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> Length Contracted Earth Diameter?, actual vs apparent contraction
mik
Posted: Nov 29 2012, 08:02 PM


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I just got banned from yet another science forum, so I'm back with my usual diatribe against length contraction.
Here is my best example of how absurd it is.
A frame of reference flies by Earth at .866c. It (the "observer") sees Earth's diameter as about 4000 miles in the direction of his travel, a severely oblate spheroid.
Of course, the measurement from the frame at rest with Earth is nearly 8000 miles.
SR insists that there is no preferred frame, that all frames are equally valid, and that length is not invariant. So SR's length contraction advocates insist that 4000 miles is an equally valid measurement of Earth's diameter.
This is of course blatantly ridiculous.
What say you experts on length contraction here?
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pascaltriangle
Posted: Nov 29 2012, 08:16 PM


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Better to ask some of the female forum posters- male members (if I can use that term) can't deal with length contraction rationally....

Jess Tauber
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Confused1
Posted: Nov 29 2012, 08:50 PM


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You need to include time dilation to make any sense of your conundrum. I am male and have come terms with length contraction - it's an age thing. -C2.
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mik
Posted: Nov 29 2012, 09:23 PM


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Does anyone here speak science and have a serious answer?
An Earth diameter contracted to 4000 miles by virtue of a frame passing at .866c... does anyone here buy that?


This post has been edited by mik on Nov 29 2012, 09:27 PM
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Confused1
Posted: Nov 29 2012, 09:37 PM


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The average muon sees the Earth approach at about 0.98c see (for example)
http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/muon.html
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mathman
Posted: Nov 29 2012, 09:55 PM


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QUOTE (mik @ Nov 29 2012, 08:02 PM)
I just got banned from yet another science forum, so I'm back with my usual diatribe against length contraction.
Here is my best example of how absurd it is.
A frame of reference flies by Earth at .866c. It (the "observer") sees Earth's diameter as about 4000 miles in the direction of his travel, a severely oblate spheroid.
Of course, the measurement from the frame at rest with Earth is nearly 8000 miles.
SR insists that there is no preferred frame, that all frames are equally valid, and that length is not invariant. So SR's length contraction advocates insist that 4000 miles is an equally valid measurement of Earth's diameter.
This is of course blatantly ridiculous.
What say you experts on length contraction here?

The "actual" diameter of the earth is the diameter in the frame where the earth is at rest.
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Confused1
Posted: Nov 29 2012, 10:17 PM


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Brucep clarifies the point here (and in many other posts):
http://www.physforum.com/index.php?showtop...ndpost&p=553309

For 'actual' substitute 'proper', add some understanding of relativity and it will all become much clearer.
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mik
Posted: Nov 30 2012, 12:07 AM


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QUOTE (mathman @ Nov 29 2012, 09:55 PM)
The "actual" diameter of the earth is the diameter in the frame where the earth is at rest.

Yes.
The diameter does not change. Only the frames of reference change.
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mik
Posted: Nov 30 2012, 12:10 AM


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If anyone here believes that physical objects shrink (as per length contraction), please explain the physics of that shrinkage. Compacted atoms? By what force?
Observation is not a force that changes physical objects.

This post has been edited by mik on Nov 30 2012, 01:04 AM
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VioletSilence
Posted: Nov 30 2012, 09:24 AM


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QUOTE (mik @ Nov 30 2012, 12:10 AM)
If anyone here believes that physical objects shrink (as per length contraction), please explain the physics of that shrinkage. Compacted atoms? By what force?
Observation is not a force that changes physical objects.


I feel you are sort of fighting with SR?!
Are you looking to the earth as particle or wave?!

http://www.aip.org/history/heisenberg/p08.htm
http://en.wikipedia.org/wiki/Uncertainty_principle smile.gif
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VioletSilence
Posted: Nov 30 2012, 09:31 AM


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QUOTE (pascaltriangle @ Nov 29 2012, 08:16 PM)
Better to ask some of the female forum posters- male members (if I can use that term) can't deal with length contraction rationally....

Jess Tauber

laugh.gif

I have made some device to sort that problema!!!call it Vibra***g device, so by adding extra horizontal sub -particle vibrations, shrink solved!! blink.gif
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Ed Wood
Posted: Nov 30 2012, 01:57 PM


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mik

When seen from the particle accelerator collisions perspective and the length contraction is very real and measured.

Particle collisions are currently the only way to truly test length contraction and so far in particle accelerators across the world collision energies match the predictions of relativity.

That being said get in your .866C ship and look out your window while approaching the earth you will see the earth contracted for a brief time because lets face it at that speed you ain't gonna see it coming for very long.
If you run into it you could tell us how big or small it is.

However I think you would probably agree that running into the earth would be inadvisable to say the least.
We on the ground could measure the energy released when you hit according to the current particle accelerator experiments we would measure E=MC^2/1/SQRTV^2/C^2.
Again I think you may probably agree for you that would be inadvisable. by the way we would have to insist that make sure you hit an unpopulated area because if you make it through the atmosphere the explosion will be very large.

Of course there is probably a safer way to do this as the earth 'appears to be length contracted' the mass of the earth fits in half the diameter this should in theory increase the gravitational field via the Schwarzschild metric and you should be able to measure the change in gravity with an accelerometer if there is an increase in gravity the length contraction is very real if not it is perceived as you suggest.

Keep in mind that where in the shell you measure the gravity @ rest is where you need to be when you make the measurement at speed for comparison and since what you are seeing out your window will make no sense you may want to have another entity plot your trajectory.

There are other things to consider for this experiment but this about as much effort as I am willing to put into it @ the moment. I know you are probably just a troll but I will make an effort to help you educate your self if you are willing to do so.

Have a nice day.
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Confused1
Posted: Nov 30 2012, 03:20 PM


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For 'proof' of length contraction see:
http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/muon.html

Section:"Relativistic, Muon-Frame Observer"
QUOTE
The muon sees distance [ 10km ] as length-contracted so that L=L_0/gamma
=0.2L_0
=2km

The experiment requires no 'acts of faith' .. just measurements.
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Ed Wood
Posted: Nov 30 2012, 05:35 PM


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QUOTE (Confused1 @ Nov 30 2012, 03:20 PM)
For 'proof' of length contraction see:
http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/muon.html

Section:"Relativistic, Muon-Frame Observer"

The experiment requires no 'acts of faith' .. just measurements.

Certainly a lot simpler.
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mik
Posted: Nov 30 2012, 06:17 PM


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I'll try another approach to the absurd task of arguing that Earth's diameter does not change ("actually"*) as it might "appear"* to change from various frames. (* see title ref.)

A thousand space ships fly by Earth at 1000 different high (relativistic) velocities and in 1000 different direction.
Each of them "sees" a different diameter and contracted in a different direction.
Q: Does Earth change into 1000 different shapes or does it just appear differently to all those ships? (Duh!... hmmmm)
Oh, and since it is a massive physical object, what force is applied in all these different directions... or even the original one... to squeeze it to radically oblate?

Ps: I am familiar with the evidence for subatomic length contraction as very small particles are accelerated by very powerful force. How does this apply to my example? I am aware of no direct evidence for large scale length contraction.
Incoming muons are often cited as such, but they simply "live longer" than expected at lower velocity and therefore travel further than expected, as high velocity slows down their rate of decay. The atmosphere does not shrink in depth/thickness around each muon.

This post has been edited by mik on Nov 30 2012, 06:21 PM
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