Relativity And Simple Algebra

[ralfcis]

This at the 5:00 mark:

 

 

I think Brian Greene comes off as a nice guy. I think other scientainers like Neil deGrasse Tyson and Prof Brian Cox also come off as nice guys. But either they're all compulsive liars (not Michio Kaku though) trying to hype up science to make a buck or are just too stupid to not understand the stream of logical contradictions spewing out of their mouths. Brian Greene seems to be trying to sell the idea that light should propagate like a thrown football but doesn't because of the miracle of relativity. All waves propagate through mediums and the physical characteristics of elasticity and inertia or, in the case of electromagnetic waves, the equivalent electromagnetic characteristics of inductance (permeability) and capacitance (permittivity) define their relative velocities to their media, not to their sources. As I just found out, thanks to Popeye, the relative velocity of the receivers to the wavefronts is not called relative velocity but closing speed.

 

Greene states the speed of the train should kick the light forward faster to the president of backwardland or pull it away faster from the president of forwardland but that's just not how waves work. There's nothing magical that relativity brings to the table here. In actual fact, from the perspective of people on the platform,  the motion of the train is pulling the president of backwardland away from the light and pushing the other guy faster toward the light. So they are seeing the motion of the train affect the closing speed (Newtonian relative velocity) of the two presidents relative to the light. But relativity states their relative velocity to the light is always c. Relativity avoids this contradiction by stating closing speed is not subject to this rule. What a fraud.

 

Well obviously, as stated, that statement is a lie made a lie by differentiating Newtonian relative velocity from relativistic relative velocity. On the train, the two presidents measure their relative velocity to the speed of light as c regardless of the speed of the train. So what? that would be true from inside the train's perspective  of baseballs or sound waves thrown from inside the train. Relativistic effects only come into play from the outside perspective of what's going on inside the train and this is what relativity fails to mention in its statement about the constancy of the speed of light.

 

If baseballs were thrown inside the train, the people on the platform would agree with the presidents inside the train that they both caught the baseballs simultaneously because baseballs are not subject to relative velocity to a medium. Soundwaves should have a different result than the baseballs because sound velocity is relative to a medium. So the air is still (motionless) inside the train which is relatively moving to the still air outside the train. So long as the train's windows are closed, there is a relative velocity between the two air mediums and the observers on the platform would hear the airhorn and agree that both presidents signed at the same moment. The only weird thing would be the difference in the pitch of the airhorn depending on where the observers were placed on the platform. But we're still not getting relativistic effects or anything different from the baseballs result.

 

So let's see what happens if we have the signing ceremony in an open box car so the outside air flows over the presidents creating a wind for them. Their velocity relative to the medium would delay the airhorn blast to the president of backwardland from both the platform's and the train's perspectives. Still not like relativity.

 

So what's the one thing different about light waves and sound waves that creates relativistic effects for light and not for sound? The answer is in the Michelson Morley experiment. Whether you have an open train or a closed train, the velocity of the train can't affect the medium so it can't affect the velocity of light through that medium. That medium can't be put in a boxcar and register a relative velocity to the medium outside that boxcar. The train can't register a relative velocity to the medium as it sees no difference in the speed of light inside the train to the speed of light outside the train. If it could register a relative velocity to light's medium, it should see a difference when comparing the two light speeds. But this does not mean that the presidents inside the train can't be pulled away or pushed towards the light so it hits them sooner or later to the outside perspective. If this wasn't renamed as closing speed, it would be a relative velocity and violate the constancy of the speed of light if light speed was not capped as the max speed limit. Please note there are two assumptions at play here. It's not only the assumption of the constancy of c but the fact that the constant is pegged to the maximum possible value.

 

The light takes longer but it travels further to hit the president being pulled away from it from the outside perspective so the speed of light is maintained as constant. The same is true of the president going toward the light from the platform's perspective. The light travels less time over less distance. So what's the big deal, the speed of light is constant without relativity's help. The problem relativity is trying to solve is the inside perspective of how far the light travels and in what time. This is where they came up with length contraction and time dilation to try to reconcile the two perspectives and maintain the constancy of the speed of light. Is this even necessary? Apparently so but I don't understand why based on Greene's example. I'm sure the real truth is out there somewhere but relativists will never share it willingly. Greene's example is a fraud of unresolved contradictions.

