I'm Writing Fiction about the Moon: Some Basic Questions!

"Mike Rhino" wrote in message
news
"Eric Chomko" wrote in message
...
How about a case where one of the poles points in the direction of the
orbital plane? IOW, at one point in the orbit the north pole points at
the
sun and on the other side of the orbit the south pole points toward the
sun. Unlike the Earth's or Mars' ~25 deg. axis tilt this other is more
on
the order of a 90 deg. axis tilt.

Uranus comes pretty close with an axis tilt of 97.86 degrees.

http://www.solarviews.com/eng/uranus.htm

And Pluto is about 120 degrees, and Venus about 180 degrees.

Bruce

Mike Rhino ) wrote:
: "Eric Chomko" wrote in message
: ...
: Mike Rhino ) wrote:
: : "Henry Spencer" wrote in message
: : ...
: : In article ,
: : johnhare wrote:
: : It seems to me that a tide-locked body in a dawn dusk polar
: : orbit could well have a permanantly dark side...
: :
: : Mmm, yes, provided the orbit was sun-synchronous -- precesses once
: around
: : the primary per primary orbital period -- which requires a rather
: exact
: : match between the orbit characteristics and the primary's equatorial
: : bulge. I can't see that persisting for very long, however; the exact
: : match is not very stable.
:
: : Suppose that it isn't an exact match so that one day lasts 100 years.
: It
: : would still be an interesting place.
:
: How about a case where one of the poles points in the direction of the
: orbital plane? IOW, at one point in the orbit the north pole points at the
: sun and on the other side of the orbit the south pole points toward the
: sun. Unlike the Earth's or Mars' ~25 deg. axis tilt this other is more on
: the order of a 90 deg. axis tilt.

: Uranus comes pretty close with an axis tilt of 97.86 degrees.

You get the prize! I was fishing for that. Anyway, it is pretty
interesting to think that the poles will be exposed to the sun for part of
the orbit. Like all gas planets it tends to rotate pretty fast, so it
might warmer than expected for the distance to the sun.

Eric

: http://www.solarviews.com/eng/uranus.htm

Bruce Sterling Woodcock ) wrote:

: "Mike Rhino" wrote in message
: news : "Eric Chomko" wrote in message
: ...
: How about a case where one of the poles points in the direction of the
: orbital plane? IOW, at one point in the orbit the north pole points at
: the
: sun and on the other side of the orbit the south pole points toward the
: sun. Unlike the Earth's or Mars' ~25 deg. axis tilt this other is more
: on
: the order of a 90 deg. axis tilt.
:
: Uranus comes pretty close with an axis tilt of 97.86 degrees.
:
: http://www.solarviews.com/eng/uranus.htm

: And Pluto is about 120 degrees, and Venus about 180 degrees.

Isn't that like saying Venus rotates 3 degrees retrograde the same thing?
And Pluto is 57.5 degrees retrograde? The latter is new to me as I had
not known that we knew the axis tilt of Pluto. Heck, I remember when they
discovered Charon its moon, and when the rotation period of 6.3 days was
discovered but the axis tilt and retrograde at that is new to me.

Also, the negative rotation period makes me think of time going backwards.

Anyway, thanks for the info.

Eric

P.S. If and when we send a probe to Pluto should we name it Tombaugh or
Lowell?

: Bruce

"Eric Chomko" wrote in message
...
Bruce Sterling Woodcock ) wrote:

: "Mike Rhino" wrote in message
: news : "Eric Chomko" wrote in message
: ...
: How about a case where one of the poles points in the direction of
the
: orbital plane? IOW, at one point in the orbit the north pole points
at
: the
: sun and on the other side of the orbit the south pole points toward
the
: sun. Unlike the Earth's or Mars' ~25 deg. axis tilt this other is
more
: on
: the order of a 90 deg. axis tilt.
:
: Uranus comes pretty close with an axis tilt of 97.86 degrees.
:
: http://www.solarviews.com/eng/uranus.htm

: And Pluto is about 120 degrees, and Venus about 180 degrees.

Isn't that like saying Venus rotates 3 degrees retrograde the same thing?

Yes, but both are valid ways of looking at the same thing.

It would be nice to know if Venus was "originally" rotating
backwards, but it's certainly possible a collision knocked it
all the way over.

How do we know Uranus isn't rotating retrograde and
wasn't simply knocked 260 degrees over?

And Pluto is 57.5 degrees retrograde? The latter is new to me as I had
not known that we knew the axis tilt of Pluto.

We determined it once we had radar pictures (and the Hubble).

Bruce

In article ,
Bruce Sterling Woodcock wrote:
And Pluto is 57.5 degrees retrograde? The latter is new to me as I had
not known that we knew the axis tilt of Pluto.

