Special Relativity

The probably is time is not fixed, it is entwined with space, and since space isn't "flat" neither is time.

The quicker you move space the slower you move through time, the slower you move through space, the quicker you go through time. The best analogy for this is to imagine your travelling on something at which the speed is fixed. Let the north-south direction represent passage through time and east-west passage through space. If you travel at you speed due north this means you use all the speed to travel through time, representing something which is not moving through space. If you travel due east you show the behaviour of a photon as all your speed is being used to travel through space, and none through time. However if you travel NE then you use some of teh speed to travel through space and some to travel through time, hence why time is slower if you travel through space. The quicker you travel the more towards the east/west direction, so less you travel through time hence why time is measured as less relative to something which is at rest.

It's not a perfect analogy, but hopefully gives the gist of what I'm trying to explain.

The Gregorian said:

Depends on your idea of a constant. You believe light is a constant, and it's speed is a magical number all things are dependant upon.

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The speed of light has been measured to be identical in all reference frames. There are only two consequences that can result from this measurement:

1. Special relativity.
2. The laws of physics are different in different reference frames (your 'optical illusion' claim), which produces a systematic error in our measurements.

By this logic, the train experiment is perfectly logical.. it's an optical illusion. The flashes happened simultaneously regardless of how others observe it.

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Why have you chosen this particular perspective to be the correct one?

This is the crux of the matter.

The Gregorian said:

Interesting example. If the moving person WAS equidistant when the lightning struck the poles, but moves, he would THEN see the light flash at the different times. Experiencing an optical illusion and therefore time dilation... but if, when the poles were struck the person was not equidistant from the poles, but as the light approached, he also intersected the images of the two lightning strikes intersecting... Still moving at the same speed, he sees light exactly as simultaneous as the person who was stationary the whole time.

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Nope, he would have been equidistant between the posts in order to see the light hit at the same time. He has to be, in fact: according to the observer on the ground, after all, he was equidistant between the two posts when the lightning hit the mirror at the same time. The person on the train can't observe himself being at an entirely different location, so he would have been equidistant between the posts.

But the problem is that he's moving towards one light source and away from the other. Because of this, when the light from the backward light source was emitted, it was still trying to catch up to him, while the light from the forward source was speeding towards his train. This means that, according to the man on the train, in order for him to see both poles light up at the exact same time when he is equidistant between them, the backward pole had to be struck first.

Remember: the same laws have to apply in all frames of reference. If the observer on the ground sees the two light beams hitting the mirror of the guy on the train at the same time, then the guy on the train must see the same thing. And the guy on the ground sees the two light beams hitting the mirror of the guy on the train at the same time only when the light hits when the guy on the train is directly between the posts.

Depending on the scale, everything spins unless it's forced not to. the galaxy spins, planets spin, balls flying through the air spins, atoms spin, electrons rotating atoms spin. Are you quite sure that muons don't spin? And what happens when a spinning object travels in a "straight" line? There's an advancing and retreating side... depending on the ratio between speed of rotation vs. linear speed, all sorts of interesting things happen.

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Umm, no. Not all things are "spinning." Spinning in the macro sense like the helicopter is an acceleration. Acceleration is not relative.

Also, electrons don't "spin" around their atoms. The idea of planet like orbits around the atom went out about 70 years ago and is demonstrable false. Furthermore, when us particle physicists talk about the "spin" of an electron or other fundamental particle, we are not talking about how it is turning around in circle (similar when we talk about the "color" of quarks we aren't talking about their actual color which would be impossible given that they are point particles).

Furthermore, non-accelerating linear motion has no affect on acceleration - i.e. the "advancing and retreating sides" are meaningless. Non-accelerating motion is simple relative to something else - it is not absolute. What you are describing would require the laws of physics to be different in different reference frames. Which is fundamentally stupid.