 

I hope some of you were able to overcome your brains redacting much of my post.

 

P.S. The answers to all my questions here were finally resolved much later in this thread. The short answer is the relativity of simultaneity on when an approaching ship starts its clock simultaneously with the start of an approaching light signal allows the light a head start from the ship's perspective. It's complicated, you need to see the detailed explanation evolve in this thread.

Edited December 19, 2019 by ralfcis

[sluggo]

Just checking the crockpot. Nope, it's not soup yet.

[Moronium]

Suit yourself, Ralf.  I tried to help you.  Maybe if you dwell on all this for a few years you'll see it for yourself.

 

As for your "religious" accusations, look in the mirror.  I can understand, compare, and contrast the pros and cons of both SR and a PFT.  You can't.  You, like many others, seem to have a quasi-religious faith in SR, and are therefore not free to think past that.

Edited February 21, 2019 by Moronium

[Moronium]

1. What does A "see" the speed between himself and E to be?  A has a VELOCITY of 0.8c with respect to E

 

2,  What does A calculate the speed be E and B to be? A calculates that B has a VELOCITY of 0.8 c with respect to E

 

E sees a closing speed between A and B of 1.6 c

 

E calculates the relative velocity between A and B of 0.975c

 

I really don't care that much about the numbers here, but I don't believe all these statements are correct.  Nor do I believe that all my questions were answered, your assurances notwithstanding, Popeye.

 

1.  I disagree with the first two claims, pertaining to what A "sees."  I'll come back to this.

 

2.  I agree that E "sees" the closing (i.e. opening) speed to be 1.6 and I agree that he "calculates" it to be .975c.  I asked a question about which one is right?  What he "sees" (i.e.actually measures) or what he calculates?  I got no answer to that. Which is reliable, his radar gun, or his pencil and paper calculations? 

 

I believe that what he actually calculating is not the speed between A and B, but rather what he thinks THEY must see the speed between them to be.  SR prohibits them from seeing the speed between them to be greater than c.

 

3. But what A "sees" must be be calculated from his own frame of reference, not that of E.  In other words, A must assume his own speed is 0 (in SR, anyway).  He will not "see" the speed between himself and E to be .8c, nor will he "see" the speed between E and B to be .8c.  The same is true of B.  What he "sees" must be determined from the perspective that his own speed is 0.  

Edited February 22, 2019 by Moronium

[Moronium]

2.  I agree that E "sees" the closing (i.e. opening) speed to be 1.6 and I agree that he "calculates" it to be .975c.  I asked a question about which one is right?  What he "sees" (i.e.actually measures) or what he calculates?  I got no answer to that. Which is reliable, his radar gun, or his pencil and paper calculations? 

 

Another thing to consider here:  Both what E measures and what he calculates are based on the premise that he is absolutely motionless in space, i.e. that HIS speed is 0.

 

If he is wrong in that assumption then his calculations regarding the relationship between A and B will not be accurate.  

 

To illustrate:   Since he assumes his speed his 0, he claims that B is moving away from him.   But what if B's speed were 0 and his was .8c?  Then he would be moving away from B, rather than vice versa.  This is where the "direction" becomes important where you treat velocity as a vector.  It's a difference between using a positive (+) sign in your calculations and a negative (-) one.

 

Furthermore, his radar gun would still measure .8c if he were going .1c and B were going .9c.  But that would change his assessment of A's motion relative to B also.

Edited February 22, 2019 by Moronium

[Moronium]

So, Ralf, if you assume that A's speed is 0, and if you use E's calculation (whether right or wrong), then A will say that B is moving .975c relative to him.  Using those numbers, what would A calculate the speed between himself and E to be?  I guarantee that it will not be .8c.  Nor will it be .975c/2.

 

 

Since you love math, I'll leave it to you.  I don't care enough to do it myself.

 

Then see what you get from B's perspective (B's speed is 0 and A's speed relative to him is .975c).  Now what does B say E's speed is relative to him?

