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Community => General Discussion => Topic started by: Cobra951 on Wednesday, July 02, 2008, 03:53:15 PM

Title: What the hell is North in the solar system?
Post by: Cobra951 on Wednesday, July 02, 2008, 03:53:15 PM
This story (http://www.cnn.com/2008/TECH/space/07/02/solarsystem.ap/index.html?iref=mpstoryview) is mildly interesting in its own right.  But what really grabbed my attention is an incidental detail that appears right here:

Quote
In 1977, NASA launched two space probes on missions beyond the solar system. Voyager 1 went north and Voyager 2 went south. What startled astronomers is that when the two of them hit the heliosheath they did so at different distances from the sun.

OK, so I'm no astronomer.  But I would think by now I would have heard about the concept of a galactic North or solar system North.  I haven't.  The Earth obviously doesn't point the way.  Its Earth-North axis points at a steep angle away from the ecliptic plane, though not 90 degrees because of the precession.  (Earth wobbles on its orbital path like a top.)  I did a quick search, and so far haven't turned up any info.  It's bugging me.

Edit:  I found some highly technical descriptions of the heliosphere, heliosheath and how the Voyagers 1 & 2 are significant, here (http://web.mit.edu/space/www/helio.review/axford.suess.html) and here (http://www.dartmouth.edu/~hrm/R/heliosphere.html).  No mention of North and South.
Title: Re: What the hell is North in the solar system?
Post by: scottws on Wednesday, July 02, 2008, 07:57:16 PM
OMG I read like 3 paragraphs of the first link before being completely bored out of my mind.
Title: Re: What the hell is North in the solar system?
Post by: Cobra951 on Wednesday, July 02, 2008, 08:06:07 PM
Being so stubborn, I waded through most of it seeking comprehension.  As near as I could figure out, the big deal is that the sun, along with the solar system, is speeding along against a form of galactic wind, which deforms the edge of the heliosphere, or heliosheath.  Voyager 1 & 2 are in the process of intersecting the heliosheath at 2 very different points, at 2 very different distances from the sun.  That supports the deformation theory.  My problem with the CNN story is the North/South bit, because as far as I know, nothing much matters outside of the ecliptic plane, which again AFAIK, coincides with the galactic plane.  So Earth North is irrelevant in this context, unless I'm missing something vital; and I have never ever heard of Earth cardinal points being applied to the rest of the universe.
Title: Re: What the hell is North in the solar system?
Post by: gpw11 on Wednesday, July 02, 2008, 09:01:35 PM
BAM (http://en.wikipedia.org/wiki/Galactic_coordinate_system)
Title: Re: What the hell is North in the solar system?
Post by: Cobra951 on Wednesday, July 02, 2008, 09:37:07 PM
Aha!  Thank you.  I searched for the wrong terms, apparently.  Read a good deal at Wikipedia and their external links, but did not get to land on this.  Yay.  Good job.  :)

Edit:
(http://www.thinkastronomy.com/M13/Manual/common/galactic_coords_files/page1_1.jpg)

Galactic North and South, not too surprisingly, are 90 degrees away from the galactic plane.  So, while I feel much more educated, I'm still just as confused about WTF they have to do with the Voyagers, who have been using slingshot maneuvers past bodies in the ecliptic plane to move further and further away from the sun, toward the edge of our solar system.  At this point, I'll have to guess that CNN is full of shit.

Edit 2:  The only way it would make sense to me now is if my assumption that the ecliptic plane lies on the galactic plane is flatly wrong.
Title: Re: What the hell is North in the solar system?
Post by: Ghandi on Wednesday, July 02, 2008, 10:07:45 PM
Trying to assign two-dimensional models to three-dimensional space is fun. 
Title: Re: What the hell is North in the solar system?
Post by: WindAndConfusion on Thursday, July 03, 2008, 03:36:03 PM
Quote from: Ghandi on Wednesday, July 02, 2008, 10:07:45 PM
Trying to assign two-dimensional models to three-dimensional space is fun. 
The Milky Way is flat.

