Relativity - Oh dear, here we go again!

[my_wan]

Laudable aim. When you're happy you do, please explain it to me.

It scares me to start this but....
[Disclaimer]
Taking this analogy literally does in fact lead to inconsistencies and flat out wrong empirical predictions any many cases. I am going to use the concept of an aether to explain how Relativity could physically work in a way that makes mechanical sense. This in no way represents that it does actually work that way.
[/Disclaimer]

We'll start with some simple (apparently invalid) assumptions.
A - Assumptions
1) Space consist of tiny indivisible particles. Hereafter just called space*.
2) Standard (mass) particle are standing waves in this space*.
3) Fields are disturbances in this same medium.

Then we have effects based on standard thermodynamics.
E - Effects
1) Moving air is less dense than still air.

Now the definitions.
D - Definitions.
1) Time - A sequence of events.
2) Event (most fundamental) - A collision of particles of space*.
3) Length (most fundamental) - The mean relative distance between collisions of space*.

Now here we have the assumption that we are not made of solid particles but of standing waves in a medium of particles, i.e. space*. Now by effect E1 when we move relative to something else the space* that defines us is less dense. This means that our fundamental measure of length is greater due to D3. If our ruler is longer our measure of distances between places is shorter allowing us to travel 10 light years in less than 10 years without going faster than light.

Time dilation works the same way. By E1 since space* is less dense collisions take place relatively slower. Now we add to this the fact that changes in time rate effects (dictates) how we measure space*. This makes space and time exactly mathematical inverses of each other. This allows what is time for one person to be measured as space by another person and visa versa.

So why is the speed of light an absolute speed limit? If we and all our machines are standing waves in space* going faster than light would be like trying to make a tornado travel faster than the wind.

The astute here can see obvious glaring holes in this analogy. The more knowledgeable can even identify empirical falsehoods. I have worked with the issues of why it don't work. It seems that by invoking the mathematical properties of division by infinity as literal while using Cantors work on infinite sets to maintain relative properties some of the issues can be made to go away. It does however also require extra assumptions about an empty set of space. Please I do NOT want to hear about the superiority of the Lorentz ether theory, one way speed of light, etc. BS. http://www.tu-harburg.de/rzt/rzt/it/Ether.html

It has been said that you can't explain to a fish about water. How much more difficult would it be if the fish itself was made of waves in the water?

 

[MortFurd]

While staring at the clock, and stopping it, I thought of something, and maybe some really smart person here will explain why it is a true thought, or a dumb thought.

It might be an already thought of thought, in which case it should be easy to explain.

Using the Doppler effect as an example, helps explain how something can seem different, depending on the observer. A note, or tone, seems different depending on your relative motion. Moving towards it, it sounds higher, moving away, it seems lower. Of course the note is what it is, for the observer who isn't moving.

So an event is different depending on the frame of reference, for the observer, or a recording device.

But that isn't the case for time? It isn't the Doppler effect causing time to change? I'm asking here. Because that is what I am understanding.

Also, according to that really cool page about the GPS situation, gravity causes time to change as well. So clocks, (time), runs different depending on gravity. Right?

OK I gotta tell you, that sounds woo. It sounded woo thirty years ago when I first heard about it as well.

In fact, that whole relativity/observer situation sounds woo. More woo than woo.

So, here is the thought, looking at a clock, moving away from it, say a really big clock, so you can still see it, moving away from it, time slows down, according to the clock you are looking at. But this isn't because of the light, but some other effect? Is that right?

The clock on the spaceship is running the same as the other clock, but according to the stationary clock, it is running slower? So the stationary clock, the one you are racing away from, appears to run slower, or faster?

Or is it running faster, but looks like it is slower? Or is it the return journey that causes the change? Or both? Moving away really fast, then moving back really fast, they both cause time changes?

Do they balance out? Or is all movement causing your on board clock to run slower? Does any movement change time, making your clock on the spaceship run slower, relatively speaking?