Even if it didn't spin on some level, though... fact is... muons "live longer" when moving. If they "think" time is going faster or slower... so what? We can clock them living longer when they're taking a certain action than they would not taking that action...

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A muon traveling at constant velocity is not "taking" any "action" - it just is. Velocity is ALWAYS RELATIVE TO SOMETHING ELSE. To the muon it is not moving - the Earth is moving towards it - there is no difference between these statements.

So your problem is with acceleration?

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Actually I have no problem with acceleration - see I understand General Relativity which explains how acceleration affects spacetime. It is unfortunately quite a bit harder and requires quite a bit more advanced math, but its is pretty clear that explaining GR to someone who doesn't understand SR would be a waste of time.

You realize the earth spins, right? As we rotate each day we are constantly accelerating, reach a peak speed, then constantly decelerate and reach a bottom speed based off our speed of rotation around the earth vs. speed around the son.

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Yes - I am aware that we are currently in an accelerating reference frame. Our angular motion however is irrelevant compared to our position in the gravity well of Earth. The reason satellites need to take into account gamma in their calculations is because they are in a much less steep part of the gravity well.

We're CONSTANTLY accelerating/decelerating relative to one thing or another.

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NO - acceleration is not relative. We are accelerating, but not all reference frames are accelerating (at least not by any appreciable amount - very deep space far from any massive bodies would still show some gravitational curving of spacetime, but it would be infinitesimal). If you didn't know, acceleration is the rate of change of velocity over time, where velocity is a vector. Forces cause accelerations while linear motion at constant speed is caused by the absence of forces acting upon the body. Very different animals. One is relative (velocity) and one is based on applied force (acceleration).

There's where we disagree... Prove THIS part outside of a thought experiment or statement relying on an appeal to authority and I'll convert.

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I don't really understand why you disagree with the second part - that is classical Newtonian physics which you seem to be stuck in. Michelson & Morely showed conclusively (any new experiments more than confirm) that light emitted will always travel at c relative to all observers - it does not ever propagate at speed greater than c - even if the emitter is moving at v relative to the observer, the light travels at c not c+v. This is also much easier to understand if you think of light as a wave propagating through spacetime. Like all waves its speed of propagation is dependent upon the medium it is moving through not the velocity of its source.

The speed of light is actually derivable from the fine structure constant, the electrostatic constant, vacuum permittivity, and the Plank constant. The speed of the light is not something inherent in photons or how they are emitted or anything like that - it is based on the structure of spacetime. This is demonstrably true because it is quite easy to change the speed of light - just change the medium it is passing through (c refers to the speed of light in a vaccuum, light travels considerably slower through an atmosphere, through water, through just about anything) just like any wave (try it with sound waves sometime - their rate of propagation is dependent upon the medium, not how they are created).

Again, however, I must ask myself, why am I bothering?

Depending on the scale, everything spins unless it's forced not to.

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By the way, this is wrong in both classical and Einsteinian physics. "Spinning" is accelerating. Things only accelerate when a force acts upon them. Things stop accelerating the moment that force is removed. You are accelerating constantly because gravity is working on you. In deep space, things far from a nearby gravity well (not appreciably at least) are not accelerating unless some force acts upon them. You don't need a force to stop an acceleration, you simply need to remove the force that is causing the acceleration.

If I'm bored all the time and time seems to be going quite slow... and I constantly travel the earth at 99% the speed of light for 10 years... regardless of what my perception is, regardless of what I think... it's still been 10 years. However long or short that seemed to me... the earth rotated the sun 10 times and therefore it's been 10 years. My relative motion or acceleration doesn't change time.

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No, your relative motion doesn't change Earth's time, but it does change yours and it is a lot more fundamental than perception (unless you believe clocks have an ability to "perceive"). All the clocks that traveled with you, including your body's own aging, will say a number less than (exactly 10 years * 1/SQRT(1-(0.99c)^2/c^2)). If you think it is just a trick of perception, fine, but I want to know how the atomic clocks, biological clocks, mechanical clocks, chemical clocks, etc are all tricked in exactly the same way.

