
#55
Aug1510, 08:02 AM

P: 169





#56
Aug1510, 08:02 AM

P: 836





#57
Aug1510, 08:05 AM

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P: 38,904

[tex]\frac{.75c .75c}{1+ \frac{(.75c)(.75c)}{c^2}}= 0[/tex], of course. 



#58
Aug1510, 08:06 AM

P: 169

We measure 2Ls of distance. In merely 1.333 secs, we measure NO distance between us. How is that not 1.5c? 



#59
Aug1510, 08:08 AM

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Is the light therefore travelling at greater than 1.5 times the speed of light? That would be totally illogical as we started by assuming it travels at the speed of light. 



#60
Aug1510, 08:08 AM

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Wow, 57 posts in less than 3 hours! That may be a record. James S Saint, you are doing all of your computations as if Newtonian physics applied. Naturally, you are going to get a contradiction to relativity.




#61
Aug1510, 08:09 AM

P: 169

To put it simply (I hope)
We measure 2Ls of distance. 1.333 secs later, we measure 0 distance. How is that possible? 



#62
Aug1510, 08:09 AM

Mentor
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You say "US", but you are actually using ground frame measurements. 



#63
Aug1510, 08:09 AM

P: 1,162





#64
Aug1510, 08:10 AM

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You are confusing a closing speed greater than c with something actually moving with a speed greater than c in some reference frame. But that's not the case. 



#65
Aug1510, 08:12 AM

P: 169

Now if I can just get them to follow logic... grin. :) 



#66
Aug1510, 08:13 AM

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Imagine a 100m race. If someone runs 100m in 10 secs (assuming constant speed), but the finsihing linen approaches them at the same speed, do we say they ran 100 m in 5 secs? No we don't bceause we're talking about the frame in which both the runner and the finsihing line are moving,therefore the runner ran 50m in 5 secs. 



#67
Aug1510, 08:14 AM

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#68
Aug1510, 08:16 AM

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It's not a problem with 'logic', but with your understanding of physics. 



#69
Aug1510, 08:18 AM

P: 169

We (my brother and I  the only people involved) measured 2Ls of distance between us. It doesn't matter where we were. It doesn't matter if there was a ground. We could have simply met in space and slowly backed away to a distance of 2Ls. No distortions involved. But 1.333 secs later, we are back where we started. The "problem" is that we are measuring speed by time and distance which tells us that one of us traveled at 1.5c. We can't really know which one of us. But SOMETHING happened faster than light. 



#70
Aug1510, 08:20 AM

P: 169




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