Instantaneous Communications plus Time Dilation Equals ???

[Wyrm Ouroboros]

Re: Instantaneous Communications plus Time Dilation Equals ???

 

The light doesn't do any of these things; light moves at a speed, covering distance over time. The idea that time actually moves slower both on the train is ... hm. Wrong. From the point of view of the person on the train, time appears to move differently on the moving train, the station behind, and the station ahead -- but it does not actually do so. Person on the train almost outruns the light from the station behind; time appears to move slower. From the station ahead, time appears to move faster.

 

For the people with the instant communicator, they'd be able to talk -- real-time -- to the people they left. The universe, when it comes down to it, all poerates on the same time....

[Zeropoint]

Re: Instantaneous Communications plus Time Dilation Equals ???

 

For the people with the instant communicator, they'd be able to talk -- real-time -- to the people they left. The universe, when it comes down to it, all poerates on the same time....

 

An attractive idea, and certainly in accord with our low-speed lives here on Earth . . . but not how things actually work. The universe, when it comes down to it, does NOT all operate on the same time. This is not "just a theory", it is experimentally verified fact with real-life implications. Note that GPS satellites ALSO have to take into account relative simultaneaity; thus placing it into the realm of experimentally verified fact as well.

 

The light appearing to do something different, I can accept. The light actually, physically doing all three and more? No, that's just goofy.

 

Goofy or not, it's the truth. "At the same time" is not absolute, it's relative. Time is not absolute. There is no one universal true time flow.

 

If you understand but refuse to accept, then all I can do at this point is shrug my shoulders and point you to work done by people smarter and better informed than both of us.

[dmjalund]

Re: Instantaneous Communications plus Time Dilation Equals ???

 

things being at the same time is like things being of the same longitude. In this analogy, if you change where the north and south poles are, things stop being in the same longitude, even though they actually haven't moved. So if you are approaching 2 events - which at rest seem to be going on at the same time - at a speed comparable to the speed of light; the "poles have moved" and the "longitudes no longer match"

[Xavier Onassiss]

Re: Instantaneous Communications plus Time Dilation Equals ???

 

How is Doppler shift a demonstration of relativity? It's a demonstration that the wave (or wave-like phenomenon) appears compressed or stretched by the motion of the source and/or the "observer"' date=' not a demontration of Special or General Relativity. Not all things that are relative are part of Relativity.[/quote']

 

"Appears"???

[Kristopher]

Re: Instantaneous Communications plus Time Dilation Equals ???

 

"Appears"???

 

What phrasing should I have used that wouldn't have taken up three more lines and wouldn't have draw a different nitpicky response, that would have summed up that fact that the motion of both the source and the "observer" have to be taken into account for Doppler shift of light or sound, while not obscuring the main point that Doppler shift and Relativity aren't the same phenomenon?

[Kristopher]

Re: Instantaneous Communications plus Time Dilation Equals ???

 

Does the light hit the front of the train car an infinite number of times, or just once?

[Lawnmower Boy]

Re: Instantaneous Communications plus Time Dilation Equals ???

 

http://www.youtube.com/watch?v=NaW0eWgmw4M&feature=PlayList&p=085AF8720DA0DA72&playnext=1&playnext_from=PL&index=9

 

This may help.

[Zeropoint]

Re: Instantaneous Communications plus Time Dilation Equals ???

 

Does the light hit the front of the train car an infinite number of times, or just once?

 

Just once.

[Nyrath]

Re: Instantaneous Communications plus Time Dilation Equals ???

 

The light appearing to do something different' date=' I can accept. The light [i']actually, physically[/i] doing all three and more? No, that's just goofy.

Ummmm, not to put too fine a point on it, there are plenty of things in physics that appear to be just goofy to the layman, but that's just because they are outside of common experience. The technical term for this is Naïve physics. In that link, note that at the end of the examples there is a note about the hard death of absolute simultaneity, which is at the heart of your question.

 

See that chair? Looks solid, doesn't it? You can sit on it and everything. But on the subatomic level, the chair is 99.999% empty space. Isn't that just goofy?

