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Question for all you physics geniuses

 
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sdinet



Joined: 25 Jun 2008
Posts: 184

PostPosted: Wed Oct 01, 2008 12:33 pm    Post subject: Question for all you physics geniuses Reply with quote

If you built a piece of conduit with a Teflon interior coating around the world.

And also developed a nano-thread with virtually zero weight or elasticity, and thread it once through the entire piece of conduit.

Then inserted yourself at the begging and end of the conduit, tug one end of the thread, see what happens to the other side and record the time it takes for the one end to move away from you as you tug the other end.

Would the thread INSTANTLY move away from you? And if so, what does this mean? Did the string move at near the speed of light, since it traveled around the world instantly?
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RacerX



Joined: 03 Jan 2006
Posts: 333
Location: Twin Cities, MN

PostPosted: Wed Oct 01, 2008 4:31 pm    Post subject: Reply with quote

Instantly is a false assumption. In the special and general theories of relativity the one constant across all frame of reference is the speed of light. Time is not universal, neither is space, only the speed of light links all frames.

That having been said, there is no material in existence that isn't governed by electromagnetic bonds. Those bonds move at the speed of light, so the upper limit on the speed at which your thought experiment would occur would be the speed of light. So you would see the effect about 0.134 seconds (assuming perfect bonds) after you did your tug.

In reality, the effect would be very imperfect, with energy being lost to radiation (heat) as the effect traveled through the thread.
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helf



Joined: 29 Dec 2005
Posts: 1097
Location: Alabama, USA

PostPosted: Wed Oct 01, 2008 5:14 pm    Post subject: Reply with quote

Several theories, including a relatively new one, state that the speed of light is not constant, either. Smile
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sdinet



Joined: 25 Jun 2008
Posts: 184

PostPosted: Wed Oct 01, 2008 5:42 pm    Post subject: Reply with quote

guess there is only one way to find out, I need to get a roll of 2,000 feet of fishing line, drop it off the side of the sears tower, and measure the time it takes for my tug to get received from the other end.

Now how to get access to an open window on the top of the sears tower....
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RacerX



Joined: 03 Jan 2006
Posts: 333
Location: Twin Cities, MN

PostPosted: Wed Oct 01, 2008 6:35 pm    Post subject: Reply with quote

There are tons of theories floating around, but for a question such as was asked, none of them have been substantiated to the effectiveness needed to even be mention here.

This was the area I went to school for and did research in, but I may be missing some dramatic new finding (though I doubt it). To my knowledge the only place where the speed of light breaks down at is at quantum scales... but then again, time breaks down at that scale too. And even in the cases where you have variable speeds of light, no information can be passed faster than the speed of light.

All of which is pointless to the thought experiment here as the forces and scales involved are all far larger than that.

Also, just as a frame of reference, I will not give any answer to a physics question that uses half-baked (as in incomplete) theories. Studying those theories (and I have been for quite some time) may be fun, but you are providing a major disservice to all if you attempt to site things that have yet to achieve a fair amount of support in the community. String Theory (and all off shoots) are a perfect example of a theory not ready for prime time yet. Sure it is sexy and exciting... but also missing most of the conclusive support that makes for a foundational theory in physics.

And I've argued against Wikipedia for NeXT and Rhapsody related topics, and I'm pretty much against it for all technical subjects.

But for anyone who is truly interested in mathematics or physics, I am launching a math and physics web page later this week. On that page will be links to online courses that are arranged in a way that would provide you with the background (to varying degrees depending on how much work you put into the courses) equivalent to either a bachelors in physics or applied mathematics (sadly I don't have enough to do pure mathematics).

While it is fun to ask these questions (and I'm happy to provide accurate answers), it is even more fun to be able to answer these questions yourself. And that is the goal of my new page.
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helf



Joined: 29 Dec 2005
Posts: 1097
Location: Alabama, USA

PostPosted: Wed Oct 01, 2008 9:03 pm    Post subject: Reply with quote

oh, wow. I'm looking forward to you launching that page. I've always been fond of mathematics, I just suck at it Smile
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RacerX



Joined: 03 Jan 2006
Posts: 333
Location: Twin Cities, MN

PostPosted: Wed Oct 01, 2008 11:17 pm    Post subject: Reply with quote

I think you'd be surprised how much easier mathematics gets the further along you get. The early stuff (that they made you learn by rote) is actually harder (and less fun) than what comes after it. I use mathematics more as a language for describing logical or geometric/topological ideas than for calculating.

