Special Relativity

[DoubtingThomas29]

Here is what I know about General Relativity. Time is relative, also, measuring, how big things are is relative. If a space ship should fly away from the Earth, you could watch it shrink in szie as it approached the speed of light, 186,000 miles per second. Also, clocks on top of sky scrapers, can be measured, with atomic clocks, to run faster than the clocks, a thousand feet below, because the force of gravity is less at the top of the sky scraper, where if you were on a really sensitive scale, measured out to a trillionth of a pound or so, you would notice you weigh less.

About the train, for any train really, could be going as fast as only sixty miles per hour, if you stand in the center of the train with a friend, and you are both carrying atomic clocks, as one person walks towards, the front of the train, and the other person walks to the back of the train, there will be a time dialation, and you will notice the clocks are not ndicating the exact same time, because of the time dialation, I forget which one will be faster, I think it is the guy who walk to the back of the train, because, he was traveling slower relative to the Earth, so time would be travleing faster, I believe. I believe the faster you go the slower time runs. Like if you were to travel at near the speed of light for a hundred Earth years, and come back to the Earth you would think only six years passed, becasue of this time dialation you experienced.

Time dialations are responsible for cosmic rays making it to the Earth, and surviving for eight Earth minutes in space, when really the rate at which the particles decay, is seconds, by a few seconds to the meson or the Barryon, traveling at the speed of light, is eight Earth minutes to us.

Here is what Daniel Dennett said about the theory of Relativity and the theory of Evolution, "for all the theories, and ideas, that have ever been discovered or invented, he would give the prize for the best idea to Charles Darwin for his idea of natural selection."

I would too, for all the math tha goes into the physics behing General Relativity, the Theory of Evolution blows it out of the water, for its importance to our understanding of nature, and for giving us te proper respect for what natural processes can do. I will take two semesters of biology, before I die, that is my promise.

 

[The Gregorian]

We have been over this ground before. The example is not flawed. It is not an "optical illusion". Time passes differently for moving observers. GPS systems would not work without taking Special Relativity into account as I am sure you know by now.

So his time is moving slower relative to the rearward flash, yet simultaneously he experiences time faster relative to the forward flash?

Yes... GPS's use SR calculations to work... but the numbers can be right without the explanation for the numbers being right.

1+1=2... Correct? Therefore, can I correctly assume 1 apple+1 apple=2 charles mansons?

No... the math is right, the explanation is wrong.

Yes, the flash is observed at different times, because the light traveled different distances... time didn't change relative to each flash.

 

[Chalnoth]

So his time is moving slower relative to the rearward flash, yet simultaneously he experiences time faster relative to the forward flash?

Yes... GPS's use SR calculations to work... but the numbers can be right without the explanation for the numbers being right.

1+1=2... Correct? Therefore, can I correctly assume 1 apple+1 apple=2 charles mansons?

No... the math is right, the explanation is wrong.

Yes, the flash is observed at different times, because the light traveled different distances... time didn't change relative to each flash.

Yes, the explanation is correct. See my post #9. Time must necessarily be different for different observers for the speed of light to be constant for all observers (which it is).

 

[The Gregorian]

Time dilation has been tested many times including placing super accurate atomic clocks on planes (jumbos) and flying them around the world for a while.

These clocks are then compared to atomic clocks that remained stationary on the earth’s surface, and they had indeed increased in speed by a measurable amount.

So no matter what you thing of the illustration, it is correct, just a shame you cannot grasp it.

Yep... cesium is known to ALWAYS decay at a constant rate... Yet, in moving jets with all their electromagnetic fields, vibrations, radio interferance, etc. The cesium decay rate was altered... But cesium MUST be a constant, therefore time MUST have changed...

Isn't it more simple to suggest that SOME less-than-laboratory-setting could have altered the rate of decay of cesium instead of suggesting that time itself was altered?


Every experiment that's been done has made some completely counter-logical assumptions to favor universal constants over the possibility of flawed means of measurement.

 

[Joe_Sixpack]

Yep... cesium is known to ALWAYS decay at a constant rate... Yet, in moving jets with all their electromagnetic fields, vibrations, radio interferance, etc. The cesium decay rate was altered... But cesium MUST be a constant, therefore time MUST have changed...