Here is a sledge hammer. Here on Earth, it weighs sixteen pounds. And it takes sixteen pounds of force to swing it. On the Moon, it weighs only about 3 pounds. But it still takes sixteen pounds of force to swing it. Isn't that just goofy?

Here is a huge bolder and a tiny pebble. The bolder should drop faster than the pebble, since it is heavier. But that clown Galileo proved that both fall at the same rate. Isn't that just goofy?

The sun rises in the morning, moves overhead, then sinks at sunset. Obviously it moves around the flat earth. But no, the earth moves around the sun. Isn't that just goofy?

 

But I repeat: FIND A PHYSICS PROFESSOR AND HAVE THEM GO OVER IT WITH YOU. They are trained in education, chances are the good folks on this forum are not.

[Kristopher]

Re: Instantaneous Communications plus Time Dilation Equals ???

 

Ummmm' date=' not to put too fine a point on it, there are plenty of things in physics that appear to be just goofy to the layman, but that's just because they are outside of common experience. The technical term for this is Naïve physics. In that link, note that at the end of the examples there is a note about the hard death of absolute simultaneity, which is at the heart of your question.

 

See that chair? Looks solid, doesn't it? You can sit on it and everything. But on the subatomic level, the chair is 99.999% empty space. Isn't that just goofy?

 

Nope, not really that goofy, it's simply a matter of the electrical repulsion of trillions of atoms, IIRC.

 

Here is a sledge hammer. Here on Earth' date=' it weighs sixteen pounds. And it takes sixteen pounds of force to swing it. On the Moon, it weighs only about 3 pounds. But it still takes sixteen pounds of force to swing it. Isn't that just goofy?[/quote']

 

Nope, not really gooy, force and inertia are a matter of mass, not weight.

 

Here is a huge bolder and a tiny pebble. The bolder should drop faster than the pebble' date=' since it is heavier. But that clown Galileo proved that both fall at the same rate. Isn't that just goofy?[/quote']

 

Not really. (Way way back as a kid, my first thought upon learning that was that the force of gravity depends on the mass, but the higher the mass, the more force is required to accelerate the body at the same rate.)

 

The sun rises in the morning' date=' moves overhead, then sinks at sunset. Obviously it moves around the flat earth. But no, the earth moves around the sun. Isn't that just goofy?[/quote']

 

Not really.

[Kristopher]

Re: Instantaneous Communications plus Time Dilation Equals ???

 

Just once.

 

That's what I tihought.

[Kristopher]

Re: Instantaneous Communications plus Time Dilation Equals ???

 

http://www.youtube.com/watch?v=NaW0eWgmw4M&feature=PlayList&p=085AF8720DA0DA72&playnext=1&playnext_from=PL&index=9

 

This may help.

 

I've watched it before.

[Zeropoint]

Re: Instantaneous Communications plus Time Dilation Equals ???

 

From the Wikipedia article on Absolute Time and Space:

 

The theory of relativity does not allow the existence of absolute time because of nonexistence of absolute simultaneity. Absolute simultaneity refers to the experimental establishment of coincidence of two or more events in time at different locations in space in a manner agreed upon by all observers in the universe. The theory of relativity postulates a maximum rate of transmission of information as the speed of light, and one consequence is that simultaneity at separated locations always is relative to the observer.

 

Basically, your options are to agree that simultaneity is relative, or to claim that Relativity is a bunch of BS.

[Kristopher]

Re: Instantaneous Communications plus Time Dilation Equals ???

 

From the Wikipedia article on Absolute Time and Space:

 

Basically, your options are to agree that simultaneity is relative, or to claim that Relativity is a bunch of BS.

 

Who said anything about "absolute time? That's never been the issue here.

 

Go back to the actual crux of the matter in the train car example: what is the interaction of the light and the train car? Does the back of the car "catch up" to the light from the flash, while the front of the car is "moving away" from it? Or is the motion of the photons independent of the motion of the train car?