And then my head explodes...

It sounds woo to you. However, your GPS receiver (if you own one) has to account for those "woo" effects in order to be accurate.

That's the difference between woo and science. If it sounds hokey and can't be calculated or verified, then it is woo. If it sounds hokey, but can be calculated and verified, it is science.

Relativity is very well supported science.

This is rather like the discussion that went on here about the Michelson/Morly experiment. They disproved the ether theory using (by comparison) very crude equipment. It was (for the day) top notch research and setup using the best equipment available.

Today, every traffic policeman on the planet repeats it everyday and thinks nothing of it. A radar gun or laser speed gun is aimed at a stationary object basically repeats the MM experiments Were there an ether, radar guns would have to account for the earth's motion and the location and aim of the gun in order to be accurate. They don't have to do any of that, so there is no ether.

GPS is the same kind of situation. An everyday object makes use of relatavistic effects to achieve its accuracy. Were those effects not accounted for, the devices would be pretty close to useless. Since they compensate using mathematics derived from the theory, the theory seems to work pretty well.

 

[my_wan]

One more thing (this one for my_wan): You started your reply with the word "no", but robinson didn't say anything wrong in the text you quoted before the reply.

Yes you are quiet right.
The confusion here is he seems to be referring to the big clock to determine that his own rate of time has slowed. The big clock is measuring time in its own frame of reference, not his. This observation only means the big clocks time has slowed as viewed from his frame of reference.

 

[BillyJoe]

....different observers disagree about which events are simultaneous, and that's caused by the existence of a universal speed, one that is the same in all frames. We call it the "speed of light" because light just happens to be traveling at that speed.

Maxwell's equations describing electromagnetism contained a constant called c which, at the time, was strongly suspected of being equivalent to the speed of light. That duly turned out to be the case. It was also thought at the time that the elctromagnetic waves required a medium in which to propagate and that its speed was relative to this medium. For a variety of valid technical reasons, others disagreed. Eventually it was experimentally proven that the speed of light was absolute. This meant, of course, that something else had to give. This something else was space and time, or simply, spacetime.

 

[BillyJoe]

So why is the speed of light an absolute speed limit?

Technically, that is not correct.
Technically, the speed of light is the upper limit for objects travelling at less than the speed of light; and the lower limit for objects travelling above the speed of light.
The second type of object is called a tachyon.
Tachyons necessarily travel backwards in time.
It is true, however, that none have ever been found.

 

[Beausoleil]

If we’re talking about human created clock time, then the “correct time” is the “correct speed” that the clock runs at according to it’s design and purpose. In other words, a correctly functioning clock runs at a predictable, constant rate when observed at a local level (in it’s frame). That the clock can be observed to be different than it’s actual existence, from the distance and movement of another frame, doesn’t mean that that it is different.

A correctly functioning clock runs at a predictable constant rate when viewed from any frame of reference. The rate predicted will depend on the relative motion of frame and clock. Any statement that tells you it is running at rate X when observed from frame moving at Y defines a unique rate for the clock. I can't see any reason to privilege the rest frame.

Part of the problem is that you are using a language (English) that is not built for relativistic concepts. The clock is running at 1 beat per second in its rest frame and it is running at 0.9 beats per second in a different frame, and these statements are not contradictory in any sense. To ask what its rate "really" is without specifying a relative rate of motion is nonsensical - the concept is undefined.

Suppose we designed a clock to show "correct time" from a frame moving at 5% of the speed of light relative to it. Which would be "its actual existence" - the one telling the "incorrect" time in its local frame or the one telling the "correct" time in the moving frame?

 

[my_wan]

Technically, that is not correct.
Technically, the speed of light is the upper limit for objects travelling at less than the speed of light; and the lower limit for objects travelling above the speed of light.
The second type of object is called a tachyon.
Tachyons necessarily travel backwards in time.
It is true, however, that none have ever been found.