We determined it once we had radar pictures (and the Hubble).

No, what quickly settled Pluto's axial tilt was the discovery of Charon
(Pluto's moon) in the early 1980s. With a moon that big and close, the
two just had to be tide-locked together, so the easily-observable orbit
of Charon also gave us Pluto's axis.
--
MOST launched 30 June; science observations running | Henry Spencer
since Oct; first surprises seen; papers pending. |

Henry Spencer ) wrote:
: In article ,
: Bruce Sterling Woodcock wrote:
: And Pluto is 57.5 degrees retrograde? The latter is new to me as I had
: not known that we knew the axis tilt of Pluto.
:
: We determined it once we had radar pictures (and the Hubble).

: No, what quickly settled Pluto's axial tilt was the discovery of Charon
: (Pluto's moon) in the early 1980s. With a moon that big and close, the
: two just had to be tide-locked together, so the easily-observable orbit
: of Charon also gave us Pluto's axis.

Wait, doesn't the Moon orbit at an inclination different than that of
the Earth's equitorial plane? Tidal lock is one thing and axis tilt is
another, at least in the Earth/Moon system. Now, since the Earth is 81
times as massive as the moon and Charon is much larger in comparison to
Pluto, you could be right based upon that. But I think I would want to
check the rotation of Pluto compared to its orbital plane based upon
something else to make sure other than rely and Charon's orbital
characteristics.

Eric

: --
: MOST launched 30 June; science observations running | Henry Spencer
: since Oct; first surprises seen; papers pending. |

On Tue, 13 Jan 2004 15:30:43 GMT, "Bruce Sterling Woodcock"
wrote:


"Mike Rhino" wrote in message
news
"Eric Chomko" wrote in message
...
How about a case where one of the poles points in the direction of the
orbital plane? IOW, at one point in the orbit the north pole points at
the
sun and on the other side of the orbit the south pole points toward the
sun. Unlike the Earth's or Mars' ~25 deg. axis tilt this other is more
on
the order of a 90 deg. axis tilt.

Uranus comes pretty close with an axis tilt of 97.86 degrees.

http://www.solarviews.com/eng/uranus.htm

And Pluto is about 120 degrees, and Venus about 180 degrees.

I'm confused here. How can you tell it's 120 deg, not 60? Or 180,
not 0? Is the northness of the pole based on rotation direction or
something?

Mary

--
Mary Shafer Retired aerospace research engineer

Mary Shafer wrote:

On Tue, 13 Jan 2004 15:30:43 GMT, "Bruce Sterling Woodcock"
wrote:



"Mike Rhino" wrote in message
news

"Eric Chomko" wrote in message
...


How about a case where one of the poles points in the direction of the
orbital plane? IOW, at one point in the orbit the north pole points at


the


sun and on the other side of the orbit the south pole points toward the
sun. Unlike the Earth's or Mars' ~25 deg. axis tilt this other is more


on


the order of a 90 deg. axis tilt.


Uranus comes pretty close with an axis tilt of 97.86 degrees.

http://www.solarviews.com/eng/uranus.htm


And Pluto is about 120 degrees, and Venus about 180 degrees.



I'm confused here. How can you tell it's 120 deg, not 60? Or 180,
not 0? Is the northness of the pole based on rotation direction

Yes.

Alain Fournier

"Mary Shafer" wrote in message
...
On Tue, 13 Jan 2004 15:30:43 GMT, "Bruce Sterling Woodcock"
wrote:


"Mike Rhino" wrote in message
news
"Eric Chomko" wrote in message
...
How about a case where one of the poles points in the direction of
the
orbital plane? IOW, at one point in the orbit the north pole points
at
the
sun and on the other side of the orbit the south pole points toward
the
sun. Unlike the Earth's or Mars' ~25 deg. axis tilt this other is
more
on
the order of a 90 deg. axis tilt.

Uranus comes pretty close with an axis tilt of 97.86 degrees.

http://www.solarviews.com/eng/uranus.htm

And Pluto is about 120 degrees, and Venus about 180 degrees.

I'm confused here. How can you tell it's 120 deg, not 60? Or 180,
not 0? Is the northness of the pole based on rotation direction or
something?

If you didn't, north and south would change if you
looked at the solar system upside-down.

Bruce

Mary Shafer wrote in message . ..
And Pluto is about 120 degrees, and Venus about 180 degrees.

I'm confused here. How can you tell it's 120 deg, not 60? Or 180,
not 0? Is the northness of the pole based on rotation direction or
something?

Yes. The sun rises in the East, and sets in the West, by definition.

Well, at least by one common definition.

-jake