On Einstein's explanation of the invariance of c

[arfa brane]

So you can't find a hole in my theory, and I've proven why Einstein's is wrong

You're saying radar doesn't work the way everyone using it thinks it does.

You're saying you can't measure the velocity of a moving object with a laser rangefinder because Einstein got it wrong.

And you're saying you can't explain your theory, you have no 'ansatz', just a vague description that conveys nothing useful or even interesting.

[Motor Daddy]

You're saying radar doesn't work the way everyone using it thinks it does.

You're saying you can't measure the velocity of a moving object with a laser rangefinder because Einstein got it wrong.

And you're saying you can't explain your theory, you have no 'ansatz', just a vague description that conveys nothing useful or even interesting.

I didn't say anything about radar, GPS, or rangefinders, you did. Just because something gets close doesn't mean it's right.

The theory is wrong, and I've shown why. Not only that, I told you how to do it the right way!

[arfa brane]

Well, bro, you better get onto the Pentagon and fill them in. They will have to adjust to this new information you have, and that right quickly!
There are a lot of pilots waiting to land somewhere. I'm not sure how they're going to take the news that they can't tell where they are.

[AlphaNumeric]

Keep using Einstein's methods and keep wondering why science isn't making progress.

You just demonstrated how ignorant and/or dishonest you are. The march of science has sped up enormously in the 100 years since Einstein's work. It's completely altered how we live our lives and how we view the universe. You need only flick through the paper titles on www.arxiv.org to see the level of detail and complexity people are doing.

You clearly have trouble accepting reality, when you claim things happen which experiments, aka reality, refute. The methods of timing and measuring distance used by relativity are used in the GPS network. Millions of people put their lives in the hands of such systems every single day. If it didn't work would the military use it?

That's the ultimate knock down punch to your claims. You can't claim a conspiracy in the scientific community when it produces results seen by non-scientists. If a Cruise missile kept missing a target by 20km someone would notice, but they are extremely accurate. If your in-car navigation kept telling you to turn where there is no road, you'd notice. Reality might not be exactly as described by relativity but its so close we currently can't measure a difference. We can measure a difference between your claims, reality doesn't work as you assert.

[James R]

Motor Daddy:

OK, but just remember, you have to measure the one-way times BEFORE you can tell me the speed of the ship or the length between the clocks. You can not tell me any information until you measure the one-way times. Yet you started this scenario with telling me how long the ship is and the velocity of the ship without knowing the one-way times. So again, how did you arrive at those figures without first having measured the one-way times?

Ah. My apologies. I didn't realise that it was impossible to measure the length or speed of anything unless you use light and one-way travel times.

Ok then. I suggest the following thought-experiment instead.

Recall that the speed of light is c=299792458 m/s. Expressed in units of light-seconds per second, this value is c=1 light second per second.

Now, consider a spaceship of unknown length moving at unknown speed. A light beam is fired from the back of the ship to the front and the one-way travel time is measured. The measured time is 2 seconds.

A light beam is then fired from the front of the shop to the back and the one-way travel time measured again. This time, the travel time is found to be 0.6667 seconds (i.e. two-thirds of a second).

Question 1 for Motor Daddy: How long is the spaceship?
Question 2 for Motor Daddy: How fast is the spaceship moving?

These should be easy starter questions.

Now for some harder questions:

Question 3 for Motor Daddy: Is it possible to measure the speed of light, or must it always be assumed that light travels at exactly 299792458 m/s? Don't bother telling me it has a defined speed, etc. etc. I know that. I'm asking you: if you try to measure the speed of light experimentally, is it possible to do so, and will your answer match the defined value? I'm not concerned about whether you think such an experiment would be a waste of time, either, since you already know the speed of light etc. etc. Just answer the question.

Question 4: If it is possible to confirm the speed of light by measurement, can the experiment be done in any reference frame other than the hypothetical "absolute zero speed" reference frame and still give results that match the defined value of the speed of light?