Technically nothing I said was correct. It was merely an analogy to make it easier to visualize relativity in a mechanical sense.

Not only has a tachyon never been found but cannot exist in our present understanding of physics. The fact that they are quantitatively described in physics doesn't make them any more possible in the standard model.

 

[Ziggurat]

Try this- forget lateral movement .Consider the limiting case, where the spaceship (it's always a spaceship) is coming straight towards you at as near the speed of light as our special effects budget can manage.
The Klingon in said spaceship now turns on his far Ultraviolet laser.
The question you have to answer- and very, very quickly-is, are you going to get x-rayed, or does it just seem like it?

The X-rays are going to be real X-rays - they cannot "seem" to be X-rays and really be something else.

HOWEVER (and this is the key point, and maybe a little tricky), a clock on the approaching Klingon ship WILL only seem to be running faster. It will be observed to be running slower. Remember, Doppler shift is direction dependent - if the Klingon ship fires backwards at you once it passes, their laser will be red-shifted, but the observed (not seen, but observed - refer to my previous explanation of the term) time dilation of their clocks will NOT be different from when they're approaching you and from when they've passed and are receeding from you.

 

[BillyJoe]

I can't see any reason to privilege the rest frame.

I can.
And apparently so can ynot.
And probably many, if not most, others.

We are wrong of course.
But the only reason we are wrong is that the speed of light is absolute.
That was actually an unexpected finding.

 

[Art Vandelay]

(I can here the moans from around the world

Hear, not here.

I believe that objects (such as the clock) only have actual existence within their own reference frame.

Objects don't have reference frames. Only observers have reference frames. Now, you may say "well, isn't an observer an object?" Well, yes and no. In relativity, the term "observer" refers to a way of considering events, separate from the physical manifestation of that considering (i.e., the brain doing the considering). Assigning a reference frame is meaningless. How can you assign a reference frame to the clock? The end caps are moving at one speed, the ball is moving in two additional different speeds. Which do you use? And if you can only consider things that are at rest within a reference frame, how can you do physics? Physics is about things interacting. If everything you're considering is at rest, how can they interact with each other?

It’s “at rest” in its rest frame (A) and the ball therefore is never actually moving in a zigzag manner. It is just being wrongly perceived by (B) that it is.

Everything is at rest in "its own reference frame". So by your criteria, everything is at rest.

It’s not said that the clock seems to be running slower, it is said that it is running slower

What does "running slower" mean? It means that the increment in the time coordinate of each tick of the clock is more than the increment in the time recorded on the clock. It's simply an artifact of the coordinate system. To say that it's "running slower" isn't a statement about the clock, it's a statement about the coordinates of the clock.

A non-mathematical explanation doesn’t have to be a "layman's explanation". Taking the math away isn’t “dumbing it down” as far as I’m concerned.

To some extent, it does. English just doesn't have the vocabulary.

It can’t be in two frames at once.

A frame is a way of describing what's happening. How can it not be in two different descriptions?

Until I find a good reason to accept that any observation is always an valid, accurate and correct representation of reality,

ANY observation?

To be more specific: when the trolley is moving at velocity V toward the clock, the Doppler shift makes the clock appear to be speeding up by a factor of (1 + V/C) disregarding the actual Relativistic effect.

Actually, it's sqrt((1+V/C)/(1-V/C))

 

[Oroborus]

I'd like to thank everyone who contributed to this thread, Fredrik and Billy especially. I found your explanations to be both comprehensive and easy to understand, making a few things clearer. Cheers

 

[PixyMisa]

I can.
And apparently so can ynot.
And probably many, if not most, others.

We are wrong of course.
But the only reason we are wrong is that the speed of light is absolute.
That was actually an unexpected finding.

Yep.

c came out of Maxwell's equations, and was assumed to be the speed of light. Reasonable enough. But with respect to what? The luminiferous ether was proposed as the medium through which light traveled; in which case the Earth would show a motion relative to the luminiferous ether. The Michelson-Morley experiment showed that this was not the case.

