The Relativity of Simultaneity

[Motor Daddy]

There you go. I was wondering how long it would take you to say we do not know how to measure the speed of light, we must not be able to measure it or you would have to admit you were wrong, which will never happen. So why do you accept the speed of light at 299,792,458 m / s if we can't measure the speed of light properly? You are really a hoot. If you were 1/10 as smart as you think you are you would be twice as smart as you appear.

Because it is defined, it can't change unless you redefine the meter or the second. I don't need to measure it, I know FOR SURE, BY DEFINITION that the speed of light is 299,792,458 m/s. I am 100% SURE of that, without measuring.

 

[Motor Daddy]

You are really a hoot. If you were 1/10 as smart as you think you are you would be twice as smart as you appear.

So if I appear to be 75% as smart as you, and I think I'm 200 times smarter than you, but really I'm only 1/20th as smart as I think I am, which is less than 1/10 as smart as I think I am, then I'm really 10 times smarter than you, which is actually 1000% smarter than you, and much smarter than I appear??

 

[origin]

Because it is defined, it can't change unless you redefine the meter or the second. I don't need to measure it, I know FOR SURE, BY DEFINITION that the speed of light is 299,792,458 m/s. I am 100% SURE of that, without measuring.

Holy crap that is funnier than Hell! You clearly aren't serious - please tell me you are joking.

Try to listen closely. The meter is defined as distance light travels in 1/299,792,458 of a second. Where do you think that number, 2997924258, came from? Do you think it is an arbitrary number just picked out of the air? If it is, it would be meaningless.

But it is not, it is the measured speed of light. The speed of light was measured to a very precise level and then it was used a the basis for defining the meter.

Do you see it? Do you see the big problem coming at you? Here it is; the length of a meter is not really the length of the meter, at least according to you, unless the earth is that special place in the universe that is at absolute rest.

You maintain that the relative speed of light changes with the observers speed. So when we measure the speed of light it is defacto relative to the motion of our instruments and the earth. If we are not that special place at absolute rest then we are not accurately measuring the "real" speed of light, which means we don't know the length of a meter because it is based on a relative speed of light. Hell, we don't even know if the REAL meter is longer or shorter than what we are measuring because we do not know what our motion is relative to absolute rest. Only someone at absolute rest who was measuring the "true" speed of light would get a accurate length for the meter.

Truly priceless.

Edited to add:
Oops, I am wrong. This whole fantasy physics stuff lead me to error. If the speed of light changed relative to motion of the observer then the meter would have the same length relative to an observer in a hypothetical absolute rest frame.

However this is still a major problem
Assuming that we are not at absolute rest and the reference point of the universe then we would have to change the definition of the meter depending on the time of year. The meter is defined by the speed of light relative to the earth over a certain time interval. If the speed of light changes depending on our velocity realtive to an absolute rest frame then length of the defined meter would change as our orbital velocity vector changed over the year. We would need to change the formula 1/(speed of light m/s) to the current speed of light. Or the length of a meter would change over the course of the year.

 

[Motor Daddy]

The meter is defined as distance light travels in 1/299,792,458 of a second. Where do you think that number, 2997924258, came from? Do you think it is an arbitrary number just picked out of the air? If it is, it would be meaningless.

Who cares where it came from, it's just a definition defining the meter. I could just as easily make up a new unit of measure for distance called the dltios. The dltios is defined as the length of the path traveled by light in vacuum in 1 second. The speed of light would then be 1 dltios/second. In other words, I don't need to measure the dltios, it is defined by the constant speed of light.

So hence forth, the speed of light is 1 dltios/second.

By the way, there are 299,792,458 meters per dltios, just in case you need to convert.

 

[quantum_wave]

I measure the speed of light to be different, depending on the frame that you measure it in. So back to the light sphere example, if you are the source, and you moved in the one second, it would be impossible for you to measure the light to be moving away from you at 299,792,458 m/s. One way you would measure the light to be less than c, and the other way you would measure it to be more than c, since the light is less than 299,792,458 meters away from you after one second in one direction, and more than 299,792,458 meters away from you in the opposite direction after 1 second. The light speed was constant in the absolute zero reference frame. Your velocity is relative to the absolute zero reference frame, but you MEASURE the speed of light to be different in your frame, because of your velocity. You measure the speed of light to be greater than c in one direction, and less than c in the opposite direction.

Knowing that the speed of light is constant, you know it is not the light that changed velocity in opposite directions, it was that you had a velocity which caused your measurements to reflect the greater and less than c in opposite directions.

OK, but for me the thing is that there are postulates that govern the derived truths in the train/embankment example. You are obligated to accept the postulates in order to dispute the derived truths. If you don't accept the postulates and use your own postulates, then you will derive different truths which is what I think is going on.

Now I agree that it is entirely possible for you to define the postulates and come up with your own "truths" but they are not comparable to the "truths" derived from Einstein's postulates.