Question 5: Would it be possible for somebody on the spaceship above to measure the speed of light, without knowing the speed or length of the spaceship in advance?

Question 6: If the answer to Question 5 is "yes", can you please give a procedure for measuring the speed of light. (Note: if the hypothetical measurer needs to work out the speed or length of the spaceship as part of the procedure, that's fine, but make sure you specify how they would do that.)

Question 7: Does it make any sense at all to talk about the speed of light relative to the spaceship?

Question 8: If the answer to Q7 is "yes", then what is the speed of light relative to the spaceship? Is it different to the absolute speed of light (299792458 m/s)?

I look forward to your answers. I feel like we're making progress towards a mutual understanding here. Maybe I can be convinced that there really is an absolute frame of reference after all.

[James R]

Motor Daddy:

I've been reading your other responses and I found this interesting:

Once you've defined a meter you can make a meter stick.

Simply find a good stick, as straight as possible. Place the stick on the ground and measure the one-way times in each direction from end to end. [etc.]

Now, since you have a meter stick you can measure things without using light!! Caution, if you bring your meter stick on a plane, and measure one meter from point A to point B, and then you use light to check the times between A and B, if the plane is not at an absolute zero velocity, the light travel times will be different each way, because the plane has a velocity.

So, metre sticks that are correctly manufactured don't measure correct distances on planes that have a velocity. The answers you get for the lengths of objects on planes, measured using your correctly-manufactured metre sticks are always too short. Is that correct?

So, when people such as builders of houses say the house has a certain length, say, they aren't quoting the real length at all (because the Earth has a velocity through space). Their rulers probably aren't calibrated correctly, and even if they were they wouldn't work properly on a moving Earth.

Is that right?

[Motor Daddy]

Motor Daddy:



Ah. My apologies. I didn't realise that it was impossible to measure the length or speed of anything unless you use light and one-way travel times.

Ok then. I suggest the following thought-experiment instead.

Recall that the speed of light is c=299792458 m/s. Expressed in units of light-seconds per second, this value is c=1 light second per second.

Now, consider a spaceship of unknown length moving at unknown speed. A light beam is fired from the back of the ship to the front and the one-way travel time is measured. The measured time is 2 seconds.

A light beam is then fired from the front of the shop to the back and the one-way travel time measured again. This time, the travel time is found to be 0.6667 seconds (i.e. two-thirds of a second).

Question 1 for Motor Daddy: How long is the spaceship?
Question 2 for Motor Daddy: How fast is the spaceship moving?

These should be easy starter questions.

Light traveled 599,584,916 meters in space in the time it took light to go from the back of the ship to the front of the ship (2 seconds of light travel time).

Light traveled 199,871,631.7486 meters in space in the time it took light to travel from the front of the ship to the back of the ship (.6667 seconds of light travel time).

The ship traveled 399,713,284.2514 meters in 2.6667 seconds, so the ship's velocity is 149,890,607.96 m/s.(rounded off).

The ship traveled 299,781,215.92 meters in 2 seconds and the light traveled 599,584,916 meters in 2 seconds. That means the ship is 299,803,700.08 meters in length.

Now for some harder questions:

Question 3 for Motor Daddy: Is it possible to measure the speed of light, or must it always be assumed that light travels at exactly 299792458 m/s? Don't bother telling me it has a defined speed, etc. etc. I know that. I'm asking you: if you try to measure the speed of light experimentally, is it possible to do so, and will your answer match the defined value? I'm not concerned about whether you think such an experiment would be a waste of time, either, since you already know the speed of light etc. etc. Just answer the question.

By defining the meter by light travel time, by definition light is a constant. It is impossible to separate the time it takes light to travel a meter. If you want to measure the speed of light using light travel times, you first must know how long a stick is , and the velocity of the stick. I know it was impossible in the past, but I figured it out for everyone, so no problem no more. If you want to measure the speed of light, simply use my method to find the length of an inertial stick. When you know the true length of the stick and the velocity of the stick, simply measure the one-way time and do the math. It is impossible to separate the time it takes light to travel a meter, so by definition the speed of light is a constant. You are wasting your time measuring the speed of light, because you've already defined it. If your measurements indicate something other than 299,792,458 m/s, you've measured improperly.

