If Two Spaceships Close at 1.4c...?

[LightHeavyW8]

I am disinclined to acquiesce to your request. Being the thread author gives you input on what is not on-topic and in the areas of the forums where you have a position (be it opinion or a proposal), the right to defend your position. i.e. you have the right to respond to questions asked of you or about a position you hold that can only be known to you. It does not, however, afford you a monopoly on questions regarding objective information, in this case established physics — you are free to answer, of course, but nobody else is required to wait around for you to do so. Nor does it prevent others from weighing in with their own opinions, when that's appropriate. I would think that having a physicist rebut an erroneous statement would be preferable, as it should carry more weight, but even of you don't agree, I don't see where your proposal is within the spirit or letter of any rules or guidelines of the site.

Then let's take a hypothetical example. X intends to hijack a thread, so he creates sock puppets Y and Z to create a bogus argument on that thread. What may the author of the thread do to prevent said hijacking?

[D H]

Then let's take a hypothetical example. X intends to hijack a thread, so he creates sock puppets Y and Z to create a bogus argument on that thread. What may the author of the thread do to prevent said hijacking?

The same thing you would do if X tried to hijack the thread without creating sockpuppets: Report the post. There's a little warning sign icon and the word "Report" at the bottom left of every post.

 

Just because you made the original post of this thread does not mean that this is "your" thread. The thread, any thread, is community property at this site. (Pretty much the same concept applies to almost all internet fora.)

 

 

[LightHeavyW8]

The same thing you would do if X tried to hijack the thread without creating sockpuppets: Report the post. There's a little warning sign icon and the word "Report" at the bottom left of every post.Just because you made the original post of this thread does not mean that this is "your" thread. The thread, any thread, is community property at this site. (Pretty much the same concept applies to almost all internet fora.)

 

What is it that Napoleon says in Animal Farm? Something like "All animals are equal, but some are more equal than others"...

[swansont]

The same thing you would do if X tried to hijack the thread without creating sockpuppets: Report the post. There's a little warning sign icon and the word "Report" at the bottom left of every post.

 

Just because you made the original post of this thread does not mean that this is "your" thread. The thread, any thread, is community property at this site. (Pretty much the same concept applies to almost all internet fora.)

 

The main difference being that sockpuppets are a more direct avenue to banning. They're a felony, while hijacking is a misdemeanor.

 

——

 

You're responsible for what you post. But if you want the level of control over the discussion you propose, LightHeavyW8, you need to start up a blog.

[steevey]

Although I have not as yet determined if time passes more slowly or more quickly after retirement, it has allowed me to explore subjects heretofore archived, such as Relativity. If the speed of light in a vacuum, c, is the same for every observer, does it follow that no information may be exchanged among observers at a speed greater than c? Quantum tunneling experiments appear to have succeeded in this regard. But how about space travelers?

 

c is constant. c is always c. Quantum tunneling or at least entanglement doesn't require distance e.i. the properties become instantaneously detirmined for ane another regardless of the distance, which is different from shooting photons at higher speeds that you are suggesting.

[LightHeavyW8]

<br />c is constant. c is always c. Quantum tunneling or at least entanglement doesn't require distance e.i. the properties become instantaneously detirmined for ane another regardless of the distance, which is different from shooting photons at higher speeds that you are suggesting.<br />

So you say c is always c? Si, si, I see! Perhaps you would to care to weigh in on THIS

 

 

LHW

Edited January 28, 2011 by LightHeavyW8

[swansont]

We do agree, however, that EO observes "A & B exchanging info at 1.7 c", do we not?

 

No, I don't think anyone agrees to that.

[LightHeavyW8]

<br />No, I don't think anyone agrees to that.<br />

 

Umm, do we agree that EO sees A & B collide at 1.4c? That WAS how I posed the experiment, you know.

 

LHW

[swansont]

Umm, do we agree that EO sees A & B collide at 1.4c? That WAS how I posed the experiment, you know.

 

LHW

 

Yes, but that's a very different statement.

[LightHeavyW8]

<br />Yes, but that's a very different statement.<br />

 

Then if the light from A precedes A itself, how does the light not reach B sooner, i.e., at 1.7c as seen by EO, as Janus' animation shows?

 

LHW

[losfomot]

Then if the light from A precedes A itself, how does the light not reach B sooner, i.e., at 1.7c as seen by EO, as Janus' animation shows?

 

LHW

 

Yes, B and the the light from A will have a 'closing speed' of 1.7c... but this question is still different from the other statement in question:

 

As far as I can tell, the bottom line is that just as there is no problem with EO observing A & B close at 1.4 c, there is no problem with EO observing A & B exchanging info at 1.7 c by using light, although A & B will not see it that way.

