Why are most galaxies/solar systems 'flat'?

Why are most galaxies and solar systems 'flat'? If there is a cloud of
dust/gas that starts to coalesce around a localized density in the middle of
the dust/gas, it seems it would attract from all 3 dimensions equally. But
galaxies and solar systems attract primarily in a single plane. What
happened to all the debris above/below the plane?

I understand there will probably be an unequal distribution of matter
surrounding the central object and there will consequently be a resultant
angular momentum after a while. But that doesn't seem to explain why there
still isn't debris spiraling in from above/below the primary plane.

When galaxies are closer together, they tend to be more spiral. This
indicate to me spirals are result of close encounter of 3d kind.
Imagine 2 basket ball nick each other in space and spin. Of course unlike
basketball, gravity makes it slightly tragect in rather than slight bounce.
Easier to picture randomely distributed galaxy then some single mass like
black hole pass by causing angular momentum, 2nd galaxy work as fine, but
not as easy to picture...

Alternatively, if our visual universe is created by collision of 2 black
holes then resultant energy distribute in chaotic way and some angular
momentum..


"Richard Dickison" wrote in message
...
Why are most galaxies and solar systems 'flat'? If there is a cloud of
dust/gas that starts to coalesce around a localized density in the middle
of
the dust/gas, it seems it would attract from all 3 dimensions equally. But
galaxies and solar systems attract primarily in a single plane. What
happened to all the debris above/below the plane?

I understand there will probably be an unequal distribution of matter
surrounding the central object and there will consequently be a resultant
angular momentum after a while. But that doesn't seem to explain why
there
still isn't debris spiraling in from above/below the primary plane.

When galaxies are closer together, they tend to be more spiral. This
indicate to me spirals are result of close encounter of 3d kind.
Imagine 2 basket ball nick each other in space and spin. Of course unlike
basketball, gravity makes it slightly tragect in rather than slight bounce.
Easier to picture randomely distributed galaxy then some single mass like
black hole pass by causing angular momentum, 2nd galaxy work as fine, but
not as easy to picture...

Alternatively, if our visual universe is created by collision of 2 black
holes then resultant energy distribute in chaotic way and some angular
momentum..


"Richard Dickison" wrote in message
...
Why are most galaxies and solar systems 'flat'? If there is a cloud of
dust/gas that starts to coalesce around a localized density in the middle
of
the dust/gas, it seems it would attract from all 3 dimensions equally. But
galaxies and solar systems attract primarily in a single plane. What
happened to all the debris above/below the plane?

I understand there will probably be an unequal distribution of matter
surrounding the central object and there will consequently be a resultant
angular momentum after a while. But that doesn't seem to explain why
there
still isn't debris spiraling in from above/below the primary plane.

Richard Dickison wrote:
Why are most galaxies and solar systems 'flat'?

According to the solar nebula model for the formation of our solar system, the
nebula that collapsed gravitationally to form into the solar system may have had
some net rotation, perhaps as small as one rotation every few million years.
Once the collapse was initiated, this would be magnified by the conservation of
momentum, causing the initial irregularly shaped cloud to flatten out into a disk.

As to the formation of spiral galaxies, there are several hypotheses that have
been proposed, none of which have observational support at this time. The
oldest of these, dating to the 60's posits a single gas cloud collapsed
gravitationally and that as it spun up, its star formation process was stunted,
allowing for the formation of a disk in a fashion similar to the solar nebula
model forming a disk. More recently, it has been proposed that the inward
collapse of either a few large gas clouds or many smaller gas clouds would
eventually form up into a galaxy, with the net motion of the clouds converted to
an overall rotation - flattening the result again, as per above.

So, with solar system formation there seems to be more observational support
than there is for galaxy formation. Since galaxy formation seems to have
occurred billions of years ago, to see such processes in action would require
seeing out to distances of billions of lightyears. The HST has been used to
spot hot blue galaxies believed to be forming from clouds of gas merging
together, but the detailed observations of those very distant clouds may have to
wait for the next generation space telescope, which promises to have even better
resolution than the HST.

Richard Dickison wrote:
Why are most galaxies and solar systems 'flat'?

According to the solar nebula model for the formation of our solar system, the
nebula that collapsed gravitationally to form into the solar system may have had
some net rotation, perhaps as small as one rotation every few million years.
Once the collapse was initiated, this would be magnified by the conservation of
momentum, causing the initial irregularly shaped cloud to flatten out into a disk.

As to the formation of spiral galaxies, there are several hypotheses that have
been proposed, none of which have observational support at this time. The
oldest of these, dating to the 60's posits a single gas cloud collapsed
gravitationally and that as it spun up, its star formation process was stunted,
allowing for the formation of a disk in a fashion similar to the solar nebula
model forming a disk. More recently, it has been proposed that the inward
collapse of either a few large gas clouds or many smaller gas clouds would
eventually form up into a galaxy, with the net motion of the clouds converted to
an overall rotation - flattening the result again, as per above.

So, with solar system formation there seems to be more observational support
than there is for galaxy formation. Since galaxy formation seems to have
occurred billions of years ago, to see such processes in action would require
seeing out to distances of billions of lightyears. The HST has been used to
spot hot blue galaxies believed to be forming from clouds of gas merging
together, but the detailed observations of those very distant clouds may have to
wait for the next generation space telescope, which promises to have even better
resolution than the HST.

Hi Richard D I posted that universes were flat like our Milky Way,and
then read that two flat universes coming together could cause a big
bang. The article refereed to the universes as two membranes. (go
figure) Bert

Hi Richard D I posted that universes were flat like our Milky Way,and
then read that two flat universes coming together could cause a big
bang. The article refereed to the universes as two membranes. (go
figure) Bert

Flat because they are spinning fast and most of the galaxy's gravity is
located at its core,and its horizon. It is a pin wheel. Helps if its
flat rim is in our exact line of view. Bert

Flat because they are spinning fast and most of the galaxy's gravity is
located at its core,and its horizon. It is a pin wheel. Helps if its
flat rim is in our exact line of view. Bert

"G=EMC^2 Glazier" wrote in message
...
Flat because they are spinning fast and most of the galaxy's gravity is
located at its core,and its horizon. It is a pin wheel. Helps if its
flat rim is in our exact line of view. Bert


Sorry Bert,

but the rotation curves of spiral galaxies suggest this is not true. In many
spirals, the tangential velocity of stars is fairly constant with increasing
distance from the centre. If most of the mass were at the centre, the speed
would be expected to decrease with increasing distance from the centre.

Dave