This would be interesting if you were to stop trying to say your are right and Einstein is wrong. I would take the position that given Einstein's postulates he is right, and if you were to state yours and then derive your truths form your own postulates that would differentiate the two theories.

Then we could set about proving or disproving your theory.

 

[origin]

Who cares where it came from, it's just a definition defining the meter. I could just as easily make up a new unit of measure for distance called the dltios. The dltios is defined as the length of the path traveled by light in vacuum in 1 second. The speed of light would then be 1 dltios/second. In other words, I don't need to measure the dltios, it is defined by the constant speed of light.

So hence forth, the speed of light is 1 dltios/second.

By the way, there are 299,792,458 meters per dltios, just in case you need to convert.

Based on your beliefs:
The speed of light is measured on earth. Earth is in motion relative to an absolute at rest frame. The speed of earth changes relative to that absolute at rest frame. Therefore the speed of light changes. Unless you change the formula to the current speed of light (depending on where in earths orbit you are) then the length of a meter will change. So the length of the dltios will change also unless you continually update to the current speed of light. Your fantasy world is very silly.

 

[Motor Daddy]

OK, but for me the thing is that there are postulates that govern the derived truths in the train/embankment example. You are obligated to accept the postulates in order to dispute the derived truths. If you don't accept the postulates and use your own postulates, then you will derive different truths which is what I think is going on.

Now I agree that it is entirely possible for you to define the postulates and come up with your own "truths" but they are not comparable to the "truths" derived from Einstein's postulates.

This would be interesting if you were to stop trying to say your are right and Einstein is wrong. I would take the position that given Einstein's postulates he is right, and if you were to state yours and then derive your truths form your own postulates that would differentiate the two theories.

Then we could set about proving or disproving your theory.

My postulate is: The speed of light is a constant. Measurements of the speed of light will vary depending on the velocity of the frame the measurements are taken in.

 

[Motor Daddy]

Based on your beliefs:
The speed of light is measured on earth. Earth is in motion relative to an absolute at rest frame. The speed of earth changes relative to that absolute at rest frame. Therefore the speed of light changes. Unless you change the formula to the current speed of light (depending on where in earths orbit you are) then the length of a meter will change. So the length of the dltios will change also unless you continually update to the current speed of light. Your fantasy world is very silly.

My postulate is: The speed of light is a constant. Measurements of the speed of light will vary depending on the velocity of the frame the measurements are taken in.

The speed of light doesn't change! Therefore, the length of a dltios never changes. Your measurements of the speed of light will not be accurate if your frame has an absolute velocity and you don't account for that velocity. When you account for the velocity in your measurements, your measurements of the speed of light will be correct.

 

[AlexG]

Measurements of the speed of light will vary depending on the velocity of the frame the measurements are taken in.

This is MD's basic postulate. The fact that it has been disproven by experimentation and observation means nothing to MD.

 

[origin]

You don't appear to understand your own conjecture.

Lets look at what you just said.

My postulate is: The speed of light is a constant. Measurements of the speed of light will vary depending on the velocity of the frame the measurements are taken in.

So if I am on a train moving then the relative speed of light will be different than the embankment. Fine. The speed of light measured on the moon will be different than the speed of light measured on the earth because they are traveling at different speeds. Got it.

The speed of light doesn't change! Therefore, the length of a dltios never changes.

Oh no, the MEASUREMENTS of the speed of light do change though! So the relative speed of light on the moon is different than the speed of light on earth. So if the lenght of the dltios is length that light travels in 1 second, then the length of the dltios will be different on the moon than the legth of a dltios on earth. Darn!

Your measurements of the speed of light will not be accurate if your frame has an absolute velocity and you don't account for that velocity. When you account for the velocity in your measurements, your measurements of the speed of light will be correct.[/

Oh good, I did not take into account the ABSOLUTE velocity. So taking into account the difference in the velocity between the moon and the earth I would get the right answer. But wait, we are talking about the ABSOLUTE velocity so it is not just the relative difference in velocity between the moon and the earth, it is the ABSOLUTE velocity. So I need to know what the ABSOLUTE velocity of earth is. Oh crap, it is worse than that, because the moon orbits the earth, so sometime the moon will be going faster than the earth or slower than the earth in an ABSOLUTE velocity frame, unless the earth has no ABSOLUTE velocity and is perfectly motionless. So to have any hope of figuring out anything we need to know the ABSOLUTE velocity of the earth.

I think you could easily clear this problem up - what is the ABSOLUTE velocity of earth?

 

[quantum_wave]

My postulate is: The speed of light is a constant. Measurements of the speed of light will vary depending on the velocity of the frame the measurements are taken in.

You mean it seems logical that if you could measure but the closer you get to catching up with that pesky light beam to clock it, the slower your clock measures time and so I bet you will always measure the speed of light from any frame to be invariant.

 

[Motor Daddy]

You don't appear to understand your own conjecture.

No, I understand it perfectly, it's you who has serious problems understanding what is being said.

