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Martin Winer
science forum addict
Joined: 01 Mar 2006
Posts: 88
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 Posted: Fri Jun 23, 2006 4:24 am Post subject:
'fast' rotating planet effects?
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Thanks so much to everyone who replied to:
http://groups.google.ca/group/sci.physics.relativity/browse_thread/thread/5ad2a9870f26641f?hl=en
the above thread. I'm sorry I didn't actively participate, but google
didn't notify me there were so many posts.
However, I have a different question, which (I think) is more
interesting.
Imagine a planet spinning at 1/2c. That is, imagine a polar view of a
planet. The pole isn't moving at all. The surface however, is moving
at 1/2c relative to the pole at a tangential course.
Next this fast rotating planet is moving away from your planet at 0.75c
ie:
^
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0.5c(<------------r------------>(pole)<------------r------------>) 0.5c
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V |
0.75c
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(observer_planet)
Question, what does this planet look like?
Here's my guess. It looks exactly the same as a planet with zero
rotation moving away from you at 0.75c (ie, larger than a planet that
has 0 relative motion). However, it appears shifted to the left by the
fast rotation.
Has this question been answered already?
Thanks again...MCW |
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Martin Winer
science forum addict
Joined: 01 Mar 2006
Posts: 88
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| Posted: Thu Jun 29, 2006 4:53 am Post subject:
Re: 'fast' rotating planet effects?
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martin.winer@gmail.com wrote:
| Quote: | Thanks so much to everyone who replied to:
http://groups.google.ca/group/sci.physics.relativity/browse_thread/thread/5ad2a9870f26641f?hl=en
the above thread. I'm sorry I didn't actively participate, but google
didn't notify me there were so many posts.
However, I have a different question, which (I think) is more
interesting.
Imagine a planet spinning at 1/2c. That is, imagine a polar view of a
planet. The pole isn't moving at all. The surface however, is moving
at 1/2c relative to the pole at a tangential course.
Next this fast rotating planet is moving away from your planet at 0.75c
ie:
^
|
|
|
|
0.5c(<------------r------------>(pole)<------------r------------>) 0.5c
| ^
|
| |
|
V |
0.75c
|
|
(observer_planet)
Question, what does this planet look like?
Here's my guess. It looks exactly the same as a planet with zero
rotation moving away from you at 0.75c (ie, larger than a planet that
has 0 relative motion). However, it appears shifted to the left by the
fast rotation.
Has this question been answered already?
Thanks again...MCW
|
Ok, stupid me... the rotation slows down right? Because of time
dilation? |
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Tim Golden
science forum Guru Wannabe
Joined: 12 May 2005
Posts: 176
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| Posted: Thu Jun 29, 2006 8:50 pm Post subject:
Re: 'fast' rotating planet effects?
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martin.winer@gmail.com wrote:
| Quote: | martin.winer@gmail.com wrote:
Thanks so much to everyone who replied to:
http://groups.google.ca/group/sci.physics.relativity/browse_thread/thread/5ad2a9870f26641f?hl=en
the above thread. I'm sorry I didn't actively participate, but google
didn't notify me there were so many posts.
However, I have a different question, which (I think) is more
interesting.
Imagine a planet spinning at 1/2c. That is, imagine a polar view of a
planet. The pole isn't moving at all. The surface however, is moving
at 1/2c relative to the pole at a tangential course.
Next this fast rotating planet is moving away from your planet at 0.75c
ie:
^
|
|
|
|
0.5c(<------------r------------>(pole)<------------r------------>) 0.5c
| ^
|
| |
|
V |
0.75c
|
|
(observer_planet)
Question, what does this planet look like?
Here's my guess. It looks exactly the same as a planet with zero
rotation moving away from you at 0.75c (ie, larger than a planet that
has 0 relative motion). However, it appears shifted to the left by the
fast rotation.
Has this question been answered already?
Thanks again...MCW
Ok, stupid me... the rotation slows down right? Because of time
dilation?
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Wouldn't the planet just fall apart?
Maybe better to ask this for a solid steel ball.
Also maybe want to state the equator travels 0.5 c relative to the
axis.
I read the other one too.
Nice challenges.
I cannot answer them.
-Tim |
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N:dlzc D:aol T:com (dlzc)
science forum Guru
Joined: 25 Mar 2005
Posts: 2835
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| Posted: Fri Jun 30, 2006 12:09 am Post subject:
Re: 'fast' rotating planet effects?
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Dear martin.winer:
<martin.winer@gmail.com> wrote in message
news:1151556792.216276.254880@j72g2000cwa.googlegroups.com...
A reality check. Solid, tiny, very strong material gyros cannot
be made to spin even close to 0.001c. Just so you know.
| Quote: | Next this fast rotating planet is moving away
from your planet at 0.75c
ie:
^
|
|
|
|
0.5c(<------------r------------>(pole)<------------r------------>)
0.5c
| ^
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| |
|
V |
0.75c
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(observer_planet)
Question, what does this planet look like?
|
http://hermes.physics.adelaide.edu.au/~dkoks/Faq/Relativity/SR/rigid_disk.html
| Quote: | Here's my guess. It looks exactly the same as a
planet with zero rotation moving away from you at
0.75c (ie, larger than a planet that has 0 relative
motion). However, it appears shifted to the left by
the fast rotation.
Has this question been answered already?
|
Pretty close. The problem is, this cannot be a real planet.