 

[ynot]

Unfortunately I don't have time at present to read or respond to the posts, but I would appreciate feedback on the following . . .

Observer A is located close to a clock and views the time it shows in real time (virtually as and when it happens). Observer B is located one light second away from the same clock and views the time shown to be one second behind the time A views. This is due to time delay and has nothing to do with time dilation. (?)

The observers each wear a wristwatch that they synchonise to the time shown on their view of the clock. A then travels away from the clock one light second to be at the same postion as B. Considering just the affects of time delay, A would view that has wristwatch is now one second ahead of the clock and one second behind B's wristwatch.

As I understand it, Relativity would say that, during the journey of A from the clock to B, time dilation would also occur.

Do I have everything correct so far?

 

[RussDill]

Unfortunately I don't have time at present to read or respond to the posts, but I would appreciate feedback on the following . . .

Observer A is located close to a clock and views the time it shows in real time (virtually as and when it happens). Observer B is located one light second away from the same clock and views the time shown to be one second behind the time A views. This is due to time delay and has nothing to do with time dilation. (?)

The observers each wear a wristwatch that they synchonise to the time shown on their view of the clock. A then travels away from the clock one light second to be at the same postion as B. Considering just the affects of time delay, A would view that has wristwatch is now one second ahead of the clock and one second behind B's wristwatch.

As I understand it, Relativity would say that, during the journey of A from the clock to B, time dilation would also occur.

Do I have everything correct so far?

Yes, the time dilation would be highly dependent on the speed that A traveled to B.

I think what is meant by reference frame and mathematical construct needs to be explained better.

For our puny brains to understand reality, we break it down into space 'x, y, z' and time 't'. Most of our equations work on these variables too.

Einstein says rubbish. Time and space are inseperable, we live in a 4 dimensional world. Can you imagine a 4 dimensional world? I can't. So we define events that occur in this 4 dimensional world with reference frames. Each moment in time in a reference frame is a 3 dimensional slice of this 4 dimensional world. Different reference frames of this 4 dimensional world will show things happening at different speeds, objects being different sizes, even events happening in different order.

The reference frames showing different things doesn't mean that there are multiple realities, it just means that they are an incomplete projection of reality. Each reference frame is kind of like taking a slice of that 4d spacetime, and moving it in a direction perpendicular to the slice as you go forward in time. A different reference frame would be another slice at a slightly different angle. Kinda like if you take slices of a cylinder. The flat slice will show a circle. Other slices will show an ellipse. You are saying that it can't be a circle and an ellipse at the same time. It isn't. Its a cylinder. You just can't visualize the cylinder.

 

[Thabiguy]

Observer A is located close to a clock and views the time it shows in real time (virtually as and when it happens). Observer B is located one light second away from the same clock and views the time shown to be one second behind the time A views. This is due to time delay and has nothing to do with time dilation. (?)

Yes.

The observers each wear a wristwatch that they synchonise to the time shown on their view of the clock. A then travels away from the clock one light second to be at the same postion as B. Considering just the affects of time delay, A would view that has wristwatch is now one second ahead of the clock and one second behind B's wristwatch.

No. A would view that his wristwatch is one second ahead of the clock and B's wristwatch. Remember that B's wristwatch is synchronized with B's view of the clock.

As I understand it, Relativity would say that, during the journey of A from the clock to B, time dilation would also occur.

Yes, depending on the speed that A travels. If A goes very fast, he'll find his wristwatch less than one second ahead when he arrives. As his speed approaches the speed of light, the difference will approach zero.

 

[BillyJoe]

A then travels away from the clock one light second to be at the same postion as B

One light second is a distance, not a time interval.
It's the distance light travels in one second.
Do you mean "one light second in a second"?

Of course, only light can travel one light second in a second.

 

[BillyJoe]

After reading Thabiguy's post, I realise that I have misread ynot's post.