 

The problem with this statement is that you are mixing frames mid-sentence. "A & B exchanging info at 1.7 c" throws us into the reference frame of either A or B, where they are clearly NOT exchanging info at 1.7c... whether or not the EO is observing them.

[LightHeavyW8]

<br />Yes, B and the the light from A will have a 'closing speed' of 1.7c... but this question is still different from the other statement in question:<br /><br /><br /><br />The problem with this statement is that you are mixing frames mid-sentence. "A & B exchanging info at 1.7 c" throws us into the reference frame of either A or B, where they are clearly NOT exchanging info at 1.7c... whether or not the EO is observing them.<br />

 

No, I am NOT mixing frames, although some of the other posters feel compelled to introduce them incessantly. My statement is that the EO observes A & B colliding at 1.4c, and if it is true that light from A reaches B even sooner, then EO observes A & B exchanging info at 1.7c, just like the operator of a particle collider uses "closing speed" to know WHEN particle collision occurs. Nothing in my statements require light to exceed c through space.

 

LHW

[losfomot]

No, I am NOT mixing frames, although some of the other posters feel compelled to introduce them incessantly. My statement is that the EO observes A & B colliding at 1.4c, and if it is true that light from A reaches B even sooner, then EO observes A & B exchanging info at 1.7c, just like the operator of a particle collider uses "closing speed" to know WHEN particle collision occurs. Nothing in my statements require light to exceed c through space.

 

LHW

 

Sorry, that is a presumption... not an observation.

 

The EO observes a light signal from A 'closing' with ship B at 1.7c

 

The EO therefore presumes (incorrectly) that A & B are exchanging info at 1.7c

[LightHeavyW8]

<br />Sorry, that is a presumption... not an observation.<br /><br />The EO <b>observes</b> a light signal from A 'closing' with ship B at 1.7c<br /><br />The EO therefore <b>presumes</b> (incorrectly) that A & B are exchanging info at 1.7c<br />

 

INCORRECTLY??? What do we have, trompe-l'œil again? Can B send a laser pulse to EO when he receives the light from A to let EO know the light got to B? If so, has not EO witnessed information exchanged between A & B at 1.7c?

 

LHW

[swansont]

No, I am NOT mixing frames, although some of the other posters feel compelled to introduce them incessantly. My statement is that the EO observes A & B colliding at 1.4c, and if it is true that light from A reaches B even sooner, then EO observes A & B exchanging info at 1.7c, just like the operator of a particle collider uses "closing speed" to know WHEN particle collision occurs. Nothing in my statements require light to exceed c through space.

 

LHW

 

Which means the information is traveling at c, and why I object to "exchanging information at 1.7c."

[losfomot]

INCORRECTLY??? What do we have, trompe-l'œil again? Can B send a laser pulse to EO when he receives the light from A to let EO know the light got to B? If so, has not EO witnessed information exchanged between A & B at 1.7c?

 

LHW

I apologize, I do not understand your (french?) reference.

 

Why would B need to send a laser pulse to EO? We already have janus' animation, so an extra laser pulse is redundant.

 

The problem is that your wording is (purposely?) misleading.

 

I don't know how I can make it any clearer than my last post.... how about this...

 

If you want to know how fast information was truly exchanged between A and B... You will have to ask either A, or B... you cannot rely on any other observer (EO) to give you a correct answer (unless you knew you could trust that observer to have the correct formula, a good calculator, and believed in the laws of physics)

 

edit - ahhh... trompe-l'œil... I love that type of art.

Edited January 28, 2011 by losfomot

[LightHeavyW8]

&lt;br /&gt;I apologize, I do not understand your (french?) reference.&lt;br /&gt;&lt;br /&gt;Why would B need to send a laser pulse to EO? We already have janus' animation, so an extra laser pulse is redundant.&lt;br /&gt;&lt;br /&gt;The problem is that your wording is (purposely?) misleading.&lt;br /&gt;&lt;br /&gt;I don't know how I can make it any clearer than my last post.... how about this...&lt;br /&gt;&lt;br /&gt;If you want to know how fast information was truly exchanged between A and B... You will have to ask either A, or B... you cannot rely on any other observer (EO) to give you a correct answer (unless you knew you could trust that observer to have the correct formula, a good calculator, and believed in the laws of physics)&lt;br /&gt;&lt;br /&gt;edit - ahhh... &lt;a href='http://en.wikipedia.org/wiki/Trompe-l%27%C5%93il' class='bbc_url' title='External link' rel='nofollow external'&gt;trompe-l'œil&lt;/a&gt;... I love that type of art.&lt;br /&gt;

Well, maybe we're getting to the heart of the matter - why would A or B have a BETTER idea about the information exchange rate than EO? Does he not, like the collider operator, have a valid idea - in fact, EO appears to be the one with the BEST idea about when they will collide, imo. The purpose of B sending a laser pulse to EO is to confirm, for any skeptics, that indeed, B received light from A before the collision, thus proving that,according to EO, A and B exchanged information at 1.7c, even though, according to A & B, the info exchange occurred at c.

