Which way is up?

[machiaventa]

Dear Fellows:
I have often wondered why our planets revolve around the sun all in the same manner. What keeps Mars from revolving diametrically to earth or vise -versa? Does the universe have an up , down or sideways or is it all laid out on a plane? :shrug: Are we oriented to north and south, east and west only on Earth? In space do these directions still remain relative only to us? I welcome your input in this dilema which inhabits my thoughts.

Sincerely, Paul Defourneaux , Chemist:shrug::shrug:

[Billy T]

Dear Fellows:
I have often wondered why our planets revolve around the sun all in the same manner. What keeps Mars from revolving diametrically to earth or vise -versa? Does the universe have an up , down or sideways or is it all laid out on a plane? :shrug: Are we oriented to north and south, east and west only on Earth? In space do these directions still remain relative only to us? I welcome your input in this dilema which inhabits my thoughts.
Sincerely, Paul Defourneaux , Chemist:shrug::shrug:HI Paul.

It is reasonably well accepted that the sun and all the planets were once a local gas "cloud" of relatively low density that began to contract under its own self gravity. Probably that cloud was roughly initially spherical, or any "arms" sticking out probably got separated during the contraction so we can neglect them, if they existed.

Now it is almost impossible that the cloud had no angular momentum, but each atom circulating roughly around their common center of mass has its own but it was constantly changing as these atoms collided. None the less the total remained unchanged. (We physicists say: "Angular momentum is conserved" to state this.) On average these collisions caused the cloud to contract and become more pancake in shape.

For example, consider a atom that was far from being in the plane of the "pancake." As it passed thru the pancake, twice in each trip around the center of mass, it had many "near misses" with many other atoms that are roughly in the pancake. Some would be scattered farther from the plane of the pancake and some that were not well in the pancake, will be knocked more into its plane; However, one can be almost certain that on each pass thru the pancake that atom which we were considering will be much more nearly in the plane of the pancake than it was when it started to try to cross. Sort of like if you were to push a shopping cart straight across a busy 5 lane highway - the cart will get hit many times and it velocity direction will much more resemble that of the cars. (This is still true even if instead of cars there are just many other shopping carts all going the same way.)

What plane these atoms all settle down to MUST be that determined by the original net, non-zero, angular momentum and they must eventually all be going around the mass center the same way. (Those that were going "the wrong way round" got hit by many going the other way until they too were.) The original net momentum was much smaller than the sum of the MAGNITUDES of all the individual atoms. The argument is not circular. You do not need to have a pancake to grow it. You only need a net angular momentum which does not change as it cannot change.

I will let you pick up the story here, with just the hit that there were also some parts of the general circulation that were denser than average and they too served as local condensation centers at their distance from the mass center, which is now inside the sun.

Also note these collisions tend to remove both the unusually fast and unusually slow atoms and give them all the same average energy (We physicists call this "Equal partisan of energy.") That means that the heaver atoms , like iron, were on average moving slower, so when two collided they had better chance of sticking together, making the "local mass center" ever denser. Earth does have an iron core, but it is not entirely due to this early aggregation as Earth was originally molten, but I think your question is now answered without more details.

[draqon]

Up is a way towards your heart, let the heart guide you to your love and find a way up towards appreciation of this life.

[spidergoat]

Actually, Uranus is tilted:

The Uranian system has a unique configuration among the planets because its axis of rotation is tilted sideways, nearly into the plane of its revolution about the Sun; its north and south poles lie where most other planets have their equators. [wiki]

[draqon]

and Venus spins the other direction...

[blobrana]

Hum,
and the outer Oort cloud is probably spherical...

[draqon]

Hum,
and the outer Oort cloud is probably spherical...

I was thinking it to be in plane of the solar system

[Vkothii]

How many solar system bodies have a retrograde orbit?

[eburacum45]

How many solar system bodies have a retrograde orbit?
Many of the smaller moons of the gas giants have retrograde orbits around thir primaries. No planets have retrograde orbits, although Venus rotates in a retrograde fashion. I suspect that Oort cloud objects may be distributed randomly between prograde and retrograde, but none have been observed yet.

[orcot]

Many of the smaller moons of the gas giants have retrograde orbits around thir primaries. No planets have retrograde orbits, although Venus rotates in a retrograde fashion. I suspect that Oort cloud objects may be distributed randomly between prograde and retrograde, but none have been observed yet.
triton one of saturn moons has a retrograde orbit so it's not impossible but it has to be a captured body and the whole isn't stable on a universal scale.
Then again if you look at triton, phobos saturns rings jupiters red spot then there are a lot of unstable places at the universe

[Billy T]

... I suspect that Oort cloud objects may be distributed randomly between prograde and retrograde, but none have been observed yet.Very unlikely man will ever know, at least not for thousands of years, but while I generally agree with you, I supect that these "few and far between" objects occupying an enormous volume do have net angular momentum roughly the same as the planets of the solar system.

