The Swing of a Pendulum

[billvon]

It's not semantics. Saying one object is faster than another object means each object has it's own speed.

No it doesn't. You could as accurately say that one object is slower than the other and be just as accurate. The only thing that matter is that there is a difference.

A relative velocity is not of one object's speed but of a closing speed, which is nothing more than measuring the distance between the objects at points in time and stating that information in terms of the units for distance and time. The distance and time is not of one object's motion but of the space between the objects.

Distance over time is velocity. It has nothing to do with the "space between the objects."

 

[Motor Daddy]

You believe that "absolute speed" exists and "relative speed" does not. You are wrong (which is why scientists don't differentiate), but at least it will be easier to discuss if we use consistent and unambiguous terminology.

When did I ever say that I don't believe in relative velocity? You are the one that's wrong. I understand absolute velocity and relative velocity. Don't put words in my mouth.

 

[Russ_Watters]

When did I ever say that I don't believe in relative velocity? You are the one that's wrong. I understand absolute velocity and relative velocity. Don't put words in my mouth.

You said:

A relative velocity is not a velocity of an object, or even a velocity at all. A relative velocity is a measure of changing distance between two objects.

Which is a mixture of gibberish and wrong assertions. I may have accidentally mixed-and matched, but in my defense, when you say "relative velocity is not a velocity", it is tough to tell if it is just wrong or if it is gibberish. Also known as "not even wrong", which means that in order to just be wrong it would need to improve.

In either case, your particular formulation of relative velocity isn't the main point here. The main point is your wrong belief in the existence of absolute velocity.

 

[AlexG]

I understand absolute velocity

Only in your own universe. In the universe everyone else inhabits, there is no absolute velocity.

I'm pretty sure this is just where we started. You never get anyplace with MD, he has his own world.

 

[Lakon]

The pendulum indicates a change in absolute velocity. The pendulum is non-responsive to changes in relative velocity between the two cars caused by the other car's change in motion. Since the pendulum indicates a change in velocity, and the relative velocity doesn't change, the pendulum is indicating a change in absolute velocity.

Hi MD;

Firstly, let me say that what is really sad in this thread, is the manner in which you've been treated by some, for simply raising this interesting thought experiment. Having read through all these posts, I find none of yours a waste of time at all - on the contrary, I find them stimulating and thought provoking. It's not like the internet just ran out of bandwidth or something .. what are these guys so upset about ? Why all the intolerance ?

Onto your proposition. If the two cars, or two rocket ships or whatever, are moving at a constant velocity, and no change in distance AT ALL to each other, then why have two ? Why not just one .. or ten ?

Why not equally transfer the thought experiment onto a rigid frame train carriage with the pendulums at each end of such carriage ? What benefit or additional criteria does seperating them into two different vehicles confer upon the experiment ?

And further, why two pendulums ? Why not just one ? They're going to behave identically in the rigid train carriage, aren't they ? Or, leaving it at two, why not bring them closer and closer together until they nearly touched .. or did touch .. or perhaps even merged in some way .. back to one. Wouldn't then, this movement of the pendulum due to a rocket boost, simply be showing it's inertia ?

Finally, I really like the way in which you've kept your arguments simple and understandable. None of it has seemed like semantics to me.

 

[Lakon]

You said: Which is a mixture of gibberish and wrong assertions. I may have accidentally mixed-and matched, but in my defense, when you say "relative velocity is not a velocity", it is tough to tell if it is just wrong or if it is gibberish. Also known as "not even wrong", which means that in order to just be wrong it would need to improve.

wow ..

 

[Lakon]

Also, another question, brought about by some commnets that Prof Layman made above, although I will reduce my aporia to an even simpler form, thus;

An object is travelling very close to light speed in a region of space as to be (largest number you can think of) miles away from any other object. How does it know what speed it is travelling at so as to grow in mass to near infinity

 

[AlphaNumeric]

You claim you recognize that each object has its own velocity. What is that velocity in relation to?

Any arbitrary inertial frame anyone might wish to work with. I explicitly said so. I've explained it to you. Others have explained it to you. You simply don't want to listen. You are so blatantly dishonest you should be ashamed of yourself.

You have no evidence for your claims about how reality supposedly works. You are clearly profoundly ignorant of relativity. It is also clear you lack even the most rudimentary of reasoning abilities. It would almost be funny if you hadn't spent so many years like this, accomplishing nothing. Then its just pathetic.

There is only 2 cars. If you like we can change the cars to rockets. Forget the road. There is two rockets with rocket engines, traveling one behind the other at the same speed. The distance between them remains constant at all times. You have no concept of absolute velocity so the only thing you have is relative velocity to work with. All your measurements are dependent on each of your motions. There is no change in distance between the rockets at all times. The relative velocity is always zero. No relative motion. None. Zilch. There is no change in velocity the entire time. There is no change is ft/sec per second.

You've just proven you don't know what an inertial frame is. If you could do even the most basic of mathematics from high school mechanics you'd grasp it. The extreme simplicity of the subject matter make it all the more obvious how ignorant you are to many more people.

If the only way you can attempt to rebuke relativity is to lie about it then you're a derisible individual.

 

[Motor Daddy]

All you can say is "the other guy is going faster than I am by 20m/s." That's the only speed he can see, thus the only speed is 20 m/s.

I'm gonna try this again, since the last ten times I explained it you missed it.

Two rockets in space and the distance between them is increasing at the rate of 20 m/s. How do you know which direction of travel they are each traveling? If at t=0 the distance between them is 100 meters, at t=1 the distance between them is 120 meters. Do you think it's possible that each rocket could be traveling in different directions, possibly even at the same speed (gasp!)?

