cjh@petsd.UUCP (Chris Henrich) (09/25/84)
[This space intentionally left blank] > In Larry Nivens book 'The Integral Tree' I don't understand the 'gravity'. In >the tree tufts there is 'gravity' and in the mid-trunk area there is zero g. How is >this possible. The tree doesn't rotate end for end, one end is always toward Voy. >Can anyone out there explain it in a relatively simple manner? In a word, "tide". An integral tree, or any other reasonably small object in orbit, moves as if its mass were concentrated at the "center of mass." (Halfway up the trunk.) If it is in a circular orbit, then the gravitational force at that distance from Voy is equal to the centripetal force needed to keep the object in that circular path. At the inner tuft, which is closer to Voy, the gravitational attraction of the star is greater, and the centripetal acceleration needed to keep in that orbit is less. So a person in the tuft feels a pull towards Voy. Likewise, in the outer tuft, the gravitational attraction is less, and the centripetal acceleration needed to keep up with the integral tree is greater, so a person there feels a pull outwards. The integral tree itself is under tremendous tension, which explains why it can come apart if it is weakened at the middle. This force is called "tidal stress" because the same mechanism explains the tides of Earth's oceans: the major gravitational attractor being the Moon. Regards, Chris -- Full-Name: Christopher J. Henrich UUCP: ..!{decvax,ucbvax,ihnp4}!vax135!petsd!cjh US Mail: MS 313; Perkin-Elmer; 106 Apple St; Tinton Falls, NJ 07724 Phone: (201) 870-5853
jerry@oliveb.UUCP (Jerry Aguirre) (09/27/84)
Larry Niven wrote another story in which tidal forces were used. It was
one of the "known space" series though I don't have the title handy but
I think it was "Tidal Stress".
It that story the main character was asked to pilot a ship in a
sling-shot orbit that took it very near a nutron star. The idea was to
collect scientific info during the near pass or something. The
reasoning was that since the ship was in free fall there would be no
gravitational attraction even at the closest approach to the star. The
ship had enough power to make minor course corrections but nowhere near
enough to pull out of the orbit.
The previous pilots have been found crushed even though the ships hull
was still entact. Needless to say the hero finds out that though the
center of mass of the ship is in free fall the two ends of it are not.
I will leave how he survives a mystery.
Jerry Aguirre
{hplabs|fortune|idi|ihnp4|ios|tolerant|allegra|tymix}!oliveb!jerryokie@ihuxs.UUCP (B.K. Cobb) (09/27/84)
The other story by Niven dealing with tides is
"Neutron Star" in the "Neutron Star" anthology.
I, too, will leave the ending a mystery.
Niven has dealt with tides in other stories.
One such is "There Is A Tide" ("Tales of Known
"Space" anthology). And in the novel "Protector"
he lets the tide and gravitational effects around
a neutron start be a "pivotal" point in the end
of the story (excuse the pun, those who've read it
and know about the "right-angle turn").
B.K. Cobb
ihnp4!ihuxs!okiegail@calmasd.UUCP (Gail B. Hanrahan) (09/28/84)
_Descent of Anansi_ by Larry Niven and Steven Barnes used
tides. As did Niven's stories "Neutron Star" and "There is a
Tide" (not "Tidal Stress" in my copy). "Neutron Star" at least
can be found in the short story collection _Neutron Star_.
(Big surprise, that).
Gail Bayley Hanrahan
{decvax,ucbvax}!sdcsvax!calmasd!gail
Calma Company, San Diegohardie@uf-csg.UUCP (Peter T Hardie [stdnt]) (11/04/84)
Me again. The Niven story is called 'Neutron Star', and the hero is Beowulf Schaffer. -- Pete Hardie, Univ. of Florida, CIS Gould username: hardie