 

Pick one. That's reality.

[Zeropoint]

Re: Instantaneous Communications plus Time Dilation Equals ???

 

Pick one. That's reality.

 

No . . . it isn't. Simultaneity is relative. The light reaches the front of the train before, at the same time as, or after the light reaches the back depending on the relative motion of the observer and train. All such occurrences are equally valid; there are no privileged observers. As much as this idea offends you, it is the truth.

 

In any case, I'm done here. I'm worked up enough already, and Kristopher is disagreeing not because he finds a flaw in the reasoning, but because the conclusion is emotionally unacceptable to him; there's nothing I can do or say in the face of that kind of "thinking".

 

Kristopher, I expect that you'll have harsh words for me; go ahead. You have the last word here, as far as I'm concerned.

[sinanju]

Re: Instantaneous Communications plus Time Dilation Equals ???

 

Who said anything about "absolute time? That's never been the issue here.[/quot]

 

You did. Not in so many words, but that's the crux of your argument. When you argue that light cannot hit the front of the train before, at the same time, and after the light hits the back of the train, you are (perhaps unknowingly) assuming a privileged frame of reference, one in which what an observer sees is TRUE, and that all other perceptions are false.

 

But there is no privileged frame of reference, and hence no privileged observer. Time is the variable, not the speed of light.

 

Go back to the actual crux of the matter in the train car example: what is the interaction of the light and the train car? Does the back of the car "catch up" to the light from the flash, while the front of the car is "moving away" from it? Or is the motion of the photons independent of the motion of the train car?

 

Pick one. That's reality.

 

No, the reality is that all of the options are equally real. There is no privileged frame of reference and thus no privileged observer who can tell us definitively what "really" happened.

[Kristopher]

Re: Instantaneous Communications plus Time Dilation Equals ???

 

No . . . it isn't. Simultaneity is relative. The light reaches the front of the train before, at the same time as, or after the light reaches the back depending on the relative motion of the observer and train. All such occurrences are equally valid; there are no privileged observers. As much as this idea offends you, it is the truth.

 

In any case, I'm done here. I'm worked up enough already, and Kristopher is disagreeing not because he finds a flaw in the reasoning, but because the conclusion is emotionally unacceptable to him; there's nothing I can do or say in the face of that kind of "thinking".

 

Kristopher, I expect that you'll have harsh words for me; go ahead. You have the last word here, as far as I'm concerned.

 

Only to say that your assertion that this is "emotional" is something of an insult.

[Kristopher]

Re: Instantaneous Communications plus Time Dilation Equals ???

 

You did. Not in so many words, but that's the crux of your argument. When you argue that light cannot hit the front of the train before, at the same time, and after the light hits the back of the train, you are (perhaps unknowingly) assuming a privileged frame of reference, one in which what an observer sees is TRUE, and that all other perceptions are false.

 

But there is no privileged frame of reference, and hence no privileged observer. Time is the variable, not the speed of light.

 

I'm not talking about time or simultineity or frames of reference. I don't care about one observer or the other, or any observer. I only care about what the light actually does.

 

No' date=' the reality is that all of the options are equally real. There is no privileged frame of reference and thus no privileged observer who can tell us definitively what "really" happened.[/quote']

 

Again, I don't care about observers, only what the light actually does.

[sinanju]

Re: Instantaneous Communications plus Time Dilation Equals ???

 

I'm not talking about time or simultineity or frames of reference. I don't care about one observer or the other, or any observer. I only care about what the light actually does.

 

Again, I don't care about observers, only what the light actually does.

 

And that's my point. "What the light actually does" assumes a privileged frame of reference (and a privileged observer) who can tell us what "really" happened, and assumes as a consequence that what the other observers see is wrong. Or incomplete.

 

That's not how the universe works. "What the light really does" depends upon your frame of reference--i.e., the relative motion (and velocities) of the train in relation to any and all observers. Everyone within a single frame of reference can agree on the sequence of events. Our experience on earth for the whole of human existence has been bounded within a single frame of reference, so we make use of concepts like "simultaneity" and an unvarying sequence of events because it works in that environment.

