Here comes Comet Lulin, a backward-flying lulu passing Earth on...

Full story: Chicago Tribune

An odd, greenish backward-flying comet is zipping by Earth this month, as it takes its only trip toward the sun from the farthest edges of the solar system.
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1 - 12 of 12 Comments Last updated Mar 19, 2009
Wrong Way

Chicago, IL

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#1
Feb 23, 2009
 
Isn't the rotation direction relative to your frame of reference? How you do determine whether any object is orbiting clockwise or counter-clockwise, when you can turn everything upside-down and everything rotates the other way, kind of like looking at a transparent clock from the back?
greg

Yankton, SD

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#2
Feb 23, 2009
 
any leftover heavens gate people out there? time to climb aboard!!!
George

Oswego, IL

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#3
Feb 23, 2009
 
Is North upward or downward?
Will

Highwood, IL

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#4
Feb 23, 2009
 
Wormwood...
HankB

Wheaton, IL

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#5
Feb 23, 2009
 
Wrong Way wrote:
Isn't the rotation direction relative to your frame of reference? How you do determine whether any object is orbiting clockwise or counter-clockwise, when you can turn everything upside-down and everything rotates the other way, kind of like looking at a transparent clock from the back?
I suppose astronomers adopt an arbitrary frame of reference like a right hand rule: Hold your hand with fingers curled and thumb extended. With fingers pointing in the direction of rotation, the thumb points up. That would explain why most everything rotates counter clockwise if that's the normal frame of reference.
Atheist

United States

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#6
Feb 23, 2009
 
Because of its distance from our solar system when it travels out, can this dispel any notion that the Earth/Universe is only 11,000 years old?

I am sure some "Christian" will have some sort of illogical explanation for it.
Doktor No

Hayfield, MN

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#8
Feb 23, 2009
 
Gnarly! Will I get up to see it? Maybe. Just to say I did.
Love that star name, Zubenelganubie. Persian name I assume?
TYPO

Chicago, IL

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#9
Feb 23, 2009
 
Atheist wrote:
Because of its distance from our solar system when it travels out, can this dispel any notion that the Earth/Universe is only 11,000 years old?
I am sure some "Christian" will have some sort of illogical explanation for it.
Amen
First Hand

Chicago, IL

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#10
Feb 23, 2009
 
Wrong Way wrote:
Isn't the rotation direction relative to your frame of reference? How you do determine whether any object is orbiting clockwise or counter-clockwise, when you can turn everything upside-down and everything rotates the other way, kind of like looking at a transparent clock from the back?
You are correct. Thanks for bringing this up. This is how I demonstrate this to my students: imagine that I am riding my bicycle in front of the class, from left to right. To a student, my front wheel seems to rotate clockwise, and yet as I return to the left side of the classroom, still going forward, the wheel appears to be turning clockwise. Is there an astronomers' agreement about 'up' in the solar system? If there is, then I take this all back.
RonMania

Easton, PA

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#11
Feb 23, 2009
 

Judged:

1

HankB wrote:
<quoted text>
I suppose astronomers adopt an arbitrary frame of reference like a right hand rule: Hold your hand with fingers curled and thumb extended. With fingers pointing in the direction of rotation, the thumb points up. That would explain why most everything rotates counter clockwise if that's the normal frame of reference.
Personally I like the overlapping grip!
Dileep Sathe

Pune, India

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#13
Mar 10, 2009
 
The recent approach of comet Lulin reminds the collision of comet Shoemaker-Levy with the Jupiter in July 1994. As Jupiter has several moons, a comet can collide with a moon. But some of them are forward orbiting and some in the opposite, so predicting the collision is bit difficult. The said difficulty takes us to a global n chronic problem in the teaching / learning of Circular Motion. Interested readers can see my Letter in Physics Education, a bimonthly from UK, November 1995, p. 327 or contact me on +91-020-65100495 or my cellphone: 9922467861or write me on "Prerana Apts / A-40 / Kasturba Society / Dighi Post / Pune / MH / 411015 / INDIA
Dileep Sathe

Pune, India

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#15
Mar 19, 2009
 
The example, discussed by i)wrong way, ii) HankB and iii) First Hand, include only one body and so the question of clockwise /counter-clockwise is not very crucial. But what if there were two bodies in the opposite directions. See my comment of 10th March again. Also see my Letter in Physics Education UK, July 2007, which regarding a high school pupil, Josie.

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