Isn't it more simple to suggest that SOME less-than-laboratory-setting could have altered the rate of decay of cesium instead of suggesting that time itself was altered?


Every experiment that's been done has made some completely counter-logical assumptions to favor universal constants over the possibility of flawed means of measurement.

Actually, this doesn't make any sense. All the changes to time of the various clocks are perfectly predictable using the equations of relativity. If you think something is interfering with the clocks (which means you have to also throw out Quantum Mechanics as well), then you would have to explain why they always are interfered with in exactly the same way and that the difference in time can be accurately predicted using only their altitude and velocity. Think you are going to have a hard time with that.

Might I suggest you go back and work through the derivation of Special Relativity from the beginning (Maxwell's equations). It is not really all that complicated, unlike General Relativity, and youshould be able to walk through the logic yourself. The implications of light traveling at the same speed for every observe necessitate that time is different for different observers.

Us physicists might be a weird bunch at times, but we are not a bunch of dummies. Don't you think if your issues with SR and GR had any weight at all, one of us working on these things every day would have thought of them? Just think about that for a moment.

 

[The Gregorian]

Let's take a different situation, then: cosmic ray muons. Cosmic ray muons are created high in the upper atmosphere as cosmic rays collide with nuclei, causing a massive shower of subatomic particles. These particles decay pretty much instantaneously into muons, which have a lifetime of 2.2 microseconds. Now, here's the apparent problem: the muons start their life at around 15km. These cosmic ray muons are moving at very close to the speed of light, which is around 300,000km/s, and thus it takes them approximately 50 microseconds to reach the ground.

Could it not also be theoretically possible that atoms become more stable while in motion? Try setting a bicycle wheel on it's edge... not easy to make it stay standing up... but while moving it stays vertical for quite some time. Could a similar principle not apply to particles?

Although, chalnoth, I do appreciate your attempt to make an actual illustration with numbers... but your illustration makes preconceived assumptions in favor of universal constants over far simpler explanations.

When moving, it decays slower... Maybe that's a function of decaying atoms.

Speaking of time dilation... what about photons moving AT "C?" At the speed of light, time stops... therefore motion is impossible... therefore it is not moving for time dilation to kick in?

SR presents all sorts of problems involving beams of light themselves.

Two photons in the same beam of light are traveling parallel in the same direction... Photon A sees photon B passing it at the speed of light. Photon B sees photon A passing IT at the speed of light... yet photon C (along with ALL other points of reference) sees A and B keeping side by side.

If all three photons leave their source at the same time, and arrive at their destination at the same time, are they not traveling at the same speed? Therefore proving any perceptions of one passing the other while the other perceives it's being passed to be simple optical illusions?

Of course the problems compound GREATLY if you imagine those three points of reference as non-photons because if they're non-photons, all frames of reference traveling the same speed/direction would see each other as not moving relative to themselves. Yet 1% faster and a different partical and all the laws of physics are thrown out the window.

 

[sinan90]

Could it not also be theoretically possible that atoms become more stable while in motion? Try setting a bicycle wheel on it's edge... not easy to make it stay standing up... but while moving it stays vertical for quite some time. Could a similar principle not apply to particles?

What keeps a bicycle wheel balanced and what governs the stability of tiny particles is not teh same, and in reality analogies don't really help in trying to understand what goes on at a quantum level, they just end up being misleading.

Speaking of time dilation... what about photons moving AT "C?" At the speed of light, time stops... therefore motion is impossible... therefore it is not moving for time dilation to kick in?

Motion through time is not possible, not motion through space. IE a photon travelling at C is the same "age" as it was when it was created.

Two photons in the same beam of light are traveling parallel in the same direction... Photon A sees photon B passing it at the speed of light. Photon B sees photon A passing IT at the speed of light... yet photon C (along with ALL other points of reference) sees A and B keeping side by side.

If all three photons leave their source at the same time, and arrive at their destination at the same time, are they not traveling at the same speed? Therefore proving any perceptions of one passing the other while the other perceives it's being passed to be simple optical illusions?

You misunderstand SR, SR just says all reference frames are equally valid, all of the views of what happened are correct, there is no one "right" recollection of what happened.