Question 4: If it is possible to confirm the speed of light by measurement, can the experiment be done in any reference frame other than the hypothetical "absolute zero speed" reference frame and still give results that match the defined value of the speed of light?

See above.

Question 5: Would it be possible for somebody on the spaceship above to measure the speed of light, without knowing the speed or length of the spaceship in advance?

NO! You can never measure the speed of light unless you know the speed and length of the object you are measuring with. How can you lay a stick on the ground of unknown velocity and measure the time it takes light to travel the stick, and then conclude you know the length of the stick? You only arrive at an elapsed time of an unknown length and unknown velocity. Worthless information. However, you can ultimately measure the speed of light using my method to determine the length and speed of a stick, to go on to measure the speed of light. But you must always first know the length and speed of the stick.

Question 6: If the answer to Question 5 is "yes", can you please give a procedure for measuring the speed of light. (Note: if the hypothetical measurer needs to work out the speed or length of the spaceship as part of the procedure, that's fine, but make sure you specify how they would do that.)

The answer was no.

Question 7: Does it make any sense at all to talk about the speed of light relative to the spaceship?

The ship is traveling relative to light, as I explain in my calculations. You can think of a light sphere. Light is emitted from a source in space. Light travels in all directions away from the point in space the sphere was when the light was emitted. If the light is traveling away and the source moves, the source will be closer to one edge of the sphere and further from the other, hence you could say the source travels relative to light, like a car travels relative to a bus that is moving away from the car.

Question 8: If the answer to Q7 is "yes", then what is the speed of light relative to the spaceship? Is it different to the absolute speed of light (299792458 m/s)?

The speed of light is always the same. The spaceship's speed can be determined by knowing the light travel times and the distance light travels in space.

I look forward to your answers. I feel like we're making progress towards a mutual understanding here. Maybe I can be convinced that there really is an absolute frame of reference after all.

It's a pleasure to be of assistance. I hope I've cleared up some of your misconceptions about the speed of light and the speed of the ship and actual length of the ship. As you can see, it's a simple way of determining absolute velocity, which was previously believed to be impossible of determining.

[Motor Daddy]

Motor Daddy:

I've been reading your other responses and I found this interesting:



So, metre sticks that are correctly manufactured don't measure correct distances on planes that have a velocity. The answers you get for the lengths of objects on planes, measured using your correctly-manufactured metre sticks are always too short. Is that correct?

The meter stick will measure the length of the plane correctly. The problem arises from the fact that you are trying to use light travel time to measure the length of the stick, when you don't know the velocity of the stick. You end up thinking the meter stick is not a meter if the stick has a velocity, because the stick travels relative to light. By not knowing the velocity of the stick you falsely conclude the meter is no longer a meter. Once you have a meter stick on board the plane there is no reason to measure the length of the plane using light. If you want to do that you MUST know the velocity of the plane before you can draw conclusions about length. Measure with the meter stick, or measure with light, but understand that if you measure using light, you must follow proper procedures, otherwise your measurements of length will be wrong!

So, when people such as builders of houses say the house has a certain length, say, they aren't quoting the real length at all (because the Earth has a velocity through space). Their rulers probably aren't calibrated correctly, and even if they were they wouldn't work properly on a moving Earth.

Is that right?

If a builder has a calibrated ruler he can measure correctly without knowing the velocity of the Earth. If he tries to use light to measure and doesn't know the velocity of the object he is measuring, he will arrive at incorrect lengths at anything other than a zero velocity.

[Neddy Bate]

Hey Motor Daddy,

Don't forget that you have to measure the "one way" times of light in ALL POSSIBLE DIRECTIONS before you can determine the absolute speed. This makes your method more complicated, but it must be done.

