originally posted by: All Seeing Eye
a reply to: wildespace
Certainly so! But just because a heavenly body can be accurately predicted
in its location, does not mean it is known how the planets are actually propelled around their orbits.
So scientists must have gotten _something_ right, right?
Propelled? What a stange word to use for bodies moving through the vacuum of space under their own inertia. Newton's First Law of Motion: "an object
in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force." Planets need no propulsion or
propelling. The only force acting on them (if we ignore any possible interaction between themselves) is the Sun's gravity, which turns an otherwise
straight path into path enclosed around the Sun (i.e. an orbit). And Kepler has pinned down _exactly_ how the planets are moving in their orbits. His
centuries' old equations stand true to this day and are used by modern astronomers and rocket scientists.
Earth's ocean beds and its core have nothing to do with celestial mechanics.
The very simple fact that oceans and the planetary cores are parts of our solar system, means, they must play some role in the bigger picture, and if
one wants to see the bigger picture, one must consider all the little pictures that make up the bigger picture.
The earths outer surface is covered by 70% give or take, water. And that water is primarily on one side of the planet "Pacific Ocean". Water and rock
have differing weights. Does our planet wobble around its solar race track, or does the planet rotate without effect, and is this expected wobble
canceled out, by the moon?
I'm not aware of any articles or papers showing how the Earth's oceans or mountains affect its rotation or orbit around the Sun. If there are any, I'd
like to see them. As far as I'm aware, Earth is considered a single unit when orbiting the Sun, and (as I have mentioned in the previous post), this
orbit is determined solely by the Sun's gravity, due to it being immensly more massive than the Earth.
Why would two dissimilar sizes and consistency's follow their orbits uniformly? Why would a dwarf planet be any different that a full size
Firstly, size and consistency have no role here; only the mass matters. The mass of an orbiting body plays no effective role when the mass of the
primary body (i.e. the Sun) is many orders more massive. Take a look at
Newton's law of universal gravitation
: F = Gm1m2/r2
When one of the masses (for example m1) is on many orders of the magnitude larger than the other mass (m2), the gravitational force F between those to
masses is effectively determined by m1 and the distance (r) of m2 to it.
It's the same reason the ISS and a spacewalking astronaut can orbit the Earth at the same speed, despite being very different in mass, size, or
composition. They are moving at the same speed because the mass of Earth is immensely greater than the mass of either the ISS or the astronaut, so
it's only their altitude above earth that matters. Interestinly, it's also why geostationary satellites can exist: they are positioned sufficiently
high above the Earth that their orbital period equals the rotation period of Earth.
It is indeed a puzzling notion that if you replaced a planet with a boulder (or even a pebble), it would continue on the same trajectory. The key to
this is that the Sun is incrediby massive and dominates the orbits of anything in the Solar System (with the notable exception of Jupiter, which is
massive enough to have its and the Sun's common centre of mass lying outside the Sun's surface).
I feel I must correct my earlier statement that the Earth's oceans play no role in the celestial motions. As it happens, the tides caused by the Moon
are carried away from the point on Earth directly below the Moon due to the fact that Earth rotates a lot faster than the Moon goes around it. This
creates a torque force, which slows the Earth's rotation, and at the same time boosts the Moon into a higher orbit. You may have heard that the Moon
is slowly receding from Earth - this is the reason.
But I'm not aware of any effect of the Earth's oceans or rocks on its rotation or orbit around the Sun.
edit on 14-7-2014 by wildespace
because: (no reason given)