I agree with Thabiguy on both counts:


Ignoring time dilation, A's watch is one second ahead of the Big Clock because the light from the Big Clock takes one second to reach him. A's watch is one second ahead of B's watch, because B synchronised his watch to the time shown on the Big Clock.

Correcting for time dilation, A's watch is actually less than one second ahead of the Big Clock and B's watch. The greater the speed of travel the closer will A's time be to B's time and the Big Clock's time until, travelling at the speed of light, there is no difference at all.

This is why a photon is said to be "everywhere in no time".
(Don't ask me to try to explain that one, it just follows from the rules)

 

[Paulhoff]

OK, let’s try this if it hasn’t been done all ready.

We have two spacemen and three clocks and they are big clocks that can be seen from a 100 feet with no problem. The speed of light for this experiment is 100 ft. per second. They are all somewhere in deep space, who cares where. The clocks are all reading the same time.

1. Now one of the spacemen takes one of the clocks and travels at 99.9999% speed of light for one second and stops and looks back at the other spaceman and the two clocks, he is 100 ft away.

Is the time on his clock is the same as the other two clocks.
Is the time on his clock is one second behind the other two clocks.
Is the time on his clock is two seconds behind the other two clocks.
Is the time on his clock is one second ahead of the other two clocks.
Is the time on his clock is two seconds ahead of the other two clocks.

2. Now the other spaceman takes one of the two remaining clocks and travels very slowly, about one inch a second to the other spaceman. When he gets to the other spaceman he looks at the other spaceman’s clock.

Is the time on his clock is the same as the other spaceman’s clock.
Is the time on his clock is one second behind the other spaceman’s clock.
Is the time on his clock is two seconds behind the other spaceman’s clock.
Is the time on his clock is one second ahead of the other spaceman’s clock.
Is the time on his clock is two seconds ahead of the other spaceman’s clock.

3. Now the other spaceman looks back at the other clock left behind.

Is the time on his clock is the same as the other clock.
Is the time on his clock is one second behind the other clock.
Is the time on his clock is two seconds behind the other clock.
Is the time on his clock is one second ahead of the other clock.
Is the time on his clock is two seconds ahead of the other clock.

Paul

 

[Thabiguy]

1. Approximately b). Being one light second away, he sees approximately a).
2. Approximately d).
3. Approximately a). Being one light second away, he sees approximately d).

 

[Gertrude]

Observer A is located close to a clock and views the time it shows in real time (virtually as and when it happens). Observer B is located one light second away from the same clock and views the time shown to be one second behind the time A views. This is due to time delay and has nothing to do with time dilation. (?)

Right. So far, this has nothing to do with relativity.

The observers each wear a wristwatch that they synchonise to the time shown on their view of the clock. A then travels away from the clock one light second to be at the same postion as B.

For simplicity, we'll assume that A travels at constant velocity and will neglect the accelerations of the beginning and end of the trip (just not to get into GR)

Considering just the affects of time delay, A would view that has wristwatch is now one second ahead of the clock...

Right.

and one second behind B's wristwatch.

No. Ahead.

As I understand it, Relativity would say that, during the journey of A from the clock to B, time dilation would also occur.

Not really. Time dilation: someone travelling at constant speed will observe an event occuring in a slower inertial reference frame to have taken more time than what an observer at rest relative to said event would have observed. This is the meaning of time dilation. When the two observers meet each other, the effects of time dilation are gone. Do not confuse this with the twin paradox. When the two twins meet, they do have different ages, but it is not because of SR and its time dilation. The effect is a result of GR: the change occurs when the traveling twin decelerates, changes direction and accelerates back towards the earth. The twin paradox imho is the worst example in teaching SR. Time dilation (SR) is an effect that occurs when an event is observed in an inertial reference frame and compared with another obervation in another inertial frame. The observer in the fastest reference frame relative to the event will have seen the longest time. When all observers meet, the effect is gone.