 

There's a point to this which goes beyond the math.

Edited February 22, 2019 by Moronium

[Moronium]

And then we have neanderthals like this

 

Polly, insulting me will not get me to respond to your nonsensical spam.  It's content may get you a response from the moderators, however.

[OceanBreeze]

I really don't care that much about the numbers here, but I don't believe all these statements are correct.  Nor do I believe that all my questions were answered, your assurances notwithstanding, Popeye.

 

1.  I disagree with the first two claims, pertaining to what A "sees."  I'll come back to this.

 

2.  I agree that E "sees" the closing (i.e. opening) speed to be 1.6 and I agree that he "calculates" it to be .975c.  I asked a question about which one is right?  What he "sees" (i.e.actually measures) or what he calculates?  I got no answer to that. Which is reliable, his radar gun, or his pencil and paper calculations? 

 

I believe that what he actually calculating is not the speed between A and B, but rather what he thinks THEY must see the speed between them to be.  SR prohibits them from seeing the speed between them to be greater than c.

 

3. But what A "sees" must be be calculated from his own frame of reference, not that of E.  In other words, A must assume his own speed is 0 (in SR, anyway).  He will not "see" the speed between himself and E to be .8c, nor will he "see" the speed between E and B to be .8c.  The same is true of B.  What he "sees" must be determined from the perspective that his own speed is 0.  

 

 

They are both right. You think there is some sort of paradox here because you are mixing relativistic and non-relativistic solutions in a relativistic problem.

 

Closing speed is, one more time, NOT a velocity. There is nothing physical moving at that speed, only the gap between the two rockets is increasing at that rate of speed. There is no information being transferred at that speed. It actually has nothing to do with relativity. It is very much the same as the intersection point on a pair of scissor blades or the laser pointer scanning across the face of the moon. It may be interesting to ponder on a rainy day, but other than that it is of no importance in physics.

 

On the other hand, E’s radar gun tells him A is moving away at 0.8c to the East and B is moving away at 0.8c to the West. These are actual measured velocities!

 

If E wants to know the relative velocity between A and B, he adds these velocities according to Einstein’s velocity addition formula. This formula is derived directly from the Lorentz transformation, which you seem to accept. That relative velocity is 0.9756c.

 

Now, I have answered your questions several times already, and I am 100% sure you still either don’t understand or don’t want to understand. Either way, I will not be answering these questions again.

[OceanBreeze]

So, Ralf, if you assume that A's speed is 0, and if you use E's calculation (whether right or wrong), then A will say that B is moving .975c relative to him.  Using those numbers, what would A calculate the speed between himself and E to be?  I guarantee that it will not be .8c.  Nor will it be .975c/2.

 

 

Since you love math, I'll leave it to you.  I don't care enough to do it myself.

 

Then see what you get from B's perspective (B's speed is 0 and A's speed relative to him is .975c).  Now what does B say E's speed is relative to him?

 

There's a point to this which goes beyond the math.

 

 

"There's a point to this which goes beyond the math"

 

 

Yes, and that point is called The Twilight Zone.

 

I'm not interested in it.

[Moronium]

On the other hand, E’s radar gun tells him A is moving away at 0.8c to the East and B is moving away at 0.8c to the West. These are actual measured velocities!

 

There is nothing physical moving at that speed, only the gap between the two rockets is increasing at that rate of speed.

 

 

 

 

Heh, Popeye, and you want to talk about a twilight zone?

[Moronium]

Closing speed is, one more time, NOT a velocity.

 

 

What is the meaningful distinction in this case?  

 

What would the significance be, seeing as how all three objects are aligned in a straight line? What is the big difference between VELOCITY and speed here?  I can see that it would make a difference if one was going north and the other east--perpendicular to each other.  But they're not.  They're going in opposite directions (forming a line).

 

The speed is the velocity.  As I said earlier:

 

But when it's all in one dimension (a straight line), velocity is speed, right?  Although velocity may technically be a vector, it's basically a scalar in those circumstances.  That's different than a guy travelling in a circle.

