Bicycle tire and FTL question

[trisco]

If I have a bicycle wheel that is spinning and the edge of the tire is near the <br />speed of light what happens if I inflate the tire a little to increase <br />the radius. Does the edge of the tire ever reach the speed of light <br />(assuming no loss of speed due to larger diameter or whatever may cause <br />it to slow down in the real world). If it does reach the speed of <br />light what will happen if I put more air in the tire? Will the tires <br />edge now be going faster than light or does it do some other wierd <br />thing that I can't imagine? <br /><br /><br />

 

[yevaud]

Look on it this way: spinning in reference to what? If everything is rotating, what is the actual velocity to an observer? <br /><br />Here's an analogy: the Earth is rotating. Do you even notice the fact? No, not without some outside reference point, such as the sun, moon, stars, etc.<br /><br />Our universe doesn't have an "outside." <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>

 

[harmonicaman]

No can do...<br /><br />When you are dealing with velocities close to "c" (the speed of light), you can't just add velocity in the usual way; you must deal with this awe-inspiring formula:<br /> <br /><b>w = (u + v)/(1 + uv/c²)</b><br /><br />No matter how fast you try to go (at relativistic velocities) you can never add enough velocity to exceed "c".<br /><br />BTW - this is a very common physics problem sometimes called the "Addition of Velocities" paradox.<br />

 

[yevaud]

Right you are. You merely get incrementally closer, but never achieve it. <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>

 

[trisco]

even if the problem is purely math and not thought of in a physical sense?

 

[yevaud]

Particularly so. <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>

 

[harmonicaman]

Time

 

[trisco]

I guess I just cant understand why it could never reach or exceed the speed of light. When I was in school my physics instructor would always things as "in a perfect situation". <br />

 

[yevaud]

Compare the analogy I made with the image you posted. Say the tire is spinning, and you're standing at the hub.<br /><br />What's moving with respect to you? Nothing, that's what. It's all the same system, and you're within it - not an independent, outside observer. Which is something of a meaningless concept here. <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>

 

[trisco]

ok but what if I am an independent outside observer?

 

[yevaud]

What you say sounds as if it would be so, but outside of our space/time region, the concept would be meaningless. And as far as we currently know, there *is* no "outside" to the universe. <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>

 

[trisco]

Wow! you guys got over my head in a quick-like hurry! LOL <img src="/images/icons/crazy.gif" />

 

[harmonicaman]

The universe is expanding at "c". To exceed "c" would<br />mean going faster than the universe itself, our laws of<br />physics don't allow this. Of course, we may someday<br />find a way around these constraints but it won't be<br />easy...<br /><br /><b><big>E=mc²</big></b><br /><br />Space is time (not to be confused with thyme, which is<br />an aromatic herb)!

 

[trisco]

I never heard of the "Addition of Velocities" paradox before this post. I think I will do a google search and do a little reading, any suggestions?

 

[harmonicaman]

Yeah, just Google "addition velocities". <br /><br />Best wishes; there's a lot of great stuff to read and<br />think about.<br /><br />Also Google: "Relativistic Rocket" for related discussions.

 

[trisco]

ok, Thanks a lot. I might have more questions after my "study session"! LOL

 

[trisco]

ok, I wasnt talking about two bodies moving toward or away from each other or putting a laser on a rocket. I was simply saying if I were to watch the tire spin could it reach light speed. It just makes sense to me at least that the speed of the tire would increase to that point.

 

[harmonicaman]

No matter how cleverly you state the problem, you'll<br />always encounter the "Addition of Velocities" paradox.<br /><br />In your example, instead of a "Relativistic Rocket", you<br />have a relativistic wheel - this bit of creativity isn't<br />enough to fool the relativity police...

 

[vogon13]

Looking at this from a different angle;<br /><br />A long object , fixed at one end and sweeping out an arc, (assuming material is strong enough to withstand strain) would experience (for lack of a better term) chronometric shearing forces along its length.<br /><br />Time would pass at different rates for atoms in physical contact with each other depending on how far from the center each is.<br /><br />Has anyone considered the behavior of matter under this weird condition?<br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[trisco]

lol, thanks harmonicaman

 

[zer01zero]

There you go vogon, you have just invented time travel. (sort of)<br />With the atoms all in physical contact, you can travel up and down to suit your needs.<br /><br />Just think of it: Want more time to cram for that test? Just travel up "the magic rope" study for a few weeks, then travel back and only a few hours have passed <img src="/images/icons/wink.gif" />