And I honestly believe that if you do nothing else but watch most of these courses (in approximate order) that you'll pick up on the language of the mathematics that is being used. And because so much of what is done in math and physics requires some understanding of what came before, this type of stuff helps lay out a good foundation.

Here are some examples of the courses I'm planning on using...

Modern Theoretical Physics I
iTunes version YouTube version
Modern Theoretical Physics II
iTunes version YouTube version
Modern Physics: The Theoretical Minimum - Classical Mechanics
iTunes version YouTube version
Modern Physics: The Theoretical Minimum - Quantum Mechanics
iTunes version YouTube version
Modern Physics: The Theoretical Minimum - Special Relativity and Field Theories
iTunes version YouTube version
Exploring Black Holes: General Relativity & Astrophysics
iTunes version YouTube version RealPlayer version
Gödel, Escher, Bach
RealPlayer version

Basically, I'll have links to course videos (multiple formats if possible), links to additional materials, and a brief review (if I've watched enough of the course to form an opinion). Most of it is laid out in in order of how it might be found at a university, but I'll also have links to articles, papers and seminars that aren't directly part of either course sets (for physics or applied mathematics). The Gödel, Escher, Bach course is that type.
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djb



Joined: 05 Jan 2007
Posts: 18

PostPosted: Fri Oct 17, 2008 4:31 pm    Post subject: Reply with quote

why not simplify the experiment.

Take a single piece of string one on a table top, (assume zero elasticity and zero friction), Pull on one end and watch the other end move at the same time!

What is moving at instantaneously. Well the string is only moving as fast as you pull it, say a few cm per second, but the information, the force is transmitted instantaneously.
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RacerX



Joined: 03 Jan 2006
Posts: 333
Location: Twin Cities, MN

PostPosted: Sat Oct 18, 2008 4:28 am    Post subject: Reply with quote

djb wrote:
why not simplify the experiment...


Which is fine... if your view of the universe is about the same as Newton's.

For the last hundred years or so it has been known that instantaneous is an illusion. But it is an illusion that is just fine for those who want to keep there physics limited to coffee table discussions and experiments.

Any question involving materials involves electromagnetic forces (those governed by Maxwell's Equations). And the development of Special Relativity (which addresses all of these instantaneous scenarios) was in part to remove perceived issues with Maxwell's Equations (which defined the speed of light as the same in every reference frame).

The interaction of atoms are governed by magnetism, which moves at the speed of light. The most perfect materials in existence are still limited by this fact for the OP's question (and your simplified experiment).
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sdinet



Joined: 25 Jun 2008
Posts: 184

PostPosted: Sat Oct 25, 2008 12:12 am    Post subject: Reply with quote

I sent my question to the Naked Scientist, and GOOD NEWS! It was selected to be featured on one of their upcoming podcasts (http://www.thenakedscientists.com/HTML/podcasts/).

I will keep everyone posted with a link to the specific podcast and post their answer!
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RacerX



Joined: 03 Jan 2006
Posts: 333
Location: Twin Cities, MN

PostPosted: Sat Oct 25, 2008 7:04 pm    Post subject: Reply with quote

sdinet wrote:
I sent my question to the Naked Scientist, and GOOD NEWS! It was selected to be featured on one of their upcoming podcasts (http://www.thenakedscientists.com/HTML/podcasts/).

I will keep everyone posted with a link to the specific podcast and post their answer!

Just a few quick questions...

Are you expecting a different answer? And if you weren't going to accept the correct answer here, why would you accept it from them? And why would you even ask the question here if you weren't planning on accepting the answer?

I'm assuming that you felt the need to ask them the question because you didn't get the answer you were expecting... so where are you going to ask this question next when you get the same answer from them? Shocked
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sdinet



Joined: 25 Jun 2008
Posts: 184

PostPosted: Sat Oct 25, 2008 8:35 pm    Post subject: Reply with quote

I submitted my question to this forum and to the naked scientist forum on the same day. They just replied to my question and said it was going to be featured in their upcoming podcast.
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RacerX



Joined: 03 Jan 2006
Posts: 333
Location: Twin Cities, MN

PostPosted: Sun Oct 26, 2008 1:49 am    Post subject: Reply with quote

sdinet wrote:
I submitted my question to this forum and to the naked scientist forum on the same day.
It took them more than three weeks to respond? Strange... it seems like a better question than to end up at the bottom of the pile.

I've never heard of that site... do they cover much physics?
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