Originally Posted by Frumious Bandersnatch
Originally Posted by The Gregorian I said it does not make sense because it does not make sense. The only way you can see the same wavelength at a different frequency is for the speed of the wave to change

Which is exactly what I said. Wavelength/amplitude/pitch... these are all traits of a wave... these aren't relative measurements, these are parts of the wave. Speed is relative for a wave just like it's relative for all things... We observe a change in frequency when we change our speed relative to light... IMO because we're changing our... speed... relative to the light.

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What you said is wrong and you are wrong now. The speed of light in a vacuum is always exactly C to any observer regards of their relavtive motion. The speed does not change, the frequency and the waveliength change.

It's suggested here, that if we change our speed relative to the light, our speed doesn't really change, but we cause the light's wavelength to change... even though technically our speed didn't?

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Our speed relative other observers is different but the speed of light in a vacuum does not change for any observer.

Excuse me... but if we can change our speed relative to something and detect a difference in that thing...

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Changing our speed relative to something is accelaration. That is GR which you are clearly not ready to discuss. Any Joe has taken that up.

it's more likely because we changed our relative speed than altering the fabric of time itself and shrinking/lengthening space.

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What is more likely does not matter. Reality is indifferent to your inability to comprehend special relativity.

... of course, this reminds me. SR suggests time dilation only works one way... moving slows down time, but there's no way to speed it up... Moving fast shrinks space, shortening wavelength, increasing frequency... i.e. a blueshift... But if there's no "Anti-time dilation" How do we see a red shift?

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We see a red shift when our relative motion is away from the source of the light and blue shift when we move toward the source of the light.

How is there a shift BEYOND the rate of time of a body not moving relative to us?

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Huh?

As far as your interpretation of the doppler effect... show me evidence of -wavelength- shrinking due to the doppler effect.

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I have measured this effect myself. It is the basis of the function of laser doppler blood flow meters. The wavelength of the monchromatic laser beam reflected from red blood cells is broadened by doppler shifting since some of the red cells are moving toward the detector and some away. It is also the principle behind the measurement of Brownian motion by dynamic light scattering. I have used both types of instruments in my work.

(and by evidence... )I mean -evidence- ... pictures, actual observed occurrences, not thought experiments, and baseless statements in a textbook dogmatically claiming that this happens because that's what accepted science says... because it says so

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Special relativity has been tested countless times in the 103 years since Einstein published his paper "On the electrodynamics of moving bodies" and passed every test AFAIK. You really don't have any idea what you are talking about do you?

Frumious Bandersnatch said:

Originally Posted by The Gregorian I said it does not make sense because it does not make sense. The only way you can see the same wavelength at a different frequency is for the speed of the wave to change


What you said is wrong and you are wrong now. The speed of light in a vacuum is always exactly C to any observer regards of their relavtive motion. The speed does not change, the frequency and the waveliength change.

Our speed relative other observers is different but the speed of light in a vacuum does not change for any observer.

Changing our speed relative to something is accelaration. That is GR which you are clearly not ready to discuss. Any Joe has taken that up.

We see a red shift when our relative motion is away from the source of the light and blue shift when we move toward the source of the light.

I have measured this effect myself. It is the basis of the function of laser doppler blood flow meters. The wavelength of the monchromatic laser beam reflected from red blood cells is broadened by doppler shifting since some of the red cells are moving toward the detector and some away. It is also the principle behind the measurement of Brownian motion by dynamic light scattering. I have used both types of instruments in my work.
Special relativity has been tested countless times in the 103 years since Einstein published his paper "On the electrodynamics of moving bodies" and passed every test AFAIK. You really don't have any idea what you are talking about do you?