 

[The Gregorian]

I'll be honest, I don't understand the train thought experiment either. I've heard some pretty great explanations for how special relativity works, but the train one just doesn't make sense. I guess the reason is that I don't understand why this would be surprising for someone who held a more traditional understanding of time. Clearly I'm missing something, and I'd appreciate it if someone could fill me in.

honesty?! WOA... Usually if I disagree with the text books people just belittle me and tell me to go read a text book... ignoring the fact that I HAVE read them... and don't agree.

Here's the thing... Both stationary and moving observers are directly equadistant from the two poles... The poles are both struck at the same time. While the light is traveling toward the middle to make both observers aware of what just happened, one observer stays still and the moving observer moves toward one pole and away from the other. By the time the light reaches the middle of the two poles, the stationary observer hasn't moved... therefore he sees both images at the same time. However the moving observer has moved. While the light moves toward him, he moves toward one pole, therefore shortening the distance the light from one pole had to travel and lengthening the distance the light from the other pole had to travel.

Because light had to travel a farther distance... it took longer, therefore he detects the image of the lightning hitting the rear pole AFTER the light hitting the first pole (because the light had to travel further, therefore taking longer.

The person on the train has no concept of the idea that "I don't see things immediately... therefore things far away take longer for me to detect" Therefore he assumes the two things happened at different times.

Either the guy's an idiot falling for an optical illusion or TIME ITSELF HAS CHANGED!

eherm.


Another way to look at this experiment... find where the moving observer would have been, on average, when he detected the two images. I.e. half way between where he was when he saw the first image and where he was when he saw the second. And have him not be moving. Just "not equidistant" from the two poles.

Have lightning hit both poles again... and guess what? Although not moving, he'll STILL see one pole hit before the other... because AGAIN... light from one pole traveled further than light from the second.

Does this mean that, whenever you're not equidistant from two poles, you're moving through time at a different rate? Or is it that light simply DOES take a little bit of time to travel?

He'll see the same "non-simultaneity" regardless of where he was BEFORE the light got there... the only reason he detected non-simultaneity is because when he detected the images, those images had traveled different distances.


That make any sense?

 

[Joe_Sixpack]

Could it not also be theoretically possible that atoms become more stable while in motion? Try setting a bicycle wheel on it's edge... not easy to make it stay standing up... but while moving it stays vertical for quite some time. Could a similar principle not apply to particles?

One, muons are not atoms, and two, you are compounding your problems by throwing out all sorts of other highly supported physics like the Standard Model.

You really need to go back to original formulation of Relativity. SR only uses two postulates to get to its core conclusions: 1) the laws of physics are the same in all inertial reference frames, and 2) speed of light is constant in free space (shown conclusively about 25 years earlier than Einstein my Michelson - light never travels at c+v or c-v in same medium, it always travels at c). Using just these postulates you can show how time must different in different reference frames (try visualizing the simplest clock: a photon emitter and a sensor plate).

 

[MasterOfKrikkit]

Us physicists might be a weird bunch at times, but we are not a bunch of dummies. Don't you think if your issues with SR and GR had any weight at all, one of us working on these things every day would have thought of them? Just think about that for a moment.

Obviously you're all part of the EAC.

I wouldn't mind if posters like this were actually trying to understand. After all, anyone here want to claim that they thought SR was straightforward the first time they encountered it? I certainly didn't. But where normal people learn -- put their preconceptions aside as much as possible, open their minds to new ideas and see where they lead -- a certain demographic revels in willful ignorance. And then has the unmitigated temerity to call into question the work of thousands of the keenest and most educated minds in the world; to believe that they, of all people, ahead of legions of scholars, have found the fatal flaw in a theory that has been intensely scrutinized for nearly a century (or, in some cases, well over). It is the level of hubris that can be achieved only by believing that, given the vast reaches of space, populated by uncountable suns too massive to comprehend, the omipotent Creator of the entire cosmos cares about the state of your Toyota's spark plugs. These people do not wish to learn; they wish only to sow desperate seeds of doubt in others, that they may more effectively delude themselves as to the rightness of their clinging to a torn and tattered scrap of flannel from their intellectual infancy, that by their devotion to this emblem of security they will ingratiate themselves with a devious and ingenuous deity undeserving of the name Almighty God.