 

So do Newton's laws of motion. But like Newton's laws, that's only an approximation, a rule of thumb that applies only to velocities below a certain fraction of C, and which are only valid in that environment. Beyond that point, what common sense tells us is _wrong_. When you begin dealing with velocities far higher than anything evolution equipped us to deal with, rules that work just fine for that environment no longer apply.

[Kristopher]

Re: Instantaneous Communications plus Time Dilation Equals ???

 

And that's my point. "What the light actually does" assumes a privileged frame of reference (and a privileged observer) who can tell us what "really" happened, and assumes as a consequence that what the other observers see is wrong. Or incomplete.

 

That's not how the universe works. "What the light really does" depends upon your frame of reference--i.e., the relative motion (and velocities) of the train in relation to any and all observers. Everyone within a single frame of reference can agree on the sequence of events. Our experience on earth for the whole of human existence has been bounded within a single frame of reference, so we make use of concepts like "simultaneity" and an unvarying sequence of events because it works in that environment.

 

So do Newton's laws of motion. But like Newton's laws, that's only an approximation, a rule of thumb that applies only to velocities below a certain fraction of C, and which are only valid in that environment. Beyond that point, what common sense tells us is _wrong_. When you begin dealing with velocities far higher than anything evolution equipped us to deal with, rules that work just fine for that environment no longer apply.

 

Again, not what I'm asking and not what I'm talking about.

[dmjalund]

Re: Instantaneous Communications plus Time Dilation Equals ???

 

"What the light really does" is hit the front of the car or the back of the car

the light has no idea at what speed the car is going.

it has even less idea of what any other photon going in the other direction is doing

 

as plain as I can put it - photons - because they are going EXACTLY at the speed of light - EXPERIENCE NO TIME WHATSOEVER

 

so the photon cannot be seen as an observer

 

but the photon is the only "observer" who can give an absolute answer - and it has no idea

[austenandrews]

Re: Instantaneous Communications plus Time Dilation Equals ???

 

It's not a wave' date=' and it's not a particle. It's an electron.[/quote']

You understand that an electron is neither a wave nor a particle, but some other concept that can behave like either one. At some point you accepted this concept, despite the apparent contradiction.

 

This works the same way. The two light rays in the train car neither strike simultaneously nor at different times, but act in a relativistic way that can behave like either one. Like the "form" of an electron, the truth is an amorphous concept that's not inherently intuitive, but exists nevertheless.

 

In reality the two events - one beam of light striking one end of the car and the other beam striking the other end - are each distinct. The spacetime between them is the amorphous concept. It exists in its own "objective reality," of the kind that you appear to be seeking. That reality, however, can behave in different ways according to what happens around it.

[Kristopher]

Re: Instantaneous Communications plus Time Dilation Equals ???

 

You understand that an electron is neither a wave nor a particle, but some other concept that can behave like either one. At some point you accepted this concept, despite the apparent contradiction.

 

This works the same way. The two light rays in the train car neither strike simultaneously nor at different times, but act in a relativistic way that can behave like either one. Like the "form" of an electron, the truth is an amorphous concept that's not inherently intuitive, but exists nevertheless.

 

In reality the two events - one beam of light striking one end of the car and the other beam striking the other end - are each distinct. The spacetime between them is the amorphous concept. It exists in its own "objective reality," of the kind that you appear to be seeking. That reality, however, can behave in different ways according to what happens around it.

 

Sure, fine, but where it breaks down in the "train example" is still in the assertion that it behaves in as many ways as there are different frames of references around it, that it does multiple things at the same time, instead of one thing.

[Zeropoint]

Re: Instantaneous Communications plus Time Dilation Equals ???

 

Now you've got it!

[Kristopher]

Re: Instantaneous Communications plus Time Dilation Equals ???

 

Now you've got it!

 

Oh, I get what it's trying to say, that's never been the issue.

 

I just don't believe that the universe, that reality, is a sideshow house of mirrors.