Consider a train rolling through the absolute rest frame. If you measure one-way times for light traveling between the floor and ceiling, you incorrectly conclude the absolute speed of the train is zero. After that, you would calculate the height of the train incorrectly, because you would not have accounted for the train's motion through the absolute frame. So you must test light signals in all directions first. That is the only way to determine the DIRECTION of the absolute speed. After that, you can make your distance calculations, but the equations will be a little more complicated than the ones you've been using.

I never said different.

You are admitting that you'd have to measure light transit times in EVERY POSSIBLE DIRECTION for your procedure to work, (even in your fictional universe). That means you can't say things like this:

Light traveled 599,584,916 meters in space in the time it took light to go from the back of the ship to the front of the ship (2 seconds of light travel time).

Light traveled 199,871,631.7486 meters in space in the time it took light to travel from the front of the ship to the back of the ship (.6667 seconds of light travel time).

The ship traveled 399,713,284.2514 meters in 2.6667 seconds, so the ship's velocity is 149,890,607.96 m/s.(rounded off).

The ship traveled 299,781,215.92 meters in 2 seconds and the light traveled 599,584,916 meters in 2 seconds. That means the ship is 299,803,700.08 meters in length.

Because you don't know if the ship is moving in any other direction, other than the obvious "rear to front" direction. What if the ship is also drifting upward and sideways through your fictional "absolute frame?" Then your above calculation for the length of the ship would be wrong.

The velocity calculation would also be wrong, unless you qualify it by saying that you are only concerned with one component of velocity -- that from "rear to front" of the space ship.

[arfa brane]

You can never measure the speed of light unless you know the speed and length of the object you are measuring with.

Except that you can use a length of conductive material--commonly known as "wire"--to measure the time it takes for a signal to propagate along its length. Electrical signals propagate at the speed of light. Maybe Maxwell got it wrong too?

How can you lay a stick on the ground of unknown velocity and measure the time it takes light to travel the stick, and then conclude you know the length of the stick?

You use a device that can measure the time it takes for a laser beam to return from either end of the stick, like surveyors do every day on planet earth.

You only arrive at an elapsed time of an unknown length and unknown velocity. Worthless information.

Unless you happen to be surveying land, and you want to know the length traveled by laser beams at a constant velocity. Or if you're landing a fighter jet at an airbase or on a carrier at night.

However, you can ultimately measure the speed of light using my method to determine the length and speed of a stick, to go on to measure the speed of light. But you must always first know the length and speed of the stick.

But you haven't described any "method". You keep saying that you need to know the length of a stick to measure the speed of light, and you keep saying you need to know the speed of light to measure the length of a stick.

[Neddy Bate]

Except that you can use a length of conductive material--commonly known as "wire"--to measure the time it takes for a signal to propagate along its length. Electrical signals propagate at the speed of light. Maybe Maxwell got it wrong too?

That's a good point, arf. I had asked MD about light traveling through water for the same reason. If his ideas about light speed through "space" were correct, (which they obviously are not), then we would need to know absolute speeds before calculating anything regarding light in a vacuum. I doubt his mindset would accept the idea that "absolute speed" of a medium affects the one-way travel times of EM waves through it. This should put the Motor Daddy brain into some kind of paradox, but I doubt it will.

[AlexG]

If you randomly choose any two pages in this thread and compare them, you'll see that they're pretty much the same. MD just keeps saying the same thing over and over, and doesn't really pay any attention to anything to the contrary.

[Motor Daddy]

You are admitting that you'd have to measure light transit times in EVERY POSSIBLE DIRECTION for your procedure to work, (even in your fictional universe). That means you can't say things like this:


Because you don't know if the ship is moving in any other direction, other than the obvious "rear to front" direction. What if the ship is also drifting upward and sideways through your fictional "absolute frame?" Then your above calculation for the length of the ship would be wrong.