I do not feel obliged to believe that the same God who has endowed us with senses, reason and intellect has intended us to forego their use (Galileo Galilei)

/rant

 

[The Gregorian]

then you would have to explain why they always are interfered with in exactly the same way and that the difference in time can be accurately predicted using only their altitude and velocity. Think you are going to have a hard time with that.

It's possible that a moving particle simply decays slower when in motion, IAW the formula presented by SR... a slower decay rate instead of a constant rate through altered flows of time.

Again... the numbers are observable, but the explanation of those numbers aren't proven by the numbers themselves.

i.e. 1 apple+ 1 apple=2 charles mansons.

Yes, 1+1=2... no, the explanation is not right.

 

[Chalnoth]

Could it not also be theoretically possible that atoms become more stable while in motion? Try setting a bicycle wheel on it's edge... not easy to make it stay standing up... but while moving it stays vertical for quite some time. Could a similar principle not apply to particles?

Step back for a second. Cosmic rays were first discovered in 1912. This particular property of cosmic rays is exactly predicted by special relativity, which was proposed in 1905. There are no free parameters here that can be fudged by experiment. Special relativity gives an exact prediction on the relative abundances of muons at high and low altitudes that is dependent upon the energies and the measured rest-frame decay time of said muons.

And you think that making up an entirely new physical process is a simpler explanation? Come on! How else could this prediction have come true if special relativity weren't rather accurate?

And all this is even before we consider the problems with even proposing that the decay rate is based upon velocity: there just isn't any way for such a physical process to exist, because the muon itself has no way of "knowing" what velocity it's moving at. Your bicycle example falls flat, by the way, because the stability comes about due to the rotation of the wheels, which, in this particular case happens to be coupled to its motion relative to the ground. There is no such coupling of the muon with any physical process: muons tend to miss almost everything as they streak through the atmosphere. It's also impossible for them to have angular momentum like a bicycle wheel can.

Although, chalnoth, I do appreciate your attempt to make an actual illustration with numbers... but your illustration makes preconceived assumptions in favor of universal constants over far simpler explanations.

When moving, it decays slower... Maybe that's a function of decaying atoms.

A muon isn't an atom. It's a fundamental particle, basically like a heavy electron. The muon decays into an electron and a pair of neutrinos.

Speaking of time dilation... what about photons moving AT "C?" At the speed of light, time stops... therefore motion is impossible... therefore it is not moving for time dilation to kick in?

SR presents all sorts of problems involving beams of light themselves.

You're confusing yourself here. A photon is moving at the speed of light. Therefore, if we could "observe" the photon's internal clock, we should see it not change with time. This doesn't say the photon isn't moving. It just says that it isn't changing as it crosses space (which is true, since the phase velocity and the group velocity of an electromagnetic wave in vacuum are identical).

Two photons in the same beam of light are traveling parallel in the same direction... Photon A sees photon B passing it at the speed of light. Photon B sees photon A passing IT at the speed of light... yet photon C (along with ALL other points of reference) sees A and B keeping side by side.

Again, you're confusing yourself. Photons can't "see" anything at all, because they're moving at the speed of light. Everything that happens from the time they're emitted to the time they're observed happens instantaneously as far as the photon is concerned.

Of course the problems compound GREATLY if you imagine those three points of reference as non-photons because if they're non-photons, all frames of reference traveling the same speed/direction would see each other as not moving relative to themselves. Yet 1% faster and a different partical and all the laws of physics are thrown out the window.

No, the solution becomes quite clear when you look at objects with mass which travel slower than the speed of light. For example, if I'm sitting on a rocket ship that is moving at 0.75c relative to you, and throw a ball forward at 0.75c in my reference frame, you would observe me throwing the ball at 0.96c. All is right with the world. It only becomes muddled when you divide by zero, by, for example, stating that something for which time has stopped can "observe" something else.

 

[RecentConvert]

Damn! I wish I had been checking this forum more often 'cause this is a subject I understand quite well, can elucide effectively (in my humble opinion) and people are screwing up their analysis all over the place...

It's possible that a moving particle simply decays slower when in motion, IAW the formula presented by SR... a slower decay rate instead of a constant rate through altered flows of time.

Slower decay rates are insufficient to explain the phenomena.