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Annother point: If you ever got a speeding ticket from either a radar gun or laser device you have been directly affected by a common use of the doppler effect. If through a ball 30 mph at an object moving toward me at 60 mph it comes back at 90 mph (assuming perfect elasticity and a square hit). A beam of electomagnetic radiation comes back with a velocity of c (in air) but both its wavelength is a little bit shorter because of the doppler shift.

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The Gregorian said:

It still doesn't explain the doppler effect, though. DR deals with speed/acceleration... not direction. If you go fast, time slows, space shrinks... shrinking space COULD explain a shorter wavelength, and assuming a constant speed, you WOULD see a blueshift... But there is no function of SR to explain a lengthening of space to account for the red-shift we observe when the source of the light is going away from us...

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Oh, well, that's just because the reason why we observe a redshift/blueshift isn't due to the shrinking of space along the direction of motion. It's just due to the plain ol' Doppler effect, just like you get with sound waves. There are some additional details due to the properties of special relativity, but they aren't important to understand the basic concept of the phenomenon.

The Gregorian said:

And the doppler effect with sound waves is observing a wave with a fixed wavelength, noting the frequency, and finding your speed relative to the wave based on the observed frequency and known wavelength.

Because we see a doppler effect with light, and can figure out the -speed- of an object based on the known wavelength and observed frequency, we find that we're measuring the speed relative to the wave. Agreed?

And if we're finding the speed of the source based off the speed of the wave relative to us... we observe redshifts/blue shifts because light is traveling C+X or C-X ... i.e. not always C.

Either way you cut it... if we can tell how fast the emitter is moving relative to us based off the light it emits, it has to be because light is moving at a constant speed relative to it's source, rather than it's observer...

breaking SR's idea of light always being constant relative to all observers.

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Let's just imagine that what you're saying is possible (it's not, by the way: the properties of how a wave propagates are completely independent of how that wave started. They are, instead, dependent upon the medium through which the wave propagates). If it were possible, then we could calculate the following relationship between speed and redshift:

First, a definition. By convention redshift is parameterized by the variable z as follows:

(observed wavelength) = (1 + z) * (wavelength at source)

Here a blueshift would be represented by values of z from -1 to 0, and a redshift would be represented by values of z from 0 to infinity.

Now, according to you, the wavelength doesn't change. This is false, but let's go with it, and redefine redshift in terms of frequency instead:

(observed frequency) = (frequency at source) / (1+z)

If we then observe an object moving away from us at a speed v, then, according to you, we should see the same wavelength but a speed c - v, giving us a redshift in frequency. The frequency we observe, then, is:

f_obs = (c - v) / wavelength

...while the wavelength is the wavelength at the source:

wavelength = c / f_source

A little substitution and we get:

f_obs = (c - v)/c * f_source

...which results in:
(1 + z) = c / (c - v)

z = v / (c - v)

Note that "v" is the velocity away from the observer, so that there should be no redshift if the source is moving perpendicular to the observer. Let's compare this to the prediction from GR (instead of computing it, I'll just present the answer from the Wikipedia entry).

When the source and the observer are moving directly away from one another, we get:
(1 + z) = sqrt((1 - v/c) / (1 + v/c))

These formulae are clearly different. We should, therefore, be able to perform observations and determine which is correct. Guess which one turns out to be accurate?

Also worth noting that when the speed of the object is much less than the speed of light, the SR result reduces to the boring old Newtonian result.

Which is why we don't notice these effects without extremely sensitive measurements, or until we encounter speeds a significant fraction of the speed of light.

Dragar said:

Also worth noting that when the speed of the object is much less than the speed of light, the SR result reduces to the boring old Newtonian result.

Which is why we don't notice these effects without extremely sensitive measurements, or until we encounter speeds a significant fraction of the speed of light.

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Yeah, and in this case, the relativistic effects actually come in relatively quickly. The error in 1+z is already 1% when the speed difference is 0.005c. It climbs to 10% at v = 0.05c, and the redshift is a factor of 2.5 off by the time you get up to v = 0.5c. This all is very important when you're dealing with how photons interact with relativistic ions, such as is routine today in particle accelerators.