The velocity calculation would also be wrong, unless you qualify it by saying that you are only concerned with one component of velocity -- that from "rear to front" of the space ship.

I am talking about the velocity from the rear to front and you know it. The times were given from the rear to front and front to rear. Did anyone ever mention anything about ceiling or floor? Is that the best defense you have? Tell me how you determine velocity of the ship? You don't know how? Einstein doesn't know how? Go figure!

[Motor Daddy]

If you randomly choose any two pages in this thread and compare them, you'll see that they're pretty much the same. MD just keeps saying the same thing over and over, and doesn't really pay any attention to anything to the contrary.

Because you guys make the same mistake over and over and over, as you stick to Einstein's mistake like flies on crap. I've already showed why Einstein's methods are wrong. Tell me your numbers of the ship's velocity and length, using Einstein's methods? You can't? Why, because he disregards an object's velocity? Because he uses round trip time that is worthless?

Tell me the length of the ship that James R. posted. Tell me your numbers, buddy.

[AlexG]

Read my tag line.

[Motor Daddy]

Except that you can use a length of conductive material--commonly known as "wire"--to measure the time it takes for a signal to propagate along its length. Electrical signals propagate at the speed of light. Maybe Maxwell got it wrong too?

How long is the wire? How did you determine the length? Did you use a meter stick? How did you make the meter stick?

You use a device that can measure the time it takes for a laser beam to return from either end of the stick, like surveyors do every day on planet earth.

How long is the stick? Did someone give you a meter stick? Great, how did they determine the stick is a meter?

Unless you happen to be surveying land, and you want to know the length traveled by laser beams at a constant velocity. Or if you're landing a fighter jet at an airbase or on a carrier at night.

Close but no cigar!

But you haven't described any "method". You keep saying that you need to know the length of a stick to measure the speed of light, and you keep saying you need to know the speed of light to measure the length of a stick.

I repeatedly told you it is a waste of time to measure the speed of light, it is defined! Do you understand anything that I say? No wonder I have to repeat things over and over and over.

[Motor Daddy]

Read my tag line.

Tell me your numbers of James R. ship and we can talk.

Let me guess. 2.6667 seconds round trip divided by two equals 1.33335 seconds each way, so the length of the ship must be 399,728,273.8743 right?

I mean, if light always travels at 299,792,458 m/s, and light traveled 1.33335 seconds in each direction, that means the ship must be 399,728,273.8743 meters in length.

Bwahahahahaahaha

That's funny right there, I don't care who you are! You're only off by 100 million meters.

[AlexG]

MD, you're a major league crank, well over the ubercrackpot line. Nothing that's ever said to you will make any difference in what you believe.

The fact that Einstein's relativity has been amply demonstrated by observation, experimentation, and prediction, to an extreme degree of accuracy mean nothing to you. On the other hand, your version of reality has never been demonstated at all. It just exists inside your head, and than appears to be a very strange place indeed.

[arfa brane]

I repeatedly told you it is a waste of time to measure the speed of light, it is defined!

Who defined it? Was it the big guy? The aliens?

How do YOU know the time it takes light in a vacuum to travel one metre? Did you look it up on Wikipedia?
What if it's wrong, like Einstein? Wouldn't it be a good idea to make sure the definition is correct? So HOW would YOU check it?

No wonder I have to repeat things over and over and over.

To yourself.

[Motor Daddy]

MD, you're a major league crank, well over the ubercrackpot line. Nothing that's ever said to you will make any difference in what you believe.

The fact that Einstein's relativity has been amply demonstrated by observation, experimentation, and prediction, to an extreme degree of accuracy mean nothing to you. On the other hand, your version of reality has never been demonstated at all. It just exists inside your head, and than appears to be a very strange place indeed.

It exists in the way we define distance and time, and math, period. There is no way to prove me wrong other than to change the definitions. Face it, Einstein doesn't know the velocity of the ship so he can't measure the length of the ship correctly using light!