If unbeknownst to the rockets the rockets were each traveling away from the center of a huge sphere inside the sphere, would each rocket eventually hit the same point on the inside of the sphere or would the rockets eventually hit at opposite points of the sphere?Maybe they would hit 90 degrees apart, or 359 degrees apart. Changing where the rockets depart the sphere changes the absolute velocity of the rockets, but the relative velocity always stays the same!

 

[Motor Daddy]

AN, I have no desire to respond to your nonsensical statements.

 

[origin]

I'm gonna try this again, since the last ten times I explained it you missed it.

Two rockets in space and the distance between them is increasing at the rate of 20 m/s. How do you know which direction of travel they are each traveling? If at t=0 the distance between them is 100 meters, at t=1 the distance between them is 120 meters. Do you think it's possible that each rocket could be traveling in different directions, possibly even at the same speed (gasp!)?

Sure, there is no way to know, you only know their relative velocity.

Changing where the rockets depart the sphere changes the absolute velocity of the rockets, but the relative velocity always stays the same!

No, you still cannot know the absolute velocity - you can only measure the velocity relative to the sphere - this is not an absolute velocity.

 

[Motor Daddy]

Sure, there is no way to know, you only know their relative velocity.

Correct, and hence, it is IMPOSSIBLE to know if one ship is traveling faster than the other! That is unless you know how to calculate the absolute velocity!

No, you still cannot know the absolute velocity - you can only measure the velocity relative to the sphere - this is not an absolute velocity.

I know the absolute velocity! I can determine that the sphere is at an absolute zero velocity. If the sphere is in absolute motion I can tell you the absolute velocity of the sphere and the absolute velocity of each rocket!

 

[Motor Daddy]

Sure, there is no way to know, you only know their relative velocity.

...and the facts are that the relative velocity remains unchanged and yet the pendulum is swinging! You have a contradiction!

 

[origin]

Correct, and hence, it is IMPOSSIBLE to know if one ship is traveling faster than the other! That is unless you know how to calculate the absolute velocity!

Correct, you only know the relative velocity between the ships. This has been stated multiple times in this thread already. You cannot calculate the absolute velocity.

I know the absolute velocity! I can determine that the sphere is at an absolute zero velocity.

All you are doing is making the sphere a reference so that you can give the rockets a velocity relative to the reference frame (your sphere).

If the sphere is in absolute motion I can tell you the absolute velocity of the sphere and the absolute velocity of each rocket!

Really? How do you propose to tell me the absolute velocity of the sphere?

 

[Motor Daddy]

Correct, you only know the relative velocity between the ships. This has been stated multiple times in this thread already. You cannot calculate the absolute velocity.

You mean YOU only know the relative velocity of the ships. I know the relative velocity and the absolute velocities of the ships. I also want to reiterate that I explain the swinging pendulum, you don't!

All you are doing is making the sphere a reference so that you can give the rockets a velocity relative to the reference frame (your sphere).

I don't need the sphere, it's just a mental visual aid to allow you to understand direction. I know the velocity of the sphere according to the light sphere.

Really? How do you propose to tell me the absolute velocity of the sphere?

You emit a light sphere from the center point of the sphere. When the expanding light sphere hits the walls of the sphere equally at all points on the sphere then the sphere is at an absolute zero velocity. If the expanding light sphere doesn't hit the walls at the same time then there is a time differential which can be used to calculate the absolute velocity of the sphere. Once the absolute velocity of the sphere is known then the absolute velocity of the rockets can be known.

 

[origin]

You emit a light sphere from the center point of the sphere. When the expanding light sphere hits the walls of the sphere equally at all points on the sphere then the sphere is at an absolute zero velocity. If the expanding light sphere doesn't hit the walls at the same time then there is a time differential which can be used to calculate the absolute velocity of the sphere. Once the absolute velocity of the sphere is known then the absolute velocity of the rockets can be known.

Once again we return to your refusal to accept reality. I know that for some reason you do not like certain aspects of reality but you do not have the power to change it!

The light emitted from the center of the sphere will hit the walls of the sphere equally at all points on the sphere regardless of the velocity of the sphere. That this is true has been shown experimentally, it is not debatable - sorry.

Reality wins and you lose.

 

[Motor Daddy]

Once again we return to your refusal to accept reality. I know that for some reason you do not like certain aspects of reality but you do not have the power to change it!

The light emitted from the center of the sphere will hit the walls of the sphere equally at all points on the sphere regardless of the velocity of the sphere. That this is true has been shown experimentally, it is not debatable - sorry.

Reality wins and you lose.

How do you know if the velocity of the sphere changes or not since all you have is relative velocity?

 

[gmilam]

You emit a light sphere from the center point of the sphere. When the expanding light sphere hits the walls of the sphere equally at all points on the sphere then the sphere is at an absolute zero velocity. If the expanding light sphere doesn't hit the walls at the same time then there is a time differential which can be used to calculate the absolute velocity of the sphere. Once the absolute velocity of the sphere is known then the absolute velocity of the rockets can be known.

Won't the light always hit the walls of the sphere simultaneously for an observer within the sphere?

 

[Motor Daddy]

Won't the light always hit the walls of the sphere simultaneously for an observer within the sphere?

Absolutely not! Light travels independently of objects.

 

[origin]

...and the facts are that the relative velocity remains unchanged and yet the pendulum is swinging! You have a contradiction!

There is no contradiction. The 2 rockets have no relative velocity between them, then they accelerate at exactly the same rate and after a certain amount of time they stop accelerating. There is still no relative velocity between the rockets. The absolute velocity before the acceleration is unknown. After the acceleration the speed is:
[the unknown initial absolute velocity] + [velocity increase due to the acceleration] = Unknown absolute velocity.