First, all actions are slowed down when their frame of reference is accelerated, not just atomic decay. That's why we say time, itself, has slowed. How else can you explain it?

Secondly, observers in the same reference frame don't see the slowdown. This can't be the case if the speed were simply affecting the progression of observed events (in your example, decday rates).

No, time slowing down really is the simplest and most sensible explanation...

Again... the numbers are observable, but the explanation of those numbers aren't proven by the numbers themselves.

i.e. 1 apple+ 1 apple=2 charles mansons.

Yes, 1+1=2... no, the explanation is not right.

This is a pointless analogy. The properties of numbers is not determined experimentally. Despite popular belief, mathematics is not a branch of science!

 

[RecentConvert]

Yes, this will get into the creation/evolution debate, so this is an on topic thread... but we're gonna start on a tangent, then work back to the topic.

I don't think so...

I was wandering around youtube and found this:
http://www.youtube.com/watch?v=AZ6N85lNgHY

Pay special attention to the train example.

If lightning strikes two poles at the same time, someone standing motionless between the poles will observe the poles being hit at the same time... therefore he's moving at "normal time"... or through it at a normal rate.

the moving observer will see lightning hit one pole sooner than the other because while the light is traveling toward him, he's also moving... the distance becomes longer for the pole he's moving away from, therefore it takes longer for the light to reach his eye, therefore HE observes the two poles as not being struck simultaneously.

This is used to suggest that his motion caused time itself to slow... because he observes it happening at different times, therefore it DID happen at different times for him.

While, I understand the illustration, I don't draw the same conclusion. Yes, he'll observe the lightning hit the poles at different times due to an optical illusion. Optical illusions don't bend the fabric of time to remain real... he simply was moving, therefore saw one flash too soon and one too late and was mistaken. That doesn't prove time changed...

What about this illustration... something readily observable: Stand a good hundred yards away from someone dribbling a basketball. Watch as you see the ball contact the earth... but hear it later.

Yet, your motion hasn't changed. Should we assume that we are experiencing time flowing at TWO rates simultaneously because we see something happen before we hear it happen? We saw the ball hit, then LATER heard the ball hit... did time stand still? Did we go back in time? Or is it more likely to see different relative speeds tricking our perceptions than to assume the fabric of time has been altered based upon what we're looking at.

Your analysis is flawed and, surprisingly (to me!), it's not exactly your fault. There's a surprising fact about light that the video only mentioned in passing when it is a pivotal detail and little will make sense without it...

That detail is that, while the speed of different objects change depending on your frame of reference, the speed of light does not!

This is truly a strange phenomena. If you are standing by a highway and see two cars pass you, the first at 90 km/h and the second at 100 km/h, then the first car will observe the second car move at 10 km/h. This is both simple and intuitive. However, if a beam of light was flashed down the highway, all three observers would observe the beam shine passed them at exactly the same speed, c. Even if a car were to tear down the highway at 90% the speed of light, it will still observe a beam of light passing it as c, and not 10% the speed of light, as one would expect...

If you can understand this, then you're ready to understand why the train analogy is valid and not just an optical illusion!

 

[Stellar Vision]

I think I got it as well. Just take the man standing between the two poles, forget about the train. Lightning hit's both poles simultaneously; does he see the flashes simultaneously??? Zoom out. He's on planet Earth, which at the equator has a rotational velocity of about 1,040 mph. But wait, he's also MOVING around the Sun at an even greater speed - 64,800 mph. And of course he's also MOVING around the Milky Way Galaxy; let me just give you that number as well - 492,120 mph.

Max speed "standing on Earth" ~ 557,960 mph

Speed of light is ~ 671,079,600 mph

We're all traveling at a max of about 0.08% the speed of light on a daily basis.


Now, how is it possible that the man between the poles still observes the lightning flashes simultaneously? I'm guessing it has something to do with c being constant in all reference frames.

 

[The Gregorian]

However, the man on the train will measure a difference in the wavelengths of the light. The light from the pole in the direction of his velocity will be blueshifted and the light from the pole that he is moving away from will be redshifted. Using our knowledge of physics, the luminosity of the lightning, and it's spectra the person on the train can independently calculate his velocity with respect to the two poles.

*He'll measure a different frequency, not wave length.

