theory, go at an infinitely fast speed. . But its actual speed is limited to just under 300,000 kps..

 

Why should the photon have this speed limit? How do we explain it?. Do we say, "Well that's just the way things are" That doesn't sound very scientific!

 

Wouldn't it be better to postulate that the speed limit is imposed by an Aether, which permeates the Universe, and exerts a resistance?

[Edgard Neuman]

No but it was implied that we don't considere that. All movement are inertiel.. I used the ocean only to serve has a absolute frame for the birds (they fly at the a fixed speed relative to ocean). I suppose boat's speed is constant by default.
And I tried to explain speed of light in my analogy by using, not the speed of birds in the ocean frame, but the speed boats mesure using birds (to count relative information come back length between relative to average bird exchange rate).

 

 

In my idea : speed limit is given by the ratio of bird and boats :

- every bird travel time is only relative to others

- because there's a finite number of birds, bird can be dense or rare among boats.

So if we considere the bird paths graph, birds frequency only depend on the permeability of the graph : more links means a bigger probability for birds to come back.

 

 

I'm not sure of that at all.. I suppose if boats are blind and without clocks, they can still use birds to mesure both time spans and length between each other, (and it would probably not depend of birds flight distortion created by their speed on the ocean, the distortion would be like SR), but I'm not sure exactly how they can do that.

Edited April 25, 2014 by Edgard Neuman

[swansont]

You still don't understand that "reference frame" exist only in the mind, constructed according to mesurements.

Boats would mesure time/distance using birds, and their "reference frame" is indeed different for any maneuver they would try to make.

They would have to say "this one is 10 bird flight hour away" for distance, or "this event will occure in 10 birds arrival", because they don't have any other information.

For anything they would try to do between boats, they have to count birds and their relative flight durations. That the only information they get about space or time.

For instance imagine 3 of them try to position themself into an equilateral triangle : they used birds to mesure length and they can triangulate using flight duration to put themself into what seems to them to be equilateral lengths. But if they are still globaly moving into the ocean, the triangle would indeed be compressed from an observer point of view.

 

Because of that, even their relative speed mesurment would depend on birds flight time (and you have here speed addivity in SR)

 

If you add an other hypothesis : birds are available in finite number, so they can still send several but they have to wait for some to come back to fill their bird stocks. It means that without clock, they can mesure relative flight time using average flight arrival count (and we have both SR effect).

 

It's important because in real matter, lengths and times are mainly the effect of electromagnetic forces (it defines the size of atoms and distance between them, by a dynamic equilibrium), information which is entirely carried by photons..

 

Your system is not self-consistent. One is unable to apply it to any real problem where there is relative motion, and still have it act like special relativity.

[Edgard Neuman]

I understood : what turns this pseudo "newtonian system" into a "special relativity" system is that birds flight define space and time for the boats (so they are not in a real newtonian spacetime because there definition of space and time is not newtonian).

[swansont]

!

Moderator Note

Discussion about absolute frames has been split http://www.scienceforums.net/topic/83405-absolute-frame-of-reference/

[robinpike]

Edgard,

 

To help make the point of your Newtonian story even clearer, have you considered using the same principle but with a more fundamental starting point than birds and boats?

 

Why not start with particles that always move at a single speed (the equivalent of your birds), but this time have the boats built from those particles too.

 

To make the boats from the particles, have the particles move in a circle - each particle moving in a circle would be a 'particle of matter' to build your boat.

And when the boat moves, the 'particles of matter' would have to change the shape of their movement from a perfect circle into a 'squashed circle' of a series of loops, in order to move forward.

 

Now you can use your story to ask the question: Can people on the boats detect when they are moving?

 

In other words, when they are moving relative to the single speed of the birds, is there a measurement that they can make that shows a different speed of the birds?