So if I am on a train moving then the relative speed of light will be different than the embankment. Fine. The speed of light measured on the moon will be different than the speed of light measured on the earth because they are traveling at different speeds. Got it.

Finally.

Oh no, the MEASUREMENTS of the speed of light do change though! So the relative speed of light on the moon is different than the speed of light on earth. So if the lenght of the dltios is length that light travels in 1 second, then the length of the dltios will be different on the moon than the legth of a dltios on earth. Darn!\

I thought you said you got it? Did you lose it again?

The length of the dltios never changes, because the speed of light is a constant. If you fail to take into account the velocity of the frame in which you are performing measurements using light, than you are not making accurate measurements. So what you think you measured to be a dltios is not actually 1 dltios, because you failed to account for your absolute velocity.

Oh good, I did not take into account the ABSOLUTE velocity. So taking into account the difference in the velocity between the moon and the earth I would get the right answer. But wait, we are talking about the ABSOLUTE velocity so it is not just the relative difference in velocity between the moon and the earth, it is the ABSOLUTE velocity. So I need to know what the ABSOLUTE velocity of earth is. Oh crap, it is worse than that, because the moon orbits the earth, so sometime the moon will be going faster than the earth or slower than the earth in an ABSOLUTE velocity frame, unless the earth has no ABSOLUTE velocity and is perfectly motionless. So to have any hope of figuring out anything we need to know the ABSOLUTE velocity of the earth.



I think you could easily clear this problem up - what is the ABSOLUTE velocity of earth?

That's your problem if you can't measure accurately. Is reality supposed to tend to your needs just because you are incapable of accurate measurements? Are you suggesting change reality to fit your needs? That's not how it works, sorry.

 

[Motor Daddy]

You mean it seems logical that if you could measure but the closer you get to catching up with that pesky light beam to clock it, the slower your clock measures time and so I bet you will always measure the speed of light from any frame to be invariant.

Wrong. You can't have your cake and eat it too. If the speed of light is constant, then it travels a specific distance in a specific duration. Objects such as light sources and trains travel in space too during that same elapsed time.

 

[origin]

Are you suggesting change reality to fit your needs?

Nope. That is your department.

You are a lost ball in high weeds.

 

[quantum_wave]

Wrong. You can't have your cake and eat it too. If the speed of light is constant, then it travels a specific distance in a specific duration. Objects such as light sources and trains travel in space too during that same elapsed time.

I guess. I always thought that it was the frequency of light that changed as you change frames anyway, not the speed.

I guess that is why this stuff can't be taken on logic without accepting the postulate that the speed of light is the same. Didn't someone say it was proven by experiment. Maybe they could link us to the test results that show the speed of light is invariant from all frames and you could evaluate those test results from your perspective.

 

[arfa brane]

So for instance, light takes 1 second to travel from the point it was emitted to the point it was received, so light traveled 299,792,458 meters in space from the time it left the transmitter to the time it was received at the receiver.

That DOESN'T necessarily mean the distance between the transmitter and receiver is 299,792,458 meters.

It does necessarily mean the distance between the transmitter and receiver was 299,792,458 metres when the light was emitted.

So how can you tell if the distance between the sources has changed, after arranging for both the sources to emit light simultaneously, and arranging for both sources to be 1 light second apart? How do you know they are or aren't moving?

 

[Motor Daddy]

It does necessarily mean the distance between the transmitter and receiver was 299,792,458 metres when the light was emitted.

So how can you tell if the distance between the sources has changed, after arranging for both the sources to emit light simultaneously, and arranging for both sources to be 1 light second apart? How do you know they are or aren't moving?

Again, all you are doing when you time the light from the transmitter to the receiver is measuring the time that light travels. You are determining light travel time, that is it. You are not determining the distance between the transmitter and receiver, you are simply determining the duration that light travels in one direction.

 

[arfa brane]

You are not determining the distance between the transmitter and receiver, you are simply determining the duration that light travels in one direction.

So it's impossible to tell if the distance has changed. You can only measure the time it takes for light to travel from one source to the other. You can't use your method to determine if the sources are moving.

But if the sources have an absolute velocity, won't the speed of light appear to be different?

 

[Motor Daddy]

So it's impossible to tell if the distance has changed. You can only measure the time it takes for light to travel from one source to the other. You can't use your method to determine if the sources are moving.

If the sources are moving compared to what? The transmitter and receiver are bolted to the floor, so the distance between them remains the same at all times.

But if the sources have an absolute velocity, won't the speed of light appear to be different?

Yes it will appear to be different. For right now, all you are doing is measuring the light travel time in one direction.

You simply are measuring the time light travels in space from the transmitter to the receiver.

 

[arfa brane]

If the sources are moving compared to what?

Compared to each other.
Sorry, I thought we were still on the inital scenario.
But, let's say the two sources are in free space instead of bolted to a train.

How do you measure their absolute velocities, again?
Or how do you measure the distance between the sources, and can you tell if the distance is changing?

So far, you've said you can only measure time intervals, which I take to mean you can't measure any changes in distance.