The Gregorian said:

Actually, that's the best analogy I've seen so far. That ALMOST even makes it seem logical. Of course, it suggests you can move through space without moving through time, but if time's not moving, you can't move because one object can't go from one place to another in the same period of time. It's suggested now that one object CAN in some situations be in two different places at the same time.... but even in that rare situation, the object hasn't moved FROM one place TO another because the act of movement designates a past and future meaning it can't be at the same "time"

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Why is it necessary? Just because what happens in day to day experience doesn't seem to fit with what happens at these vast speeds doesn't mean it's wrong. Wave-particle duality doesn't seem to make sense but all the experiments show that holds true.

It still doesn't explain the doppler effect, though. SR deals with speed/acceleration... not direction. If you go fast, time slows, space shrinks... shrinking space COULD explain a shorter wavelength, and assuming a constant speed, you WOULD see a blueshift... But there is no function of SR to explain a lengthening of space to account for the red-shift we observe when the source of the light is going away from us...

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SR explains movement through space, redshift seen on earth is due to the expansion of space so the wavelength of light is physically stretched since spacetime itself is expanding.

Also, if the speed of light is fixed in the universe based on the observer rather than the source of the light... wrap your head around this:

A star is being observed from earth and we detect a blueshift... we know the star is traveling toward us. Without the earth changing direction, a something happens causing the star to change directions quickly... and while we didn't accelerate in any direction... we still detect a red shift.

Relative to us, the star accelerated... away from us... should that not have shrunk timespace causing a greater blueshift? Because it was a red-shift, did timespace expand?

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It doesn't shrink the space time between the earth and the planet. The blue shift you see is itself red shifted so it looks less blue shifted than it would fi space didn't expand. Plus SR only relates to constant uniform motion, if you want to deal with acceleration you need to use GR.

The problem I'm trying to get you to come to is, SR deals with objects not moving relative to each other... or moving toward each other... If two objects are not moving relative to each other, there is no speed, therefore they experience time "normally"... they accelerate toward each other and there's a blue shift because space shrinks because of speed... but when they pass each other, they're still moving at the same speed, so space should still be shrunk.... yet they see a red-shift... meaning space has expanded... therefore, did time expand?

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Actually SR deals with anything in uniform, constant motion. As soon as acceleration is involved it's not applicable. It's like a special case of GR, hence the names. Just because you don't understand it doesn't make it wrong. How about going along and spending a few years working towards a physics university matriculation and then trying to find flaws in it?

/snip

Plus SR only relates to constant uniform motion, if you want to deal with acceleration you need to use GR.

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This isn't strictly true. You can use SR with accelerating frames, or with accelerating objects, but you have to add in extra 'rules', just like you must add in extra rules in Newtonian mechanics when you work in a non-inertial frame.

The difference is GR treats all frames equally.

The Gregorian said:

Either way you cut it... if we can tell how fast the emitter is moving relative to us based off the light it emits, it has to be because light is moving at a constant speed relative to it's source, rather than it's observer...

breaking SR's idea of light always being constant relative to all observers.

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So, how does the Doppler effect work for sound?

Edit: please also refer to my earlier response about experimental data which conclusively shows that light does not travel at a speed relative to the emitter. This is very well trodden ground you're walking over now. Google "emission theory".

I don't like this wave-particle duality thing. I'm no physicist, but it seems that saying something is "both a wave and a particle" is a poor explanation; It seems to me that instead of saying "x is a wave and a particle", it's better to say "x is something that exhibits both wave-like and corpuscular behavior". I think Richard Feynman once said something about the issue like "Light is a wave on mondays, tuesdays, and wednsdays, and a particle on thursdays, fridays and saturdays", and then proceded to declare that light was strictly a particle (whose behaviour was governed by quantum electrodynamics)