From Newsgroup: alt.comp.os.windows-11
On Thu, 27 Nov 2025 01:54:33 -0800, The Horny Goat wrote:
On Wed, 1 Oct 2025 19:26:59 +0200, "Carlos E.R."
<robin_listas@es.invalid> wrote:
The farther a planet is from the Sun, the slower the orbit is. So close
to the Sun it would go very fast.
No question Pluto moves much faster than Mercury - that said, it takes
a LOT longer to orbit (can't remember but several human lifetimes) vs
Mercury (88 days)
You meant to say Pluto moves much _slower_ than Mercury. It's
Kepler's third law: The ratio R³/T² is the same for all bodies that
orbit a given central body, where R = the semimajor axis and T = the
time to complete one orbit.
https://en.wikipedia.org/wiki/Kepler%27s_laws_of_planetary_motion
Another way to write it is T² = k*R³, or T = sqrt(k*R³), where k
depends on the mass of the central body. (This is how the masses of
the planets that have moons can be determined so accurately.)
The average orbital velocity is v = 2*pi*R/T or v = 2*pi*R/sqrt(k*R³)
= 2*pi/sqrt(k*R), which makes it pretty obvious that the larger the
orbit around a given body, the faster the orbiting object moves. A nonmathematical way to think about it is that the sun's gravity is
stronger at the orbit of Mercury that at the orbit of Pluto, and the
stronger field whips Mercury along faster than Pluto.
--
"The power of accurate observation is frequently called cynicism by
those who don't have it." --George Bernard Shaw
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