 

Relative to a given point you can say a guy is going north at 100 mph but nothing changes if you leave out the word "north."  You could substitute east, south, or west, and it would still be the same, i.e, 100 mph relative to that given point.

 

 

 

What difference does it make, with respect to relative speed, to say that one is going east and the other west?  Does that change their speed?  If so, how? If not, how does capitalizing the word VELOCITY answer my questions?

 

It seems to me that it's a distinction without a difference.

 

In most contexts the words "sufficient" and "enough" are synonyms.  It's true that they are different words, but the meaning is the same, so there's no meaningful difference.

 

What does using the word VELOCITY instead of speed explain?  If it were a speed would it be something other than .975c?  Like maybe .900c?  What is the difference between speed and velocity in this case?  Brian Greene (and many, many others) use the two words interchangably in this context.  Are they wrong to do so?

 

What is magic about the word VELOCITY that changes everything?

Edited February 22, 2019 by Moronium

[Moronium]

I'll give you my answer.  In SR a THIRD party is allowed to see a closing speed between two objects which exceeds c (but it can never exceed 1.99c)  But the two objects he is viewing CANNOT (because they're not allowed to) see themselves that way.  But that is not because there's a difference between velocity and speed.

 

Your answer seems to be a mystical one:  If two objects are moving away from each other at a speed that appears (to a third party) to exceed c, then they are not moving at all.  Each is motionless.  It's just that the space between them is expanding.  Or they are partly moving, and partly space is just expanding. Something like that.

 

There is nothing physical moving at that speed, only the gap between the two rockets is increasing at that rate of speed.

 

 

You're right, I don't understand. And I'm afraid that capitalizing the word VELOCITY doesn't help me understand it.

Edited February 22, 2019 by Moronium

[Moronium]

I'll give you my answer.  In SR a THIRD party is allowed to see a closing speed between two objects which exceeds c (but it can never exceed 1.99c) 

 

If there's nothing physically moving, then why can't an observer in SR see a "closing speed" of 3c, or 4c, or 5c?

 

The answer:  Because, just like everyone else in SR, he is not allowed to see any object physically moving at a speed in excess of c.

Edited February 22, 2019 by Moronium

[Moronium]

This formula is derived directly from the Lorentz transformation, which you seem to accept.

 

 

You're right, I do accept the LT.  I don't accept the way it's original meaning, purpose, and use has been modified by SR, though.

Edited February 22, 2019 by Moronium

[Moronium]

Just in case you doubt me, here's some backup from wiki:

 

The rate at which two objects in motion in a single frame of reference get closer together is called the mutual or closing speed. This may approach twice the speed of light, as in the case of two particles travelling at close to the speed of light in opposite directions with respect to the reference frame....Special relativity does not prohibit this.

 

 

https://en.wikipedia.org/wiki/Faster-than-light#Closing_speeds

 

The closing speed can approach, but never equal or exceed, 2c.  But that's not because there is no physical motion.  Physical motion is presupposed.  If it weren't, then the closing speed could exceed 2c. A closing speed is NOT the same thing as moving a laser beam across the face of the moon.

Edited February 22, 2019 by Moronium

[Moronium]

They are both right. You think there is some sort of paradox here because you are mixing relativistic and non-relativistic solutions in a relativistic problem.

 

No, I'm not mixing relativistic and non-relativistic solutions.   This should have been clear from what I said in the post you were responding to:

 

I believe that what he actually calculating is not the speed between A and B, but rather what he thinks THEY must see the speed between them to be.  SR prohibits them from seeing the speed between them to be greater than c.  

Edited February 22, 2019 by Moronium

[Moronium]

I believe that what he actually calculating is not the speed between A and B, but rather what he thinks THEY must see the speed between them to be.  SR prohibits them from seeing the speed between them to be greater than c.

 

 

This is also confirmed by wiki:

 

Special relativity does not prohibit this. It tells us that it is wrong to use Galilean relativity to compute the velocity of one of the particles, as would be measured by an observer traveling alongside the other particle. That is, special relativity gives the correct velocity-addition formula for computing such relative velocity.

 

 

Same link as last.