I think that because I think they are what I called "local condensation centers" in post 2 AND because most* were part of the original gas cloud I spoke of in post 2. They just have not had enough time yet to get more into a "pancake" configuration with only a few individual objects having dramatically different orbit planes about the sun from from the majority in the "pancake." Come back and look and see if I am not right in about 100 billlion more years. ;)
---
*comets often have stable orbits with a modest ecentricity, far from the sun, until they have a "close encounter" with another object. One of these object, that we will later call a "comet" will get scattered into an orbit with near unity ecentricity and the other will get the escape velocity (which may not be very large as already only weakly bound to the sun.) Thus it will wander free thru space. Space is so large that probably it never will have another "interesting encounter" with anything, just slowly getting a coating of hydrogen on its skin. This is true of the "Ort Clouds" of other solar systems too. Perhaps one of their "escaped objects" did try to pass thru the Ort cloud of the sun and "got lucky" to have a "close encounter" with an object there. I doubt that, but perhaps one object in the sun's ort cloud was a captured "escaped object" created in some other solar system.

[machiaventa]

Does the whole universe lie in a plane paralell to our system? Why don't planets rotate north to south instead of east to west or west to east?I suspect that dark matter and dark energy have much to do with this phenomenom. Gravitaional forces are being manipulated by these forces and one day we will understand it much clearer.

Machiaventa Speaks

[cosmictraveler]

Which way is up?

Depends on how the word is used. "Shut the fuck UP" would mean one thing while "UP yours" would bring into light a new definition for its meaning. "We are being sold UP the river" is another clever way to use the word as well as "suck it UP". "I'm going UP to see aunt Betty" and "put it UP on the shelf " are even more usages for that word. So it is really UP to each of us to really understand what's UP! :D

[Billy T]

Does the whole universe lie in a plane paralell to our system? ...No. We can see it does not. But if you are asking does the whole universe have it total angular momentum oriented much like that of the solar system, then certainly that is possible, but it would surprise me if true. That is because that is but one of many possibilities. Sort of like rolling "snake eyes" twice in a row - possible, but not likely.

Each of the "local condensation centers" that we now see as planets got some of its mass from particles in orbiting the sun at less than 1 AU (distance to the sun) and from others with slightly more than 1AU. The near to sun part went around in less than a year, but was actually going slower than Earth is now. Likewise the mass collected from farther than 1AU was going faster. Thus, when it was collected to become Earth (or another planet) it gave them an initial spin, all in the same direction. (Spin angular momentum was pointing the same way as the orbital angular momentum). Some, however, had "interesting encounters" with other objects and if an actual collision occurred it added or subtracted to the spin angular momentum. Earth, very likely got it moon this way. It is at least certain that the moon was not part of the original Earth formation process, but a later development. This is known as the tides are slowing the Earth's rotation (Earth is losing spin momentum and days are growing longer. Two keep the total unchanged, the moon is slowing moving away from Earth. How is works is well understood, but I will skip that.)

The tides were much larger long ago when the moon was closer and this transfer of angular momentum to the moon was much more rapid. We can calculate backwards from the moon's present state and to give the separation at an earlier date. The moon as a sphere was never touching the Earth for reason related to the gradient of gravity that I will not go into but if that were not the case, it would had hit the Earth back when Earth was still young - but long after Earth had formed. Some believe that the Moon is, at least in part, made from Earth that was where the Pacific basin is now. I do not have a POV as I am too ignorant about when this occurred relative to the time of the brake up of the single land mass "early Earth" into five continents we have today. Perhaps that break up and "birth of the moon" are related. In any case Earth got its moon when a "teenager" - not at "birth of the Earth." During the "birth of the moon" there was an "interesting encounter" with some other object playing an essential role in the process. - I will not go into details as to why/ how we are sure of that.

PS “dark mater” had not much, if anything, to do with the way the solar system is, but perhaps was a controlling factor in the shape or distribution of mater in much larger “local regions” (volumes holding at least several galaxies) of the universe.

[blobrana]

...Oort cloud objects may be distributed randomly between prograde and retrograde, but none have been observed yet.

Yeah,
long period comets seem to come from all directions.