3-dimensional space

[bored_teen]

space is 3D (so i'm told), but models of the planets all seem to be revolving around the sun (more or less) on the same horizontal plane. what's "above" or "below"?

[iNow]

Your starting premise is false. While to you they may "seem" to be in the same orbital plane, they are not.

 

http://www.qrg.northwestern.edu/projects/vss/docs/space-environment/2-whats-orbital-plane.html

[bored_teen]

if my premise is false, then the link you posted makes no sense. what i'm getting from that link is that planets orbit on the same orbital plane. that's what the first picture is telling me. you're telling me they're not on the same orbital plane, but your link says they do. am i misunderstanding?

[iNow]

Where does it say that they all "orbit on the same plane?"

 

I read "near."

[bored_teen]

The planets all orbit on or near one plane in space like the picture above.

it says on or near. either way, they don't move like in that second picture. my question is what is "above" or "below" these orbital planes? the milky way spreads out more or less horizontally, so what is "above" it?

[D H]

The planets do orbit in more or less the same plane. Pluto is an exception, but then again, it isn't a planet. Pluto is a dwarf planet plutoid (but Pluto's status different subject).

 

That doesn't mean space is not 3D. The planets do not have exactly the same orbital planes. Their orbital planes are slightly inclined with respect to one another, and that can't happen in a 2D world. That the planets do have similar orbital planes is a result of conservation of angular momentum.

[Klaynos]

The reason the planets are on an orbital plane is because they form in a disc.

 

The reason it is a disc and not a sphere is quite easy to understand, it starts off as a rotating sphere with a pretty much random rotation of individual particles up and down, because it's pretty much random you get collisions the majority of which will be in the plane in the middle of the rotation so all the up and down motion cancels out near the plane of rotation so quite quickly you end up with a disk instead of a sphere... We've actually got photos of planet forming disks around young stars.

[bored_teen]

i understand that they're on a disk. my question is, what the heck is above that disk? space is 3D, but it doesn't have an "up" or "down" due to the lack of gravity. for the sake of argument (and clarification), let's assume it does. using this pic for our frame of reference, if we zoomed out to see more of space, what would be above this galaxy?

[insane_alien]

more space. might have some stars in it, might not. whats above/below your dinner plate? might be some chicken, might not be.

[D H]

i understand that they're on a disk. my question is, what the heck is above that disk? space is 3D, but it doesn't have an "up" or "down" due to the lack of gravity.

First, what in the world do you mean by "up"? There is no universal "up". There isn't even a worldly "up". Points diametrically opposed to one another on the surface of the Earth have diametrically opposite concepts of "up".

 

Second, there sure the heck is gravity "up" there.

[Klaynos]

http://hubblesite.org/newscenter/archive/releases/1996/01/image/a/format/large_web/

 

That's a deep space image from hubble shows lots of galaxies up and down all oriantated different ways some are close some further away...

[bored_teen]

more space. might have some stars in it, might not. whats above/below your dinner plate? might be some chicken, might not be.

 

thanks. from all the pictures of the solar system it seemed that there isn't really anything above the orbital disk. i guess the pictures didn't show enough is all.

 

First, what in the world do you mean by "up"? There is no universal "up". There isn't even a worldly "up". Points diametrically opposed to one another on the surface of the Earth have diametrically opposite concepts of "up".

 

Second, there sure the heck is gravity "up" there.

 

there is gravity, but only if you are within the gravitational pull of an object. space itself doesn't have gravity.

 

http://hubblesite.org/newscenter/archive/releases/1996/01/image/a/format/large_web/

 

That's a deep space image from hubble shows lots of galaxies up and down all oriantated different ways some are close some further away...

 

thanks. that, conjoined with insane_alien's post pretty much cleared it all up.

 

but now i have a different question. if you reoriented the space telescope (or turned it around and moved it to the other side of the milky way) what would you see? i'm assuming pretty much the same kind of stuff. but all the pictures i've seen of the milky way show the same "side". what's on the other "side"? would it just be more unidentified galaxies and whatnot?

[Klaynos]

space is isotropic. So ignoring the milkyway (because we're in it, stuff is much closer so it clouds our judgemnent), no matter where you look you always see pretty much the same thing...

 

And gravity's effective range is infinite btw

[bored_teen]

space is isotropic. So ignoring the milkyway (because we're in it, stuff is much closer so it clouds our judgemnent), no matter where you look you always see pretty much the same thing...

 

And gravity's effective range is infinite btw

 

wait, what? so, if i were in space, viewing all of those galaxies, and i turned around, i'd see the same thing? it's like the ultimate fourth wall!

 

gravity's effective range is infinite? wouldn't that only be true if there was only one central source of gravity and absolutely nothing else in space?