Alternatively, the Earth is three-dimensional.
Title: Re: What the hell is North in the solar system?
Post by: Cobra951 on Thursday, July 03, 2008, 06:29:09 PM
Quote
The plane of the Milky Way is inclined by about 60° to the ecliptic (the plane of the earth's orbit), with the North Galactic Pole situated at right ascension 12h49m, declination +27.4° (B1950) near beta Comae Berenices. The South Galactic Pole is near alpha Sculptoris.
http://en.wikipedia.org/wiki/Milky_way

Well, that's a surprise.  I guess I've been wrong about that one long enough.  60° angle.  Way steeper than the zero I was assuming.
Title: Re: What the hell is North in the solar system?
Post by: Ghandi on Thursday, July 03, 2008, 08:29:37 PM
Quote from: WindAndConfusion on Thursday, July 03, 2008, 03:36:03 PM
The Milky Way is flat.

Alternatively, the Earth is three-dimensional.

Do I even have to attempt a comeback to this?
Title: Re: What the hell is North in the solar system?
Post by: WindAndConfusion on Friday, July 04, 2008, 12:54:07 AM
You're a twat and your every post consumes electricity that could better be used to feed starving robots.
Title: Re: What the hell is North in the solar system?
Post by: Ghandi on Friday, July 04, 2008, 07:09:53 AM
Your insults would come off as pathetic if only I didn't feel sorry for you. Didn't your mom ask you to clean your room? Move along now.

Quote from: Cobra
Well, that's a surprise.  I guess I've been wrong about that one long enough.  60° angle.  Way steeper than the zero I was assuming.
.

Interesting. It's a little disorienting if you begin to think about how many different directions we are moving at once.

Title: Re: What the hell is North in the solar system?
Post by: Cobra951 on Friday, July 04, 2008, 10:00:13 AM
Yeah, shouldn't we be perpetually dizzy?  We spin, precess (word?), orbit the sun, and ultimately orbit the galaxy like a corkscrew.  Oh, and I forgot the 28-day hula-hoop wobble with the moon.
Title: Re: What the hell is North in the solar system?
Post by: WindAndConfusion on Sunday, July 06, 2008, 02:12:38 AM
Re why we don't get dizzy:

Acceleration due to the sun's gravity: ~6 millimeters per second^2 (http://www.google.com/search?q=gravitational+constant+*+(mass+of+the+sun)+%2F+(1+astronomical+unit)^2)
Acceleration due to the Milky Way's gravity: ~1 nanometer per second^2 (http://www.google.com/search?q=(gravitational+constant)+*+(400+billion+solar+masses)+%2F+(25000+light-years)^2)
Acceleration due to the moon's gravity: ~30 micrometers per second^2 (http://www.google.com/search?q=(gravitational+constant)+*+(mass+of+the+moon)+%2F+(250%2C000+miles)^2)
Acceleration due to centrifugal force of the earth's rotation, measured at the equator: ~1 millimeter per second^2 (http://www.google.com/search?q=((radius+of+the+earth)%2F(24+hours))^2%2F(radius+of+the+earth))

You'll notice the earth's gravity is about 1500 times stronger than the number two force, the sun.

I don't think the human vestibular sense can detect acceleration lower than about 1 centimeter per second^2, and even then only if the acceleration is sudden. The sun's gravity is strong enough that we could almost notice it, but only if it suddenly changed by a significant fraction.

The other thing to consider is angular acceleration. I can just barely notice when my spinning chair starts moving, at about 1 degree per second. The earth's rotation makes us complete one 360 degree rotation every 24 hours, which is about one ten-thousandth of a degree per second. The sun causes a rotation about one 360th of that, and the Milky Way causes a rotation an infinitesimal fraction of that.
Title: Re: What the hell is North in the solar system?
Post by: Antares on Sunday, July 06, 2008, 05:48:16 PM
The other other thing to consider is that Cobra's post was in jest.


