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relativity

 
 
Reply Wed 29 Jan, 2014 11:40 am
On the ground Albert and Isaac inspect the new spaceship their university has purchased. They find it nice and spacious measuring 25 m in length. Later in the day Isaac takes off in the new spaceship to explore the galaxy. After the spaceship has reached cruisespeed, Albert find that its length has contracted to 10 m. What is the speed of the spaceship?
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Type: Question • Score: 3 • Views: 3,514 • Replies: 47
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dalehileman
 
  0  
Reply Wed 29 Jan, 2014 12:41 pm
@alexjlaonnae,
Roughly .9c

http://www.fourmilab.ch/cship/lorentz.html

The time required to reach this speed however might be six months

http://books.google.ca/books?id=ehV-updqqKoC&pg=PA32&lpg=PA32&dq=to+reach+.9c&source=bl&ots=on3ehK88GV&sig=oV4UsWrI5qZe5xiYrs3RBftd3fM&hl=en&sa=X&ei=m0rpUpS8HM7xoATQ0YLwBA&ved=0CD8Q6AEwAw#v=onepage&q=to%20reach%20.9c&f=false
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Romeo Fabulini
 
  1  
Reply Wed 29 Jan, 2014 12:57 pm
But somebody on board would find that their tape measure has shrunk by 10 metres too, so there'd be no way of knowing the ship had shrunk
dalehileman
 
  1  
Reply Wed 29 Jan, 2014 02:47 pm
@Romeo Fabulini,
Yea Fab and in fact maybe it hadn't. Suppose in our corner of the Universe it's the local galaxies traveling at .97c, and after his takeoff it's Isaac who's stationary

Incidentally I have a theory countering the Einsteinian assertion that a moving object shrinks; though OT here and earlier rejected by a2k's Great Intellectual Majority. If you're at all interested however I could revisit in a new thread
Romeo Fabulini
 
  1  
Reply Wed 29 Jan, 2014 05:03 pm
@dalehileman,
Post your theory here if you like, Alex titled it 'Relativity' so he'd probably be interested too..Smile
dalehileman
 
  1  
Reply Wed 29 Jan, 2014 06:32 pm
@Romeo Fabulini,
In a few inadequate words, to satisfy the intuitive quest for more nearly consistent answers, I maintain strange phenomena entailed in relative motion such as mass gain, shrinkage of length, slowing of clock, etc are easily seen to be the result of underestimating an object's velocity. Where its apparent speed is c, its actual speed would instead be infinite. This doesn't contradict Einstein but only gives us a different way of looking at time-at-a-distance

Let's say Albert and Marty synchronize clocks by the usual means, then later Isaac takes off at noon, almost instantly arriving at Mars 12:05 Marty's time, confirming that yes, Al, Marty must be 5 light minutes distant. But an explanation more welcome to the intuition says at Isaac's noon takeoff Marty's time is not also noon but instead 12:05

(I hasten to explain the above slightly simplified: Actually Isaac takes off from Victorville, Ca, passing Al noon in New York at apparent velocity c. Yes he's a very sturdy fella to withstand such acceleration

….and of course Isaac can't quite reach that speed because it's impossible)

By conventional relativity, at noon by Al's clock it's 11:55 to 12:05 on Marty's, depending on the observer's state of motion. So I merely ask Al to adopt Isaac's viewpoint, that the distant clock actually is reading 12:05 at his takeoff.

So at any point in the Universe the individual may think of himself contained in concentric spheres each representing a successive time reading

Al's observation that Isaac gets heavier is because he underestimates Isaac's speed, the evident shrinking of Isaac's ship because he sees both front and rear of the vehicle at the same instant, and the "slowing" of his clock because the trip is in fact instantaneous
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rosborne979
 
  1  
Reply Wed 29 Jan, 2014 08:47 pm
@Romeo Fabulini,
Romeo Fabulini wrote:

But somebody on board would find that their tape measure has shrunk by 10 metres too, so there'd be no way of knowing the ship had shrunk

I suspect that's why alexjlaonnae implied that Albert remained on the ground and was the one doing the measuring.

You are correct however that the person on board the ship would not be able to detect any change.
dalehileman
 
  1  
Reply Thu 30 Jan, 2014 12:03 pm
@rosborne979,
Quote:
I suspect that's why alexjlaonnae implied that Albert remained on the ground and was the one doing the measuring.
Yea Fab, we always have to leave Al behind. As I had outlined, at that instant on Earth Al supposes Marty's time is noon even though Isaac pegs it at 12:05

For purpose of simplicity I hadn't detailed this third assertion: Without any sort of prior announcement Marty had fired up his own ship at 11:55 his time, was just passing by Al and Isaac at noon their time. However to him it's still 11:55 at Home Base

(I should explain however that Isaac's clock reads 12:00. However he's aware that conventional relativity teaches the later reading upon clocks left behind by Marty)

Relativity entertains a largely unspoken assumption that in spite of the above relativistic relationships placing the time on mars as 12:00 plus or minus 5 minutes that the observations of both parties in motion are somehow invalid, that it really is noon upon Mars. This I dispute, maintaining that Isaac's observation is the most nearly realistic and the basis for my theory above

….which so nearly explains all the apparent peculiar relativistic mutations of Isaac and his ship observed by Al, makes 'em available to the Mind's Eye