Additionally, every part of the planet (except the axis of
rotation) is accelreating.
| Quote: | Thanks again...MCW
Ok, stupid me... the rotation slows down right?
Because of time dilation?
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Would only change the "magnitude", not the "sign".
David A. Smith |
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Spoonfed (www.spoonfedrel
science forum Guru Wannabe
Joined: 28 Apr 2006
Posts: 144
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| Posted: Fri Jun 30, 2006 4:27 pm Post subject:
Re: 'fast' rotating planet effects?
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martin.winer@gmail.com wrote:
| Quote: | Thanks so much to everyone who replied to:
http://groups.google.ca/group/sci.physics.relativity/browse_thread/thread/5ad2a9870f26641f?hl=en
the above thread. I'm sorry I didn't actively participate, but google
didn't notify me there were so many posts.
However, I have a different question, which (I think) is more
interesting.
Imagine a planet spinning at 1/2c. That is, imagine a polar view of a
planet. The pole isn't moving at all. The surface however, is moving
at 1/2c relative to the pole at a tangential course.
Next this fast rotating planet is moving away from your planet at 0.75c
ie:
^
|
|
|
|
0.5c(<------------r------------>(pole)<------------r------------>) 0.5c
| ^
|
| |
|
V |
0.75c
|
|
(observer_planet)
Question, what does this planet look like?
Here's my guess. It looks exactly the same as a planet with zero
rotation moving away from you at 0.75c (ie, larger than a planet that
has 0 relative motion). However, it appears shifted to the left by the
fast rotation.
Has this question been answered already?
Thanks again...MCW
|
I happened to find this article online with the example of the
appearance of a fast-rotating cube.
http://bkocay.cs.umanitoba.ca/Students/Theory.html.
Since all of the motion of the spinning cube is perpendicular to the
measurable lengths, the only visible effect is caused by differences in
propagation time for light from different parts of the cube.
If you were to travel at constant velocity with respect to the cube,
then length contraction and desynchronization (more commonly
"relativity of simultaneity") would have to be considered as well. To
give some idea of what this would look like, have a look at
http://casa.colorado.edu/~ajsh/sr/contraction.html (Note that the wheel
here appears stationary, but it should be pictured rolling across the
screen, or else the distortions shown would not appear.)
You can mathematically define this spinning cube, but I think that if
you tried to accelerate a physical cube from a stop to spinning with
its outer diagonal moving at .5c with respect to the axis, you would
have to consider material properties of the cube. |
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Martin Winer
science forum addict
Joined: 01 Mar 2006
Posts: 88
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| Posted: Wed Jul 05, 2006 8:47 pm Post subject:
Re: 'fast' rotating planet effects?
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is it me or have we 'discovered' a black hole? Look at a fast spinning
body from the polar view. As we've discussed it would have to have
extremely high density to hold together. From the polar view, it would
be a black hole, nothing, not even light itself could escape. However,
as we've discussed, the high spin rate would cause anything beyond a
certain radius to spin off. This could/would release energy exactly as
hawkins predicted (that black holes have silver linings).
The high spin rate would cause any particle to have a high relative
velocity relative to a given frame of reference. This would time-slow
the particle such that the ball would spin itself apart slowly over
time relative to any given observation frame.
So basically, a black hole is a super dense ball, spinning itself to
pieces but it appears slow to us because of relativity. Perhaps?
Spoonfed wrote:
| Quote: | martin.winer@gmail.com wrote:
Thanks so much to everyone who replied to:
http://groups.google.ca/group/sci.physics.relativity/browse_thread/thread/5ad2a9870f26641f?hl=en
the above thread. I'm sorry I didn't actively participate, but google
didn't notify me there were so many posts.
However, I have a different question, which (I think) is more
interesting.
Imagine a planet spinning at 1/2c. That is, imagine a polar view of a
planet. The pole isn't moving at all. The surface however, is moving
at 1/2c relative to the pole at a tangential course.
Next this fast rotating planet is moving away from your planet at 0.75c
ie:
^
|
|
|
|
0.5c(<------------r------------>(pole)<------------r------------>) 0.5c
| ^
|
| |
|
V |
0.75c
|
|
(observer_planet)
Question, what does this planet look like?
Here's my guess. It looks exactly the same as a planet with zero
rotation moving away from you at 0.75c (ie, larger than a planet that
has 0 relative motion). However, it appears shifted to the left by the
fast rotation.
Has this question been answered already?
Thanks again...MCW
I happened to find this article online with the example of the
appearance of a fast-rotating cube.
http://bkocay.cs.umanitoba.ca/Students/Theory.html.
Since all of the motion of the spinning cube is perpendicular to the
measurable lengths, the only visible effect is caused by differences in
propagation time for light from different parts of the cube.
If you were to travel at constant velocity with respect to the cube,
then length contraction and desynchronization (more commonly
"relativity of simultaneity") would have to be considered as well. To
give some idea of what this would look like, have a look at
http://casa.colorado.edu/~ajsh/sr/contraction.html (Note that the wheel
here appears stationary, but it should be pictured rolling across the
screen, or else the distortions shown would not appear.)
You can mathematically define this spinning cube, but I think that if
you tried to accelerate a physical cube from a stop to spinning with
its outer diagonal moving at .5c with respect to the axis, you would
have to consider material properties of the cube. |
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