You're now officially worse than D.  Hang your head in shame.
Title: Re: What the hell is North in the solar system?
Post by: WindAndConfusion on Sunday, July 06, 2008, 06:28:40 PM
Quote from: Antares on Sunday, July 06, 2008, 05:48:16 PM
The other other thing to consider is that Cobra's post was in jest.
BotE calculations are only fun when they're applied to irrelevant questions.
Quote
You're now officially worse than D.  Hang your head in shame.
Enrico Fermi is laughing at your expense.
Title: Re: What the hell is North in the solar system?
Post by: Quemaqua on Sunday, July 06, 2008, 07:15:22 PM
God, he really is worse than D.
Title: Re: What the hell is North in the solar system?
Post by: WindAndConfusion on Sunday, July 06, 2008, 11:33:32 PM
(click to show/hide)
Title: Re: What the hell is North in the solar system?
Post by: Quemaqua on Sunday, July 06, 2008, 11:45:32 PM
(click to show/hide)
Title: Re: What the hell is North in the solar system?
Post by: WindAndConfusion on Sunday, July 06, 2008, 11:48:38 PM
"Failing"? I only ever used that troll once before, on a forum full of thimerosal paranoiacs. The resultant flamewar was so intense, the entire forum was shut down for at least several weeks.
Title: Re: What the hell is North in the solar system?
Post by: gpw11 on Sunday, July 06, 2008, 11:54:51 PM
Reboot:


(http://graphics8.nytimes.com/images/2007/10/26/us/26bush.600.jpg)


LETS ALL THINK OF FUNNY CAPTIONS!!!
Title: Re: What the hell is North in the solar system?
Post by: Quemaqua on Sunday, July 06, 2008, 11:56:49 PM
From discussion of the solar system to captioning comical political figures.  We're known for complete randomness and frequent thread hijacking, but this is pretty classic.
Title: Re: What the hell is North in the solar system?
Post by: Cobra951 on Monday, July 07, 2008, 08:40:48 PM
Well, I reached the end of my quest.  So I fully endorse this reboot or hijack.

(http://graphics8.nytimes.com/images/2007/10/26/us/26bush.600.jpg)

"Clint was right!  This squinty stare can make this asshohl fade away."
Title: Re: What the hell is North in the solar system?
Post by: scottws on Tuesday, July 08, 2008, 02:43:07 PM
(http://graphics8.nytimes.com/images/2007/10/26/us/26bush.600.jpg)

"Hmm... You know, he kind of does look like a monkey!"
Title: Re: What the hell is North in the solar system?
Post by: Quemaqua on Tuesday, July 08, 2008, 05:00:01 PM
(http://graphics8.nytimes.com/images/2007/10/26/us/26bush.600.jpg)

"I've beaten and maimed four other presidents before him, but I cannot get cocky.  He is a clever beast.  I must wait for the right time to strike."
Title: Re: What the hell is North in the solar system?
Post by: ren on Tuesday, July 08, 2008, 08:02:27 PM
(http://graphics8.nytimes.com/images/2007/10/26/us/26bush.600.jpg)


"California Governor Arnold Schwarzenegger looks at George W. Bush."
Title: Re: What the hell is North in the solar system?
Post by: Ghandi on Tuesday, July 08, 2008, 08:40:30 PM
Quote from: gpw11 on Sunday, July 06, 2008, 11:54:51 PM
(http://graphics8.nytimes.com/images/2007/10/26/us/26bush.600.jpg)

"Wow, this guy makes me sound great when I speak."
Title: Re: What the hell is North in the solar system?
Post by: ren on Tuesday, July 08, 2008, 09:01:50 PM
My emoticon signature is better than your emoticon signature.
Title: Re: What the hell is North in the solar system?
Post by: Ghandi on Tuesday, July 08, 2008, 09:12:05 PM
If you're into that kind of thing.
Title: Re: What the hell is North in the solar system?
Post by: ren on Tuesday, July 08, 2008, 09:14:26 PM
The frog definitely is not
Title: Re: What the hell is North in the solar system?
Post by: Ghandi on Tuesday, July 08, 2008, 09:29:49 PM
He's playing along. Obviously you don't have much experience with these sorts of arrangements. Talk to gpw, he's been in that situation plenty of times.
Title: Re: What the hell is North in the solar system?
Post by: gpw11 on Wednesday, July 09, 2008, 12:03:29 AM
My favorite is still the original one I saw:  "If it bleeds we can kill it"