[swansont]

wait, what? so, if i were in space, viewing all of those galaxies, and i turned around, i'd see the same thing? it's like the ultimate fourth wall!

 

gravity's effective range is infinite? wouldn't that only be true if there was only one central source of gravity and absolutely nothing else in space?

 

Gravity also adds, vectorally, and has an inverse-square strength. So you are attracted to a hydrogen atom 10 billion light years away, though that can be swamped be more mass closer by, and effectively canceled by a hydrogen atom at the same distance in the opposite direction.

[Klaynos]

If you turned around you wouldn't see exactly the same thing but it would fundementally be the same, so about the same number of glaxies/square light year, they'll be made up of the same stuff have the same average age etc...

[D H]

Gravity also adds, vectorally, and has an inverse-square strength.

The inverse square strength swansont mentioned depends on distance and distance only. The strength of the gravitational acceleration does not depend on direction. For example, all objects located at a distance of one astronomic unit (AU) away from the sun are pulled equally toward the sun by gravity. While the direction of the force varies, the strength (magnitude) of the force does not vary if the distance remains constant.

[bored_teen]

Gravity also adds, vectorally, and has an inverse-square strength. So you are attracted to a hydrogen atom 10 billion light years away, though that can be swamped be more mass closer by, and effectively canceled by a hydrogen atom at the same distance in the opposite direction.

 

actually, since i have more mass, wouldn't the atom be attracted to me?

 

If you turned around you wouldn't see exactly the same thing but it would fundementally be the same, so about the same number of glaxies/square light year, they'll be made up of the same stuff have the same average age etc...

 

but it would still be different? i can turn around on my street and see basically the same stuff: grass, trees, houses, sidewalk, cars, etc., but it's not the same as before.

[Royston]

actually, since i have more mass, wouldn't the atom be attracted to me?

 

Perhaps you should review Newtons laws specifically the third law, but essentially you're right as gravity is per unit mass, and obviously you have (or I should hope) more mass than an atom

 

but it would still be different? i can turn around on my street and see basically the same stuff: grass, trees, houses, sidewalk, cars, etc., but it's not the same as before.

 

It wouldn't be, for obvious reasons, just as if I was on Andromeda I'd see the Milky Way, and vice versa. However when you view distant objects, and I mean distant, this is where the universe displays it's isotropic nature, as Klaynos stated. The further you look out, the faster the objects you're viewing are moving away from your frame of reference. This holds for any part of the universe you're viewing.

 

Also you're looking back in time, when the universe was more dense, and you'll observe galaxy formation et.c the field of view, appears the same, but you'll happen upon the same objects.

 

Note: The last bit, isn't a particularly good explanation, hopefully an expert <cough>Martin<cough> will give a better summary.

[bored_teen]

Perhaps you should review Newtons laws specifically the third law, but essentially you're right as gravity is per unit mass, and obviously you have (or I should hope) more mass than an atom

 

 

 

It wouldn't be, for obvious reasons, just as if I was on Andromeda I'd see the Milky Way, and vice versa. However when you view distant objects, and I mean distant, this is where the universe displays it's isotropic nature, as Klaynos stated. The further you look out, the faster the objects you're viewing are moving away from your frame of reference. This holds for any part of the universe you're viewing.

 

Also you're looking back in time, when the universe was more dense, and you'll observe galaxy formation et.c the field of view, appears the same, but you'll happen upon the same objects.

 

Note: The last bit, isn't a particularly good explanation, hopefully an expert <cough>Martin<cough> will give a better summary.

 

i should hope so. what you're saying is that i'll see the same objects in different places?

[Cap'n Refsmmat]

No. It's just that the universe looks the same in all different directions on a higher level: there are galaxies splattered about randomly in every direction, so wherever you look, you'll just see some more galaxies.

[bored_teen]

No. It's just that the universe looks the same in all different directions on a higher level: there are galaxies splattered about randomly in every direction, so wherever you look, you'll just see some more galaxies.

 

but they will be different galaxies, right? i understand the idea that you're going to see a smattering of galaxies no matter how you turn, because there are just so many. but i would still be seeing different galaxies than are "behind" me.

[insane_alien]

but i would still be seeing different galaxies than are "behind" me.

 

that depends on the curvature of the universe. current readings suggest it is very flat so light will not have had time to come round the universe yet

[bored_teen]

that depends on the curvature of the universe. current readings suggest it is very flat so light will not have had time to come round the universe yet

 

so i'd see nothing?

[kamikaze323]

No, you would see what was in front of you more or less (light does wiggle a bit over large distances though) but if if the universe does turn out to be really curved all bets are off.