 

LHW

Edited January 28, 2011 by LightHeavyW8

[phyti]

This correctly reflects the rate at which the distance between the two particles is decreasing, from the observer's point of view and is called the closing speed.

...

Did not traveler A receive "information" about the impending collision even faster, at 2.39c? Do travelers A and/or B still merrily exist in their own space-time continua even AFTER observers on Earth see them annihilated?

 

You answered your own question here, but are confusing closing speed with absolute propagation speed of light.

The speed of an object is the rate of change of position relative to a reference point. The rate of change of the space between A and B by E is not the same thing as the speed of A or B by E. The space is not an object moving relative to E, but is the rate of A moving relative to B as measured by E. For consistency, all measurements should have a common ref. point, which in this case is E.

Light at c, A at .7c, B at -.7c.

If A sends a warning signal to B, it requires:

distance/speed = 1.4 light sec/ 1.7c = approx .8 sec, giving a warning of approx .2 sec.

The warning signal still moves at c in space relative to E, but B is simultaneously moving toward the signal at .7c in the same space, i.e., time is a function of both speeds.

[LightHeavyW8]

You answered your own question here, but are confusing closing speed with absolute propagation speed of light.

I will yield the point that light will get from A to B before the collision, but if you pick up the thread from HERE, I maintain that I am not the one who is confused. And will at least ONE poster at least acknowledge that scaling up the known behavior of particle colliders to spaceships makes for an interesting discussion?

 

LHW

[Janus]

I will yield the point that light will get from A to B before the collision, but if you pick up the thread from HERE, I maintain that I am not the one who is confused.

This does not change the fact that you are confused. The fact that, in the EO frame, A transmits information from its starting point to some point at c and that B travels from its starting point to that same point in the same time, is not the same as A transfering information to B at greater than c.

And will at least ONE poster at least acknowledge that scaling up the known behavior of particle colliders to spaceships makes for an interesting discussion?

 

But it doesn't. Scaling up adds nothing significant to the discussion.

[LightHeavyW8]

This does not change the fact that you are confused. The fact that, in the EO frame, A transmits information from its starting point to some point at c and that B travels from its starting point to that same point in the same time, is <i>not</i> the same as A transfering information to B at greater than c. <br /><br />But it doesn't. Scaling up adds nothing significant to the discussion.<br />

1. Does EO see A & B close and collide at 1.4c? (yes or no)

2. Does EO see the light from A reach B sooner, i.e., at 1.7c? (yes or no)

3. If B sends a laser pulse to EO when B receives the light from A, will this not confirm to EO that EO has seen information exchanged between A & B at 1.7c? (yes or no)

 

LHW

[swansont]

You seem to be hell-bent on changing the definition of information exchange. Under your personal definition, yes. Under the definition the rest of us are using, no. Generally we prefer to all use the same definitions so that we can discuss things, instead of wasting time squabbling about definitions.

 

The information is contained in the light signal. It travels at c.

[LightHeavyW8]

You seem to be hell-bent on changing the definition of information exchange. Under your personal definition, yes. Under the definition the rest of us are using, no. Generally we prefer to all use the same definitions so that we can discuss things, instead of wasting time squabbling about definitions. The information is contained in the light signal. It travels at c.

Well, this seems to be as close to vindication as I am going to get - Thank you!

 

 

LHW

[phyti]

1. Does EO see A & B close and collide at 1.4c? (yes or no)

 

 

yes, if .2 sec is not enough time for an evasive maneuver!

 

2. Does EO see the light from A reach B sooner, i.e., at 1.7c? (yes or no)

 

no, at c.

Light speed is constant in space, independent of the motion of any object, thus it only has one speed, c.

E sees the signal leave A at (t=0,x=-.7) and meet B at (t=.8,x=.1). Light traveled at .8 ls/.8 s = 1c.

 

3. If B sends a laser pulse to EO when B receives the light from A, will this not confirm to EO that EO has seen information exchanged between A & B at 1.7c? (yes or no)

 

no, as explained in 2.

 

If there was no time dilation for A and B, they would calculate the 1.4c closing speed relative to each other.

For E it's a comparison of A-speed to B-speed, but that's not the same as calculating the speed of an object,since there is no object moving at 1.4c.

 

The only reason particles are directed in head-on collisions is because it's not possible to accelerate them in one direction to c.

[LightHeavyW8]

Phyti - You must have missed Janus' Animation

 

 

LHW

Edited January 31, 2011 by LightHeavyW8