| Topic: |
Science > Physics |
| User: |
"Martin Johansen" |
| Date: |
07 Mar 2004 06:24:40 AM |
| Object: |
Rotating bodies and speed |
The moon orbits around the earth at an absolute speed.
To what is the speed absolute?
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| User: "Old Man" |
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| Title: Re: Rotating bodies and speed |
07 Mar 2004 05:20:10 PM |
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"Martin Johansen" <martinfj@is.online.no> wrote in message
news:xvE2c.8869$rj4.118003@news2.e.nsc.no...
The moon orbits around the earth at an absolute speed.
To what is the speed absolute?
The orbit being slightly elliptical, the speed of the Moon in it's orbit
about the Earth is neither absolute nor is it conserved. Neglecting the
effects of Solar tidal forces, the total angular momentum of the Earth-
Moon system is absolutely conserved. Because of tidal friction on Earth,
the spin angular momentum of the Earth is slowly being transferred to the
orbital angular momentum of the Moon. [Old Man]
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| User: "Sam Wormley" |
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| Title: Re: Rotating bodies and speed |
07 Mar 2004 07:56:16 AM |
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Martin Johansen wrote:
The moon orbits around the earth at an absolute speed.
The Earth and Moon orbit their common barycenter and a first
approximation. Motions are perturbed by other masses in our
solar system.
With respect to the Earth, like all bodies in elliptical orbits
its orbital speed increases and decreases. Kepler's Second Law
describes this motion.
http://scienceworld.wolfram.com/physics/KeplersLaws.html
All motion is relative
Velocity
http://scienceworld.wolfram.com/physics/Velocity.html
How Do You Add Velocities in Special Relativity?
http://hermes.physics.adelaide.edu.au/~dkoks/Faq/Relativity/SR/velocity.html
http://www.edu-observatory.org/physics-faq/Relativity/SR/velocity.html
Observational and Experimental Evidence Bearing on General Relativity
http://math.ucr.edu/home/baez/RelWWW/tests.html
General Relativity Tutorial
John Baez
http://math.ucr.edu/home/baez/gr/gr.html
Relativity on the World Wide Web
http://math.ucr.edu/home/baez/relativity.html
General Relativity and Cosmology FAQs
http://math.ucr.edu/home/baez/physics/
Developments in General Relativity: Black Hole Singularity and Beyond
http://arxiv.org/abs/gr-qc/0304052
Improved Test of General Relativity with Radio Doppler Data from the Cassini Spacecraft
http://arxiv.org/abs/gr-qc/0308010
What is the experimental basis of Special Relativity?
http://math.ucr.edu/home/baez/physics/Relativity/SR/experiments.html
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| User: "Bart Van Hove" |
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| Title: Re: Rotating bodies and speed |
07 Mar 2004 12:45:52 PM |
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On Sun, 07 Mar 2004 13:24:40 +0100, Martin Johansen wrote:
The moon orbits around the earth at an absolute speed.
To what is the speed absolute?
It's not, it slows down at the "ends" (moon is at maximum distance of the
earth) of its elliptical orbit, and speeds up at the more straight parts
(closer to earth). There is a constant though:
The radius sweeps equal areas in equal times, visit this site:
http://www-istp.gsfc.nasa.gov/stargaze/Skepl2nd.htm
This is called Kepler's 2nd Law
--
Greetings,
Bart Van Hove
http://www.bartendavid.be
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