……and why c is impossible of achievement. It's not because the object gets so massive but simply because an infinite velocity is impossible
contrex
 
  1  
Reply Thu 30 Jan, 2014 04:57 pm
@dalehileman,
dalehileman wrote:
……and why c is impossible of achievement. It's not because the object gets so massive but simply because an infinite velocity is impossible


But c isn't infinite.
dalehileman
 
  1  
Reply Thu 30 Jan, 2014 05:18 pm
@contrex,
Quote:
But c isn't infinite.
Of curse not Con but if you'll review my posts above you'll see I was proposing a view of relativity supposing that velocity is underestimated and that the speed of light is actually infinite
contrex
 
  2  
Reply Fri 31 Jan, 2014 02:09 am
@dalehileman,
dalehileman wrote:

Quote:
But c isn't infinite.
Of curse not Con but if you'll review my posts above you'll see I was proposing a view of relativity supposing that velocity is underestimated and that the speed of light is actually infinite


But c has been measured; and just one example - radio altimeters would not work unless c was finite and known.
dalehileman
 
  1  
Reply Fri 31 Jan, 2014 11:43 am
@contrex,
Quote:
But c has been measured
Sorry Con if you've misunderstood but please do review my postings above. Certainly by conventional thinking the speed of light c is 186,283 mps more or less. I merely propose a different way of viewing Einstein's observations in which conventional velocity is underestimated

At Isaac's takeoff while the relativity of time-at-a-distance places the reading of Marty's clock at noon plus or minus five minutes, my view, which out of sheer chutzpa I call "relative relativity" carries Einstein one step further: It affords special significance to Isaac's supposition

At risk of repetition, then, at that moment it isn't noon on Mars but 5 minutes later

Emphasizing again my perspective by no means denies Einstein, merely explains without resort to complex math of no significance to Minds' Eye, all the peculiar changes apparently taking place in the moving object

So Isaac having made the trip instantaneously for instance explains why the journey seemed to him so quick, why at his arrival Marty's clocks reads 12:05
contrex
 
  1  
Reply Fri 31 Jan, 2014 02:29 pm
@dalehileman,
dalehileman wrote:
I merely propose a different way of viewing Einstein's observations in which conventional velocity is underestimated


Between 1924 and 1931, Albert Abraham Michelson didn't "calculate" or "estimate" the speed of light, he measured it. He used a light beam shining along paths of known lengths and reflected back by an 8 sided rotating mirror.

Knowing the rotational speed of the mirror, the angle of reflection, and the length of the path, the speed of the light beam may be obtained. Michelson got a figure of 299,774 km/s with a possible error of plus or minus 11 km/s. (The current best estimate is 299,792.458 km/s)

I would be interested to know what you think was wrong with Michelson's experiment.


dalehileman
 
  1  
Reply Fri 31 Jan, 2014 02:56 pm
@contrex,
Quote:
I would be interested to know what you think was wrong with Michelson's experiment.
Absolutely nothing Con. You have misunderstood my speculation, and again I invite you to reread my postings above, apologizing most profusely for your confusion

Please anybody, I need help here
Romeo Fabulini
 
  1  
Reply Fri 31 Jan, 2014 03:37 pm
Sorry guys I can't keep up with all this abstract speculation stuff (sniffle)
All I know is that if the chap at the top bounces a ball at the exact same time as a guy in the train at the bottom bounces his, time is FORCED to slow down for the guy on the train to allow the ball to cover the greater distance from A to B in the same time relative to the guy at the top, at least I think so...

http://i53.photobucket.com/albums/g64/PoorOldSpike/RelativityH_zps7a110ab4.png~original
rosborne979
 
  1  
Reply Fri 31 Jan, 2014 04:29 pm
@Romeo Fabulini,
Ugh. What a mess your brain is.
0 Replies
 
rosborne979
 
  1  
Reply Fri 31 Jan, 2014 04:31 pm
@dalehileman,
dalehileman wrote:
Please anybody, I need help here

I can't see any way to help you. Nothing you're saying seems to make any sense at all.
dalehileman
 
  1  
Reply Fri 31 Jan, 2014 04:55 pm
@rosborne979,
Quote:
Nothing you're saying seems to make any sense at all
Specifically Ros what might I clarify
rosborne979
 
  1  
Reply Fri 31 Jan, 2014 05:18 pm
@dalehileman,
dalehileman wrote:

Quote:
Nothing you're saying seems to make any sense at all
Specifically Ros what might I clarify

As Contrex has said, the speed of light has been measured, it's not infinite. You need to clarify how your argument about it being infinite (or in any way different from measured speed) can be valid.
dalehileman
 
  1  
Reply Fri 31 Jan, 2014 05:40 pm
@rosborne979,
Quote:
You need to clarify how your argument about it being infinite (or in any way different from measured speed) can be valid.
But Ros I thought I had

Maybe it isn't convincing but neither were Einstein's assertions at the very first. Hitler called 'em "Jewish Science." It's not that I'm comparing myself to Einstein of course, it's only that I'm comparing your reaction to that of Hitler

Forgive me Ros, I couldn't resist the temptation

Please help me, anyone who gets my drift, even if you basically disagree, I will understand

 

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