Wave length is a function of any given wave regardless of observer. People moving relative to a wave will see the same wave length at a different frequency.

Unless you believe light knows to have one wavelength for a observer not moving relative to it's source, but simultaneously have different wavelengths "for" each observer traveling at each speed.

Or you can accept the simpler explanation of "We see different colors because we're moving relative to the waves. Our speed adds or subtracts from their speed, taking it's fixed wavelength and changing the frequency.

... or you can keep with your "one piece of light will have multiple wavelengths depending on the relative speed of the observer."

But keep in mind, if all things are moving at exactly "C" relative to light, then from each photon's perspective, ALL things must be moving the same speed.

Which means none of us ever really move, we only bend time around us to change positions.

 

[The Gregorian]

I think it might be helpful to go back to the Physics before relativity. At that time it was thought there was thought any wave had to have a medium to travel through. The invisible ether. If it should exist then it should be detectable. Tests to do this failed and in fact showed it did not exist.

With no ether the question is raised just which frame of reference is stationary?

Lack of evidence is not evidence for the contrary. Basic logical fallacy. Because your test failed doesn't mean your failed test PROVES what you were looking for doesn't exist. For example:

I believe in monkies... therefore I'll conduct a test... look in my living room... hrm.. no monkies... therefore monkies have NEVER existed anywhere in the universe. They're actually snakes in disguise!

... Yes.. there are 0 monkies in my living room... the number is right... but that doesn't mean I can draw whatever insane conclusions I like.

 

[Frumious Bandersnatch]

*He'll measure a different frequency, not wave length.

Wave length is a function of any given wave regardless of observer. People moving relative to a wave will see the same wave length at a different frequency.

Unless you believe light knows to have one wavelength for a observer not moving relative to it's source, but simultaneously have different wavelengths "for" each observer traveling at each speed.

Or you can accept the simpler explanation of "We see different colors because we're moving relative to the waves. Our speed adds or subtracts from their speed, taking it's fixed wavelength and changing the frequency.

... or you can keep with your "one piece of light will have multiple wavelengths depending on the relative speed of the observer."

But keep in mind, if all things are moving at exactly "C" relative to light, then from each photon's perspective, ALL things must be moving the same speed.

Which means none of us ever really move, we only bend time around us to change positions.

Wavelength is the inverse of frequency. This incoherent ramble shows that you have no idea of the physics you are claiming is wrong. As I said before reality is indifferent to your inability to comprehend special relativity.

 

[BrainHertz]

*He'll measure a different frequency, not wave length.

Wave length is a function of any given wave regardless of observer. People moving relative to a wave will see the same wave length at a different frequency.

How so? There's quite a few assumptions buried in here.

Unless you believe light knows to have one wavelength for a observer not moving relative to it's source, but simultaneously have different wavelengths "for" each observer traveling at each speed.

Knows? How do you mean knows? But yes, since length is dependent on the observer's frame of reference, there's no reason to think the wavelength should be the same.

Or you can accept the simpler explanation of "We see different colors because we're moving relative to the waves. Our speed adds or subtracts from their speed, taking it's fixed wavelength and changing the frequency.

...or we could make some observations and accept that as what happens.

... or you can keep with your "one piece of light will have multiple wavelengths depending on the relative speed of the observer."

If you want to overturn Einstein's math, you're probably going to have to show a little more working. Just a thought.

But keep in mind, if all things are moving at exactly "C" relative to light, then from each photon's perspective, ALL things must be moving the same speed.

From the point of view of a photon, there is no time. Everything happens simultaneously.

Which means none of us ever really move, we only bend time around us to change positions.

That depends on your definition of "move"...

 

[keith99]

Lack of evidence is not evidence for the contrary. Basic logical fallacy. Because your test failed doesn't mean your failed test PROVES what you were looking for doesn't exist. For example:

I believe in monkies... therefore I'll conduct a test... look in my living room... hrm.. no monkies... therefore monkies have NEVER existed anywhere in the universe. They're actually snakes in disguise!

... Yes.. there are 0 monkies in my living room... the number is right... but that doesn't mean I can draw whatever insane conclusions I like.

Your ignorence of science and scientific history is truely amazing. You try to pick apart word. The Michelson Morley (sp) Experiment proved there the ether does not exist.